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switch between two pwm sources

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mshh

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I have two PWM sources to control mosfet gate driver. the first source is MCU which isn't connected all the time (when needed)(it is not on the pcb), the second is timer 555 which is connected just when i push the buttons (right or left)(manual control and it is on the pcb). I isolated the two sources with pnp transistors to connect the timer 555 when i push the buttons assuming that the MCU isn't connected. the output of the transistors is connected to AND gate. then when i connect the MCU to drive the circuit according to the code without pushing the buttons , it will be isolated from 555 timer.
do you have comments on this circuit?

 
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Don't think that it will work expected. Q8 will be permanently enabled through R10, R12, R16. Load resistor R15 is probably too low.

What does your simulation tell?
 

In simulation there is output and transistors are enabled when i push the button. But it stops suddenly due to timing error message
 

Hi,

Is it too much to ask to show us the simulation results and the exact error message?

Klaus
 

I simulated the circuit in separate sheet and it works fine. here is the results of right and left switch but when i connect it in the main circuit it stopped and the error message attached
 

The report says timestep is too small. Try increasing it so that 100 or 1,000 of them fit in one cycle of your carrier frequency, or pulse generator, etc.
 

Which time step should i increase please elaborate?or show it.
 

mshh said:
Which time step should i increase please elaborate?or show it.
Click to expand...

You need to find what menu command to choose. Sorry, I have no direct experience with your simulator. The timestep tells the simulator to calculate each frame of circuit action as it would appear after that amount of time. Suppose your pulse generator is 10kHz. Then a reasonable time step is 1 uSec.

Your 'small' timestep appears to be 1.25 x 10 ^ (-19). This is a tiny amount. Your circuit action advances so little in that timestep, that the simulator decides to halt and display an error message. It also states trouble with a node, although that may be unrelated to the timestep.
 

I can't solve the simulation error. what about the attached circuit ,is it complete?
 

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