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Originally Posted by Jacob Morgan
ooo I see, I always thought the potentiometer was always just essentially a dimmer switch like you use in your house for lights, that it would go in between the motor and the battery and by turning it you would increase the motor speed, vice versa..
Guess not :-p..
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A pot will act just like a resistor if you put in line with the motor. The more resistence it is set for, the more voltage it will convert to heat and the less voltage your motor will see. The less voltage to the motor, the slower it will turn. You can prove it to your self with a small motor, pot and battery.
This means that a pot will act as a very crude speed control. The problems are big though. One, unlike PWM, the motor is not running at its normal voltage- it will turn slower but with far less power, just as if your battery were dying. Secondly, all that power your dropping across the pot is becoming heat. If your pot is not designed to dissapate enough power, it will burn up. Thirdly, you may not be able to find a pot that has the range and correct number of turns.
Rember that when the pot/speed controller has the motor 'stopped', it will be making its self into a neat little space heater. This is a sure way to let out magic smoke.
All in all, pots make poor speed controllers.
-Andy A.