Transcript Revision - Downend School

Timer Circuit (timed light)
1. Is this an Astable or Monostable circuit?
2. Which two components control the time delay?
3. What is D1 and what does it do?
4. What is D2 and what does it do?
5. How could you identify where pin 1 is on a 555 IC chip?
6. Why should an IC socket be used to assemble the 555 IC to the PCB?
7. What sort of switch is SW2?
8. Which pin is the output?
9. Which pin is the trigger?
10. Which are the timing pins?
Monostable circuit
Fill in the missing words or value:
1.
If the output (pin 3) is 0 then the LED will be _____________.
2.
When switch SW2 is pressed, a signal is sent to the t__________ (pin ____)
causing the output (pin 3) to go h_____ and the LED switches ______.
If a 9V battery is used, the actual voltage at pin 3 will be ______V.
3.
When the circuit is switched on, the voltage between pin 8 and the 0V rail will
be _________.
4.
When on, the resistance between pins 6 and 7 will be _________.
5.
When the voltage at the threshold (pin 6) reaches _____ of the input voltage
supply, the output (pin 3) returns to 0 and the LED switches off.
The capacitor is emptied by the discharge (pin ______).
6.
The time delay that the LED stays on is controlled by components ______
and ________.
7.
Calculate the time delay for the timed light circuit: