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Problems with PIC16F877A and two PWM outputs

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batdin

batdin

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Hi,
I am working on a project using PIC 16F877A.Part of the duties of the chip is controlling the speed of several fans using the two PWM outputs.
At first everything worked fine.Then (after two months) the outputs failed, producing some funny signals.At first I was puzzled,but then I programmed the device again and everything was fine.
Until recently.Now even the programming doesn't help and I have no idea what the problem might be.I am sure the program itself is OK.
The programmer is JDM,the software is IC-prog.
Do you have any idea as to what might have happened?
Thank you.
 

16f877a + pwm

What did the circuit look like?

PWM switching motors can cause some nasty voltage spikes...
 

Re: 16F877A PWM problem

If possible disconnect the motors and measure the pic's output. If it's ok then check the driver and power switches. If they are ok then check the motors.
 

Re: 16F877A PWM problem

Use another PIC to veify if the problem is PIC-dependent. Like what cyr has mentioned, voltage spikes may have damaged the PIC.
 

Re: 16F877A PWM problem

opto - Isolate the motors.
 
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