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keep homopolar motor cool

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masterens

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Hi all,

So I am building this robot, a dog to be precise, and I am using homopolar motors for its muscles. But they heat up very fast and I think that if I keep going on with this it will eventually burn through. Also, I do not know how close the magnets of the (homemade) homopolar motors can get to the PIC i am using (6 volt operating voltage, if it is better I can limit it to 5). Does anyone have answers for me?

Thanks in advance,
masteRens
 
It is too bad that your motors are overloaded. If you use gears or a pulley system then the motors will run faster and the robot will move slower without overloading the motors.
 
thank you for your response. Your response made me think that you understood my question as: my motors are having a hard time pulling their weight; how do I do this? But that is not my problem, as the power supply has not been a problem so far. But though when I leave them spinning for a while their temperature starts to rise very quick. And the different motors might (I have not put together all parts yet, so I don't know exactly) disturb each others magnetic fields, as my motors are made to carry some weight.
I hope I have made myself clear now.

Thank you for your response anyway,
masteRens
 
A properly designed PM DC motor draws a very low current when it has no mechanical load due to it producing a back EMF voltage (it becomes a generator as well as a motor). The back EMF cancels most of its current. Then it runs without producing any heat.

I guess your motor is not properly designed (it is too simple) so it has a very high current which causes it to heat too much.
The homopolar motors shown in Google are just a loop of wire, a magnet and a battery cell. The loop of wire is almost a dead short and is not many turns of wire on an iron core like a real[b/] motor so of course it produces a lot of heat.
 
Are this motors regular cheap DC motors? And do you have speed measurement and control the rpm?
 
thank you for your responses
audioguru: my motor is not one of those hp motors, but is similar. Would a high value resistor solve it? And I do not see many other ways to produce my own motors very cheap (buying them is not realy an option; electrical components are extremely hard to get in my country). Is there?
Grossel: I have built the motors myself, they are direct current powered, they are homopolar. The speed is not being measured, but I can say without any weight to carry it goes superfast, over 8000 rpm if not more.
 
Since you did not attach a photo of your homopolar motor and did not describe it then I guessed that it is a simple garbage one like many that are shown in Google like this one:
 

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And how would you keep thát motor from overheating? btw this one looks more like my motor than the google crap motor I was thinking of, only mine has way more spokes and has a different construction, not involving a battery.
By the way, everytime I test it, I do not realy understand which component overheats; the battery or the spokes? Does anyone know this and as I have 7 motors connected it would be disastrous if every motor heats up the battery more.
 
The simple motor is nearly a dead short to the battery so the power supply/battery heats a lot.
A real PM electric motor has many turns of wire on an iron core so it is efficient and is not a dead short when running. It is nearly a dead short only when it is working very hard like when it is stalled.

We still have no photo of your "motor".
 
Oh yes I cant currently find my camera but I hope to upload it soon
ps: my core is falling out everytime, can I use a bunch of alluminium foil as a core?
 
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my core is falling out everytime, can I use a bunch of alluminium foil as a core?
You need to learn a little about how a PM DC motor works. Maybe begin by taking apart an electric motor to see how it is made.

The coils become electromagnets. A coil with an aluminum core makes an extremely poor electromagnet.
An iron core (or steel) is used because it has good magnetic qualities. It is usually laminated with layers insulated from each other to avoid eddy currents between them.
 
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