Work is progressing, albeit slowly, on my new and improved (and hopefully functional) ball mill. I blew my last motor by overloading it, since it was entirely too weedy for this application. I tore out the motor from a garage door opener today and am presented with a problem:

It's got three wires: Red, white, and blue. I know my basic circuitry - The red is likely the +120 vac, and the white is probably the ground, Here's the trouble, though... What the hell is the blue wire? Spare ground? Speed control? Self destruct?

Anyone take one of these things apart before?

~Zero the Inestimable

Neutral ? Is this battery powered or mains powered ?

Mains. Well, AC powered, here in the states. 120 volts AC. So sayeth the sticker on the side of the motor...

~Zero the Inestimable

sounds like a 3 phase motor

Kill switch? Direction control? You should probably read a manual. If not for that particular model, then for another similar model.

I doubt it's a 3 phase motor because most homes (garages) don't have 3 phase mains supply. Also, I think 3 phase motors have 6 connections.

I think it could be an earth, would make sense since the motor casing and the mechanism it's attached to is likely to be metal.

It may very well be an earth. I wanted to figure it out before I plug the thing in and blow a fuse, though...

The manual is of no help, of course. It details mounting the motor, chain, and track, but mentions nothing of the internal schematics. Typical, really, because the end user isn't supposed to take the thing apart.

Well, I guess there's one way to find out. Tomorrow I solder a plug on it and stick the bugger in a socket. We'll see who was right then, eh?

~Zero the Inestimable

If you can open it up you should be able to easily identify if one wire is an earth. Polarity between the other two connections *shouldn't* make anything at all bad happen, besides the motor possibly spinning in a different direction.

If one is an earth and you happen to connect it to live, just don't touch the casing :)

Or let the casing touch the other negative wire. Can you say "short circuit?"

~Zero the Inestimable

Blue is most likely your ground, although green is usually used, you don't have a green. So I'd have to go with the blue as a ground. The other red and white shouldn't matter which side they're connected to because it's AC, not DC current.
I reccomend you ask an electrician or even just go to a hardware store and ask one of the salesmen. They should be able to confirm this. I'm just going on what I remember my dad telling me.
You could also take a receptical out of a wall, or take the plug off of an extension cord to figure out what goes where. The little round hole in the bottom (or top, depends which way your plugs were mounted) is the ground. Don't believe me? Stick a clothes hangar in there, you won't feel a thing.

Your best bet would be to check with the manufacturer, the manual, or the place where you bought it. Because although the NEC (national electrical code) is usually quite clear cut, many companies tend to have their own colors for the unstated reason that you will be more apt to buy their brand of accessories because everything they make will have the same colors, while connecting to another brand would require you to open up a translating manual and do something that not many electricians like to do... read.

Anyways my guess would be that red is hot, white is ground, and blue is what is often known as an accessory connection (if you work with AC switches you will often see three connections on the bottom labeled power, ground, and accessory). Using the accessory connection just allows you to run something small off of the same power supply.. mainly for your convience so you don't have to run another connection if you wanted to hook something like a lightbulb near it. Or it could simply just be a three way connection used so that when power is not running through one connection, it will be sent through the other.

<small>[ May 14, 2002, 11:22 PM: Message edited by: NoltaiR ]</small>

And the correct answer is...

D. All of the above.

D'oh.

It seems that no matter how I connect my AC power supply the motor fires up. Well, tries to fire up. It apparently can't start itself, but if I give it a little twist it takes off. Once it gets wound up it seems to have enough torque, though.

Next up: Bike parts.

~Zero the Inestimable

Anthony is probably right. It'll be an Earth. To confirm it, use a multimeter and see which of the three wires is connected to the metal casing of the motor.

Edit: you beat me to it. Careful, you don't want to connect the motor's earth lead to the mains active.

<small>[ May 15, 2002, 09:25 AM: Message edited by: mrloud ]</small>

If it won't self start, maybe it was intended to be used with a starting capacitor?

You may find that the blue wire is "common" and the other wires spin the motor in one direction or the other depending on which is hooked up to the mains.

Yes. That idea hit me at about three in the morning a few days back. I remembered that the fan on the range hood in the kitchen has the same setup - And I remembered that it's reversible.

Regardless, I have it more or less working now.

~Zero the Inestimable