How to adjust rpm on this dc motor

[kprice1658]

Thought I'd try here to get some help for this project - since the other CNC forums are very helpful.

This is one of the types of motors that I have : http://www.surpluscenter.com/item.as...50&item=5-1676
(there is a little wiring diagram on the wiring tab on the page)

Trying to figure out what I need and specs on what to buy to be able to control this motor for adjusting rpm, forward/reverse and input voltage. I know a little electronics, but not sure how to get this done. I realize that I need a ac/dc transformer for the input, and probably a potentiometer to vary the rpms. Not sure what amps the transformer should be able to handle or the pot should be. No idea on how to forward/reverse it.

Thanks

[Al_The_Man]

My estimation you would need a 18vac secondary transformer around 100VA, one 10amp bridge rectifier, 10,000µf 40vdc capacitor, 2 SPDT toggle switch.
It does not mention the pot value but 5k ~ 10k should suffice.
Forward reverse is built in the controller CW/CCW?.
Al.

[kprice1658]

Originally Posted by Al_The_Man My estimation you would need a 18vac secondary transformer around 100VA, one 10amp bridge rectifier, 10,000µf 40vdc capacitor, 2 SPDT toggle switch. It does not mention the pot value but 5k ~ 10k should suffice. Forward reverse is built in the controller CW/CCW?. Al.

I thought it take a 120ac/24dc transformer? You say 18vac, I assuming that you're doing something with the bridge / cap ? Could you elaborate ?

Thanks for the quick reply.

[Al_The_Man]

The transformer produces 18vac RMS secondary, this number is derived from your desired 24v x .707.
The 18v will produce ~24vdc peak DC voltage after rectification and ripple removal by the capacitor.
Peak DC is RMS (root mean square value of the AC) value x 1.414.
Al.

[kprice1658]

Originally Posted by Al_The_Man The transformer produces 18vac RMS secondary, this number is derived from your desired 24v x .707. The 18v will produce ~24vdc peak DC voltage after rectification and ripple removal by the capacitor. Peak DC is RMS (root mean square value of the AC) value x 1.414. Al.

Sorry I asked - all over my head .

Seriously, I think I follow what you're saying. That'll give me clean voltage? I'll start looking for the parts you suggest. May need a diagram on how to wire everything up.

Will that transformer be relatively small? Form factor is a concern.

Thank-you.

[p38nut]

Originally Posted by kprice1658 I thought it take a 120ac/24dc transformer? You say 18vac, I assuming that you're doing something with the bridge / cap ? Could you elaborate ? Thanks for the quick reply.

There is no such thing as a 120vac/24vdc transformer. That being said, the transformer, bridge, and cap make up a 120vac/24vac POWER SUPPLY which is exactly what you need.
As being a newbie, things will get very confusing as you get deeper into this, and then all of a sudden, wham, the light goes out completely. Ask me how I know!!

[Al_The_Man]

There is lots of info on the web referring to bridge supplies e.g. http://www.kpsec.freeuk.com/powersup.htm
Also if you search here in the Electronics section, there are build details.

Hammond recommend no lower than 50va for this application, That will give you a transformer around a 2.5" cube.
Al.

[keebler303]

Originally Posted by p38nut There is no such thing as a 120vac/24vdc transformer. That being said, the transformer, bridge, and cap make up a 120vac/24vDC POWER SUPPLY which is exactly what you need. As being a newbie, things will get very confusing as you get deeper into this, and then all of a sudden, wham, the light goes out completely. Ask me how I know!!

Fixed it for ya!

Matt

[kprice1658]

Thanks guys. Great link you provided. I'll do some reading to make sure I get the drift on the process. Hopefully, that "light" will start to glow a little...

I'll run my parts by you guys before I order anything...