Electronics Tutorial

Welcome to the electronics tutorial! If you want to learn electronics, it's a great place to start. You can also revise for your GCSE here, as it's written to GCSE standard for the year 2000 (so if you're taking it in 1999, forget it. but have a look anyway!). It's suitable for all, and anyone can learn electronics using a combination of this & the other material available on my site. Whether you want to learn as a hobby, are taking a course in it, or just want to brush up on a few points, there should be something here to help you.
If you have any questions about electronics, this tutorial, or just fancy a chat, you can e-mail me on alex_tb@hotmail.com . If you've got a PhD in electronics or something, & you think I've stated something wrongly in here, please e-mail me & tell me about it, so I can correct it.

Note that the electronics tutorial is ©1998 Alex Pounds. All rights reserved.

1. Electronic systems
2. The resistor
   • Wire wound resistor
   • Carbon film resistor
   • Production Spread
   • Colour coding
   • The resistor printed code
3. Current
4. Resistances in series
5. Parallel circuits
6. Parallel circuits experiment
7. Resistors in parallel
8. Power & energy
   • Power rating
9. Digital & analogue voltmeters
10. Logic - Digital electronics
    • The OR gate
    • The AND gate
    • The NOT gate
    • The NOR gate
    • The NAND gate
    • The XOR gate
11. The potential divider
12. Measuring potential dividers
13. Using different voltmeters
14. The potentiometer
15. The Light Dependent Resistor
16. The Thermistor
17. Binary numbers
    • Binary counting
18. The Seven-segment display
19. The Binary Coded Decimal (BCD)
20. Diodes
    • Silicon diode
    • Germanium diode
    • Zener diode
    • Light Emitting Diode (LED)
    • Use of diodes
    • Testing diodes
21. Which indicator?
22. Switches
    • Toggle switch
    • Slide switch
    • Rotary switch
    • Push switch
    • Microswitch
    • Reed switch
    • Tilt switch
    • Ways & poles
23. Transistors
    • The NPN transistor
    • Experiment to turn a lamp on by touch
    • Experiment to determine the current characteristic & find its hFE
    • The transistor load driver
    • The Field Effect Transistor (FET)
    • Properties comparison between a FET transistor & an NPN transistor
    • The MOSFET transistor
    • Properties comparison between a MOSFET transistor & an NPN transistor
    • Transistors as gates
24. Integrated Circuits
25. The relay
26. The Capacitor
    • Types of capacitor
      • The non-electrolytic capacitor
      • The variable capacitor
      • The electrolytic capacitor
      • The tantalum capacitor
    • Charging a capacitor
27. The bistable (latch)
    • From NOR gates
    • From NAND gates
    • The Memory Register
    • The D-Type (Data Type) Bistable
    • The Timing Diagram
    • Counting circuit
    • The Binary Up Counter
    • The BCD counter
    • Uses of bistables
    • Contact Bounce
    • Stopwatch using a pulse generator (astable)
28. The Astable (or pulse generator)
29. The Cathode Ray Oscilloscope (CRO)
30. The 555 timer as an astable
31. The monostable multivibrator
    • Uses of a monostable
32. The 555 timer as a monostable
    • Design a monostable
33. Alarms
34. Alternating voltage and current (AC)
    • Types of AC
      • Sine wave
      • Triangular wave
      • Square wave
      • Astable

1. Electronic systems

All circuits can be designed as a system.

eg. a radio receiver

The processing can the be further subdivided:

 

 

Each block can then be designed in isolation, and the blocks coupled together. We need to know the input & output properties of each block, but no details of how they work.

NB. Each block also needs a power supply input, but this is not normally shown on the diagram.

 

2. The resistor

 

A resistor has a resistance, which is measured in ohms. If you haven't got the symbol font installed, the following character will not display correctly - W . This is the symbol for Ohms.

Wire wound resistor

 

• For a higher resistance, we use a longer or thinner wire. This is quite an accurate method.
• They are temperature-stable.
• They can take a large power (gets hot) without failing.
• But they are expensive.

   

Carbon film resistor

 

 

• Higher resistance - thinner carbon or narrower tracks increases the resistance.

 

Production spread

 Resistors are made in large batches, and very cheaply. This means that the resistance value obtained is rarely exactly right. This variation is known as the production spread. The accuracy of a resistor is given to ± a percentage. The ± means that it is within + or - that amount. The accuracy is known as its tolerance.

 

Colour coding

Black	0
Brown	1
Red	2
Orange	3
Yellow	4
Green	5
Blue	6
Violet	7
Grey	8
White	9

Band 1 = First digit of resistance
Band 2 = Second digit of resistance
Band 3 = Number of following zeros
Band 4 = Tolerance

Tolerances

No band = ± 20 %
Silver = ± 10 %
Gold = ± 5 %

 

The resistor printed code

R = ohms
K = thousands of ohms
M = millions of ohms

The position of the letter determines the decimal point.

1800 = 1K8
120 = 120R

Tolerances are shown by using postfixes:

J = ± 5 %
K = ± 10 %
M = ± 20%

So:

56000 ± 10 % = 56K0K
6800000 ± 5 % = 6M8J

 

3. Current

Voltage = Current x Resistance
V = I x R
Volts = amps x ohms
Volts = milliamps x kilo ohms

NB. 1mA = 0.001 A
1 Kilo ohm = 1000 ohms

 

4. Resistances in series

R1	R2	V1 (V)	V2 (V)	V3 (V)	VT (V2+V3)
2K2	3K3	15.12	6.50	8.60	15.10
4K7	1K2	15.12	12.08	3.04	15.12
270R	150R	15.12	9.25	5.84	15.09
39K	69K	15.12	5.46	9.61	15.07

 From this experiment, we can conclude:

• The currents are all equal ( IT = I1 = I2 = I3 )
• The voltages (Potential differences) add together ( VT = V1 + V2 )
• The resistances add together ( RT = R1 + R2)

 

5. Parallel circuits

The 2 circuits on parallel each have 9V across them.

I1 = V / R = 9 / 10 = 0.9 mA

I2 = V / R = 9 / 0.3 = 30 mA

So the total current from this battery is 30.9 mA. Note that the resistance for the second half of the circuit = 300R = 0K3 , because 200 + 100 =300 .

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