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Microcontroller pin not working after some time.

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Ranbeer Singh

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Hello experts
I made a pcb with pic18f25k20 microcontroller. I programmed it and powered it for few days. After 2 weeks microcontroller pin that connected with 7segment/3digit display dot pin stopped to working.
In the circuit microcontroller pin connect to 7seg pin with a series resistance 470E. 3.3v power supply for whole circuit.
3.3/470 = 7ma
Microcontroller pin capable to carry 25ma according to datasheet. I wonder why this pin stopped to working.

I will be thankful if you give me some advice about it.
 

Hamm
May be not protect to every pin from electrostatic discharge. I never seen any additional circuit with 7seg display. It will be best practice if external protection against ESD, EOS etc.

Second is temperature, that i didn't measure. May be it can be cause of fault. A 0.5va 230 to 12v transformer is present near by controller but not more close.
 

The current driving the 7-segments display sounds comfortably dimensioned, so it is unlikely that there was a burning problem, except of course due to improper handling when energized; frankly, I believe that the problem lies in programming scope, review the code to check this possibility.
 

How did it stop working? What tests did you do to confirm it? (i.e. did you check with a scope, DVM etc.)
When you powered the device off and (a little later) back on again, did it start working again or is it permanently 'dead'?
Susan
 

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