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#10 Anne Roudaut hci2: building interactive devices hasso-plattner institute tangible & electronic.

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1 #10 Anne Roudaut hci2: building interactive devices hasso-plattner institute tangible & electronic

2 assignment design, prototype, and laser cut a robotic vehicle that you can control by projecting on it upload sketches, drawings, & photos to the wiki

3 design & built a motorized tangible object your task: shape allows users to pick up and move (onmi) wheels and motor, so it can move itself light sensors, to allow sending commands to the tangible

4 electronic part with an arduino board

5 and a set of components (battery / motors / photoresistors / chips / resistors …)

6 arduino

7 board

8

9

10

11 program on PC (simplified C++) upload to the board separate and run independently main advantage of Arduino!

12 processor usb plug (5V) external power (max 12v) some LEDs reset button pins when programming and testing to run independently

13 usb plug (5V) external power (max 12v) some LEDs reset button pins pins: to plug in components such as… processor

14 LEDs long leg is the + +-

15 pin “gnd” (ground)pin “12” (we will see later why we need the resistor) what’s happening? the LED blinks continuously

16 step by step

17 configure 0

18 pluging in 1 pin “gnd” (ground)pin “12”

19

20 e.g. all these pins are connected It is the same here etc. test board

21 compiling 2

22 uploading 3

23 it is blinking: the board is uploading the binary code (1 = light on / 0 = light off) 3

24 executing 1st loop 4

25 5 reseting executes setup ()

26 test 1 (5 mn) 1.plug in a resistor and an LED in pin 12 2.launch the File/Examples/Basic/Blink arduino files 3.modify the code to make the LED says “SOS” in Morse (3 shorts, 3 longs, 3 shorts) pin 12 (5 V) pin gnd Blue LED -+-+ blinking LED 82 ohm

27 don’t forget your programming skills! write functions

28 test 2 (5 mn) (with the same circuit) 1.upload File/Examples/Basic/Blink to the board 2.change the first delay value to 1 and the second to 1. upload the code to the board 3.change the first delay value to 1 and the second to 10. upload the code to the board 4.compare the three cases and tell me more! more blinking

29 1 2 3 blink bright less bright even less bright HIGH LOW delay(1) … delay(10) delay(1) … delay(1) delay(1000) … delay(1000)

30 1 2 3 HIGH LOW voltage is either 0 or 5v voltage is ½ of 5V voltage is a 1/11 of 5 V delay(1) … delay(10) delay(1) … delay(1) delay(1000) … delay(1000)

31 pulse width modulation :: technique using a rectangular pulse wave whose pulse width is modulated resulting in the variation of the average value of the waveform it serves to create an analog signal from a digital one

32 digitalWrite("pin number", HIGH or LOW) or analogWrite("pin number", "value in [0;255]") (% of voltage) there are special pins that produce PWM signals (in addition to digital signals)

33 test 3 (5 mn) 1.change your circuit to use a PMW pin 1.write code with analogWrite() to make the led smoothly blink (the brightness progressively increases) smooth blinking

34 pins are input and output

35 digitalWrite("pin number”,”HIGH or LOW”) digitalRead("pin number”) -> 1 or 0 (0 if voltage < 3v) digital pins are for input and output

36 analogWrite("pin number”,[0;255]) PWM pins are analog output

37 analogRead("pin number”) -> [0;1023] (1023 being the maximum voltage in the board) analog pins are for analog input

38 both digital and analog pins deal with voltages reading input works with every components that generate voltages

39 battery

40 pin “gnd” pin “A0” 1.5V battery on A0 pin to read it voltage by the way, components that generate high voltage will damage the board, be careful!

41 digitalWrite(A0,HIGH)

42 Monitor display Serial.print() Serial,println() of [0;1023] so 305x5/1023 = 1,49V

43 so it works with components that generate voltages such as…

44 photodiode voltage increases when the intensity of light increases

45 piezoelectric cells voltage increases when pressure increases

46 but also with components that generate resistance (and we will see the trick later)

47 conductive foam material in what components are plug in it removes electrostatic charges

48 conductive foam the more you squeeze it, the less it resists to the travel of the charges it lets the charge passing thought: it conduces charges

49 pin “gnd” pin “A0” let’s play with a piece of conductive foam

50 test 4 (5 mn) 1.plug in two wires and a piece of foam between pin A0 and GND 1.write code to display the change of voltage on pin A0 1.write code to make an LED more or less bright when you squeeze the foam read pins

51

52

53 it is a simple way to make a pressure sensor

54

55 at this point you know the basics of arduino you are almost ready to go what remains now is some math in order to understand…

56 why do we need a resistor with the LED? how does an input pin read different values of resistance whereas we said it reads voltage? 1 2

57 let’s forget arduino for a moment

58 electric quantities voltage / current / resistance battery resistor

59 -+-+ voltage is the amount of cars it is measured in Volt battery resistor traffic jam analogy

60 resistance defines the type of road it is measured in Ohm (Ω) 10 Kilo OHM vs. 60 OHM vs highways let more cars passing through current is the amount of cars that pass through the circuit per units of time (the flow) it is measured in Ampere

61 Current Voltage plumbing analogy

62 the smaller the road is (resistance increases), the slower the flow of cars is (current decreases) the harder a pipe is pressed, the smaller the water flow is

63 the relation between these 3 quantities is given by Ohm’s law U = R x I Volt Ohm Ω Ampere

64 U=RI works for resistors Current (I) 1 Ω resistor

65 resistors color code = value

66 more generally, U=RI works for ohmic materials Current (I) 1 Ω resistor Voltage (U) 1 meter silver (1.59×10 −8 Ω) 1 meter air (1.3×10 16 Ω) 1 meter sea water (0.2 Ω) conductors insulators

67 most components are not ohmic e.g. light bulb / LED / motor

68 ligh bulb U I the resistance of the filament increases with its temperature

69 LED works in a small interval of voltage steep slope: small variations of voltage = large variations of current U I

70 U I LED offLED on (brightness increasing) LED blows max current indicated on the spec working voltage interval indicated on the spec

71

72 to reduce current we put a resistor in serie to know it value, we use Ohm’s law Red LED [1.8;2.2] V 0,02 A -+-+ (5-2.2) = R x 0,02 R = 140Ω V battery

73 we can also adapt the voltage but … Red LED [1.8;2.2] V 0,02 A V battery -+-+

74 U I LED offLED on (brightness increasing) LED blows steep slope: when the voltage decreases a little bit, the current dramatically decreases, thus decreasing the brightness

75 the resistor also regulates the LED voltage, that stays almost constant Red LED [1.8;2.2] V 0,02 A V battery 140Ω

76 so LEDs must always be mounted with a resistor in serie

77 true for several LEDs in serie V battery Red LEDs [1.8;2.2] V 0,02 A (5-2x2.2) = R x 0,02 R = 30Ω 30Ω

78 true for several LEDs in parrallel V battery Red LEDs [1.8;2.2] V 0,02 A (5-2.2) = R x 0,02 R = 140Ω 140Ω (voltage is the same in each branch)

79 if LEDs are the same, we can also serialize the resistor V battery Red LEDs [1.8;2.2] V 0,02 A (5-2.2) = R x (2x0,02) R = 70Ω 70Ω 0.04 A is drained from the battery (current splits in each branch)

80 why do we need a resistor with the LED? how does an input pin read different values of resistance whereas we said it reads voltage? 1 2 done and we know how to compute it value

81 squeezing the foam changes the resistance but the voltage of A0 pin was changing

82 Battery 5 V conductive foam -+-+ the resistance changes and thus the current (Ohm’s law) but still not the voltage

83 so there must be a trick somewhere … we must use a tension divider circuit layout

84 tension divider R foam + R pullup R foam x V in V out = V in -+-+ pull-up resistor V out

85 V in -+-+ V out demonstration V in = R pullup I + R foam I (1)ohm’s law U = RI (2) Kirchhoff 2 nd law Σ voltage drop by components = Σ voltage generates in the circuit by the way, Kirchhoff 1 st law at any nodes, Σ current floating in = Σ current floating out

86 V in -+-+ V out demonstration V in = R pullup I + R foam I (1)ohm’s law U = RI (2) Kirchhoff 2 nd law Σ voltage drop by components = Σ voltage generates in the circuit V out = R foam I V out = R foam x V in (R pullup + R foam ) So

87 pin 5V R foam + R pullup R foam X 5 A0 = so the arduino circuit can look like that e.g. 10 KΩ (to have precise A0 value) pull-up resistor pin A0 pin GND

88 pin 5V pull-up resistor pin A0 pin GND but arduino also have an internal pull-up resistor -> we can plug in the foam between A0 and gnd Optional if internal pull up resistor is enabled

89 potentiometer by the way, a potentiometer is a tension divider circuit Vout Vingndresistor adjustable

90 why do we need a resistor with the LED? how does an input pin read different values of resistance whereas we said it reads voltage? 1 2 done and we know how to compute it value

91 use multimeter (in the shop) to check voltage: in parrallel current: in serie

92 more components

93 motor M

94 photoresistor resistance decreases when the intensity of light increases

95 relays to switch on higher voltage

96 transistors a small current at the Base can control or switch a much larger current between the Collector and Emitter It serves as a switch or current amplifier

97 capacitors they store electric charge

98 capacitors

99 chips or integrated circuits (the notch shows the orientation when reading the spec) more pins!

100 chips 7400 serie = 4 NAND GATES A B out A B out example:

101 Gleichrichter chips H-BRIDGE It can inverse the polarity of two motors (one on each side) It doesn't control the amount of voltage (i.e. the speed). For that, you must reduce or increase the voltage sent on pin 8

102 chips H-BRIDGE

103 chips H-BRIDGE Pin 8 is the power for the chip. It has to be max 5V. Just plug in it to a digital pin always HIGH Pin 6 is the control pin for the left motor. If it is HIGH the left motor do something, otherwise nothing (same principle for the pin 7 controlling the motor on the right) If pin 2 LOW pin 3 HIGH, then the left motor will turn in one direction If pin 2 HIGH pin 3 LOW, the left motor will turn in the other direction If both pin 2 and 3 have the same value the left motor stop (same principle for right motor and pin 4 and 5)

104 555 timer (e.g. toaster timer) 741 operational amplifier (amplify current) Accelerometers … chips etc.

105 without the computer

106 external power max 12 V (some versions can handle more) max 40mA per pins max 50mA on 3.3V pin

107 for your 9V battery

108

109 assignment design, prototype, and laser cut a robotic vehicle that you can control by projecting on it upload sketches, drawings, & photos to the wiki Go! be sure your design is feasible : - check materials before - ask Professor or TA

110 end

111 have you ever tasted a 9V battery? no more than 9V!

112 try different flavors ! wetdry

113 Ampere (current/flow) (A) Resistance (Ohm Ω) Voltage (pressure) (V) Water level

114 = electron particle

115 different flavors = different resistance electrons flow more or less easily wetdry

116 encoder

117


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