Motor speed controller question.

[BenFett]

Hey guys, so for a project I'm working on I need a speed controller for a single motor. I bought a PWM that I thought would work, but it's too high of voltage and doesn't affect the circuit. My project will be running at ~6V DC off of two batteries. So I'm looking for a way to have some sort of dial to change how fast the motor is turning. Anyone have any clue what would work for this?

 

[KMoffett]

Do you have a link to the PWM controller you purchased?

Ken

 

[BenFett]

http://m.ebay.com/itm?itemId=400569517437

This is the one I purchased. I was recommended this by someone when I was first discussing this idea, and stupid me I didn't read the description... Haha. It requires 12-24 Volts.

 

[BenFett]

I just found some batteries with high enough voltage to get this PWM to work, and it works fine with those, but I need a lot less power for this, since it's only running a single motor, and I'll fry the poor little thing with the 12 volts.

 

[KrisBlueNZ]

You can use a 555 to produce a control signal with adjustable duty cycle, and feed this into a transistor or MOSFET. There are many versions of this idea out there:

http://www.pcbheaven.com/circuitpages/PWM_Fan_controller_using_a_555/
http://www.talkingelectronics.com/projects/50 - 555 Circuits/50 - 555 Circuits.html#9
http://www.backyardaquaponics.com/forum/viewtopic.php?f=50&t=10775&start=45
http://www.circuitdiagram.org/dc-motor-control-pwm-555.html
http://www.apdigitallight.com/2010/08/diy-laser-spirograph-part-2.html

If your circuit is running from 6V and you use a MOSFET as the switching device you should make sure it's a "logic-level gate" or "Low V_GS" MOSFET. An excellent choice is the NTD4906 from ON Semiconductor which is available from Digi-Key: http://www.digikey.com/product-detail/en/NTD4906N-35G/NTD4906N-35GOS-ND/2194521