How can I make a really simple speed controller?

I have a 100w 12V 360RPM motor and a 12V battery.
I'd like to know how to make a really simple speed controller to control the speed of the motor.


Burf5 years ago
Drop by a thrift store and pick up an old, battery operated, variable speed drill. Amputate the trigger switch and graft it onto your motor.
rmayesjr1 year ago
You have to remember that 100 watts is close to 10 amps, especially if it's a battery and running down. The drill trigger assembly is great if you have a 12 volt supply powered by the grid. A better choice is a low cost PWM controller in my opinion. I saw a 10 amp 12 vdc model online for $11. Can you buy a drill that cheap?
You can buy one potentiometer and connect it to your motor.
Dannne114 years ago
I hope this works
I am not an electronic expert by any means, but I would think a pedometer (rheostat) should do the trick and would be very simple.  A pedometer would basically change the power reaching the motor by varying the resistance.  For a little motor like that... i would think that would work.
When you reduce the voltage to a motor, it will slow down, but it will also lose power and draw more current..
Your motor is a 100 Watt motor. That means that it will draw about 8 amps at 12 volts and deliver 3600 RPM. If you cut the voltage to 10 volts it will then attempt to draw 10 amps to feed its 100 watt need. The more current you draw, the more things will heat up. At some point you will reach the threshold where that heat becomes fire. This technique will burn up your motor, plain and simple.
Using PWM (Pulse Width Modulation) delivers the full voltage and varies the speed by slicing up the time that the voltage is delivered.
Let's say you want the motor to run at 3000 RPM. That's about 85% of full speed. The PWM controller will deliver full voltage (allowing the motor to deliver full power) for 85 milliseconds, then shut off for 15 milliseconds. These slices of time are practically imperceptable to us because they are so short.
golfer1 Marsh4 years ago
I have a 12 volt scooter BLADE Z XTRSE 400 motor runs but the controller will not just need to Oaky Rig a trigger
I think you mean potentiometer. That would certainly work, but potentiometers as power controllers aare not very accurate.
Oops.. yes... potentiometer.  Didn't know about the draw more current issue.
dacflyer4 years ago
look, the easiest thing i'd do is look on craigslist or flea markets, thrift stores etc, find you a old junker electric scooter, the cheap ones are a dime a dozen. i have about 4-5 in my junk box.. you would get the motor controller and the control..
a simple potentiometer is not going to work. the 100 watt motor would fry the potentiometer in a instant.
you need something that is controlled by mosfets or transistors.
the 555 circuit mentioned may work for you, but its range is limited..
good luck :o)
Use a flyball governor and a potentiometer...
Try to use an variable resister. If you can't figure it out, then make one with a pencil. It would be harder to control though.
Something like the 555 PWM controller, plus one or more switching transistors.  Possibly transistors salvaged from a scrapped car stereo amp, like the one I found in a gravel pit (with a bullet hole through the case and board).  Google for pwm speed controller.
Marsh5 years ago
This 555 PWM controller should do fine for about $7.00
Using a Micrel Mic502 is a neat way to do it. You have a fair current there, so you'll need a fatter transistor than the application note shows