year 1 timing circuits

Question 1

what is the time constant equation?

Answer 1

time constant = R/C

Question 2

what is the charging C through R equation?

Answer 2

Vc=Vo x(1-e^(-t/RC))

t=-RC x ln(1-Vc/Vo)

Question 3

what is the discharging C through R equation?

Answer 3

Vc=Vo x e^(-t/RC)

t=-RC x ln(Vc/Vo)

Question 4

what is the equation for the time delay produced by a 555 monostable?

Answer 4

T=1.1RC

Question 5

how does the 555 monostable work?

Answer 5

1. trigger goes below 1/3 Vs
2. output goes high, discharge turns off
3. C charges through R, until
4. threshold is above 2/3 Vs
5. output goes low, discharge goes high
6. discharges instantly

Question 6

how does the 555 astable work?

Answer 6

1. trigger goes below 1/3 Vs
2. output goes high, discharge turns off
3. C charges through Ra and Rb, until
4. threshold is above 2/3 Vs
5. output goes low, discharge turns on
6. C discharges through Rb, until
   Repeats

Question 7

what is the equation for the mark:space ratio?

Answer 7

0.7(Ra+Rb)C / 0.7(Rb)C
(Ra+Rb)/Rb

Question 8

what is the equation of the total pulse time period?

Answer 8

0.7(Ra+2Rb)C

Question 9

what is the frequency equation for a 555 astable?

Answer 9

1.44/(Ra+2Rb)C