Capacitor connected to a motor??

[wizardofza]

I don't know much about circuitry but I'm interested in hooking up my barely crusher to a motor instead of using my drill and I came across this : http://www.brewheads.com/mill.php.

I'm confused as to exactly what the purpose of the capacitor is?

I haven't done much circuitry building, but is it there to ease the strain on the motor when the switch is hit to go from one direction to the other? I know basically what a capacitor is, but just not why it's used in this setup.

Also, would it be possible to throw a dimmer switch in there to adjust the speed of the motor, or is there a better way to go about that?

Thanks for any info guys. Sorry if what I'm asking doesn't make much sense.

 

[mrkristofo]

The capacitor has two purposes. First, it provides the necessary "jolt" to start the motor. Second, a smaller capacitor inside the run capacitor is is used to stabilize the movement of the motor as the phase flips with the AC current. As far as speed regulation goes, I'd use a voltage regulator (variable resistor) over a dimmer switch. Most dimmer switched augment the frequency of the AC current vs dropping the voltage.

Someone with more physics/EE background feel free to correct me, but that's how I understand that it works.

 

[wizardofza]

Ok, that makes sense. I guessI was just wondering because I've seen setups with mills connected to motors in the past that didn't have a capacitor connected - at least not visibly.

Thanks for the post, much appreciated.

 

[CodeRage]

The cap helps limit the amount of current the motor draws under heavy load. ie startup.

I would recomend a light dimmer for speed control, they will not handle the current that motor requires . They also arent designed for variable load. Harbor freight has a router speed controller
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060
You are better off using that and it is around the same price.

 

[wizardofza]

The cap helps limit the amount of current the motor draws under heavy load. ie startup.

I would recomend a light dimmer for speed control, they will not handle the current that motor requires . They also arent designed for variable load. Harbor freight has a router speed controller
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060
You are better off using that and it is around the same price.

Awesome idea. I know exactly what you're talking about too. I'll check it out.

Thanks!