ATO Leon Hatot clock - Bad Coil or Magnet?

[malloy1]

I hope somebody here knows these clocks.

Pretty sure it's from the 1920's, Serial Number 49441 - Leon Hatot clock movement

Clock doesn't work. Made a LED test light, and when pendulum swings, I get a pulse (very constant) at the coil. Seems like 1.5V and a ground signal is getting to the coil.

So I think it's the coil or the magnet.

I get 2.7K ohms at the coil.

Is there a test for the magnet?

Paul

 

[malloy1]

Ok - Got the clock running on a 9V battery - pendulum swings pretty fast. Runs on 6V. I'm happy that it's running, but need to get it to run on 1.5V now.

Tried 3V, 4.5V doesn't run.

I checked the magnet using the one I used to check my Bulle magnet (using a compass, what distance the magnet is from the compass to change the compass needle by 45 degrees). I got about 60mm at 45 degrees.

 

[eskmill]

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.

 

[malloy1]

I do get the coil to move the compass needle a little bit with 1.5V applied to it (with the magnet removed).

LED test light is 1.5V LED bulb with some lead wires. I'm observing the contacts of the clock.

Battery is hooked up to run the clock. + end of of the LED is hooked up to the + side of the battery, the - end of of the LED is hooked up to the - side of the coil. The LED turns on when the ground pulse from the clock's contact sends the ground to the coil, which activates the coil (since the coil always has + to it). With the pulse making it to the coil, this tells me that the clock is working up to the coil. With 6V, the clock runs, which tells me that the clock works up to the coil. I'm guessing that either the coil or magnet is weak.

Anybody have the specs on these coils and magnets? Would have to be similar to Bulle clocks. I think the bulle clocks need the magnet strength at about 120mm with the compass test, and 1200ohms resistance for the coil.

I can't see anything else wrong with it? Any suggestions?

The LED will not work with lower voltage than 1.5V, so any small voltage made by the magnet going through the coil would not activate the test light. Plus, I have the test light set up to test the ground from the contacts to the coil ground side. I can get the LED to turn on when the pendulum is slow moved across its arc (LED turns on when the contact closes, and off when the contact opens).

 

[eskmill]

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.

 

[sophiebear0_0]

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

 

[malloy1]

I think I tried everything suggested so far, except re-zapping the magnet.

The magnet is set so the south pole is the end that goes through the coil. I did flip it around, and the clock didn't work.

I flipped the battery leads around, and the clock didn't work.

I added rare earth magnet (3/16" diameter) to the south pole of the pendulum magnet. Set it so the south pole was facing out (I did try it also with the north pole facing out). The clock still needs the higher voltage to run.

I took the movement out so just the pendulum part could run without excess friction. The clock still needs the higher voltage to run.

Went through all the electrical connections, unscrew screws, applied a small amount of Deoxit to it, and screwed it back tight. Cleaned the silver contacts, applied a small amount of Deoxit to them (One of the silver pins is worn - It's the one opposite of the coil - Attached picture). The clock still needs the higher voltage to run.

Paul

 

[sophiebear0_0]

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

 

[sophiebear0_0]

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

 

[malloy1]

Got it to run down to 4.5 V. Will not run on 3.0V yet.

Peter, I checked the clock with your list.

1. The resistance is 2.7K ohms as I slowly ran the pendulum through it's swing.

2. Taking the copper ring off didn't do anything.

3. Didn't move the magnet, but I did tilt the movement position a few degrees counterclockwise to allow the magnet to move through the coil a little more. It didn't make it run on any lower voltage than the 4.5V.

4. Didn't do it.

5. Still haven't zapped the magnet yet, but getting the clock to run on 4.5V is encouraging, so I'll wait on trying that.

6. The contact pin block (at least on my clock) is offset, so swinging it 180 degrees puts them too far inboard to fit into the cage.

Everything I took apart, I cleaned and inspected, so maybe it's doing some good. The ground spring (as seen in photo below) to the pendulum arm broke off when I was taking it off. I made another one. So maybe there was something wrong with it?





Paul

 

[sophiebear0_0]

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

 

[Russ Keller]

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