How do I control the speed of a DC electric motor?

Question

I've build a home-made fly dryer from an electric dc toy motor. It basically works like a rotisserie to make the glues dry evenly along the whole of the fly. Here is an example. http://www.nuwavetackle.com/headspin_pro.htm

I'd like to slow the RPMs according to application, sometimes i need a slower turn to get a better coating. Is there something I can purchase that connects between the batteries and the motor that can do this? I've searched the net, but since I don't even know what I'm looking for, I've had little luck in finding anything.

Answer 1

Change the voltage supply of your motor. Increasing the voltage than the the specified rating will increase the speed of the motor. On the other hand, decreasing the voltage supply will decrease the speed either. You can also use a resistor in series with that to control the current. But it is more advisable to use the standard rating of you motor. Increasing the voltage might burn your motor. Decreasing the voltage will...well,,, waste your money for purchasing it because you didn't use the full performance of your motor. Hehe. Look for a motor suitable for your project. Good luck for that :-)

Answer 2

Use a resistor called "controller" in series with the armature.

connections are the same for a starter.

Answer 3

Using a resistor or lowering the voltage  will also reduce the power (torque) the motor can generate. THe motor will strain under the load if it is set too slow with these methods and can burn out.   Also the resistors used will be generating heat so if the esistors are not sized with enough wattage rating they will burn up.

If you want true speed control you need a Pulse Width Modulated (PWM) controller.   This type of control applies full power to the motor in brief pulses. The more pulses and the longer the pulse the faster the motor will go.   The advantage to this method is that full torque of the motor is always available no matter what speed and that excess energy in not wastes in the form of heat like when using a resistor.

If your handy with a solder iron you can get a kit for around $25 to $15.

Also consider using the same set up but using mechanical speed reduction with either gears or pulleys.   If you use two stepped pulleys you can easily change belt positions to obtain different speeds. Mechanical speed adjustment will easily provide a fixed series of speeds.

Answer 4

You could just buy one of those universal wall wart power supplies and use the adjustable voltage to control the speed. It may not provide all the steps you need.

If you don't mind building a kit, there are many small motor speed controller kits out there. All Electronics, Goldmine Electronics, etc.

Answer 5

alien steves answer about the wall mount unit is good if you are using 9 or 12V battery

if u r presently using a few 1.5 V cells ( its not so good idea because the units normally 3, 4.5, 6, 9, 12, 13V)) but a solution would be to then tap off fewer cells

if you can use steves idea think of the money u will save on batteries

Answer 6

Go to your nearest electronics outlet and ask for a resistor that enables you to controll the power

Answer 7

Call Radio Shack and ask if they have a 25-Ohm 3-Watt Rheostat catalog number 271-265 in stock. If you buy that and connect it between one terminal of the battery and one terminal of the motor, it will have a good chance of doing what you want. Use the center terminal of the three terminals on the rheostat and the terminal that is in counterclockwise direction from the center terrminal looking at the front. Turning the shaft fully clockwise should give full speed and couterclockwise from ther should slow it down. While you are at Radio Shack, buy a k**b that will fit.

If you want to run the motor from one, two, three or more batteries, you can get individual battery holders with wires on them at Radio Shack also. I don't think they have multiple position switches, so you will need to use single pole double throw (SPDT) switches. I if you use more than one switch, wire them so one feeds the next to avoid accidently shorting a battery.

25-Ohm 3-Watt Rheostat catalog number 271-265

http://www.radioshack.com/product/index....

Battery holder

http://www.radioshack.com/product/index....