556 time zones

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Dr_Doggy

Well-Known Member
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?
 

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

LTspice Sim both options
 

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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?
 
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.
 
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