ATO Leon Hatot clock - Bad Coil or Magnet?

Hmm. I really need to know more details. You stated that a signal that seems like 1.5 is observed at the coil when the pendulum moves is an interesting observation.

But...we need to know if the observed signal or impulse is a result of the pendulum magnet moving through the coil, or is the observed impulse a signal from the dry cell and suspension contact to the coil?

Are you using your LED test light to observe a voltage at the coil terminals with the dry cell connected in its holder? Please explain your LED test light circuit.

With the clock held in the operating position, a small voltage will be generated at the terminals of the coil when the magnet end swings through the coil first in one polarity and opposite as he pendulum magnet returns.

More details please.

 

You wrote: "With 6V, the clock runs." This tells me that the clock works up to the coil. I'm guessing that either the coil or magnet is weak. "

You've proved that the circuit contact is working and the coil gets energized but it may be energized in the wrong direction relative to the fixed magnetic polarization of the pendulum magnet. Are you certain that the polarity of the battery circuit is "correct" for the north-south orientation of the pendulum magnet?

You could "re-zap" the pendulum magnet or, for a test, put a tiny "super-magnet" at the "business-end" of the pendulum magnet as a test.

I beleve you are working in the right direction but need to assure that the mechanical parts of the motion works are free of excessive friction or lost motion. If you are able to detach the motion works and let the pendulum operate without indexing the hands would help isolate the frictional elements.

I don't recall all the details of these little ATO clocks, and I think that there may be some issues relative to cleanliness of the pendulum suspension electrical circuit.

 

Paul

The coil resistance of 2.7K is correct for this type of ATO.

I would suggest that you firstly check that all the wire connections are fully screwed down and tight. Any additional electrical resistance can be significant with the low current flowing. I would also check that the rocking contacts at the top of the pendulum are meticulously clean. Also check that the strip contact that engages with the arbour at the back of the pendulum is perfectly clean. It can be that the small round disc gets an oxide accumulation which needs to be removed.



I would then look to give the clock some running hours. Since the contacts are self-wiping, you may find that the swing will gradually increase with time as the contacts bed-in. I would use a 5K variable resistor in series with the battery, so that you can gradually reduce the voltage as & when the swing increases.

eskmill has made a very good suggestion on temporarily removing the mechanical movement to just test the electromechanical aspects. You should be able to remove the movement by removing the 2 holding screws (no need to remove the pendulum etc). If you still have no joy, then it would be worth looking at re-zapping the magnet.

Good luck

Regards,

Peter

 

Paul

I'm running out of suggestions.

The only things I would check would be:

1) Double check that the make/break of the rocker contacts is working as it should. Just replace the battery with a ohm-meter and manually swing the pendulum gently from side to side. Make sure you get electrical resistance (ca 3k ohms) in one direction and open circuit in the other.

2) Try removing the copper coil that decelerates the bar magnet. This should makes sure that the copper coil is not causing excessive breaking. Excessive breaking may be cause if the magnet strength at the pole is high - or if the magnet penetrates the coil too far.

3) If you suspect that the breaking force is too great (from (2) above), you could then try sliding the bar magnet slightly towards the primary coil. This will reduce the penetration of the magnet into the copper coil on the return swing. Clearly this will put the pendulum off balance, so is not ideal. However I have had success with this method, providing the offset from centre isn't too great.

4) If (3) above proves encouraging, you could also try to trim off part of the copper breaking coil so that the magnet penetration reduces.

5) Magnet re-zapping is also a good candidate. Its pretty straight forward, but do follow sensible safety procedures.

Regards,

Peter

 

Paul

One final thing on the contact pins attached to the swinging arbour. the contact pins are attached to a small brass block which is screwed into the arbour. I believe it would be possible to rotate the block through 180 degrees so that the pin positions are reversed. Might be worth a try if you are concerned about the condition of the pins ?

Regards,

Peter

 

Paul

Good to hear that you are making some progress - albeit a little frustrating. I'm sure you'll get there eventually.

Sorry that the idea of turning the contact block isn't viable. I was just working from memory.

I just wanted to clarify that you have checked that you get open circuit when the pendulum swings away from the coil. The make & break is key for the pendulum to swing. I had a problem with one ATO whereby the electrical contacts were causing the coil to be energised on both sides of the swing. So it is worth checking that the stack of fibre blocks are doing their job.

I am surprised that removing the copper coil had no effect ? My expectation would be that for the same going voltage, the swing amplitude would increase (since the eddy current breaking function would be removed).

Your replacement grounding spring looks fine. I am sure that you have set this up so their is no excessive friction. It just needs to ensure good electrical continuity.

I think your next best step is to just give the clock a good run at 4.5 volts and to see whether the amplitude gradually increases with time as the contacts bed-in. If not is does seem that you will need to re-zap the magnet.

Good luck !

Peter

 

Hi Paul
Was the ground spring the final issue on the ATO?