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Potentiometre for 3v DC Motors? Answered

Hey Guys,

Today I Need help selecting a potentionmeter for my 3v dc batteries, The setup will be like this, There will be 4 3v dc motors in parelllel drawing about 800 mah i think with a 6v 2 amp 4 aa cell battery pack. I want it to be so that when i turn the potentiometer to the lowest the motor goes to the slowest speed (or close) and when i do it the other way it goes to the highest speed (at 6v).

Thanks in advance.
-Prickly Potato

12 Replies

user
icengBest Answer (author)2015-09-18

800ma at 6v means the motors parallel resistance is 7.5 ohms.

It makes no sense to run 3v motors on 6v. In fact it is destructively bad to do so.

Any way to slow the motor in half use a 7.5 ohm resistor to slow it by ten try 100 ohms. Now you need a 100 ohm 800ma pot.

Using Power = A * A * R = o.8 x o.8 x 100 = 64 Watt

http://www.aliexpress.com/store/product/25W-50-OHM...

This picture is of a 50 ohm 25W pot that might work.

OR http://www.aliexpress.com/store/product/High-Power...

Second pic is 100 ohm 150W pot that probably should work.

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user
steveastrouk (author)iceng2015-09-20

adding resistance like that destroys the speed regulation of the motor!

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user
iceng (author)steveastrouk2015-09-20

Agreed speed de-regulation is politically incorrect :-) ........ sUNDaY silly

That's why 555 below. Unfortunately the 555 needs 6V, so add series diodes to lower voltage to the 3v motor.

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user
iceng (author)iceng2015-09-18

BTW a 555 and a transistor doing PWM will give you the best zero to full speed that U can imagine.

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Downunder35m (author)2015-09-17

You can get replacement regulators for vibrators in good sex shops and online.
They have a wire potentiometer inside that should be able to handle the currents.

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user
rickharris (author)Downunder35m2015-09-18

I don't even want to ask how you know!

:-)

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user
Downunder35m (author)rickharris2015-09-18

Same way as the thread starter ;)
Needed a small but powerful wired potentiometer for a project.
Asked around and that was the best suggestion.
Best of all was that it came from a girl LOL

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user
rickharris (author)Downunder35m2015-09-18

Of course! I should have guessed. I imagine the "speed control" on a vibrator is pretty rough.

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user
steveastrouk (author)2015-09-17

Don't use a pot. You'll find the motors will run very badly. Ideally, you want a simple PWM controller.

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verence (author)steveastrouk2015-09-17

Woops, took somewhat long to answer and didn't see your reply.

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user
verence (author)2015-09-17

Will not work. First, the potentiometer can not handle the wasted power (unless you find some kind of wire wound device). Potis are there to adjust signal volatges not supply voltages. Second, you can not reliably control a DC motor's speed be controlling the voltage. It will go slower with reduced voltage but it will lose torque too. The it will stall. What you need is some kind of PWM (pulse width modulation). You may use a NE555 and a driver transistor and control the pulse width of the 555 with a poti. Google for "PWM control 555"

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