how to slow a motor

[turbotec]

how do I set up a knob to be able to slow down my 12V motor? I am limited to my electronic knowledge, and I am hoping to mas produce a product, so if I can buy the product made already that would be great! what I am doing is making a pitching machine, so I want to be able to slow down the motor and speed it up for the distance and speed of the ball. any help would be great!!

 

[Vleugels]

I'm thinking of just using a variable resistor (I'm new to technical english in electronics, someone please give me a name for this component ) as your knob.

I don't know what's on the market for this object, but I'm pretty sure you'll find something that will do the trick for reducing ampère.
Just dissect something from another appliance .

How much power gives your motor ?

 

[crust]

You are probably thinking of a potentiometer. Unfortunately, that is unlikely to work. Most pots cannot handle the typical currents in a motor. What you need to build is a speed control. You can use a pot to adjust the base current into a transistor. The transistor collector current is a multiple of the base current, you can use that to power the motor. Effectively, the transistor collector current is controlled by the base current. You can lookup terms such as hfe and beta to find the relationship.

 

[Nigel Goodwin]

What you need is a PWM (Pulse Width Modulation) speed controller, doing it with a plain analogue regulator will be expensive, large, and get hot (and isn't suitable for a battery powered device - it wastes too much energy).

PWM speedcontrollers are commonly used in golf trollies, you may be able to source a supply through a manufacturer of those.

 

[bmcculla]

JR Kerr makes a speed controller board that works fairly well. I think Jameco.com has them. They also make a PWM board with 10A current capability (with some added heat sinks) that would work for open loop control. JR Kerr also has an OEM volume discounts. Both of these would only work wit DC motors. If its an AC motor one of those light dimmer switches might work.

Brent

 

[stevez]

Regarding an AC motor - light dimmers may not be appropriate. A client of mine wanted speed control on some fans so light dimmers were installed. The motors did operate at a reduced speed but only for a short time before failing completely. At 12 volts it's most likely a DC motor and the advice offered so far is good.

One option that I've wondered about myself: build a simple AC to DC supply consisting of a transformer, rectifier and simple filter to deliver 12 volts DC. Now to the primary, add a "light dimmer" to reduce the power to the primary. I don't know if the dimmer can work into a transformer or what the chopped waveform will do. On the surface it seems like it might work but it's also possible that the inductive load makes it impossible.

 

[Klaus]

Simple light dimmers do not like inductive loads (not even fluorescent lights unless one uses special ballasts), however, those speed controls for power tools might work for a transformer.

With a 12 V Dc motor, rather than a variable speed how about a range of fixed speeds? Something like the controls of electric trolling motors perhaps. They are 12V, are mass produced and can handle heaps of Amps.