TMR0 stops working

[shahidali55]

Thanks for that Darrel . . .
I've added a .1uf from MCLR to ground, 1k from buttons to VCC. Datasheet states minimum operating voltage is 2 volts. (http://ww1.microchip.com/downloads/e...doc/35007b.pdf)
Sometime back i have also run the clock from a 12 volt lead acid battery (with 7805).
After 3 days, the clock stopped incrementing time, though the display was being multiplexed and the input buttons responded fine.
16F628A also shows the same behavior.
I tried writing a piece of code that resets all TMR0 registers and variables when the time set button is pressed, but no matter what ,TMR0 doesn't seem to come to life until a powerdown reset is done.

[shahidali55]

I think i have found the fault...
Sometimes when i turn on the tubelight in my room, the clock resets or hangs or stops incrementing time,even tough i'm power it from a battery.
Does this mean that i have to provide RF shielding to the PCB ? ? ?

[Darrel Taylor]

I have a similar problem with my breadboards, ... when I turn on the fluorescent light on my desk.

I pretty much ignore it (mostly because I can't fix it).

It doesn't seem to be related to proximity, but seems to be related to it being plugged into the same "Power Strip" as the project.

If I plug the project into the wall, and the light into the power strip, it doesn't happen.

Surely there's an explanation .. (that will surface real soon).
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[shahidali55]

It happens even if i run the clock from a battery.
It sometimes locks up when i plug in the cellphone charger adapter.
Will decoupling capacitors or line filters help?

[Darrel Taylor]

If you don't have decoupling capacitors, it could be a problem.

I usually put a .1uF (100nf) across the power rails for every 2-3 chips.
Some people say 1 cap per chip, but I think that's a little more than necessary.

You shouldn't need RF sheilding.
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[shahidali55]

Decoupling capacitors don't seem to help . . .
Using the 16F628A with MCLR disabled while programming solves the problem (for now)...

[Archangel]

Hi shahidali55,
If your display is large and has long wires , it may well be acting as an antenna, try decoupling caps on each output line going to it, as well as any inputs, also try hooking all ground connections to a single ground connection, as ground loops often cause electronic circuits to oscillate, That is what they used to do in high end audio gear.
HTH
JS