steer for a toy car

I have a remote controlled toy car and I am to modify it as a line follower. I opened the car and happened to disconnect the wires. What I have is a couple of cylindrical plastics where the copper (or bronze) wires are wound. These two cylinders are facing each other. When I separated them, what I saw was a cylindrical magnet that has a plastic inside it. (Imagine a hotdog on a stick). The magnet can rotate and therefore the plastic rotates with the magnet. It serves as the steer for the front wheels.

I don't know if I accidentally cut a wire. Now, I have the two separate cylinders and a copper (or bronze) wire is wound around them. I tried connecting a battery (AA size, 1.5 volts) at the two ends of the separate wires but it didn't work. Kindly teach me how to repair this stuff. Thank you in advance.

I don't know if I accidentally cut a wire

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I think you do know. That's why it isn't working
If the thin wire making up the cylindrical electromagnet coil is broken very close to the coil it is probably not repairable. If the break is at least 1cm from the coil then you may be able to carefully use a scraper or burning match [taking necessary fire precautions] to remove the wire's enamel insulation layer so that the broken wire ends can be soldered together.

There were three wire ends before. Now,I only have two. I think the two wire ends left are connected. I tried to inspect the coil if there was any part of broken wire but I can't find any.

If this is not repairable already, at least I can learn how the winding and magnet works to create rotation. Please teach me sir.

Can you post a pic of the cylindrical electromagnet coil ?

Sorry sir, I can't post it tonight. I'll post it tomorrow.

There were three wire ends before. Now,I only have two.

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That suggests another breakage, right at/in the coil. The only repair possible is to locate the broken end and unwrap a turn or two from the coil.

photos

These are the photos of the steer of the toy car.

I pasted them in Microsoft word and attached them separately since the allowable limit is just 12 MB.

Sorry for my mistake in the post. The coils are not wound in a cylindrical thing.

Sorry also that I posted it late.

The left and right electromagnets pull the one pole of the round grey permanent magnet (on the top) towards them. The reason there are two of them and 3 wires is because this design was once considered less expensive to produce as it used a pair of open-collector NPN drive transistors (+ and "off") and a pair of coils than an H-bridge driver (which can reverse polarity) and a single coil.

Wow, I have never seen anything like that before. Who made it?

You must find the ends of the wires where you took it apart. Every coil must have two ends.

This design was common back in the 1970's, it was called a "galvo".

Is this galvo still repairable? I'm planning to run it using h bridge. Is it possible?

duffy said:

This design was common back in the 1970's, it was called a "galvo".

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I can not find any reference to that on the web.
Do you have any further info?

Is this galvo still repairable?

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If you can find the other ends of the coil wires.

I'm planning to run it using h bridge. Is it possible?

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Sould be, but I have never seen galvometers this used this way.

What if I remove the windings and wind it myself?

But my problem is I don't know how to do it.

I don't know what wire ends should be present.

I also don't know if what I'm thinking is recommended to be done...

I could not also find any references to pattern whatever I will do.

You can always re-wind it, you might even be able to use the same wire - but try to find the broken end first, it can save you a lot of trouble if there is any way to connect to it. Use a magnifying glass. Try to find the broken end. If it is on the outside winding, you are in luck. If it is on the inside winding you still may be able to find a way to solder to it, even if you have to dig through the plastic it will be less trouble than rewinding.

If you have to rewind, there is no "pattern", the coil is just wound around in the same direction. If you cannot re-use the same wire (because of shellac or something), be sure to count the number of turns when you are unwinding the old one.

Yes, you can use an H-pattern driver with this. In fact, it will give you TWICE as much torque! This is because you will be using both coils instead of one at a time.

4pyros said:

I can not find any reference to that on the web.
Do you have any further info?

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No, I have not seen one of these in 30 years. They used to be common - there were designs like this, and another where the coil was in the center and the permanent magnet was a ring around the outside of it.

Luckily I found the missing wire end. Unfortunately I was not able to test it and the wires are now entangled together.