Robotics workshop PPT


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Robotics workshop PPT

  1. 1. Robotics Workshop @RVCE
  2. 2. Basic Electronics in Robotics
  3. 3. Topics to be Covered• Analog Electronics1. Resistors,Capacitors,Diodes ,Transistors and their use in circuits.2. Relays,Transformers,Op-amp,comparators and schmitt trigger.• Digital electronics1. Logic levels,basic gates,digital IC’s,flip flops and its applications in counters .
  4. 4. ResistorsVoltage divider circuit and Potentiometer
  5. 5. Capacitors
  6. 6. The water analogy for capacitor
  8. 8. Diodes• LED’S Photodiode
  9. 9. Application of LED and Photodiode in IR Sensor
  10. 10. Zener diode
  11. 11. • Zener diodes are used to "clamp" a voltage in order to prevent it rising higher than a certain value.• This might be to protect a circuit from damage or it might be to "chop off" part of an alternating waveform for various reasons.• Zener diodes are also used to provide a fixed "reference voltage" from a supply voltage that varies. They are widely used in regulated power supply circuits.
  14. 14. Transistors
  16. 16. • My transistor runs on water current. You see there are three openings which I have labelled "B" (Base), "C" (Collector) and "E" (Emitter) for convenience. By an amazing coincidence, these also happen to be the names used by everyone else for the three connections of a transistor!• We provide a reservoir of water for "C" (the "power supply voltage") but it cant move because theres a big black plunger thing in the way which is blocking the outlet to "E". The reservoir of water is called the "supply voltage". If we increase the amount of water sufficiently, it will burst our transistor just the same as if we increase the voltage to a real transistor.• We dont want to do this, so we keep that "supply voltage" at a safe level.
  17. 17. • If we pour water current into "B" this current flows along the "Base" pipe and pushes that black plunger thing upwards, allowing quite a lot of water to flow from "C" to "E". Some of the water from "B" also joins it and flows away. If we pour even more water into "B", the black plunger thing moves up further and a great torrent of water current flows from "C" to "E".
  18. 18. • 1. A tiny amount of current flowing into "B" allows a large amount to flow from "C" to "E" so we have an "amplification effect". We can control a BIG flow of current with a SMALL flow of current. If we continually change the small amount of water flowing into "B" then we cause corresponding changes in the LARGE amount of water flowing from "C" to "E". For example, if we measure the current flow in gallons/minute: Suppose 1 gallon/minute flowing into "B" allows 100 gallons/minute to flow from "C" to "E" then we can say that the transistor has a "gain" or "amplification" factor of 100 times. In a real transistor we measure current in thousandths of an Ampere or "milliamps". So 1mA flowing into "B" would allow 100mA to flow from "C" to "E".• 2. The amount of current that can flow from "C" to "E" is limited by the "pipe diameter". So, no matter how much current we push into "B", there will be a point beyond which we cant get any more current flow from "C" to "E". The only way to solve this problem is to use a larger transistor. A "power transistor".
  19. 19. • 3. The transistor can be used to switch the current flow on and off. If we put sufficient current into "B" the transistor will allow the maximum amount of current to flow from "C" to "E". The transistor is switched fully "on".• If the current into "B" is reduced to the point where it can no longer lift the black plunger thing, the transistor will be "off". Only the small "leakage" current from "B" will be flowing. To turn it fully off, we must stop all current flowing into "B".• In a real transistor, any restriction to the current flow causes heat to be produced. A transistor must be kept cool or it will melt. It runs coolest when it is fully OFF and fully ON. When it is fully ON there is very little restriction so, even though a lot of current is flowing, only a small amount of heat is produced. When it is fully OFF, provided we can stop the base leakage, then NO heat is produced. If a transistor is half on then quite a lot of current is flowing through a restricted gap and heat is produced. To help get rid of this heat, the transistor might be clamped to a metal plate which draws the heat away and radiates it to the air. Such a plate is called a "heat sink". It often has fins to increase its surface area and, thereby, improve its efficiency.
  20. 20. Rules for Operation• Lets start by stating what needs to be done to a transistor to make it operate as a transistor.• Suppose we have the following:• 1. VC > VE, by at least a few (0.1) V.• 2. VB > VE• 3. VC > VB• 4. We do not exceed maximum ratings for voltages or currents.• When these conditions are not met, then (approximately) no current flows in or out of the transistor.• When these conditions are met, then current can flow into the collector (and out the emitter) in proportion to the current flowing into the base:• IC = (hfe)IBwhere hFE = is the current gain.
  23. 23. • When a transistor is used as a switch it must be either fully on or off. If driving a inductive load like a relay or any type of coil you should connect a diode in reverse bias across the load so that back EMF will not flow into the transistor, destroying it.
  24. 24. Concept of pull up resistor
  25. 25. • The pull-up resistor assures that the wire is at a defined logic level even if no active devices are connected to it.• When the switch is open the voltage of the gate input is pulled up to the level of Vin. When the switch is closed, the input voltage at the gate goes to ground.
  26. 26. Pull down resistor
  27. 27. Op-Amp
  28. 28. Comparator and Schmitt Trigger
  30. 30. Digital Electronics
  31. 31. Digital IC’s• Gates• Encoder• Decoder• Multiplexer• Demultiplexer
  33. 33. SR Latch
  34. 34. Clocked SR FLIP FLOP
  35. 35. D FLIP FLOP
  36. 36. T FLIP FLOP
  37. 37. Flip Flops and their use in counters
  38. 38. Over to Suhas
  39. 39. Microprocessors and MicrocontrollersMicroprocessor :Central processing unit (CPU) on a single integrated circuit (IC).Ex: AMD Athlon, Intel Pentium. :An integrated CPU, memory (a small amount of RAM, program memory, or both)and peripherals capable of input and output.Ex: Atmel AVR, PIC.
  40. 40. Atmel AVRThe AVR is a Modified Harvard architecture 8-bit RISC single chipmicrocontroller developed by Atmel in 1996.The AVR was one of the first microcontroller families to use on-chip flashmemory for program storage.Basic Families:•tinyAVRs. Ex: ATtiny11•megaAVRs. Ex: ATmega8, ATmega16, ATmega32•XMEGA. Ex: ATxmega64
  41. 41. Device ArchitectureALU: Fetching, Decoding and Execution of Instructions.Registers: Usually 32x8bit registers. The CPU does allthe calculations on these registers.Program Memory: Storage of instructions that form the program. A non-volatile Flash memory is used to store the program.The size of the program memory is occasionally indicated in the naming of thedevice itself (e.g., the ATmega64x line has 64 kB of Flash).SRAM: Storage of data-variables, stack etc.EEPROM: Internal Electrically Erasable Programmable Read Only Memory(EEPROM) for semi-permanent data storage. Like Flash memory, EEPROM canmaintain its contents when electrical power is removed.
  42. 42. Types of sensorsInfrared LEDsPhotodiodes & PhototransistorsPhotointerruptersPhotoreflectorsPhotoresistors (LDR)IR-Receiver modulesLight SensorsDigital Hall SensorsProgrammable Hall SensorsAnalog Hall SensorsMagneto-resistive SensorsVibration SensorAir Pressure Change SensorThermistorsThick-film ThermistorsThermopilesUltrasonic SensorsPyroelectric Sensors
  43. 43. Infrared-LEDs emit light over a range of 700nmup to1,000nm, which is no longer visible to thehuman eye, but canbe very well detected by silicon photodiodesand phototransistors.The wavelength emitted depends upon thematerial usedfor the semiconductor chips. Standardwavelengths are 880nmand 950nm, whereby the 950nm are generallymore favourablepriced. Apart from the wavelength andswitching speed, importantcharacteristics of infrared LEDs are thedirection of emission(sideways, upwards or downwards) and theangle of beam(decisive for the optical power in the forwarddirection).
  44. 44. Silicon Photodiodes and Phototransistors candetectradiation ranging between 400nm and1,100nm. Since themaximum sensitivity is approx.880nm, infrared radiation is particularywell detected by silicon components.Photodiodes andphototransistors are available with black epoxyresin mold, whichsuppresses the sensitivity within the visiblespectral area. Forslow optical switchingapplications, phototransistors are generallyused, wherby photodiodes are used formeasuring applicationsor data transmission.
  45. 45. Photoresistors (LDRs) are light-sensitiveresistors. Theresistance value can vary strongly dependingon incident light. Thedark resistance is typically within the range ofMΩ, at 10 Lux howeverin the lower range of kΩ. The advantage bycomparisonwith silicon photodiodes is in the spectralsensitivity of the LDRs.Whereas photodiodes are sensitive from 400nm (blue) up to1100 nm (infrared area) LDRs are only sensitivewithin the visiblespectral range. LDRs are therefore particularlysuitable as lightsensors because these sensors do not detectthe infrared radiationgenerally present in daylight that could lead toinaccurate measuringresults.
  46. 46. Ultrasonic sensors use a piezo element togenerateacoustic oscillations in a range above 25 kHz,which is beyondthe human auditory threshold. The ultrasonicwavelength is in arange of a few centimeters or less. This canmeasure objects ordistances with a high level of precision.Transmitter and receivercan either be produced as separate units(transmitter and receivertype) or one transmitter can be operatedjointly as transmitterand receiver (common type).Applications» Distance measurement (parking devices)» Spatial monitoring(burglary alarm for motor vehicles)
  47. 47. VIBRATION SENSORThe vibration sensor VS1 is ideally suited for detectingsmall oscillations and vibrations. The well-known principle ofball switch gave birth to this component. Here, it is miniaturisedto the size of a TOPLED and integrated within a hermeticallysealed package. A 0.8 mm high-grade steel ball is set within asmall tube with 1mm diameter tube. The wall and base of thetube constitute two contacts that are bridged by the ball when inthe quiescent state. With the smallest movement, the contact isbriefly interrupted and detected. The sensor is suitable for thequalitative measurement of any vibration or shaking.
  48. 48. Applications THERMISTORS » Battery packs » Heat metersThermistors generally refer to a temperature- » Temperature measuring devicesdependent resistor that has a negative » Precision temperature compensationtemperature coefficient (NTC). » Temperature monitoringThe resistance decreases exponentially withincreasing temperatureof the component. SEMITEC thermistorsconsist of sinteredmetallic oxide ceramics. Thermistors arecharacterised bythe resistance value at 25°C (R25) and thematerial constant B,which defines the increase in the resistancecurve in the log R-1/T diagram. SEMITEC thermistors have atolerance in R25 andB of 1% or less. This makes highly precisetemperature measurement possible. The NTCscan also be assembled in accordancewith customers’ wishes.
  49. 49. Over to Gautam
  51. 51. Types of Batteries• Alkaline• Lead Acid• Lithium• NiCad• NiMH• LiPo
  52. 52. How to select a battery?• Current rating(in terms of mAh)• Load• Weight• Voltage• Battery life• Cost
  53. 53. Alkaline Batteries• Alkaline batteries are the most common, easiest to get, and cheapest too.• Low power capacities• Short battery life
  54. 54. Ni-Mh & Ni-Cad• These batteries are good for small to medium size range robots• They have memory effect problem• To prevent memory effect, whenever you wish to recharge your NiCad, you must first fully discharge it.• NiMH battaries can last many more cycles than your typical NiCad battery.
  55. 55. Li-ion Batteries• Very Small in size and weight compared to Ni-Cd, Ni-MH and Lead Acid Batteries• Normally full charge in 60 minutes with special charger• Long life with full capacity for upto 1000 charge cycles• Low maintenance
  56. 56. Li-Po batteries• Very Small in size and weight compared to Ni-Cd, Ni-MH and Lead Acid Batteries• Full Charge in 180 minutes with special charger• Long life with full capacity for upto 1000 charge cycles• Low maintenance• For example, – 3X Li-Po 4.2V 2200mAh cells – 192Grams Weight – Discharge Current: 20*2200maH = 44Amp – Max Charging Current: 1A – Price:Rs.3500
  57. 57. End of session 1Please be back by __
  58. 58. Introduction to Arduino Avik Dhupar
  59. 59. Arduino ARRRR, like a pirate // DWEE, just say "do we“ fast / / NO, as in no.”ARRR-DWEE-NO”
  60. 60. What is Arduino?• Open Source Hardware Development Platform• Serial Programmable Microcontroller (MCU) Investment!
  61. 61. Why Arduino?• It is Open Source, both in terms of Hardware and Software.• It is cheap(1300 – Original, 800 - Clone), the hardware can be built from components or a prefab board can be purchased online.• It can communicate with a computer via serial connection over USB.• It can be powered from USB or standalone DC power.• It can work with both Digital and Analog electronic signals. Sensors and Actuators.• You can make cool stuff! Some people are even making simple robots, and we all know robots are just cool. 
  62. 62. Overview ofThe C Programming Language
  63. 63. Lets get it started, hah! Lets get it started in here, yeah Lose control, all body, all soulDont move too fast, people just take it slow Dont get ahead, just jump into it!
  64. 64. Programming an Arduino• Write program• Compile(Check for errors)• Reset board• Upload to board
  65. 65. An Arduino “Sketch” • Declare variables at top • Initialize – setup() – run once at beginning, set pins • Running – loop() – run repeatedly, after setup()
  66. 66. • 14 Digital I/O (pins 0 - 13) • 6 Analog In (pins 0 - 5)• 6 Analog Out (pins 3,5,6,9,10,11)
  67. 67. Functions for digital i/o pinMode() digitalWrite() digitalRead()
  68. 68. DemonstrationStart up the Arduino software andopen up the Blink sketch.For the most basic kind of program you’ll need a simple actuator, an LED withthe long leg (+) pushed into pin 13 and the short leg (-) in the adjacent groundpin (GND). Pin 13 is special, in the sense that it has a built in resistor tocorrectly control the voltage going into a testing LED just like this.
  69. 69. Code Structure: Header Header provides information
  70. 70. Code Structure: setup function setup function is executed only once at the start
  71. 71. Code Structure: loop function loop function is repeated indefinitely
  72. 72. CodepinMode(13, Output)prepare pin 13 foroutputs of voltage Digital I/O Functions: pinMode digitalWrite digitalRead
  73. 73. Code digitalWrite(13, HIGH) Sets pin 13 to a voltage that means “on” Digital I/O Functions: pinMode digitalWrite digitalRead
  74. 74. Code delay(1000); Tells microcontroller to do nothing for 1000 ms = 1 s Digital I/O Functions: pinMode digitalWrite digitalRead
  75. 75. Code digitalWrite(13, LOW) Sets pin 13 to voltage that means “off” Digital I/O Functions: pinMode digitalWrite digitalRead
  76. 76. Over to Ganesh
  77. 77. ADC
  78. 78. Mux
  79. 79. Over to Gautam
  80. 80. 555 TIMERApplications• Precision timing• Pulse generation• Sequential timing• Time delay generation• Pulse width modulation (PWM)
  82. 82. ASTABLE MULTIVIBRATOR• Duty cycle = ((RA + RB)/( RA + 2RB)) x 100%• T =0.693(RA + 2RB)C
  84. 84. EXPLAINATION• This is a simple yet effective IR proximity sensor built around the TSOP 1738 module.• Commonly found at the receiving end of an IR remote control system; e.g., in TVs, CD players etc.• These modules require the incoming data to be modulated at a particular frequency and would ignore any other IR signals. It is also immune to ambient IR light, so one can easily use these sensors outdoors or under heavily lit conditions.• Such modules are available for different carrier frequencies from 32 kHz to 42 kHz.• In this particular proximity sensor, we will be generating a constant stream of square wave signal using IC555 centered at 38 kHz and would use it to drive an IR led. So whenever this signal bounces off the obstacles, the receiver would detect it and change its output.• Since the TSOP 1738 module works in the active-low configuration, its output would normally remain high and would go low when it detects the signal (the obstacle).
  85. 85. Over to Avik
  86. 86. Pulse Width Modulation aka PWM• Not all digital pins allow PWM – Pin 13 does not work – Pin 11,10,9,6,5,3 does• analogWrite function takes care of this
  87. 87. PWM• Microcontroller only allows 2 states – HIGH or LOW• “fake” analog using PWM• Virtual digital to analog converter• It is a technique for getting analog results with digital means
  88. 88. P…What!?Digital control is used to create a square wave, asignal switched between on and off. This on-offpattern can simulate voltages in between full on (5Volts) and off (0 Volts) by changing the portion ofthe time the signal spends on versus the time thatthe signal spends off. The duration of "on time" iscalled the pulse width. To get varying analogvalues, you change, or modulate, that pulse width.If you repeat this on-off pattern fast enough with anLED for example, the result is as if the signal is asteady voltage between 0 and 5v controlling thebrightness of the LED.
  89. 89. PWM on Arduino? The green lines represent a regular time period. This duration or period is the inverse of the PWM frequency. In other words, with Arduinos PWM frequency at about 500Hz, the green lines would measure 2 milliseconds each. A call to analogWrite() is on a scale of 0 - 255, such that analogWrite(255) requests a 100% duty cycle (always on), and analogWrite(127) is a 50% duty cycle (on half the time) for example.
  90. 90. End of session 2
  91. 91. Over to Aalok
  92. 92. Basics of actuators
  93. 93. Actuators• An actuator is something that converts energy into motion.• They are the part of a robot that actually makes it to move and do stuffs.• Actuators can create a linear motion, rotary motion or oscillatory motion.
  94. 94. Rotational and linear actuators• Dc gearless motor• Dc geared motor• Brushless motor• Stepper motor• Servo motor• DC Linear Actuator• Solenoid
  95. 95. Dc gearless motor• Moderately high speed(rpm)• Less torque• Can be used for low power application• Usually used as propeller in small boats, in beambots and other solar bots
  96. 96. Geared dc motor• Good torque• Relatively lesser speed• Used where the torque is the main criteria• Low speed application• Usually used to drive a robot and for robotic arm
  97. 97. A simple npn transistor can be used to drive a motor with variablespeed.Note: the direction of rotation of motor cant be controlled usingthis setup.
  98. 98. Brushless motor• Very high speed(rpm)• Low torque• Used as propellers in UAV, aerial robot and as air propeller RC controlled boats• Requires a good power source(like LiPo batteries)
  99. 99. Stepper motor• Pretty good torque• Speed is variable• Used where precise rotation is• Require special circuit to make it work• Usually used with a microcontroller
  100. 100. Servo motor• Good torque• Rotates a maximum of 180 degree (360 degree in some case)• Rotates to a particular position depending of the duty cycle of pwm
  101. 101. DC Linear Actuator• Provide linear movement• made up of a DC motor connected to a lead screw• Similar to dc motor and hence speed can be controlled using pwm
  102. 102. Solenoid• They can be electromechanical, hydr aulic, or pneumatic driven• Stroke is usually very small but they are pretty fast• Can be made to work using a simple MOSFET or transistor
  103. 103. Choosing an Actuator• Is the actuator being used to move a wheeled robot?• Is the motor being used to lift or turn a heavy weight?• Is the range of motion limited to 180 degrees and need good torque?• Does the angle need to be very precise?• Is the motion in a straight line?
  104. 104. Types of LEDs• Single (polar) LEDs• Bi-colour LEDs• Tri-colour LEDs• RGB LEDs
  105. 105. Choosing series resistor for LEDs Colour Current Voltage {I} {VL} Red 30mA 1.7V Bright red 30mA 2.0V Yellow 30mA 2.1V Green 25mA 2.2VR = (VS - VL) / I Blue 30mA 4.5V
  106. 106. Drive multiple LEDs using transistor• Easier to use, simpler circuit• Not many components are required• Can be used with any controller(even with the low power microcontrollers)
  107. 107. Home Lighting• Why can’t we directly use the circuits for home lighting?• Any simpler solution for that?
  108. 108. Relays• Works on both AC and DC• Easier to use (compared to transistor)• Require no extra components(like resistors)
  109. 109. Pros Cons• Can be used to switch both • Bulkier than transistors for AC and DC (transistors can switching small currents. only switch DC) • Relays cannot switch• Can switch higher rapidly (except reed relays) voltages than standard • Require use more power transistors. • Require more current than• A better choice for many ICs can provide(low switching large power transistor can be currents (> 5A). used)• Can switch many • Relatively costlier when contacts at once. used in smaller circuits
  110. 110. A better solution OPTOISOLATORS• Cheaper than relays• Works well even for AC power supply(some of them… moc3021 for eg)*• Easier to use• No extra circuit needed to make the ic work• Fast switching rate * not preferred in most of the case though
  111. 111. Over to Prashant
  112. 112. H-Bridge
  113. 113. L293D
  114. 114. Differential Drive(basics)
  115. 115. Over to Prashant :P
  116. 116. SerialCommunication
  117. 117. Basics of Serial CommunicationParallel-expensive-short distance-fastSerial-short distance-slow
  118. 118. Other concepts involvedFraming:start and stop bitBaud rate:Number of state changes
  119. 119. USART/UART
  120. 120. Activities1-simple functions to do with serial communication-begin, print,read,available2-send data from arduino to computer using serialmonitor3-send data from computer to arduino
  121. 121. Activity-Controlling the speed of motor based onthe temperatureImportant steps involves:1-interfacing temperature sensor andmotors appropriately.2-getting the analog values of thetemperature sensor.3-depending on the sensor inputs, supplypwm to the motors.4-code :)