Embedded systems training in Bangalore

Embedded systems training in Bangalore(
http://www.5square.in)
http://www.5square.in
5square is a highly focused embedded systems training institute in Bangalore. We offer
state of art training in embedded Systems, device drivers, linux, ARM, Kernel, C, C++
Data Structures, RTOS and Android Applications, aiming to bridge the gap between
the demands of the industry and the curriculum of educational institutions. Our
training methodology is mainly focused on hands-on practical approach with relevant
projects which provides reasonable exposure to various phases of Software and
Application development life cycle.
ABSTRACT
This bicycle machine pumps water at 5-10 gallons per minute from wells and boreholes up to
30 in meters depth, (compared to an electric pump that only pumps up to 12 meters deep).
Provides irrigation and drinking water where electricity is not available.
This project consists of a simple bicycle and a centrifugal pump. The bicycle is still on
main stand of bicycle. Embedded system training in Bangalore. The paddle is driven by
any person who is connected wheel excel by chain drive. The wheel is rotting the pulley
which is mounted on the shaft of the impeller. The wheel and the pulley are meshed which
other and transmit the power from wheel to pulley. The diameter ratio between wheel and
pulley is 8:1. the pulley rotates the shaft of impeller and drive of the casing impeller and
suction pipe and deliver pipe. The impeller is strike the water and water is reach at a
particular head due to rotating high RPM. http://www.5square.in
The water come from the suction pipe and enters the impeller where impeller
strike the water and water is reach at a particular head due to rotating high RPM. Embedded
rtos training in Bangalore. The water come from the suction pipe and enters the impeller
where impeller strike the water and water goes to the delivery pipe.
INTRODUCTION
1 ENERGY

Energy is the primary and most universal measure of all kind of work by human Being and
nature. Everything what happen in the world in the expression of flow of energy is one of its
forms. Most people use the world energy for input to their bodies or to the machines and thus
about fuels and c power embedded rtos training in Bangalore.
Energy is an important input in all sectors of counters economy. The standard of living of a
given country can be directly related to per capita energy consumption energy crisis is due to
the two reasons; firstly is that the population of the world has increased rapidly second the
standard of living of human being has increased. http://www.5square.in
If we take the annual per capita income of various counter and plot them against per head
energy consumption. It will appear that the per capita energy consumption is a measure of the
property of the nation.
This technology is an adaptation of conventional RO & UF. The unit is an off-grid, stand-
alone, bicycle mounted brackish water reverse osmosis (BWRO) system of 10 -20 litres/hr
(lph) capacity which can treat water contaminated with, salinity (up to 1000 mg/l), toxic
elements, pathogens & turbidity. Embedded linux training in Bangalore. It can be operated
throughout the day with the help of the dual energy systems provided. The same unit can be
modified by incorporating an Ultrafiltration (UF) membrane, for removing only pathogens &
turbidity from the raw water. In such case, the production will be increased to 120-200 lph.
this manual describes the design and construction of a device which, when attached to a
standard bicycle, will permit it to be used as a pedal-power machine. The resulting machine,
known as a dual-purpose bicycle, can be used to power numerous small-scale mechanical

devices such as grain threshers, grinders, water pumps, electrical generators, and a variety of
small machine tools. When desired, the dual-purpose bicycle can be converted from its
transportation mode to its pedal-power mode, or vice versa within a matter of minutes.
It should be noted that the design criteria, materials used, and the procedures adopted in
construction may be modified to suit local situations. It is suggested that low-cost and readily
available materials and standard bicycle parts be substituted whenever possible. Changes in
construction method and in dimensions should be made according to the availability of
materials and manufacturing capability. Embedded systems courses in Bangalore . so
2 MECHANISMS
The mechanism consists of single centrifugal pump which is fixed with the rear wheel
bicycle.
Paddling for just a minute for just a minute or two is enough to pump 30-40 liters of water to
a height of 100 feet. Our project could prove helpful for rural areas. Which are facing load
shedding problem? It can be used mainly for irrigation and water drawing water from wells
and other water bodies.
This is a centrifugal water pump which is run by rotating the pedal of a cycle. The system
comprises a bicycle, rim, impeller, pulley and inlet and delivery pipes. A wheel is connected
to another pulley with a smaller diameter the final supporting shaft is connected with an
impeller through this process of paddling is used to lift water from a pipe into the form for
cultivation. This innovation is useful for pumping water from river, ponds , wells and similar
water sources thus enabling poor formers for pumping water for irrigation and cultivation
We drive a bicycle by using a paddling the wheel of the bicycle rotates a particular rpm. And
this wheel rotates the impellers of the centrifugal pump by sliding action between wheel and
pulley but the rpm of the wheel is very low so we can’t get require head and power effort on
the paddling is low so we can use the pulley which is mounted on the shaft of the pump and
create the high rpm by using less power

In process operations, liquids and their movement and transfer from place to place, plays a
large part in the process. Liquid can only flow under its own power from one elevation to a
lower elevation or, from a high pressure system to a lower pressure system.
The flow of liquid is also affected by friction, pipe size, liquid viscosity and the bends and
fittings in the piping.
To overcome flow problems, and to move liquids from place to place, against a higher
pressure or to a higher elevation, energy must be added to the liquid. To add the required
energy to liquids, we use ' PUMPS '. A pump therefore is defined as ' A machine used to add
energy to a liquid '.
Pumps come in many types and sizes. The type depends on the function the pump is to
perform and the size (and speed) depends on the amount (volume) of liquid to be moved in a
given time.
3 TYPES OF PUMP
Most pumps fall into two main categories.
I. Centrifugal Pump
II. Positive Displacement pump
Rotary Pumps:
Rotary pumps are positive displacement pumps that utilize rotary, rather than
reciprocating, motion in their pumping action. They can be designed to pump liquids, gases,
or mixtures of the two. As is the case with reciprocating pumps, their capacity per rotation is
independent of driven speed. Unlike reciprocals, however, they develop a dynamic liquid seal
and do not require inlet and discharge check valves. Since the rotating element of the pump is
directly connected to its driver via a shaft, some sort of drive shaft sealing arrangement is
required. This is usually accomplished via a stuffing box, lip seal, or a mechanical seal.
Embedded systems training institute in Bangalore .
The pumping cycle, which can appear complicated, is actually no more complex than that of
piston or plunger pumps. All rotary pumps, regardless of their design, undergo three

rotational conditions. In this age of acronyms they have been designated as OTI/CTO, CTIO,
and OTO/CTI. These conditions are the equivalent of the suction and discharge strokes of a
reciprocating pump. The acronyms stand for open to inlet / closed to outlet, closed to inlet
and outlet, and open to outlet / closed to inlet.
PERISTALTIC PUMPS
The peristaltic pump, seen on the left side of the figure, belongs to a rotary family known as
flexible member pumps. It is one of the simplest of the rotaries, and offers the clearest
portrayal of the three pumping cycles. The peristaltic pump gets its name from the muscular
action of the human esophagus which, during the swallowing process, contracts progressively
and moves solids and liquids through the alimentary canal. Its rotor is a bar with a roller at
either end while its pumping chamber, or stator, is a continuous length of flexible tubing or
hose set in a U-shaped housing. The rolling motion of the rotor “pinches” the inner walls of
the tubing together and forces liquid through the pump. http://www.5square.in
Peristaltic pumps are popular in chemical applications because corrosive fluids are
completely contained within the tubing and do not come into contact with other parts of the
pump. In the drawing the rotor is turning counter clockwise. Embedded systems training
centres in Bangalore.
The portion of the tubing to the right of the upper roller is open to the inlet and closed to the
outlet of the pump (OTI/CTO) and is at suction pressure. The section between the rollers is
closed to both the inlet and the outlet (CTIO) and is at a similar pressure. Finally, the portion
of the tube to the right of the lower roller is open to the outlet but closed to the inlet
(OTO/CTI) and is at discharge pressure. In the example shown, the pressure “stroke” is a
little less than one half revolution and all of the torque necessary to produce application
pressure is placed upon the CTI roller.Another sibling of the flexible member family is the
flexible vane or rubber impeller pump. http://www.5square.in
The right side of the figure on the previous page is a cross section of such a pump. The rotor
is made of rubber or some other elastic material. The vanes of the rotor are flexible and are in
direct contact with the inner periphery of the pump case. The OTI, CTIO, and OTO volumes

exist between any two of the vanes. In this example, four volumes are CTIO while two each
are OTI and OTO. A major application for these pumps is raw water cooling in the marine
industry.
GEAR PUMPS
One of the most common rotary pumps is the gear pump. A typical cross section is shown in
the left hand side of the figure to the right. It consists of two gears (rotors), one of which is
driven by a shaft. The other acts as an idler and rotates through meshing action with the
driven gear. Unlike the peristaltic pump, the gear pump has extremely close tolerances
between its rotors and the walls of the pump case. It is these clearances and the meshing of
the gear teeth that allow the liquid sealing process to occur. These same clearances also
determine the amount of leakage (slip) that occurs during operation.
Although it is a bit more difficult to envision, the gear pump exhibits the same three pumping
conditions. You will notice that more than one tooth to tooth chamber is involved in all three
parts of the cycle at any given time. Because fluid is discharged by both driven and idler
gears, each shares the torque produced.
LOBE PUMPS
The right side of the figure on the previous page is a cross section of a typical multiple lobe
pump. These pumps are often seen in sewage aeration applications where high volume and
low pressure is the norm. A major difference between lobe and gear pumps is that the rotors
are designed to remain in close contact throughout rotation. http://www.5square.in
By close contact, I mean that the lobes rotate about one another at extremely close tolerances.
Also, unlike the gear pump, the rotors of the lobe pump do not mesh. Therefore exterior
timing gears are required to maintain proper rotation. As before, the pumping cycles are
readily apparent. In the figure the CTIO volume is seen below the lower rotor while the inlet
and outlet volumes are bounded by both rotors. Pumping torque is shared equally by both

rotors; however, their individual loading at any given point in time depends upon their axial
position to one another.
SCREW PUMPS
The screw pump differentiates itself from other rotary pumps in the way fluid moves through
it pumping chamber. Fluid flows axially within the screw pump, but circumferentially in all
others. They are available in single and multiple rotor designs and offer flows to 5000 gpm
and pressures to 5000 PSI. To the right is a cross section of a single rotor, single end screw
pump.
It consists of auger like rotor with lobe shaped surfaces that mesh with a mating stator made
of rubber or some other synthetic elastomer. Its pumping action creates a number of moving
seals as CTIO volumes move axially through the stator. Since each CTIO volume appears to
move intact through the entire length of the pumping chamber, this particular design is often
referred to as a progressing cavity pump. These pumps will accommodate a wide range of
liquids and viscosities. They are most often seen pumping
• sewage sludge and other process solutions with suspended solids.
 RoHS
 200 steps per revolution, 1.8 degrees
 Coil #1: Red & Yellow wire pair. Coil #2 Green & Brown/Gray wire pair.
 Bipolar stepper, requires 2 full H-bridges!
 4-wire, 8 inch leads
 42mm/1.65" square body
 31mm/1.22" square mounting holes, 3mm metric screws (M3)
 5mm diameter drive shaft, 24mm long, with a machined flat

 12V rated voltage (you can drive it at a lower voltage, but the torque will drop) at 350mA
max current
 28 oz*in, 20 N*cm, 2 Kg*cm holding torque per phase
 35 ohms per winding. http://www.5square.in
SALIENT FEATURES
 The unit instantaneously converts contaminated raw water from any inland source to
clean & safe drinking water
 No need of grid electricity or battery
 Compact and lightweight
 The power source is a one - time investment. No electricity bill is to be paid .

WORKING PRINCIPLE
In this unit, water purification/desalination takes place by a pressure driven, membrane based
process. Pressurization is effected by pumps run by electrical and mechanical energy.
Pedalpower attachment

Embedded system training in Bangalore .As bicycles come in various sizes and there are a
variety of tube sizes used for frames, only photos and schematic of the pedal power
attachment are given below.
Please note that the schematic does not have measurements and hence, we recommend that
you use a machinist to fabricate this part. Village craftsmen in India, Thailand, Mexico, and
Belize were able to produce this part using the schematic given below.
Fig : Schematic of Pedal Power Attachment (click for larger view)
It is a pedal water pump which is particularly useful for pumping water from the canal for
irrigation purposes and to draw water from wells, tube wells and reservoirs. It comprises two
cylinders each having a piston and an inlet and outlet connected to a common source and
outlet, respectively.
The unit has five valves, one located at suction at the bottom, two at the entry of the twin
cylinders and two at the delivery pipes located at the top. The user sits on the seat and pedals
the unit, thereby operating the flywheel, which runs the gear which drives two sets of pistons
located in two vertical cylinders. The rotary motion of the pedal is translated into alternate
vertical up and down movement of the pistons in their respective cylinders. While the piston

in one cylinder goes up, the piston in the second cylinder goes down and this ensures constant
discharge of water and no dead stroke for the pumping operation. The advantages of the unit
delivers 100 liters of continuous flow per minute compared to 70-80 liters per minute of
intermittent flow for a normal reciprocating hand pump. It is portable and can be taken and
installed on site at will. Embedded systems training in Bangalore
stepper motor
A stepper motor or step motor or stepping motor is a brushless DC electric motor that divides
a full rotation into a number of equal steps. The motor's position can then be commanded to
move and hold at one of these steps without any feedback sensor (an open-loop controller), as
long as the motor is carefully sized to the application in respect to torque and speed.
Switched reluctance motors are very large stepping motors with a reduced pole count, and
generally are closed-loop commutated.
Fundamentals of operation
A steppermotor

A bipolarhybridsteppermotor
Brushed DC motors rotate continuously when DC voltage is applied to their terminals. The
stepper motor is known by its property to convert a train of input pulses (typically square
wave pulses) into a precisely defined increment in the shaft position. Each pulse moves the
shaft through a fixed angle. Embedded rtos training in Bangalore
Stepper motors effectively have multiple "toothed" electromagnets arranged around a central
gear-shaped piece of iron. The electromagnets are energized by an external driver circuit or a
micro controller. To make the motor shaft turn, first, one electromagnet is given power,
which magnetically attracts the gear's teeth. When the gear's teeth are aligned to the first
electromagnet, they are slightly offset from the next electromagnet. This means that when the
next electromagnet is turned on and the first is turned off, the gear rotates slightly to align
with the next one. From there the process is repeated. Each of those rotations is called a
"step", with an integer number of steps making a full rotation. In that way, the motor can be
turned by a precise angle. http://www.5square.in
Types
There are three main types of stepper motors:
1. Permanent magnet stepper
2. Hybrid synchronous stepper
3. Variable reluctance stepper

Permanent magnet motors use a permanent magnet (PM) in the rotor and operate on the
attraction or repulsion between the rotor PM and the stator electromagnets. Variable
reluctance (VR) motors have a plain iron rotor and operate based on the principle that
minimum reluctance occurs with minimum gap, hence the rotor points are attracted toward
the stator magnet poles. http://www.5square.in
Two-phase stepper motors
There are two basic winding arrangements for the electromagnetic coils in a two phase
stepper motor: bipolar and unipolar.
Unipolar motors
A unipolar stepper motor has one winding with center tap per phase. Each section of
windings is switched on for each direction of magnetic field. Since in this arrangement a
magnetic pole can be reversed without switching the direction of current, the commutation
circuit can be made very simple (e.g., a single transistor) for each winding. Typically, given a
phase, the center tap of each winding is made common: giving three leads per phase and six
leads for a typical two phase motor. Often, these two phase commons are internally joined, so
the motor has only five leads.
A micro controller or stepper motor controller can be used to activate the drive transistors in
the right order, and this ease of operation makes unipolar motors popular with hobbyists; they
are probably the cheapest way to get precise angular movements.
Unipolar stepper motor coils

(For the experimenter, the windings can be identified by touching the terminal wires together
in PM motors. If the terminals of a coil are connected, the shaft becomes harder to turn. one
way to distinguish the center tap (common wire) from a coil-end wire is by measuring the
resistance. Resistance between common wire and coil-end wire is always half of the
resistance between coil-end wires. This is because there is twice the length of coil between
the ends and only half from center (common wire) to the end.) A quick way to determine if
the stepper motor is working is to short circuit every two pairs and try turning the shaft.
Whenever a higher than normal resistance is felt, it indicates that the circuit to the particular
winding is closed and that the phase is working.
Bipolar motors
Bipolar motors have a single winding per phase. The current in a winding needs to be
reversed in order to reverse a magnetic pole, so the driving circuit must be more complicated,
typically with an H-bridge arrangement (however there are several off-the-shelf driver chips
available to make this a simple affair). There are two leads per phase, none are common.
Static friction effects using an H-bridge have been observed with certain drive topologies.[2]
Dithering the stepper signal at a higher frequency than the motor can respond to will reduce
this "static friction" effect.
Because windings are better utilized, they are more powerful than a unipolar motor of the
same weight. This is due to the physical space occupied by the windings. A unipolar motor
has twice the amount of wire in the same space, but only half used at any point in time, hence
is 50% efficient (or approximately 70% of the torque output available). Though a bipolar
stepper motor is more complicated to drive, the abundance of driver chips means this is much
less difficult to achieve.
An 8-lead stepper is wound like a unipolar stepper, but the leads are not joined to common
internally to the motor. This kind of motor can be wired in several configurations:

 Unipolar.
 Bipolar with series windings. This gives higher inductance but lower current per winding.
 Bipolar with parallel windings. This requires higher current but can perform better as the
winding inductance is reduced.
 Bipolar with a single winding per phase. This method will run the motor on only half the
available windings,whichwill reducethe available low speedtorque butrequirelesscurrent
Higher-phase count stepper motors
Multi-phase stepper motors with many phases tend to have much lower levels of vibration.[3]
While they are more expensive, they do have a higher power density and with the appropriate
drive electronics are often better suited to the application[citation needed].
Stepper motor driver circuits
Stepper motor with Adafruit Motor Shield drive circuit for use with Arduino
Stepper motor performance is strongly dependent on the driver circuit. Torque curves may be
extended to greater speeds if the stator poles can be reversed more quickly, the limiting factor
being the winding inductance. To overcome the inductance and switch the windings quickly,
one must increase the drive voltage. This leads further to the necessity of limiting the current
that these high voltages may otherwise induce. http://www.5square.in

L/R driver circuits
L/R driver circuits are also referred to as constant voltage drives because a constant positive
or negative voltage is applied to each winding to set the step positions. However, it is
winding current, not voltage that applies torque to the stepper motor shaft. The current I in
each winding is related to the applied voltage V by the winding inductance L and the winding
resistance R. The resistance R determines the maximum current according to Ohm's law
I=V/R. The inductance L determines the maximum rate of change of the current in the
winding according to the formula for an inductor dI/dt = V/L. Thus when controlled by an
L/R drive, the maximum speed of a stepper motor is limited by its inductance since at some
speed, the voltage U will be changing faster than the current I can keep up. In simple terms
the rate of change of current is L / R (e.g. a 10 mH inductance with 2 ohms resistance will
take 5 ms to reach approx 2/3 of maximum torque or around 24 ms to reach 99% of max
torque). To obtain high torque at high speeds requires a large drive voltage with a low
resistance and low inductance.
With an L/R drive it is possible to control a low voltage resistive motor with a higher voltage
drive simply by adding an external resistor in series with each winding. This will waste
power in the resistors, and generate heat. It is therefore considered a low performing option,
albeit simple and cheap.
Chopper drive circuits
Chopper drive circuits are referred to as constant current drives because they generate a
somewhat constant current in each winding rather than applying a constant voltage. On each
new step, a very high voltage is applied to the winding initially. This causes the current in the
winding to rise quickly since dI/dt = V/L where V is very large. The current in each winding
is monitored by the controller, usually by measuring the voltage across a small sense resistor
in series with each winding. When the current exceeds a specified current limit, the voltage is
turned off or "chopped", typically using power transistors. When the winding current drops
below the specified limit, the voltage is turned on again. In this way, the current is held

relatively constant for a particular step position. This requires additional electronics to sense
winding currents, and control the switching, but it allows stepper motors to be driven with
higher torque at higher speeds than L/R drives. Integrated electronics for this purpose are
widely available.
Phase current waveforms

Different drive modes showing coil current on a 4-phase unipolar stepper motor.
A stepper motor is a polyphase AC synchronous motor (see Theory below), and it is ideally
driven by sinusoidal current. A full-step waveform is a gross approximation of a sinusoid,
and is the reason why the motor exhibits so much vibration. Various drive techniques have
been developed to better approximate a sinusoidal drive waveform: these are half stepping
and microstepping.
Wave drive (one phase on)
In this drive method only a single phase is activated at a time. It has the same number of steps
as the full-step drive, but the motor will have significantly less than rated torque. It is rarely
used. The animated figure shown above is a wave drive motor. In the animation, rotor has 25
teeth and it takes 4 steps to rotate by one tooth position. So there will be 25×4 = 100 steps per
full rotation and each step will be 360/100 = 3.6 degrees.
Full-step drive (two phases on)
This is the usual method for full-step driving the motor. Two phases are always on so the
motor will provide its maximum rated torque. As soon as one phase is turned off, another one
is turned on. Wave drive and single phase full step are both one and the same, with same
number of steps but difference in torque.
Half-stepping
When half-stepping, the drive alternates between two phases on and a single phase on. This
increases the angular resolution. The motor also has less torque (approx 70%) at the full-step
position (where only a single phase is on). This may be mitigated by increasing the current in
the active winding to compensate. The advantage of half stepping is that the drive electronics
need not change to support it. In animated figure shown above, if we change it to half-
stepping, then it will take 8 steps to rotate by 1 teeth position. So there will be 25×8 = 200

steps per full rotation and each step will be 360/200 = 1.8°. Its angle per step is half of the
full step.
Microstepping
What is commonly referred to as microstepping is often sine–cosine microstepping in which
the winding current approximates a sinusoidal AC waveform. Sine–cosine microstepping is
the most common form, but other waveforms can be used.[4] Regardless of the waveform
used, as the microsteps become smaller, motor operation becomes more smooth, thereby
greatly reducing resonance in any parts the motor may be connected to, as well as the motor
itself. Resolution will be limited by the mechanical stiction, backlash, and other sources of
error between the motor and the end device. Gear reducers may be used to increase resolution
of positioning.
Step size repeatability is an important step motor feature and a fundamental reason for their
use in positioning.
Example: many modern hybrid step motors are rated such that the travel of every full step
(example 1.8 degrees per full step or 200 full steps per revolution) will be within 3% or 5%
of the travel of every other full step, as long as the motor is operated within its specified
operating ranges. Several manufacturers show that their motors can easily maintain the 3% or
5% equality of step travel size as step size is reduced from full stepping down to 1/10
stepping. Then, as the microstepping divisor number grows, step size repeatability degrades.
At large step size reductions it is possible to issue many microstep commands before any
motion occurs at all and then the motion can be a "jump" to a new position.[5]
Theory
A step motor can be viewed as a synchronous AC motor with the number of poles (on both
rotor and stator) increased, taking care that they have no common denominator. Additionally,
soft magnetic material with many teeth on the rotor and stator cheaply multiplies the number

of poles (reluctance motor). Modern steppers are of hybrid design, having both permanent
magnets and soft iron cores.
To achieve full rated torque, the coils in a stepper motor must reach their full rated current
during each step. Winding inductance and reverse EMF generated by a moving rotor tend to
resist changes in drive current, so that as the motor speeds up, less and less time is spent at
full current — thus reducing motor torque. As speeds further increase, the current will not
reach the rated value, and eventually the motor will cease to produce torque.
Pull-in torque
This is the measure of the torque produced by a stepper motor when it is operated without an
acceleration state. At low speeds the stepper motor can synchronize itself with an applied step
frequency, and this pull-in torque must overcome friction and inertia. It is important to make
sure that the load on the motor is frictional rather than inertial as the friction reduces any
unwanted oscillations.
The pull-in curve defines an area called the start/stop region. Into this region, the motor can
be started/stopped instantaneously with a load applied and without loss of synchronism.
Pull-out torque
The stepper motor pull-out torque is measured by accelerating the motor to the desired speed
and then increasing the torque loading until the motor stalls or misses steps. This
measurement is taken across a wide range of speeds and the results are used to generate the
stepper motor's dynamic performance curve. As noted below this curve is affected by drive
voltage, drive current and current switching techniques. A designer may include a safety
factor between the rated torque and the estimated full load torque required for the
application>>

Detent torque
Synchronous electric motors using permanent magnets have a resonant position holding
torque (called detent torque or cogging, and sometimes included in the specifications) when
not driven electrically. Soft iron reluctance cores do not exhibit this behavior.
Ringing and resonance
When the motor moves a single step it overshoots the final resting point and oscillates round
this point as it comes to rest. This undesirable ringing is experienced as motor vibration and
is more pronounced in unloaded motors. An unloaded or under loaded motor may, and often
will, stall if the vibration experienced is enough to cause loss of synchronisation.
Stepper motors have a natural frequency of operation. When the excitation frequency
matches this resonance the ringing is more pronounced, steps may be missed, and stalling is
more likely. Motor resonance frequency can be calculated from the formula:
Stepper motor ratings and specifications
Stepper motors' nameplates typically give only the winding current and occasionally the
voltage and winding resistance. The rated voltage will produce the rated winding current at
DC: but this is mostly a meaningless rating, as all modern drivers are current limiting and the
drive voltages greatly exceed the motor rated voltage.
A stepper's low speed torque will vary directly with current. How quickly the torque falls off
at faster speeds depends on the winding inductance and the drive circuitry it is attached to,
especially the driving voltage.
Steppers should be sized according to published torque curve, which is specified by the
manufacturer at particular drive voltages or using their own drive circuitry.
Step motors adapted to harsh environments are often referred to as IP65 rated.[6]

The US National Electrical Manufacturers Association (NEMA) standardises various aspects
of stepper motors. They are typically referred with NEMA DD, where DD is the diameter of
the faceplate in inches × 10 (e.g., NEMA 17 has diameter of 1.7 inches). There are further
specifiers to describe stepper motors, and such details may be found in the ICS 16-2001
standard (section 4.3.1.1). There are also useful summaries and further information on the
Reprap site.
Applications
Computer controlled stepper motors are a type of motion-control positioning system. They
are typically digitally controlled as part of an open loop system for use in holding or
positioning applications.
In the field of lasers and optics they are frequently used in precision positioning equipment
such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. Other
uses are in packaging machinery, and positioning of valve pilot stages for fluid control
systems.
Commercially, stepper motors are used in floppy disk drives, flatbed scanners, computer
printers, plotters, slot machines, image scanners, compact disc drives, intelligent lighting,
camera lenses, CNC machines and, more recently, in 3D printers.
Stepper motor system
A stepper motor system consists of three basic elements, often combined with some type of
user interface (host computer, PLC or dumb terminal):
Indexers
The indexer (or controller) is a microprocessor capable of generating step pulses and
directionsignalsforthe driver.Inaddition,the indexeristypicallyrequiredto perform many
other sophisticated command functions.

Drivers
The driver(or amplifier) convertsthe indexercommandsignals into the power necessary to
energize the motor windings. There are numerous types of drivers, with different voltage
and current ratings and construction technology. Not all drivers are suitable to run all
motors, so when designing a motion control system the driver selection process is critical.
Stepper motors
The steppermotoris an electromagneticdevice thatconvertsdigital pulses into mechanical
shaft rotation. Advantages of step motors are low cost, high reliability, high torque at low
speeds and a simple, rugged construction that operates in almost any environment. The
maindisadvantagesinusingasteppermotor is the resonance effect often exhibited at low
speeds and decreasing torque with increasing speed.[7]
Advantages of stepper motors
Advantages
 Low cost for control achieved
 High torque at startup and low speeds
 Ruggedness
 Simplicity of construction
 Can operate in an open loop control system
 Low maintenance
 Less likely to stall or slip
 Will work in any environment
 Can be used in robotics in a wide scale.
 High reliability
 The rotation angle of the motor is proportional to the input pulse.
 The motor has full torque at standstill (if the windings are energized)

 Precise positioning and repeatability of movement since good stepper motors have an
accuracy of 3 – 5% of a step and this error is non-cumulative from one step to the next.
 Excellent response to starting/stopping/reversing.
 Very reliable since there are no contact brushes in the motor. Therefore, the life of the
motor is simply dependent on the life of the bearing.
 The motors response to digital input pulses provides open-loop control, making the motor
simpler and less costly to control.
 It is possible to achieve very low-speed synchronous rotation with a load that is directly
coupled to the shaft.
 A wide range of rotational speeds can be realized as the speed is proportional to the
frequency of the input pulses.
bicycle pedal
The bicycle pedal is the part of a bicycle that the rider pushes with their foot to propel the
bicycle. It provides the connection between the cyclist's foot or shoe and the crank
allowing the leg to turn the bottom bracket spindle and propel the bicycle's wheels. Pedals
usually consist of a spindle that threads into the end of the crank and a body, on which the
foot rests or is attached, that is free to rotate on bearings with respect to the spindle.
Pedals were initially attached to cranks connecting directly to the driven (usually front)
wheel. The safety bicycle, as it is known today, came into being when the pedals were
attached to a crank driving a sprocket that transmitted power to the driven wheel by means of
a roller chai
Types
Just as bicycles come in many varieties, there are different types of pedals to support different
types of cycling.

Flat and platform
Wellgo DMR V8 Copy pedal
Traditionally, platform pedals were pedals with a relatively large flat area for the foot to rest
on, in contrast to the quill pedal which had very little surface area.
One form of the platform pedal had a large flat top area and flat bottom for use with toe clips
and toe straps. They were designed for greater comfort when using shoes with less than rigid
soles. They typically had a smaller cutaway underside giving greater cornering clearance,
which was often needed for track cycling. They were often marketed as being more
aerodynamic than conventional quill pedals.
Attaching the shoes to the pedals gives the user more control over the pedal movements.
There are two methods for attaching a cyclist's shoes to their pedals: toe clips, a basket-and-
strap device which hold the foot in place; and so-called clipless pedals, where specialized
shoes with built-in bindings attach to compatible pedals.
In mountain biking (MTB) and BMX, platform pedals typically refer to any flat pedal
without a cage. BMX riders typically use plastic pedals made of nylon, polycarbonate, or
carbon reinforced plastic, although aluminum alloy, and magnesium are not uncommon pedal
body materials. Mountain bikers tend to use aluminum or magnesium because of the
necessary use of metal studs to offer grip while the pedals are wet, muddy and slippery.
BMX'ers tend to prefer platforms to cage pedals because they offer more support and grip for
flexible "skate" shoes by using short metal studs. Cage pedals are more popular in the low

end mountain bike range. In general, cage pedals are uncommon in all types of biking,
although there is a niche market within mountain biking.
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Application development life cycle
Platform pedals are available in a wide variety of types and prices, ranging from disposable
plastic units used for test rides on new bicycles to high-end downhill models. Budget models
may be made of steel or aluminum and incorporate reflectors for safer riding on streets at
night, in addition to complying with some traffic laws. Less expensive platform pedals are
generally considered disposable and cannot be rebuilt when worn out.
More expensive platform pedals for the mountain bike market are available with replaceable
metal traction pins and cartridge bearings. Lightweight pedals intended for Freeride and
downhill cycling have been made from exotic metals such as magnesium.
Toe clips typically are generally not installed on this type of pedal because they are
considered unsafe by some MTB and BMX riders. In downhill racing, the extra power and
grip offered by clipped pedals is utilized at the risk of clipped in crashing in which the
bicycle can potentially stay attached to the foot of the victim. However, fixed gear riders have
started using fabric straps instead.
Bicycle pedal, quill road type, with toe clip and toe strap (1970s)
The quill pedal is a common pedal system on bicycles. It consists of a main axle section that
is attached to the bicycle crank arm and contains extensions from the axle to which parallel

cage plates are attached at the front and rear of the pedal. In order to utilize the quill pedal,
the cyclist pushes his foot against the platform formed by the parallel cage plates.[1]
To improve the performance of the quill pedal toe clips were added. The toe clip is a thin
metal or plastic attachment to the front cage of the pedal. The toe clip is shaped like the toe of
a shoe and its function is to prevent a cyclist's shoe from slipping off the pedal during the
forward pedaling motion. A further enhancement of the quill pedal was modifying the toe
clip to allow a strap and buckle to go around or through both the pedal and the toe clip to
encircle the cyclist's foot on the top of the pedal.[1] This strap is generally made of leather or
nylon.
Mikashima track pedal
To further improve the quill pedal's efficiency a "cleat" was developed. This cleat consists of
a small metal or plastic attachment to the cyclist's shoe. The cleat is slotted and is adapted to
engage a quill section of the bicycle pedal. The use of the slotted cleat enhances a cyclist's
ability over that provided by toe clips and strap, enabling for greater pedaling efficiency.
Although quill pedals can be used with smoothed-soled cycling shoes or ordinary shoes, they
were designed to be used with cycling shoes which had a slotted shoeplate attached to its
sole. The disadvantage with this system is that to remove the shoe from the pedal a rider had
to reach down and loosen the strap by hand or leave the toe strap loose and thus give up some
efficiency. This type of pedal and pedal setup was common for racing cyclists until the mid to
late 1980s.

Quill pedals are sometimes said to be named for the quill or "pick up tab" on the rear of the
pedal. The weight of the toe clip and strap would make the pedal hang upside down, and the
rider would tap the quill with their shoe to flip the pedal over so the shoe could be inserted
into the pedal.
The main difference between track, road, and touring quill pedals is width. Track pedals are
narrow and the front and back plates of the cage are separate, road being a little wider with a
one piece cage in a shape of a sideways "U", and touring being the widest to allow for
comfort when used with wider, non-racing shoes during longer rides. While quill pedals can
be used for mountain biking, the use of clips here is dangerous as they do not grip well. Cage
pedals built for mountain biking are typically serrated so that even when muddied, the pedals
can be gripped well by any flat shoe.
Clipless pedals
LOOK road pedals
Clipless pedals (also clip-in or step-in) require a special cycling shoe with a cleat fitted to the
sole, which locks into a mechanism in the pedal and thus holds the shoe firmly to the pedal.
Most clipless pedals lock onto the cleat when stepped on firmly and unlock when the heel is
twisted outward, although in some cases the locking mechanism is built into the cleat instead
of the pedal. Clipless refers to the toe clip (cage) having been replaced by a locking
mechanism and not to platform pedals which would normally not have toe clips. The clipless
pedal was invented by Charles Hanson in 1895. It allowed the rider to twist the shoe to lock
and unlock and had rotational float (the freedom to rotate the shoe slightly to prevent joint

strain). The M71 was a clipless pedal designed by Cino Cinelli and produced by his company
in 1971. It used a plastic shoe cleat which slid into grooves in the pedal and locked in place
with a small lever located on the back side of the pedal body. To release the shoe a rider had
to reach down and operate the lever, similar to the way a racing cyclist had to reach down and
loosen the toestrap. The lever was placed on the outside edge of the pedal so that in the event
of a fall the lever hitting the ground would release the foot. The pedal was designed for
racing, in particular track racing, and because of the need to reach them to unclip they have
been referred to as "death cleats". In 1984, the French company Look applied downhill snow
skiing binding or cleat technology to pedals producing the first widely used clipless pedals.
Initially used by triathletes in order to facilitate faster "transitions", Bernard Hinault's victory
in Tour de France in 1985 then helped secure the acceptance of quick-release clipless pedal
systems by cyclists. Those pedals, and compatible models by other manufacturers, remain in
widespread use today. The cleat is engaged by simply pushing down and forward on the
pedal, or, with some designs, by twisting the cleat in sideways. Then, instead of loosening a
toestrap or pulling a lever, the cyclist releases a foot from the pedal by twisting the heel
outward.
SPD Dual Choice with shoe
The next major development in clipless pedals was Shimano's SPD (Shimano Pedaling
Dynamics) pedal system. Whereas Look cleats are large and protrude from the sole of the
shoe, SPD cleats are small and could be fitted in a recess in the sole, making it possible to
walk (although comfort will vary, as the soles of different cycling shoes vary in their rigidity

depending on design). Cycling shoes have rigid soles to maximize power transfer and
efficiency. They may be specific to road or mountain biking, or usable for both. Shoes
designed for mountain biking typically have recessed cleats that do not protrude beyond the
sole of the shoe, and have treads for walking on trails, as walking or carrying the bike is often
required. Road cycling shoes are typically lighter than their mountain bike counterparts, and
feature a protruding cleat and less weather proofing. The protruding cleat makes these shoes
impractical for walking, as doing so can damage the cleat. Mountain bike cleats can generally
be mounted without difficulty to road shoes although sometimes an adapter is required. Such
attachment is not usually possible for road pedals, as the cleats are normally too large to be
mounted on mountain shoes. The smaller mountain bike cleats are attached to the sole of the
shoe by two bolts; larger road-specific cleats are attached by three. Various manufacturers
have produced their own designs of clipless pedal systems over the years.
Xpedo M-FORCE 4 TI pedals with 6 dgr float
Platform adapters are designed to temporarily convert clipless pedals into more traditional
platform pedals which have a larger and flatter area for the foot to rest on. Clipless pedals can
have advantages over flat ones, especially in mountain biking and racing. They keep the foot
from slipping in wet and muddy conditions and provide better transfer of power. Since the
pedal platform adapters temporarily converts these into platform pedals, this allows riders to
wear normal shoes without switching to another bike with a different pedal setup. They can
be fastened by using bolts but as they are normally in temporary use, it is also common for
them to be mounted using different snap-on techniques. Although it's possible to use clipless

pedals with regular footwear, they will be much less comfortable than platform pedals, as the
shoe sole is more likely to bend or slip.
Float and tension
"Float" is defined as the degree of movement offered by the cleat within the pedal before
release begins. This can be highly important to prevent damage to knees, as most peoples'
legs do not remain in a single plane as they pedal. Many standard road pedal systems offer
with a 6 degree float cleat. SPD-SL, Look Delta, Look Kéo, and Time cleats are also
available in 3 degree and 0 degree float. Road pedal systems commonly colour-code cleats by
the amount of float offered. Some pedal systems have a fixed non-adjustable float, such as 6
degrees for Crank Brothers and 4.5 degrees for the Kéo Easy. Most cleats develop more float
as they wear.
Magnet pedals
Davtus magnet pedal
Magnetic pedals were introduced as early as 1897, and the Exus Mag Flux Road was
available in 1996. Norbert Sadler and Wolfgang Duerr filed for a patent in 2005, and it has
not been granted as of 2012. Established bicycle component manufacturer, Mavic, introduced
a magnetic pedal and dedicated shoe for casual riding in 2009. Others have received mixed
reviews.

Folding
Folding pedal on a Brompton bicycle
To maximize compactness, folding bicycles often have pedals that fold as well.
Attachment
The pedal spindle is threaded to match a threaded hole at the outboard end of the cranks.
Multi-piece cranks have a 9⁄16-inch (14.2875 mm) hole with 20 TPI (a diameter/pitch
combination fairly unusual to this application). One-piece cranks use a 1⁄2-inch (12.7 mm) by
20 TPI hole. French pedal spindles use M14 x 1.25 (14 mm or 0.55 in metric diameter with
1.25 mm or 0.049 in pitch) threads, and thread loosely into a 9/16 pedal hole. The threading
size is often stamped into the crank, near the pedal hole. The right-side (usually the drive-
side) pedal spindle is right-hand threaded, and the left-side (usually the non-drive-side) pedal
spindle is left-hand (reverse) threaded to help prevent it from becoming loose by an effect
called precession.[14][15] Although the left pedal turns clockwise on its bearing relative to the
crank (and so would seem to tighten a right-hand thread), the force from the rider's foot
presses the spindle against the crank thread at a point which rolls around clockwise with
respect to the crank, thus slowly pulling the outside of the pedal spindle anticlockwise
(counterclockwise) because of friction and thus would loosen a right-hand thread. For a short
time in the early 1980s, Shimano made pedals and matching cranks that had a 1-inch
(25.4 mm) by 24 TPI interface. This was to allow a larger single bearing, as these pedals were
designed to work with just one bearing on the crank side rather than the conventional design
of one smaller bearing on each side.

lead-acid battery
The lead-acid battery was invented in 1859 by French physicist Gaston Planté and is the
oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a
low energy-to-volume ratio, its ability to supply high surge currents means that the cells have
a relatively large power-to-weight ratio. These features, along with their low cost, makes it
attractive for use in motor vehicles to provide the high current required by automobile starter
motors.
As they are inexpensive compared to newer technologies, lead-acid batteries are widely used
even when surge current is not important and other designs could provide higher energy
densities. Large-format lead-acid designs are widely used for storage in backup power
supplies in cell phone towers, high-availability settings like hospitals, and stand-alone power
systems. For these roles, modified versions of the standard cell may be used to improve
storage times and reduce maintenance requirements. Gel-cells and absorbed glass-mat
batteries are common in these roles, collectively known as VRLA (valve-regulated lead-acid)
batteries.
In 1999 Lead–acid battery sales accounted for 40–45% of the value from batteries sold
worldwide excluding China and Russia, and a manufacturing market value of about $15
billion.
The French scientist Gautherot observed in 1801 that wires that had been used for electrolysis
experiments would themselves provide a small amount of "secondary" current after the main
battery had been disconnected. In 1859, Gaston Planté's lead–acid battery was the first battery
that could be recharged by passing a reverse current through it. Planté's first model consisted
of two lead sheets separated by rubber strips and rolled into a spiral. His batteries were first
used to power the lights in train carriages while stopped at a station. In 1881, Camille

Alphonse Faure invented an improved version that consisted of a lead grid lattice, into which
a lead oxide paste was pressed, forming a plate. This design was easier to mass-produce. An
early manufacturer (from 1886) of lead–acid batteries was Henri Tudor.
Using a gel electrolyte instead of a liquid allows the battery to be used in different positions
without leakage. Gel electrolyte batteries for any position date from 1930s, and even in the
late 1920s portable suitcase radio sets allowed the cell vertical or horizontal (but not inverted)
due to valve design (see third Edition of Wireless Constructor's Encyclopaedia by Frederick
James Camm). In the 1970s, the valve-regulated lead acid battery (often called "sealed") was
developed, including modern absorbed glass mat types, allowing operation in any position.
Electrochemistry
Discharge
Fully discharged: two identical lead sulfate plates
In the discharged state both the positive and negative plates become lead(II) sulfate (PbSO
and the electrolyte loses much of its dissolved sulfuric acid and becomes primarily water. The

discharge process is driven by the conduction of electrons from the negative plate back into
the cell at the positive plate in the external circuit.
As electrons accumulate they create an electric field which attracts hydrogen ions and repels
sulfate ions, leading to a double-layer near the surface. The hydrogen ions screen the charged
electrode from the solution which limits further reactions unless charge is allowed to flow out
of electrode.
The sum of the molecular masses of the reactants is 642.6 g/mol, so theoretically a cell can
produce two faradays of charge (192,971 coulombs) from 642.6 g of reactants, or 83.4
ampere-hours per kilogram (or 13.9 ampere-hours per kilogram for a 12-volt battery). For a 2
volts cell, this comes to 167 watt-hours per kilogram of reactants, but a lead–acid cell in
practice gives only 30–40 watt-hours per kilogram of battery, due to the mass of the water
and other constituent parts.
Charging
Fully recharged: Lead anode, Lead oxide cathode and sulfuric acid electrolyte
In the fully charged state, the negative plate consists of lead, and the positive plate lead
dioxide, with the electrolyte of concentrated sulfuric acid.
Overcharging with high charging voltages generates oxygen and hydrogen gas by electrolysis
of water, which is lost to the cell. The design of some types of lead-acid battery allow the
electrolyte level to be inspected and topped up with any water that has been lost.

Due to the freezing-point depression of the electrolyte, as the battery discharges and the
concentration of sulfuric acid decreases, the electrolyte is more likely to freeze during winter
weather when discharged.
Ion motion
During discharge, H+
produced at the negative plates moves into the electrolyte solution and then is consumed into
the positive plates, while HSO−
4 is consumed at both plates. The reverse occurs during charge. This motion can be by
electrically driven proton flow or Grotthuss mechanism, or by diffusion through the medium,
or by flow of a liquid electrolyte medium. Since the density is greater when the sulfuric acid
concentration is higher, the liquid will tend to circulate by convection. Therefore, a liquid-
medium cell tends to rapidly discharge and rapidly charge more efficiently than an otherwise
similar gel cell.
Measuring the charge level

A hydrometercanbe usedto testthe specificgravityof eachcell as a measure of its state of charge.
Because the electrolyte takes part in the charge-discharge reaction, this battery has one major
advantage over other chemistries. It is relatively simple to determine the state of charge by
merely measuring the specific gravity of the electrolyte; the specific gravity falls as the
battery discharges. Some battery designs include a simple hydrometer using colored floating
balls of differing density. When used in diesel-electric submarines, the specific gravity was
regularly measured and written on a blackboard in the control room to indicate how much
longer the boat could remain submerged.
The battery's open-circuit voltage can also be used to gauge the state of charge. If the
connections to the individual cells are accessible, then the state of charge of each cell can be
determined which can provide a guide as to the state of health of the battery as a whole,
otherwise the overall battery voltage may be assessed.
Note that neither technique gives any indication of charge capacity, only charge level. Charge
capacity of any rechargeable battery will decline with age and usage, meaning that it may no
longer be fit for purpose even when nominally fully charged. Other tests, usually involving
current drain, are used to determine the residual charge capacity of a battery.

Voltages for common usages
For the three-stage charging procedure of lead acid batteries, see IUoU battery charging. The
theoretical voltage of a lead acid battery is 12 V for 6 cages and 2 V for one cage. These are
general voltage ranges per cell:
 Open-circuit (quiescent) at full charge: 2.10 V
 Open-circuit at full discharge: 1.95 V
 Loaded at full discharge: 1.8 V
 Continuous-preservation (float) charging: 2.23 V for gelled electrolyte; 2.25 V for absorbed
glass mat (AGM) and 2.32 V for flooded cells. Float voltage recommendations vary among
manufacturersdue todifferentleadacidconcentrationandpositive plate grid alloy. Precise
floatvoltage (±0.05 V) is critical to longevity;insufficientvoltage(causes sulfation) is almost
as detrimental as excessive voltage (causes positive plate corrosion, expansion and
electrolyte loss.)
 Typical (daily) charging: 2.28–2.4 V (depending on temperature and manufacturer's
recommendation)
 Equalization charging (for flooded lead acids): 2.5–2.67 V (5 A per 100 Ah, Battery temperature
must be absolutely monitored very closely, check manufacturers recommendation)
 Charging in sulfated state (stored discharged for days or weeks) not accepting small charge
current: > 3 V (only until a charge current is flowing)
 Charging in sulfated state: up to 2.6–2.66 V
 Discharging in sulfated state: 1.6 V (when charging at low rates doesn't improve, discharge rate
approximately 5 A per 10 Ah)
 Gassingthreshold:2.415 V–2.48[]
for sealed,2.41 V for PzS, 2.36–2.41 V for GiS, PzV, GiV (the
value is manufacturer specific, gas is always produced even in storage, 99% of the gas production
recombines under normal charging conditions, the higher the voltage exponentially more gas is
produced: from 2.3 to 2.5 is factor 1 to > 20, charging above the gassing voltage with high chargi ng
current the side reaction will occur enhanced

All voltages are at 20 °C (68 °F), and must be adjusted for temperature changes. The open-
circuit voltage cannot be adjusted with a simple temperature coefficient because it is non-
linear (coefficient varies with temperature). See voltage vs. temperature table.
Construction
Plates
Internal view of a small lead-acid battery from an electric-start equipped motorcycle
The lead–acid cell can be demonstrated using sheet lead plates for the two electrodes.
However, such a construction produces only around one ampere for roughly postcard-sized
plates, and for only a few minutes.
Gaston Planté found a way to provide a much larger effective surface area. In Planté's design,
the positive and negative plates were formed of two spirals of lead foil, separated with a sheet
of cloth and coiled up. The cells initially had low capacity, so a slow process of "forming"
was required to corrode the lead foils, creating lead dioxide on the plates and roughening
them to increase surface area. Initially this process used electricity from primary batteries;
when generators became available after 1870, the cost of production of batteries greatly
declined. Planté plates are still used in some stationary applications, where the plates are
mechanically grooved to increase their surface area.

In 1880, Camille Alphonse Faure patented a method of coating a lead grid (which serves as
the current conductor) with a paste of lead oxides, sulfuric acid and water, followed by curing
phase in which the plates were exposed to gentle heat in a high humidity environment. The
curing process caused the paste to change to a mixture of lead sulfates which adhered to the
lead plate. Then, during the battery's initial charge (called "formation") the cured paste on the
plates was converted into electrochemically active material (the "active mass"). Faure's
process significantly reduced the time and cost to manufacture lead–acid batteries, and gave a
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ubstantial increase in capacity compared with Planté's battery. Faure's method is still in use
today, with only incremental improvements to paste composition, curing (which is still done
with steam, but is now a very tightly controlled process), and structure and composition of
the grid to which the paste is applied.
The grid developed by Faure was of pure lead with connecting rods of lead at right angles. In
contrast, present-day grids are structured for improved mechanical strength and improved
current flow. In addition to different grid patterns (ideally, all points on the plate are
equidistant from the power conductor), modern-day processes also apply one or two thin
fibre-glass mats over the grid to distribute the weight more evenly. And while Faure had used
pure lead for his grids, within a year (1881) these had been superseded by lead-antimony (8–
12%) alloys to give the structures additional rigidity. However, high-antimony grids have
higher hydrogen evolution (which also accelerates as the battery ages), and thus greater
outgassing and higher maintenance costs. These issues were identified by U. B. Thomas and
W. E. Haring at Bell Labs in the 1930s and eventually led to the development of lead-calcium

grid alloys in 1935 for standby power batteries on the U.S. telephone network. Related
research led to the development of lead-selenium grid alloys in Europe a few years later. Both
lead-calcium and lead-selenium grid alloys still add antimony, albeit in much smaller
quantities than the older high-antimony grids: lead-calcium grids have 4–6% antimony while
lead-selenium grids have 1–2%. These metallurgical improvements give the grid more
strength, which allows it carry more weight, i.e. more active material, and so the plates can be
thicker, which in turn contributes to battery lifespan since there is more material available to
shed before the battery becomes unusable. High-antimony alloy grids are still used in
batteries intended for frequent cycling, e.g. in motor-starting applications where frequent
expansion/contraction of the plates needs to be compensated for, but where outgassing is not
significant since charge currents remain low. Since the 1950s, batteries designed for
infrequent cycling applications (e.g., standby power batteries) increasingly have lead-calcium
or lead-selenium alloy grids since these have less hydrogen evolution and thus lower
maintenance overhead. Lead-calcium alloy grids are cheaper to manufacture (the cells thus
have lower up-front costs), and have a lower self-discharge rate, and lower watering
requirements, but have slightly poorer conductivity, are mechanically weaker (and thus
require more antimony to compensate), and are strongly subject to corrosion (and thus a
shorter lifespan) than cells with lead-selenium alloy grids.
Allegedly the US Navy submarines have switched from trickle charging AGM (lead calcium
plate technology) to cycling the battery between trickle discharging, and trickle charging their
batteries to prevent the open circuit effect caused by the calcium in the lead grids. This open
circuit effect is caused by the calcium oxidizing.
The open circuit effect is also known as the antimony free effect.
Modern-day paste contains carbon black, blanc fixe (barium sulfate) and lignosulfonate. The
blanc fixe acts as a seed crystal for the lead–to–lead sulfate reaction. The blanc fixe must be
fully dispersed in the paste in order for it to be effective. The lignosulfonate prevents the
negative plate from forming a solid mass during the discharge cycle, instead enabling the
formation of long needle–like dendrites. The long crystals have more surface area and are

easily converted back to the original state on charging. Carbon black counteracts the effect of
inhibiting formation caused by the lignosulfonates. Sulfonated naphthalene condensate
dispersant is a more effective expander than lignosulfonate and speeds up formation. This
dispersant improves dispersion of barium sulfate in the paste, reduces hydroset time,
produces a more breakage-resistant plate, reduces fine lead particles and thereby improves
handling and pasting characteristics. It extends battery life by increasing end-of-charge
voltage. Sulfonated naphthalene requires about one-third to one-half the amount of
lignosulfonate and is stable to higher temperatures.
Once dry, the plates are stacked with suitable separators and inserted in a cell container. The
alternate plates then constitute alternating positive and negative electrodes, and within the
cell are later connected to one another (negative to negative, positive to positive) in parallel.
The separators inhibit the plates from touching each other, which would otherwise constitute
a short circuit. In flooded and gel cells, the separators are insulating rails or studs, formerly of
glass or ceramic, and now of plastic. In AGM cells, the separator is the glass mat itself, and
the rack of plates with separators are squeezed together before insertion into the cell; once in
the cell, the glass mats expand slightly, effectively locking the plates in place. In multi-cell
batteries, the cells are then connected to one another in series, either through connector
through the cell walls, or by a bridge over the cell walls. All intra-cell and inter-cell
connections are of the same lead alloy as that used in the grids. This is necessary to prevent
galvanic corrosion.

So-called "deep cycle" batteries employ a different geometry for their positive electrodes. In
this geometry, the positive electrode is not a flat plate but a row of lead-oxide cylinders or
tubes strung side by side (hence the term "tubular" or "cylindrical" batteries for this
geometry). The advantage of this geometry is an increased surface area in contact with the
electrolyte, which in turn allows higher discharge/charge currents than a flat-plate cell of the
same volume and depth-of-charge. Tubular-electrode cells thus exhibit a higher power
density than flat-plate cells. This makes tubular/cylindrical geometry plates especially
suitable for high-current applications with storage weight/space limitations, such as for
forklifts or for starting marine diesel engines. However, because tubes/cylinders have less
active material in the same volume, they also have a lower energy density than flat-plate
cells. And, less active material at the electrode also means they have less material available to
shed before the cell becomes unusable. Tubular/cylindrical electrodes are also more
complicated to manufacture uniformly, which tends to make them more expensive than flat-
plate cells. These trade-offs limit the range of applications in which tubular/cylindrical
batteries are meaningful to situations where there is insufficient space to install higher
capacity (and thus larger) flat-plate units.
About 60% of the weight of an automotive-type lead–acid battery rated around 60 A·h
(8.7 kg of a 14.5 kg battery) is lead or internal parts made of lead; the balance is electrolyte,
separators, and the case.[8]
Separators
Separators between the positive and negative plates prevent short-circuit through physical
contact, mostly through dendrites ("treeing"), but also through shedding of the active
material. Separators obstruct the flow of ions between the plates and increase the internal
resistance of the cell. Wood, rubber, glass fiber mat, cellulose, and PVC or polyethylene
plastic have been used to make separators. Wood was the original choice, but deteriorated in
the acid electrolyte. Rubber separators are stable in battery acid and provide valuable
electrochemical advantages that other materials cannot.

An effective separator must possess a number of mechanical properties; such as permeability,
porosity, pore size distribution, specific surface area, mechanical design and strength,
electrical resistance, ionic conductivity, and chemical compatibility with the electrolyte. In
service, the separator must have good resistance to acid and oxidation. The area of the
separator must be a little larger than the area of the plates to prevent material shorting
between the plates. The separators must remain stable over the battery's operating
temperature range.
Absorbed glass mat -AGM
In the absorbed glass mat design, or AGM for short, the spaces between the cells is replaced
by a glass fibre mat soaked in electrolyte. There is only enough electrolyte in the mat to keep
it wet, and if the battery is punctured the electrolyte will not flow out of the mats. Likewise,
the mat greatly reduces evaporation, to the point that the batteries do not require periodic
refilling of the water. This combination of features allows the battery to be completely sealed,
which makes them useful in portable devices and similar roles.
To reduce the water loss rate calcium is alloyed with the plates, however gas build-up
remains a problem when the battery is deeply or rapidly charged or discharged. to prevent
over-pressurization of the battery casing, AGM batteries include a one-way blow-off valve,
and are often known as "valve regulated lead–acid", or VRLA, designs.
Another advantage to the AGM design is that the electrolyte becomes the separator material,
and mechanically strong. This allows the plate stack to be compressed together in the battery
shell, slightly increasing energy density compared to liquid or gel versions. AGM batteries
often show a characteristic "bulging" in their shells when built in common rectangular
shapes.
The mat also prevents the vertical motion of the electrolyte within the battery. When a normal
wet cell is stored in a discharged state, the heavier acid molecules tend to settle to the bottom
of the battery, causing the electrolyte to stratify. When the battery is then used, the majority

of the current flows only in this area, and the bottom of the plates tend to wear out rapidly.
This is one of the reasons a conventional car battery can be ruined by leaving it stored for a
long period and then used and recharged. The mat significantly prevents this stratification,
eliminating the need to periodically shake the batteries, boil them, or run an "equalization
charge" through them to mix the electrolyte. Stratification also causes the upper layers of the
battery to become almost completely water, which can freeze in cold weather, AGMs are
significantly less susceptible to damage due to low-temperature use.
While AGM cells do not permit watering (typically it is impossible to add water without
drilling a hole in the battery), their recombination process is fundamentally limited by the
usual chemical processes. Hydrogen gas will even diffuse right through the plastic case itself.
Some have found that it is profitable to add water to an AGM battery, but this must be done
slowly to allow for the water to mix via diffusion throughout the battery. When a lead-acid
battery loses water, its acid concentration increases, increasing the corrosion rate of the plates
significantly. AGM cells already have a high acid content in an attempt to lower the water
loss rate and increase standby voltage, and this brings about short life. If the open circuit
voltage of AGM cells is significantly higher than 2.093 volts, or 12.56 V for a 12 V battery,
then they have a higher acid content than a flooded cell; while this is normal for an AGM
battery, it is not desirable for long life.
AGM cells intentionally or accidentally overcharged will show a higher open circuit voltage
according to the water lost (and acid concentration increased). One amp-hour of overcharge
will liberate 0.335 grams of water; some of this liberated hydrogen and oxygen will
recombine, but not all of it.
Gelled electrolytes
Main article: VRLA battery § Gel_battery
During the 1970s, researchers developed the sealed version or "gel battery", which mixes a
silica gelling agent into the electrolyte (silica-gel based lead-acid batteries used in portable
radios from early 1930s were not fully sealed). This converts the formerly liquid interior of

the cells into a semi-stiff paste, providing many of the same advantages of the AGM. Such
designs are even less susceptible to evaporation and are often used in situations where little or
no periodic maintenance is possible. Gel cells also have lower freezing and higher boiling
points than the liquid electrolytes used in conventional wet cells and AGMs, which makes
them suitable for use in extreme conditions.
The only downside to the gel design is that the gel prevents rapid motion of the ions in the
electrolyte, which reduces carrier mobility and thus surge current capability. For this reason,
gel cells are most commonly found in energy storage applications like off-grid systems.
"Maintenance free", "sealed" and "VRLA"
Both gel and AGM designs are sealed, do not require watering, can be used in any
orientation, and use a valve for gas blowoff. For this reason, both designs can be called
maintenance free, sealed and VRLA. However, it is quite common to find resources stating
that these terms refer to one or another of these designs, specifically.
Applications
Most of the world's lead-acid batteries are automobile starting, lighting and ignition (SLI)
batteries, with an estimated 320 million units shipped in 1999. In 1992 about 3 million tons of
lead were used in the manufacture of batteries.

Wet cell stand-by (stationary) batteries designed for deep discharge are commonly used in
large backup power supplies for telephone and computer centres, grid energy storage, and
off-grid household electric power systems. Lead–acid batteries are used in emergency
lighting and to power sump pumps in case of power failure.
Traction (propulsion) batteries are used in golf carts and other battery electric vehicles. Large
lead-acid batteries are also used to power the electric motors in diesel-electric (conventional)
submarines when submerged, and are used as emergency power on nuclear submarines as
well. Valve-regulated lead acid batteries cannot spill their electrolyte. They are used in back-
up power supplies for alarm and smaller computer systems (particularly in uninterruptible
power supplies; UPS) and for electric scooters, electric wheelchairs, electrified bicycles,
marine applications, battery electric vehicles or micro hybrid vehicles, and motorcycles.
Lead-acid batteries were used to supply the filament (heater) voltage, with 2 V common in
early vacuum tube (valve) radio receivers.
Portable batteries for miners' cap lamps headlamps typically have two or three cells.
Cycles
Starting batteries
Main article: Automotive battery
Lead–acid batteries designed for starting automotive engines are not designed for deep
discharge. They have a large number of thin plates designed for maximum surface area, and
therefore maximum current output, but which can easily be damaged by deep discharge.
Repeated deep discharges will result in capacity loss and ultimately in premature failure, as
the electrodes disintegrate due to mechanical stresses that arise from cycling. Starting
batteries kept on continuous float charge will have corrosion in the electrodes which will
result in premature failure. Starting batteries should be kept open circuit but charged regularly
(at least once every two weeks) to prevent sulfation.

Starting batteries are lighter weight than deep cycle batteries of the same battery dimensions,
because the cell plates do not extend all the way to the bottom of the battery case. This allows
loose disintegrated lead to fall off the plates and collect under the cells, to prolong the service
life of the battery. If this loose debris rises high enough it can touch the plates and lead to
failure of a cell, resulting in loss of battery voltage and capacity.
Deep cycle batteries
Main article: Deep cycle battery
Specially designed deep-cycle cells are much less susceptible to degradation due to cycling,
and are required for applications where the batteries are regularly discharged, such as
photovoltaic systems, electric vehicles (forklift, golf cart, electric cars and other) and
uninterruptible power supplies. These batteries have thicker plates that can deliver less peak
current, but can withstand frequent discharging.
Some batteries are designed as a compromise between starter (high-current) and deep cycle
batteries. They are able to be discharged to a greater degree than automotive batteries, but
less so than deep cycle batteries. They may be referred to as "marine/motorhome" batteries,
or "leisure batteries".
Fast and slow charge and discharge
Charge current needs to match the ability of the battery to absorb the energy. Using too large a
charge current on a small battery can lead to boiling and venting of the electrolyte. In this image a
VRLA battery case has ballooned due to the high gas pressure developed during overcharge.

The capacity of a lead–acid battery is not a fixed quantity but varies according to how quickly
it is discharged. An empirical relationship between discharge rate and capacity is known as
Peukert's law.
When a battery is charged or discharged, only the reacting chemicals, which are at the
interface between the electrodes and the electrolyte, are initially affected. With time, the
charge stored in the chemicals at the interface, often called "interface charge" or "surface
charge", spreads by diffusion of these chemicals throughout the volume of the active
material.
Consider a battery that has been completely discharged (such as occurs when leaving the car
lights on overnight, a current draw of about 6 amps). If it then is given a fast charge for only a
few minutes, the battery plates charge only near the interface between the plates and the
electrolyte. In this case the battery voltage might rise to a value near that of the charger
voltage; this causes the charging current to decrease significantly. After a few hours this
interface charge will spread to the volume of the electrode and electrolyte; this leads to an
interface charge so low that it may be insufficient to start the car. As long as the charging
voltage stays below the gassing voltage (about 14.4 volts in a normal lead–acid battery),
battery damage is unlikely, and in time the battery should return to a nominally charged state.
Valve regulated (VRLA)

In a valve regulated lead acid battery (VRLA) the hydrogen and oxygen produced in the cells
largely recombine into water. Leakage is minimal, although some electrolyte still escapes if
the recombination cannot keep up with gas evolution. Since VRLA batteries do not require
(and make impossible) regular checking of the electrolyte level, they have been called
maintenance free batteries. However, this is somewhat of a misnomer. VRLA cells do
require maintenance. As electrolyte is lost, VRLA cells "dry-out" and lose capacity. This can
be detected by taking regular internal resistance, conductance or impedance measurements.
Regular testing reveals whether more involved testing and maintenance is required. Recent
maintenance procedures have been dev 5square is a Highly focused Embedded systems
training institute in Bangalore. We offer state of art training in embedded Systems,
device drivers, linux, ARM, Kernel, C, C++ Data Structures, RTOS and Android
Applications, aiming to bridge the gap between the demands of the industry and the
curriculum of educational institutions. Our training methodology is mainly focused on
hands-on practical approach with relevant projects which provides reasonable exposure
to various phases of Software and Application development life cycle eloped allowing
"rehydration", often restoring significant amounts of lost capacity.
VRLA types became popular on motorcycles around 1983, because the acid electrolyte is
absorbed into the separator, so it cannot spill. The separator also helps them better withstand
vibration. They are also popular in stationary applications such as telecommunications sites,
due to their small footprint and installation flexibility.
The electrical characteristics of VRLA batteries differ somewhat from wet-cell lead–acid
batteries, requiring caution in charging and discharging.
Sulfation and desulfation
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citations to reliable sources. Unsourced material may be challenged and removed. (
Sulfated plates from 12 V 5 Ah battery
Lead–acid batteries lose the ability to accept a charge when discharged for too long due to
sulfation, the crystallization of lead sulfate. They generate electricity through a double sulfate
chemical reaction. Lead and lead dioxide, the active materials on the battery's plates, react
with sulfuric acid in the electrolyte to form lead sulfate. The lead sulfate first forms in a
finely divided, amorphous state, and easily reverts to lead, lead dioxide and sulfuric acid
when the battery recharges. As batteries cycle through numerous discharges and charges,
some lead sulfate is not recombined into electrolyte and slowly converts to a stable crystalline
form that no longer dissolves on recharging. Thus, not all the lead is returned to the battery
plates, and the amount of usable active material necessary for electricity generation declines
over time. 5square is a Highly focused Embedded systems training institute in
Bangalore. We offer state of art training in embedded Systems, device drivers, linux,
ARM, Kernel, C, C++ Data Structures, RTOS and Android Applications, aiming to
bridge the gap between the demands of the industry and the curriculum of educational
institutions. Our training methodology is mainly focused on hands-on practical
approach with relevant projects which provides reasonable exposure to various phases
of Software and Application development life cycle
Sulfation occurs in lead–acid batteries when they are subjected to insufficient charging during
normal operation. It impedes recharging; sulfate deposits ultimately expand, cracking the
plates and destroying the battery. Eventually so much of the battery plate area is unable to

supply current that the battery capacity is greatly reduced. In addition, the sulfate portion (of
the lead sulfate) is not returned to the electrolyte as sulfuric acid. It is believed that large
crystals physically block the electrolyte from entering the pores of the plates. Sulfation can be
avoided if the battery is fully recharged immediately after a discharge cycle. A white coating
on the plates may be visible (in batteries with clear cases, or after dismantling the battery).
Batteries that are sulfated show a high internal resistance and can deliver only a small
fraction of normal discharge current. Sulfation also affects the charging cycle, resulting in
longer charging times, less efficient and incomplete charging, and higher battery
temperatures.
SLI batteries (starting, lighting, ignition; i.e., car batteries) suffer most deterioration because
vehicles normally stand unused for relatively long periods of time. Deep cycle and motive
power batteries are subjected to regular controlled overcharging, eventually failing due to
corrosion of the positive plate grids rather than sulfation.
There are no known, independently verified ways to reverse sulfation. There are commercial
products claiming to achieve desulfation through various techniques (such as pulse charging),
but there are no peer-reviewed publications verifying their claims. Sulfation prevention
remains the best course of action, by periodically fully charging the lead-acid batteries.
Stratification
A typical lead–acid battery contains a mixture with varying concentrations of water and acid.
Sulfuric acid has a higher density than water, which causes the acid formed at the plates
during charging to flow downward and collect at the bottom of the battery. Eventually the
mixture will again reach uniform composition by diffusion, but this is a very slow process.
Repeated cycles of partial charging and discharging will increase stratification of the
electrolyte, reducing the capacity and performance of the battery because the lack of acid on
top limits plate activation. The stratification also promotes corrosion on the upper half of the
plates and sulfation at the bottom. 5square is a Highly focused Embedded systems training
institute in Bangalore. We offer state of art training in embedded Systems, device

drivers, linux, ARM, Kernel, C, C++ Data Structures, RTOS and Android Applications,
aiming to bridge the gap between the demands of the industry and the curriculum of
educational institutions. Our training methodology is mainly focused on hands-on
practical approach with relevant projects which provides reasonable exposure to
various phases of Software and Application development life cycle
Periodic overcharging creates gaseous reaction products at the plate, causing convection
currents which mix the electrolyte and resolve the stratification. Mechanical stirring of the
electrolyte would have the same effect. Batteries in moving vehicles are also subject to
sloshing and splashing in the cells, as the vehicle accelerates, brakes, and turns.
Risk of explosi
Excessive charging causes electrolysis, emitting hydrogen and oxygen. This process is known
as "gassing". Wet cells have open vents to release any gas produced, and VRLA batteries rely
on valves fitted to each cell. Catalytic caps are available for flooded cells to recombine
hydrogen and oxygen. A VRLA cell normally recombines any hydrogen and oxygen
produced inside the cell, but malfunction or overheating may cause gas to build up. If this
happens (for example, on overcharging) the valve vents the gas and normalizes the pressure,
producing a characteristic acid smell. However, valves can fail, such as if dirt and debris
accumulate, allowing pressure to build up.
Accumulated hydrogen and oxygen sometimes ignite in an internal explosion. The force of
the explosion can cause the battery's casing to burst, or cause its top to fly off, spraying acid

and casing fragments. An explosion in one cell may ignite any combustible gas mixture in the
remaining cells. Similarly, in a poorly ventilated area, connecting or disconnecting a closed
circuit (such as a load or a charger) to the battery terminals can also cause sparks and an
explosion, if any gas was vented from the cells.
Individual cells within a battery can also short circuit, causing an explosion.
The cells of VRLA batteries typically swell when the internal pressure rises. The deformation
varies from cell to cell, and is greater at the ends where the walls are unsupported by other
cells. Such over-pressurized batteries should be carefully isolated and discarded. Personnel
working near batteries at risk for explosion should protect their eyes and exposed skin from
burns due to spraying acid and fire by wearing a face shield, overalls, and gloves. Using
goggles instead of a face shield sacrifices safety by leaving the face exposed to possible
flying acid, case or battery fragments, and heat from a potential explosion.
Environment
Environmental concerns
According to a 2003 report entitled "Getting the Lead Out", by Environmental Defense and
the Ecology Center of Ann Arbor, Mich., the batteries of vehicles on the road contained an
estimated 2,600,000 metric tons (2,600,000 long tons; 2,900,000 short tons) of lead. Some
lead compounds are extremely toxic. Long-term exposure to even tiny amounts of these
compounds can cause brain and kidney damage, hearing impairment, and learning problems
in children.[37] The auto industry uses over 1,000,000 metric tons (980,000 long tons;
1,100,000 short tons) every year, with 90% going to conventional lead–acid vehicle batteries.
While lead recycling is a well-established industry, more than 40,000 metric tons (39,000
long tons; 44,000 short tons) ends up in landfills every year. According to the federal Toxic
Release Inventory, another 70,000 metric tons (69,000 long tons; 77,000 short tons) are
released in the lead mining and manufacturing process.[38]

Attempts are being made to develop alternatives (particularly for automotive use) because of
concerns about the environmental consequences of improper disposal and of lead smelting
operations, among other reasons. Alternatives are unlikely to displace them for applications
such as engine starting or backup power systems, since the batteries, although heavy, are low-
cost. http://www.5square.in
Recycling
See also: Automotive battery recycling
A worker recycling molten lead in a battery recycling facility.
Lead–acid battery recycling is one of the most successful recycling programs in the world. In
the United States 99% of all battery lead was recycled between 2009 and 2013. An effective
pollution control system is a necessity to prevent lead emission. Continuous improvement in
battery recycling plants and furnace designs is required to keep pace with emission standards
for lead smelters.
Additives

Chemical additives have been used ever since the lead–acid battery became a commercial
item, to reduce lead sulfate build up on plates and improve battery condition when added to
the electrolyte of a vented lead–acid battery. Such treatments are rarely, if ever, effective.
Two compounds used for such purposes are Epsom salts and EDTA. Epsom salts reduces the
internal resistance in a weak or damaged battery and may allow a small amount of extended
life. EDTA can be used to dissolve the sulfate deposits of heavily discharged plates.
However, the dissolved material is then no longer available to participate in the normal
charge/discharge cycle, so a battery temporarily revived with EDTA will have a reduced life
expectancy. Residual EDTA in the lead–acid cell forms organic acids which will accelerate
corrosion of the lead plates and internal connectors.
The active materials change physical form during charge/discharge, resulting in growth and
distortion of the electrodes, and shedding of electrode into the electrolyte. Once the active
material has fallen out of the plates, it cannot be restored into position by any chemical
treatment. Similarly, internal physical problems such as cracked plates, corroded connectors,
or damaged separators cannot be restored chemically.
Corrosion problems
Corrosion of the external metal parts of the lead–acid battery results from a chemical reaction
of the battery terminals, lugs and connectors.
Corrosion on the positive terminal is caused by electrolysis, due to a mismatch of metal
alloys used in the manufacture of the battery terminal and cable connector. White corrosion is
usually lead or zinc sulfate crystals. Aluminum connectors corrode to aluminum sulfate.
Copper connectors produce blue and white corrosion crystals. Corrosion of a battery's
terminals can be reduced by coating the terminals with petroleum jelly or a commercially
available product made for the purpose.[41]

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