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help me find a rheostat

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phil68

New Member
hello, i have the following motors: Gear Head Motor - 7.2vdc 50:1 175rpm (6mm shaft) , they are going to be ran off of 5 AA batteries and i need to have a variable speed for them and i went to radio shack and they had a 25 ohm rheostat they said should work, but it only works and varies the speed for about 1/16 of a turn and it is all they have. none of the hobby stores can help me. all i need is a dial to control this, any one know of any

thanks
 

phil68

New Member
i was also told to look into a pwm and look on ebay, i dont know what these are and i was looking to spent around 10 bucks on the switch if possible
 

phoenox

New Member
go to www.digikey.com

choose a rheostat rated for at least 4 amps.

measure the resistance of the rheostat you have when it stops the motor and order one with that resistance or slightly higher.

A pwm controller (basically a switch that turns on and off very quickly) would be much more efficient but also more complex and expensive.
 

MikeMl

Well-Known Member
Most Helpful Member
How long do your AA's have to run this motor; I'm guessing you will get about 5min.
 

phil68

New Member
I was thinking i may want to run 4 D cell batteries at 6 volts do you think the run time will be much longerthat way? what is the cost of a pwm for this size application, got a link to one?
 

phoenox

New Member
MikeMl, 4 amps is the stall current of the motor. At 7.2 V no load current spec says
< 221 ma. Rated load current < 556 ma. if the motor is being slowed I would expect the current to be less than that.

I expect the AA batteries will last quite a bit longer than 5 min. More like 5 hours.
 
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