Thread Starter

dorydan

Joined Jul 1, 2020
9
I built the novelty motor below and I am having a problem keeping it running. It will run from several hours up to 10 or more days and then suddenly stall. It chugs along nicely at about 60 RPM. I have wound at least a dozen different size coils and I have tried all sorts of different resistor combinations and the results are generally similar --- works great at first, then stalls. I have removed the capacitor and it makes no difference at all. The problem is not the battery because it will sometimes stall with a freshly charged 1.2v battery. Is there any possibility of some harmonic issue? Anything else that I am missing?
Thanks,
dan
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Thread Starter

dorydan

Joined Jul 1, 2020
9
Wow, all that feedback in 12h! Thanks guys, I am a curious rookie so I appreciate the help. So here ya go:

1. heat build up? Doesn't seem to get hot. No smoke got out (yet)!
2. mechanical friction? Great question but I don't think so. It can run down to around 45 rpm if I mess with the resistors. It uses a VERY low friction needle bearing. Still a possibility, but my gut says it is electrical rather than mechanical.
3. Stuck transistor? I don't know what that is, but maybe you nailed it. It stalled last night and by golly the Q1Ve this morning was 1.2. I restarted it, ran it for a few minutes, then manually stopped it and tested V emitter again and it was 0.0! I should mention here that I previously replaced the transistors with the same type to no avail.
4. Danko circuit? Thanks, Danko, I might order up those transistors pending feedback on above. What does "R-ser" mean? Is it a 50 ohm resistor?

Can you fellows recommend a "modestly priced" simulation software that hobbyists can use to test different circuits?
Also, I'd like to read about the "click" noise that is made when the magnets pass the coil at certain resistance values? Is there a name for that?

Thanks again guys!
 

Danko

Joined Nov 22, 2017
1,263
4. Danko circuit? Thanks, Danko, I might order up those transistors pending feedback on above. What does "R-ser" mean? Is it a 50 ohm resistor?
You do not need to order transistors, because 2N3906, 2N2907 and 2N3904, 2N2222 are interchangeable in this circuit.
R_ser (R series) is resistance of coil's wire. Another important parameter of coil is its inductance.
You can calculate inductance using online coil calculator: https://coil32.net/online-calculators/multilayer-coil-calculator.html
or with help of program Coil64: https://coil32.net/download.html.
 

Thread Starter

dorydan

Joined Jul 1, 2020
9
OK guys, that is unbelievably helpful! I got LTspice and, using Danko's asc file, I am beginning to see how you can draw and test a circuit. This will help me a LOT. Will redo the circuit and test it soon! Really appreciate your help.
 
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