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Old 10-08-2020, 05:27 AM   #1
EasyGoing1
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Default Can a DC motor start then just ... stop?

I have a DC motor and when I apply voltage to it, it starts to spin for about a good full second, then it just ... stops ...

How is this possible?
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Old 10-08-2020, 06:35 AM   #2
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Default Re: Can a DC motor start then just ... stop?

maybe the winding has a break that opens when it heats up.
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Old 10-08-2020, 07:14 AM   #3
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Default Re: Can a DC motor start then just ... stop?

does it have brushes ?
are the bearings free ?
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Old 10-08-2020, 11:14 AM   #4
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Default Re: Can a DC motor start then just ... stop?

Quote:
Originally Posted by stj View Post
maybe the winding has a break that opens when it heats up.
Quote:
Originally Posted by petehall347 View Post
does it have brushes ?
are the bearings free ?
So I put it on a Buck converter and started it out at 1 volt... it ran continuously ... but when I bring it to about 2.5V, it stops. But under 2.5, it runs. It's rated for 12 volts.

Thoughts?
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Old 10-08-2020, 11:47 AM   #5
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Default Re: Can a DC motor start then just ... stop?

Does it work at 12V?
If not, stj had the most likely reason.

If it works at 12V (and 8V)...then we're probably dealing with the behavior of the buck PSU that's turning the motor.
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Old 10-08-2020, 02:23 PM   #6
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Default Re: Can a DC motor start then just ... stop?

12V DC motor runs at 1V?
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Old 10-08-2020, 04:23 PM   #7
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Default Re: Can a DC motor start then just ... stop?

Does the motor have a speed control terminal? How about a picture?
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Old 10-16-2020, 11:36 AM   #8
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Default Re: Can a DC motor start then just ... stop?

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Does the motor have a speed control terminal? How about a picture?
It was just a 2 post standard 12 Volt motor. I bought a replacement for it cause it was only $7.

I was just wondering what might cause the problem I was having.
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Old 10-16-2020, 01:15 PM   #9
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Default Re: Can a DC motor start then just ... stop?

try spraying it with freezer after it stops - ir just keep it powered and see if it start again after a while
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Old 10-19-2020, 07:55 AM   #10
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Default Re: Can a DC motor start then just ... stop?

Quote:
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try spraying it with freezer after it stops - ir just keep it powered and see if it start again after a while
"Freezer"?
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Old 10-19-2020, 02:58 PM   #11
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Default Re: Can a DC motor start then just ... stop?

coolant spray
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Old 10-19-2020, 06:16 PM   #12
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Default Re: Can a DC motor start then just ... stop?

Why don't you show us the motor we are dealing with?
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Old 10-26-2020, 09:35 PM   #13
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Default Re: Can a DC motor start then just ... stop?

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Why don't you show us the motor we are dealing with?
It was this exact motor.
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Old 10-27-2020, 02:45 AM   #14
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Default Re: Can a DC motor start then just ... stop?

And that's a 6-9V motor?
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Old 10-27-2020, 07:05 PM   #15
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Default Re: Can a DC motor start then just ... stop?

Quote:
Originally Posted by EasyGoing1 View Post
That looks like a standard "280" size motor, more or less, but with sealed metal back instead of usual plastic cap. Of course, this being from Amazon, there's very little technical information, let alone a proper product datasheet. (I love how they give a vague RPM and rated voltage range. What about stall current? Stall torque? Maximum efficiency at ___ RPM?? A datasheet could answer all of that. On that note, I really don't understand why people buy so much junk from Amazon. It's the worst place when it comes to product info. Even the most terribly translated eBay listings I've seen usually provide better product specs. And Amazon prices are usually pretty ripoff too. $7 for that motor? Hope you at least got one with carbon brushes. But truthfully, I really wish Amazon would stop selling electrical components. /rant.)

Anyways, is the motor about 30 mm long and 22-23 mm in diameter?
If so, that probably is a 280 size motor. If that's the case, I suspect it may be stopping due to worn/bad sleeve bearing(s). Was this motor brand new when you got it or was it used for a while? Being motor with vibration cam makes it even more susceptible to bearing wear.

When I was a kid, I had at least a dozen of toy RC cars end up with seized drive motors like that after many years of use. The way to fix a motor like that is to disassemble it and clean/resurface the sleeve bearings - something probably not worth doing on a cheap/small motor like that, especially if it has a metal back cover (harder to remove.) But it is doable and similar to fixing sleeve bearing computer fans.

Of course, before you conclude anything, how about first try connecting the motor to a known good DC power source to see if it stops or not. I suggest using a standard 5V power adapter or something similar. If it doesn't stop, then whatever circuit you had this in may not be functioning or driving the motor correctly. Otherwise, it's likely worn/bad bearing, as I mentioned above.
* OR *
If the motor stops randomly after running for a while, it is also possible that it may have bad/misaligned/worn brushes. It's rare, but it can happen sometimes on these small cheap motors.

Last edited by momaka; 10-27-2020 at 07:13 PM..
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