Explain odd digital clock behavior?

Yep, most plug-in-the-wall digiclocks use the line frequency to count time because it's very accurate. Your CNC machine is probably distorting the line voltage due to non-sinusoidal current draw by the machine and high source impedance somewhere in your power feed.

Also, your clock isn't do a good job of ignoring non-monotonic line voltage so it's multi clocking on each true waveform edge.

The best thing to do is to let me come take your CNC machine and I'll give you a better clock in exchange. I've always wanted a CNC mill.

Bob

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** Is that an electronic clock ( with LED, LCD or a fluorescent display ) or a digital mechanical clock with numbered wheels or flip cards ?? ** Assuming you clock is of the electronic kind, my hunch is that the neutral line is heavily contaminated with harmonic current pulses from the 3 phase supply.

If you owned a scope you could easily check the neutral voltage waveform in the house for this.

Harmonic voltages on the neutral will create additional, false zero crossings in the AC supply - and it is likely your clock is detecting zero crossings to derive it's 60 Hz time base.

..... Phil

Do you mean digital as in electronic or those clocks that had numbers that flipped over mechanically ?

Graham

I understand your sentiments on that point !

However, given the tiny amount of power required, a simple LC or even RC filter in the supply might fix it.

Graham

Greetings Bob, If you can carry the CNC out of the shop yourself then I'll do the trade. Mind you, there are a few obstacles that you will need to lift the machine over. But if you can clean and jerk 5000 lbs then I guess you could just get the machine anytime without my permission. Eric

Greetings Graham, I should have said it was the type with an electronic (LED in this case) display, not mechanical. Cheers, Eric

Got a pallet jack? ;-p

Cheers! Rich

It's very likely line harmonics from the 3-phase converter, overclocking the clock.

If the clock is important to you, you could add a crystal osc. and counter chain to give you a decent 60Hz pulse stream.

Good Luck! Rich