2. ELECTRONIC BICYCLE LOCK
Introduction
A bicycle lock is a physical security device used on a bicycle to prevent theft. It is generally used to fasten
the bicycle to a bicycle stand or other immovable object.
An important difficulty in preventing the theft of a bicycle is that the wheels are easily detachable from
the frame, and that unless both wheels and frame are secured, wheels can easily be carried away after
being detached. The most secure locking method therefore is to lock the wheels and frame to each other
and to an immovable object.
Locking devices vary in size and security; the most secure tending to be the largest, heaviest and least
portable. Lesser equipment is used to deter attempts by less skilled and determined thieves. Thus like
other security equipment, bicycle locks must compromise between security, portability and cost. Some
are made of particularly expensive materials chosen for their acceptable strength and low density.
The electronic bicycle lock described here is a worthwhile alternative for bicycle owners who want to
make their bicycles
‘Intelligent’ at reasonable cost. One of the benefits of building it yourself is that the circuit can be used for
virtually any make of bicycles.
Working of electronic bicycle lock
In the circuit, input jacks J1 and J2 are two standard RCA sockets. A home-made security loop can be
used to link these two input points. Around 50cm long, standard 14/36 flexible wire with one RCA plug per
end is enough for the security loop.
Fig. 1 shows the circuit of the electronic bicycle lock. It is powered by a compact 9V battery (6F22). Key
lock switch S1 and smoothing capacitor C2 are used for connecting the power supply. A connected loop
cannot activate IC1 and therefore the speaker does not sound. When the loop is broken, zener diode ZD1
(3.1V) receives operating power supply through resistor R2 to enable tone generator UM3561 (IC1). IC1
remains enabled until power to the circuit is turned off using switch S1 or the loop is re-plugged through
J1 and J2.
Assemble the circuit on a general purpose PCB and house in a small tinplate enclosure. Fit the system
key lock switch (S1) on the front side of the enclosure as shown in Fig. 2. Place RCA sockets (J1 and J2)
at appropriate positions. Now, mount the finished unit in place of your existing lock (as shown in Fig. 3) by
clamps and screws.
3.
4. Advantage
It is optional for length of cable
Easy to carry
New innovative anti-theft device
Maximum security.
Keeps all your bikes / motorcycles safe and secure.
Easy to use and carry.
IT is easy to operate.
It is the only bicycle locker specifically designed to embrace modern technology
and to offer the full range of secure bicycle parking options that modern micro-
electronics can offer. Functional characteristics long desired by both cyclists and
facilities managers such as keyless on-demand parking, pay-parking, usage
monitoring, unattended bicycle rental.
It’s highly economical electronic system and allows the user to open and close
the lockers electronically.
6. IC: UM3561
Features:
Four sounds can be selected
Typical 3v operating voltage
RC oscillator with an external resistor
A magnetic speaker can be driven connecting an NPN transistor
Power on reset
General Description
The M3561 is a low-cost, low-power CMOS LSI designed for use in a larm and toy applications. Since the
integrated circuit includes oscillator and selector circuits, a compact sound module can be constructed
with only a few additional components. The M3561 contains a programmed mask ROM to simulate siren
sound
Absolute Maximum Ratings DC Supply Voltage .......................................... -0.3V to +5.0V
Input Voltage Range....................................... Vss-0.3V to Vdd+0.3V Operating
Ambient Temperature.................... -10°C to +60°C
Storage Temperature ....................................... -55°C to +125°C
7. Typical Application Circuits
FOUR SOUND APPLICATIONS:
1. Police Siren
2. Fire Engine Siren
3. Ambulance Siren
4. Machine Gun
Zener Diode
In the previous Signal Diode tutorial, we saw that a "reverse biased" diode blocks current in the reverse
direction, but will suffer from premature breakdown or damage if the reverse voltage applied across it is
too high. However, the Zener Diode or "Breakdown Diode" as they are sometimes called, are basically
the same as the standard PN junction diode but are specially designed to have a low pre-
determined Reverse Breakdown Voltage that takes advantage of this high reverse voltage. The point at
which a zener diode breaks down or conducts is called the "Zener Voltage" (Vz).
The Zener diode is like a general-purpose signal diode consisting of a silicon PN junction. When biased in
the forward direction it behaves just like a normal signal diode passing the rated current, but when a
reverse voltage is applied to it the reverse saturation current remains fairly constant over a wide range of
voltages. The reverse voltage increases until the diodes breakdown voltage VB is reached at which point
a process called Avalanche Breakdown occurs in the depletion layer and the current flowing through the
zener diode increases dramatically to the maximum circuit value (which is usually limited by a series
resistor). This breakdown voltage point is called the "zener voltage" for zener diodes.
The point at which current flows can be very accurately controlled (to less than 1% tolerance) in the
doping stage of the diodes construction giving the diode a specific zener breakdown voltage, (Vz) ranging
from a few volts up to a few hundred volts. This zener breakdown voltage on the I-V curve is almost a
vertical straight line.
Zener Diode I-V Characteristics
8. The Zener Diode is used in its "reverse bias" or reverse breakdown mode, i.e. the diodes anode connects
to the negative supply. From the I-V characteristics curve above, we can see that the zener diode has a
region in its reverse bias characteristics of almost a constant negative voltage regardless of the value of
the current flowing through the diode and remains nearly constant even with large changes in current as
long as the zener diodes current remains between the breakdown current IZ (min) and the maximum current
rating IZ (max).
This ability to control itself can be used to great effect to regulate or stabilize a voltage source against
supply or load variations. The fact that the voltage across the diode in the breakdown region is almost
constant turns out to be an important application of the zener diode as a voltage regulator. The function of
a regulator is to provide a constant output voltage to a load connected in parallel with it in spite of the
ripples in the supply voltage or the variation in the load current and the zener diode will continue to
regulate the voltage until the diodes current falls below the minimum IZ (min) value in the reverse
breakdown region.
The Zener Diode Regulator
Zener Diodes can be used to produce a stabilized voltage output with low ripple under varying load
current conditions. By passing a small current through the diode from a voltage source, via a suitable
current limiting resistor (RS), the zener diode will conduct sufficient current to maintain a voltage drop of
Vout. We remember from the previous tutorials that the DC output voltage from the half or full-wave
rectifiers contains ripple superimposed onto the DC voltage and that as the load value changes so to
does the average output voltage. By connecting a simple zener stabilizer circuit as shown below across
the output of the rectifier, a more stable output voltage can be produced.
Zener Diode Regulator
9. The resistor, RS is connected in series with the zener diode to limit the current flow though the diode with
the voltage source, VS being connected across the combination. The stabilized output voltage Voutis taken
from across the zener diode.The zener diode is connected with its cathode terminal connected to the
positive rail of the DC supply so it is reverse biased and will be operating in its breakdown condition.
Resistor RS is selected so to limit the maximum current flowing in the circuit.
With no load connected to the circuit, the load current will be zero, ( IL = 0 ), and all the circuit current
passes through the zener diode which in turn dissipates its maximum power. Also a small value of the
series resistor RS will result in a greater diode current when the load resistance RL is connected and large
as this will increase the power dissipation requirement of the diode so care must be taken when selecting
the appropriate value of series resistance so that the zeners maximum power rating is not exceeded
under this no-load or high-impedance condition.
The load is connected in parallel with the zener diode, so the voltage across RL is always the same as the
zener voltage, (VR = VZ). There is a minimum zener current for which the stabilization of the voltage is
effective and the zener current must stay above this value operating under load within its breakdown
region at all times. The upper limit of current is of course dependent upon the power rating of the device.
The supply voltage VS must be greater than VZ.
One small problem with zener diode stabilizer circuits is that the diode can sometimes generate electrical
noise on top of the DC supply as it tries to stabilize the voltage. Normally this is not a problem for most
applications but the addition of a large value decoupling capacitor across the zeners output may be
required to give additional smoothing.
