Electronics: Design and Build Training Session. Presented By: Dr. Shakti Singh Hazem Elgabra Amna Siddiqui

Transcription

1 Electronics: Design and Build Training Session Presented By: Dr. Shakti Singh Hazem Elgabra Amna Siddiqui

2 Basic prototyping and measurement tools

3 Breadboard basics Back View VCC GND VSS

4 Breadboard basics (contd.) Beware of isolations!

5 Variable Power Supply Has 3 voltage sources (two variable and one fixed at 5 V) Don t play with these Can be used in 3 ways to create: 1. Two independent supply voltages 2. Two reference voltages for same circuit 3. +V and V Make sure always green! Fixed 5 V

6 Variable Power Supply (contd.) Two independent supply voltages Two reference voltages for same circuit +VCC and -VSS - - GND - V1 + - V2 + V1+ V2+ - V + V +3 V +5 V +3 V +5 V -3 V +3 V

7 Digital Multimeter (DMM) To measure voltage (connect in parallel):

8 Digital Multimeter (DMM) (contd.) To measure current, disconnect nodes and connect in series!

9 Digital Multimeter (DMM) (contd.) How to measure resistance?

10 Potentiometers 1 R1 = <10 kω 2 10 kω R2 = 10 kω R kω

11 Digital Multimeter (DMM) (contd.) How to find out if two nodes are connected?

12 Function Generator Can be used to simulate the analog inputs to your circuit 1. Select function to set (sine, square) + Vout - 1. Enter values for amplitude, frequency, offset etc. 2. Use keypad or knob 3. Make sure units are right!

13 Oscilloscope (voltage signal viewer) Like voltmeter but for analog signals Can view up to two signals at a time (2 channels) Measure (use F1-F4) Autoset (to reset viewing settings) - CH1 + - CH2 +

14 Oscilloscope (contd.) Increases/decreases voltage resolution for CH1 signal Increases/decreases voltage resolution for CH2 signal View/Hide signal at CH1 Increases/decreases time resolution for both channels voltage Shift CH1 signal up or down Shift view right or left Shift CH2 signal up or down time

15 Oscilloscope (contd.) 3 Coupling modes DC coupling: show the signal as it is AC coupling: remove DC shift of the signal by setting the vertical zero point to (signal max + signal min) / 2 This is a modified version of your signal! It will show any battery s voltage as ZERO GND coupling: just shows zero

16 DC Motor

17 DC Motor

18 DC Motor

19 DC Motor

20 DC Motor

21 DC Motor

22 DC Motor

23 DC Motor

24 DC Motor To increase speed, increase voltage With increased voltage, you draw more current No worries when connected directly to a power supply

25 DC Motor To increase speed, increase voltage With increased voltage, you draw more current No worries when connected directly to a power supply

26 DC Motor But what happens when it is integrated within a circuit?

27 DC Motor If the motor is turning that doesn t mean that it is working as you want yet The motor will have to move something which will resist it (because physics) The more resistance it faces the more current it requires If your circuit cannot support the extra current, the motor will simply stop

28 Datasheets

29 Part number What is it Some chips tell you what are they made for Chip pin out Pins description Quick description

30 Comprehensive symbol Chip pin out Pins description

31 Rating values i.e. maximum supply voltage is 36 V Some datasheets have recommended conditions

32

33

34 Specifications Rating values i.e. maximum supply voltage is +/- 22V Sometimes the datasheet is for a series of similar components Will have everything you might need

35 Comprehensive symbol Inner circuit

36 Will always show the inner circuit

37 Transistors

38 Diodes The main function of a diode is to control the direction of control flow. Current only flows in forward direction, in reverse the current is blocked. ideal diode

39 Diodes Forward Bias Reverse Bias

40 Diodes Real Diode 1.Forward bias: When the voltage across the diode is positive the diode is on and current can run through. The voltage should be greater than the forward voltage (V F ) in order for the current to be anything significant. 2.Reverse bias: This is the off mode of the diode, where the voltage is less than V F but greater than -V BR. In this mode current flow is (mostly) blocked, and the diode is off. A very small amount of current (on the order of na) called reverse saturation current is able to flow in reverse through the diode. 3.Breakdown: When the voltage applied across the diode is very large and negative, lots of current will be able to flow in the reverse direction, from cathode to anode.

41 Diodes

42 Diodes 1N4148 diode If a diode is subject to more voltage or current than it can handle, expect it to heat up (or worse; melt, smoke, ). Some diodes are well-suited to high currents 1A or more others like the 1N4148 small-signal diode shown above may only be suited for around 200mA.

43 Light-emitting Diodes (LEDs) LEDs are a particular type of diode that convert electrical energy into light.

44 Light-emitting Diodes (LEDs) current Cathode (-) Anode (+)

45 Light-emitting Diodes (LEDs) The brightness of an LED is directly dependent on how much current it draws. The super bright LEDs drain batteries more quickly, because the extra brightness comes from the extra power being used. it s important to limit the amount of current flowing across the LED, otherwise it will burn. Use current limiting resistor.

46 Light-emitting Diodes (LEDs) The first row in the table indicates how much current your LED will be able to handle continuously. In this case, you can give it 20mA or less, and it will shine its brightest at 20mA. The second row tells us what the maximum peak current should be for short bursts. This LED can handle short bumps to 30mA, but you don t want to sustain that current for too long. The first row tells us what the forward voltage drop across the LED will be. This number will help you decide how much voltage your circuit will need to supply to the LED. If you have more than one LED connected to a single power source, the forward voltage of all of the LEDs added together can t exceed the supply voltage

47 Zener Diodes Zener diodes are a special kind of diode which permits current to flow in the forward direction. What makes them different from other diodes is that Zener diodes will also allow current to flow in the reverse direction when the voltage is above a certain value. This breakdown voltage is known as the Zener voltage.

48 Diode application

49 Transistors An electronic device which can be used as a Switch Amplifier Major Types Bipolar Junction Transistors (BJT) Metal Oxide Semiconductor Field Effect Transistors (MOSFET)

50 Transistors Bipolar Junction Transistor npn or pnp Small input base current leads to large current between emitter and collector. Major Types nmos or pmos Voltage applied to base controls current between source and drain.

51 Transistors Bipolar Junction Transistor

52 Transistors

53 Transistors

54 Transistor as switch The transistor needs a certain voltage (0.6V to 0.7V) to turn ON. Current limiting resistor Don t forget to add this resistor! The base resistor needs to be large enough to effectively limit the current, but small enough to feed the base enough current. 1mA to 10mA will usually be enough, but check your transistor s datasheet to make sure. Here we use an NPN to control an LED

55 Transistor as switch Here we use an PNP to control motor

56 Transistors as Amplifier One quirk of the common emitter, though, is that it inverts the input signal

57 Transistor as Amplifier The Darlington pair is a great tool if you need to drive a large (current hungry ) load with a very small input current.

58 Transistors - MOSFET Operation similar to a BJT

59 Transistors - MOSFET Gate-source voltage less than threshold voltage V GS < V TH MOSFET is OFF ( Cut-off region ) No Drain current flows ( I D = 0 ) V OUT = V DS = V DD = 1 MOSFET operates as an open switch Gate-source voltage is much greater than threshold voltage V GS > V TH MOSFET is ON ( saturation region ) Max Drain current flows ( I D = V DD / R L ) V DS = 0V (ideal saturation) Min channel resistance R DS(on) < 0.1Ω V OUT = V DS = 0.2V due to R DS(on) MOSFET operates as a low resistance closed switch

60 Transistors - MOSFET

61 Power MOSFET A power MOSFET is a specific type of metal oxide semiconductor field-effect transistor (MOSFET) designed to handle significant power levels. The power MOSFET is the most widely used low-voltage (that is, less than 200 V) switch. It can be found in most power supplies, DC to DC converters, and low voltage motor controllers.

62 Power MOSFET IRFD120

63 BJT vs MOSFET Unlike bipolar transistors, MOSFET is voltage controlled. While BJT is current controlled, the base resistor needs to be carefully calculated according to the amount of current being switched. Not so with a MOSFET. Just apply enough voltage to the gate and the switch operates. Because they are voltage controlled, MOSFET have a very high input impedance, so just about anything can drive them. MOSFET has high input impedance.

64 Skills

65 Skills Troubleshooting steps: Recheck connections Check voltage using DMM Breakdown the circuit and make sure every part is doing what it is supposed to do You can use power supplies to simulate signal inputs from other parts in the circuit Try to change one thing at a time

66 Skills Example. You made the following circuit but it is not working: Motor Driving circuit

67 Skills Example. You made the following circuit but it is not working: Motor Driving circuit

68 Skills Example. You made the following circuit but it is not working: Motor Driving circuit

69 Skills Example. You made the following circuit but it is not working: Same voltage Motor Driving circuit

70 Skills Example. You made the following circuit but it is not working: Motor Driving circuit Both working?

71 Skills Example. You made the following circuit but it is not working: Motor Driving circuit No Yes Both working?

72 Skills Example. You made the following circuit but it is not working: Motor Driving circuit troubleshoot

73 Skills Example. You made the following circuit but it is not working: Motor Driving circuit Yes Yes Both working?

74 Skills Example. You made the following circuit but it is not working: Motor Driving circuit Not working?

75 Skills Example. You made the following circuit but it is not working: Different than

76 Skills Common errors: Power not connected or turned ON Always check your source Circuit wiring Break the circuits into parts, and debug it using DMMs and power supplies Common ground Ground is an imaginary reference point All circuit parts should share a common ground All power supplies should also share that same common ground

77 Skills Common errors: Components are burnt out ICs and transistors can be burnt out and not working Based on what is not working in the circuit, you can guess which part might be burnt out There are IC testers to test you IC Also try exchanging the IC or transistor and see if the circuit work

78 Skills Common errors: Using components incorrectly If the IC passes, but circuit is still not working, then you might simply be using your IC incorrectly Check the datasheet Loose connections You know you have a loose connection when the circuit sometimes works and sometimes doesn t

79 Skills Common errors: Current issues Usually happens when independent parts work, but don t work when integrated Power supplies usually give you as much current as you need Use them to simulate signal inputs from other parts in the circuit If it works, then current issue confirmed Use the signal to control a switching circuit that powers your next part Use amplifier/more efficient transistors to supply more current within the circuit

80 Skills Example. You made the following circuit but it is not working:

81 Skills Example. You made the following circuit but it is not working:

82 Skills Example. You made the following circuit but it is not working: correct

83 Skills Example. You made the following circuit but it is not working: correct

84 Skills Example. You made the following circuit but it is not working: Wrong!

85 Skills Example. You made the following circuit but it is not working: This could be burnt

86 Skills Example. You made the following circuit but it is not working: Connections might be wrong

87 Skills Example. You made the following circuit but it is not working: Current might not be enough

88 Skills Example. You made the following circuit but it is not working: etc...

89 References