1. GCSE Electronic Products
Revision Flashcards

2. 555 timer 8 pin Integrated Circuit (I.C.) Analog
can be used as an astable or monostable
Low cost

3. Monostable (the egg timer)
Has a single (mono) stable state
when it is timing
The output is normally off

4. Pin 2 = Trigger The trigger sets the timer going
Timer starts when trigger is < 2V
Connects to a 10K pull-up resistor

5. Pull-up resistor Pulls the voltage up on a wire to supply voltage
Makes a “nice” logic high

6. Pull Down Resistor Pulls the voltage on a wire down to 0V
Gives a “nice” logic 0

7. Pin 6 = Threshold Detects when the bucket (capacitor) is 2/3rds full
The capacitor fills up through a resistor
Time to fill to 2/3rds full = Resistor Value x Capacitor Value (T = RC)

8. Pin 7 = discharge
Empties the bucket (capacitor)

9. Astable (The “flasher” circuit)
Has no stable states
Keeps on flashing forever
Number of flashes per second = frequency
Automatically triggers

10. The Op-Amp - input = inverting + input = non-inverting
used as an inverting amplifier or a comparator
An analog device
A 741 I.C. is an example of an op-amp

11. Inverting
Means it turns the signal upside down

12. Gain The ability of a device to make a signal bigger
Op-amps have huge “open loop” gain
Transistors also have gain

13. Feedback Gain can be reduced by using feedback
Some of the output is taken away and added to the input
We use resistors to do this

14. Comparator (Which input is bigger)+ -
If “+” is bigger than “-” we get a logic 1
If “+” is smaller than “-” then we get a logic 0
A simple analog to digital converter

15. Ohms Law As resistance increases, current decreases
As resistance increases, voltage increases

16. Sources of power

17. P.I.C. (Peripheral Interface Controller)
Digital
A mini-computer in a single Integrated Circuit
Programmable using flowcharts
Can be programmed many times
Remembers program even when the power is off

18. Diode (A one way valve) Current flows from anode to cathode
Prevents current flowing the wrong way
Protects circuits if the power supply is connected up wrong

19. Transducer (A device for converting energy from one form to another
Motor – converts electrical energy to kinetic energy
LED – converts electrical energy to light
Microphone - converts sound energy to electrical energy

20. Transducer Drivers (Things that provide power to output transducers)
Bipolar Transistors
FET’s
Darlington Pairs

21. Tolerance The amount of “spread” in a components value
100Ω and 10% tolerance gives a spread between 90Ω and 110Ω

22. E12 Series
The values that 10% tolerance resistors are made in to avoid value overlap
10, 12, 15, 18, 22 etc
100, 120, 150, 180 etc

23. Polymorph – Smart Material
Used to rapidly model complex shapes
Granules put in hot water turn solid and can be immediately shaped +

24. clock A digital signal that has a regular repeating on/off pattern
Often generated by an astable
Used by PICs & counters

25. HIPS Plastic material used for vacuum forming
Available in different colours
Used to make complex 3d shapes
Boxes must have angled sides to get the mold out

26. Breadboard Used to model circuit using real component No soldering
Easy to change connections
Components can be re-used

27. CAD (Computer Aided Design)
Testing by simulation
Links to CAM (Computer Aided Manufacture)
Easy to share designs with others and keep track of changes
Making changes is a quick & easy process

28. Latch Circuit Can be made using a thyristor
Can be made with NOR or NAND gates
When activated, stays activated until reset
Remembers that it has been activated

29. Thyristor Used in latch circuits
A pulse on the gate causes current to flow from Anode to Cathode until reset
Reset by making the Anode voltage the same as the Cathode

30. Potential Divider A circuit for dividing voltages
Voltage splits based upon the ratio of two resistors

31. Schmitt Trigger
A type of circuit used to remove switch bounce

32. Thermistor Device for measuring temperature
As temperature increases, resistance decreases
Often used as part of a potential divider

33. LDR (Light Dependent Resistor)
As light increases, resistance decreases
Often used as part of a potential divider

34. Multimeter Device for measuring: Has red & black probes Current
Voltage
Resistance
Has red & black probes

35. The 3 R’s (Helping The Environment)
Reduce cut the materials you use
Reuse make use of existing products
Recycle stop the product going to landfill when obsolete

36. Resistors Measured in Ohms (Ω) Used to reduce current
Colour bands indicate the value

37. Integrated Circuits Pin 1 is to the left of the notch
Lots of components on a single piece of silicon
Examples are:
PICS
555’s
741’s

38. Switch Bounce A problem with mechanical PTM & PTB switches
One press of the switch generates more than one pulse

39. AND Gate Both inputs must be at logic 1 to get a logic 1 out
A = 1 AND B= 1

40. OR GATE
Either one of the two inputs can be at logic 1 to create a 1 on the output
A=1 OR B=1

41. Relay
A device that allows one circuit to turn on another circuit that works at a different voltage
Uses electro-magnets

42. Variable Resistor Used for volume controls
Changing astable frequencies
Changing mono-stable time periods

43. 4017 Output 0 is on When a clock pulse is received:
Output0 turns off
Output1 turns on
On next clock pulse
Output1 turns off
Output2 turns on

44. SPDT SWITCH (Single Pole Double Throw)
One circuit
Two positions
Three pins
Two different sets of components can be switched into one circuit

45. Life Cycle Analysis What happens to a product when it is disposed of:
Reused in a new product
Recycled
Goes to landfill

46. Multipliers
1,000,000, = 1G = 1 x 109
1,000, = 1M = 1 x 106
1, = 1K = 1 x 103
1 = 1 = 1 x 101
= 1m = 1 x 10-3
0.000,001 = 1µ = 1 x 10-6
0.000,000, = 1n = 1 x 10-9
0.000,000,000,001 = 1p = 1 x 10-12

47. Units of Measure Measurement Unit Symbol Resistance Ohms Ω Capacitance
Farads F
Voltage
Volts V
Current
Amps I
Power
Watts W
Time
Seconds S