Antique AC clock runs too fast

Thread Starter

Bottleguy

Joined Nov 21, 2020
14
Do you have a way of programming any MCU if I send you the file?
Otherwise I can send you a chip or the chip already mounted on a circuit board.
I have discovered some more info on the clock. "INDUSTRIA ARGENTINA 5 amp 220 V" embossed on the plastic housing of the plug recepticle inside the cabinet. So, it was designed for a 50hz current. Hope this helps.
 

Thread Starter

Bottleguy

Joined Nov 21, 2020
14
I have discovered some more info on the clock. "INDUSTRIA ARGENTINA 5 amp 220 V" embossed on the plastic housing of the plug recepticle inside the cabinet. So, it was designed for a 50hz current. Hope this helps.
I also measured the resistance of the coil at 6.5 to 7 ohms. (analog gauge, so I can't be more accurate) The wire gauge of the coil is less than 34 AWG, but I don't know the exact size.
 

Dodgydave

Joined Jun 22, 2012
9,852
220V @ 7 ohms coil is 31 Amps,,,

So there must be some Transformer or other voltage limiter in it, can you measure the resistance of the mains lead with the clock connected.. you're still going to need a separate 50Hz oscillator.
 

s14rs4

Joined Sep 15, 2016
53
220V @ 7 ohms coil is 31 Amps,,,

So there must be some Transformer or other voltage limiter in it, can you measure the resistance of the mains lead with the clock connected.. you're still going to need a separate 50Hz oscillator.
It is an inductor, not a resistor.
You need to measure the current in the supply when it is running, even at 60Hz it will give an idea of the required supply. I suspect it will be very low.

Also here is another 50Hz oscillator circuit. https://www.elmelectronics.com/ic/elm446/
 

Thread Starter

Bottleguy

Joined Nov 21, 2020
14
You can use a crystal on the MCU instead of AC LINE frequency if you wish but the time-keeping ability will not be as good. I can put together a circuit for you if you wish but you will have to do some assembly.

We suspect that the coil takes very little current. More importantly we would like to know what is the lowest voltage at which the clock will still run.
Well, it's a new year but I still haven't been able to determine the current draw of the coil for the clock motor. The scale of my friend's meter was too large to register anything. He claims to have another meter buried "somewhere", but there's no telling if he can find it or if it will be able to measure a current that is probably in milliamps. Also, he says he didn't have the equipment to build a shunt if we can find an appropriate meter. Comments? Suggestions? Prayers?
 
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