Why a PIC16F628A resets?

[lythanhthuan]

I have strange issue with a 16F628A. Its running a LCD display with a clock on it, and for some reason after a few days (time varies) it does a reset. I know this, because when I change the time, I store it in EEPROM, so after a reset, it reads the stored time..

Anyone an idea why this could be.. I've tried running it with MPASM debuger for over a day or two, but i got no errors..

Its powered by a small (400mA transformer) dc circuit with a 2200uf capicitor before a 7805..

I also tried another PIC, but same problem. Could it be caused by powerdips in the 230v? (would surprise me, because the capicitor is quite large..)

 

[IanP]

Re: PIC16F628A Reset?

It looks lik =e mains problem and 2200µF cap, of course helps, but may not cope with "longer" breaks ..

As this PIC can work with wide range of voltages you may consider adding a battery connected to 5V rail through a diode ( 3 x AAA = 4.5V ), so in normal operation this battery will be sitting there and doing nothing, if the 5V voltage falls below 4.5V-Vf(diode) power will be delivered from the battery pack ..

Maybe worth trying ..

Regards,
IanP