I got a motor out of an electrical screwdriver. The motor runs off of a 3V battery. I also have a 12V DC/ 5V DC convertor
(4.97 to be exact). I created a thread about having a large motor that does not run off of 12V. (Because it draws 2.2 amps and my power supply only feeds 1 amp) Though the motor will run off of my convertor which supplies 3 amps. The motor I first started talking about only draws 2.8 amps and 3V but it will not run off my convertor unless I spin the axel the direction that the motor will go.
So what I am trying to say is why do I have to spin the axel of the motor get it running but the large motor runs fine even though the 12V power supply is only 1 amp which won't run the large motor on its own. NOTE: The electrical screwdriver motor is not AC!

Thanks!

 

Starting current requirements are much higher than currents required to keep running. By spinning the shaft, you are helping to get the motor started.

John

 

Possibly it is the starting current as John says.
Did the motor work when it was in the screwdriver?
If not probably the brushes are worn out. I have had quite a few brushed motors which show this effect from a small 12VDC permanent magnet motor (which is probably what your motor is) to washing machine motors (AC mains powered 'universal' motors).

 

Starting current requirements are much higher than currents required to keep running. By spinning the shaft, you are helping to get the motor started.

John

Thanks for the help! Is there any way I can bypass/start the motor another way as I am going to put a blade on it and if you try and spin the axel, it won't go to well for you.

 

The motor worked fine in the screwdriver and also it works when being powered with 9V.

 

You could try a large capacitor across the supply so the capacitor is charged up and then switch the motor across the supply/capacitor so the capacitor can supply the starting current. Try 1000uF to 10,000uF.

 

You could try a large capacitor across the supply so the capacitor is charged up and then switch the motor across the supply/capacitor so the capacitor can supply the starting current. Try 1000uF to 10,000uF.

Thanks! I probably have to do that. Is there a temporary fix because I have to order the capacitor as I don't have one on me.

 

Try the cap suggested above ... be sure to place it so the + and - polarity is correct.
Another thing to try ... see if there is any carbon or other sort of build-up on the commutator. A little work with some fine grade emery cloth might make a difference.

.. Even a spray or two of electrical contact cleaner could remove a build-up of varnish or whatever.

 

I don't think commutators and emery are good together. Perhaps clean with tissue and IPA or meths.
If the motor runs OK otherwise then the brushes/commutator are probably OK.

I have to order the capacitor as I don't have one on me.

In that case go for the higher end of the range (10,000uF) as I don't have any way to tell just how much capacitance would be needed.

 

I was told long ago ( USN 1945 ? ) not to use emery on commutators as it is conductive and could wedge in slots, sandpaper would be better.

 

Many think that because a com is black it requires cleaning which is not true, the only time you need abrasive is when you bed in new brushes and this is a done with a abrasive stick intended for the purpose while the motor is running.
http://www.electrographite.co.za/cu...n-brushes/fitting-and-bedding-carbon-brushes/
Max.

 

Sorry for the late reply forgot about the thread,
Thanks you for the help and I will definitely keep this in mind.