How to Test a Brushed Motor?

[katou]

Hey, I need a hand. I just found a brushed motor that I may be able to use. It's got a controller, but it doesn't work as a system right now.

So, I'm trying to figure out which bit is the problem. I'd like to test just the motor, and then the controller.

I have a 12v power supply, and a DMM.

Can I just hook the DC power supply up to the motor? Last time I thought I could do something like that, it turns out the load was a dead short and I blew the fuse, which was a pain to replace.

I figure that if I just give the motor (90vdc nameplate rating) 12v dc, it should turn unless it's toast. Am I on the right track?

Katou

PS electronics gurus, I'm about to be given an oscilloscope, any suggestions on starting to learn how to use it?

 

[SamTexas]

My stand-up scooter has a brushed motor (just two power wires). Connecting the motor to the battery would run the motor. It's a 36V motor and it works fine with 36 and 48V, no controller needed. I have never tried it with 12 or 24V.

 

[liveforphysics]

Hook up the motor. Then turn the supply on.

However, if the 12v supply can't pull at least 10amps, don't bother and just touch the leads to a battery.

 

[amberwolf]

Can I just hook the DC power supply up to the motor? Last time I thought I could do something like that, it turns out the load was a dead short and I blew the fuse, which was a pain to replace.

I'd use either a current limited power supply (so that if it *is* a dead short you won't have to worry about the fuse blowing), or a battery, as LFP suggests, but yeah, that's all you need to do.

If it doesn't spin something is wrong in the motor--wire connection, brushes, or windings. Windings you'd probably smell already unless it's sealed.

PS electronics gurus, I'm about to be given an oscilloscope, any suggestions on starting to learn how to use it?

What brand/model? Many of the old ones I've used like Tektronix, B&K, etc. have good manuals that could teach you some of the basics.

There's also a few websites around that teach basics, but it's pretty easy to do most things with one, even though at first all the knobs on the front are intimidating.

I was going to give you a link, but google still hasn't fixed their search, so most of the time if I search for a quoted phrase, I end up with lots of sites containing a word or two, or even all of them, but nothing with the actual phrase itself. I'm too lazy/tired to sort thru all of the garbage it gives me for the stuff I actually want.

 

[Solcar]

PS electronics gurus, I'm about to be given an oscilloscope, any suggestions on starting to learn how to use it?

To add to the prior good advice, you might obtain an old battery-operated AM transistor radio and after opening up the case, connect the ground clip to the negative battery circuit. Then turn it on and after turning up the volume knob to get sound, probe different points inside to observe the waveforms.

I just found a brushed motor that I may be able to use.

I like that idea. I prefer keeping things on the simple side, given a choice between two comparable options. Though good quality brushed motors are generally more difficult to manufacture, their not requiring control electronics in order to run is something that I love about them.

I bought some of the surplus Currie motors that used to float around the DIY market, and I became disappointed with the idea of using one on my ebike when it failed to turn during testing on the bench. With brushed, if it has DC, it turns.

 

[TylerDurden]

How big is the motor?

If motor has no permanent magnets, it could be series-wound... apply low voltage and be ready to disconnect if it tries to overspeed (they need a mechanical load).

 

[katou]

Thanks for all the good support! I know that the PS isn't amp limited, (that's how I blew it last time) so I'm just going to pull the battery out of my car and use that.

That transistor radio idea is a pretty neat idea too. I'll keep my eyes open, but I'm not expecting to find one too soon.

I'll let you know what I find out.

Katou