Monostable Vibrator

Question 1

R1 and C1

Answer 1

R1 (timing resistor) C1 (Timing Capacitor), controls duration of pulse, connected to Pin 6, Threshold, and Pin 7, Discharge.

Question 2

R2

Answer 2

Pull-up resistor. Ensures that trigger pin 2 remains at constant voltage

Question 3

C2

Answer 3

Stabalises circuit, filtering any noise

Question 4

How does it work (Stage1, Waiting)

Answer 4

-Output, Pin 3, is low (Stable state)
-Capacitor C1is fully discharged, as transistor on pin 7 is taking priority for the supply
-Circuit remains in this state until triggered

Question 5

How does it work (Stage2, Triggering)

Answer 5

-R2 keeps pin 2 high
-When button is pressed, Pin 2 is pulled low, overriding R2
-Sets Flip Flop, as Pin 2 falls below 1/3 Vcc: Output goes high, discharge transistor turns off, allowing C1 to charge

Question 6

How does it work (Stage3, timing)

Answer 6

• Capacitor charges through R1 and its voltage gradually increases
• Output remains high as long as C1 is below 2/3 Vcc

Question 7

How does it work (Stage4, Resetting)

Answer 7

-Threshold pin detects when capacitor goes above 2/3 Vcc
-Internal comparators of the timer reset the flip flop, causing Pin 3 (Output) to go low
-Discharge transistor (Pin 7) goes high again
-Circuit is now in stable state