556 time zones

[Dr_Doggy]

I am actually using this circuit to encode PWM to ir pulses using the 556 timer(unlike schematic)
So far I have the PWM circuit working, and am trying to attach my 2nd timer(40khz), but as i do that the PWM I/O periods cut in half, How do I correct this?

 

[ericgibbs]

I am actually using this circuit to encode PWM to ir pulses using the 556 timer(unlike schematic)
So far I have the PWM circuit working, and am trying to attach my 2nd timer(40khz), but as i do that the PWM I/O periods cut in half, How do I correct this?

hi,
I dont see any difference between connected and not connected.???

LTspice Sim both options

 

[Dr_Doggy]

IT worked on my simulator too, but i hardwired the PWM circuit (1-2ms/18-20ms) it works ok,, but when i activate the 40khz pulse circiut, that is when the pwm cuts in half

the only thing i did different was used a 556,,is that normal?

 

[ericgibbs]

IT worked on my simulator too, but i hardwired the PWM circuit (1-2ms/18-20ms) it works ok,, but when i activate the 40khz pulse circiut, that is when the pwm cuts in half

the only thing i did different was used a 556,,is that normal?

On the actual circuit do you have power rail decoupling, say a 10uF and a 100nF cap.

Also try connecting a 10nF cap from the Vc control pins to 0V.

 

[Dr_Doggy]

k, thnx, i was wondering about that, do I put all 3 of those across my 9v battery?

 

[ericgibbs]

k, thnx, i was wondering about that, do I put all 3 of those across my 9v battery?

The 10uF and 100nF go close to the 556, the 10nF are from the 556's Vc pins 3 & 11 to 0V.

 

[Dr_Doggy]

k, thnx again!