OK. So, this is my attempt. It doesn’t work.
From left to right:
Monostable for pulse 3 - > Astable for pulse 2 -> Astable for pulse 1.
Calcs:
For pulse 1:
f= 1/T = 1/1m = 1k
Choose
C3=100n
R4=3.6k
R5=7.2k
Then f= 1.44/((R5+2*R4)*C3)
= 1.44/((7.2k+2*3.6k)*100n)
=1k as required
Duty cycle = (R5+R4)/(R5+2*R4)
=(7.2k+3.6k)/(7.2k+2*3.6k)
=0.75 as required
For pulse 2:
I reasoned that (I don’t know if this is right) the up time for pulse 2 is equal to (trailing edge of last cycle of pulse 1) – (leading edge of first cycle of pulse 1)
=4*1m+1m*0.75
=4.75m
Then the period is
T=4.75m/0.75=6.33m
Then f= 1/6.33m
=0.158k
Choose
C2=100n
R2=22.8k
R1=45.6k
Then
f= 1.44/((R1+2*R2)*C3)
= 1.44/((45.6k+2*22.8k)*100n)
= 0.158k as required
Duty cycle = (R1+R2)/(R1+2*R2)
=(45.6k+22.8k)/(45.6k+2*22.8k)
=0.75 as required
For pulse 3:
I reasoned that (I don’t know if this is right) the up time for pulse 3 is equal to (trailing edge of last cycle of pulse 2) – (leading edge of first cycle of pulse 2)
Then pulse width is
tpw3=4*6.33m+4.75m
=30.07m
Choose
C4=100n
R5=273.48k
Then
tpw = 1.1*R5*C4
=1.1*273.48k*100n
=30.08m as required (nearly)
The circuits for pulses 1 and 2, when run individually – not connected to other circuits – do produce the required values. If I run the circuit for pulse 3 on its own, output just stays high, and does not return to low.
The measurement I’m interested in is at OUT2. As I said, it’s not correct. The up time for the 1st and last pulse in a cluster is either too long, or too short.
I have tried connecting the 555s in a million different ways, but have had no luck. Any help will be much appreciated.
THANKS!