> The strange thing is that once I turn on a standard DC power supply
> unit(using the same AC outlet), the counter goes haywire. The DC power
> supply unit is not connected to anything except the incoming mains. I move
> the power supply unit to another mains(which is isolated from the
> microcontroller) and the problem is solved. Is there anything I can do to
> prevent this?

This sounds like the DC power supply is putting lots of noise on the AC
line, and the noise is confusing the counter.  Your counter circuit needs a
better power supply that can tolerate noise on the AC line.  You should also
check the ground connections and bypasses in your DC circuit.


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