24VDC Motor Drive From 120VAC

[andor]

I am looking for a micro DC motor maybe 50mm x 35mm in size. If I could find a 120VDC motor and use it with a full wave rectifier that would be great, but most of the motors I see are 24VDC (or lower).

What is the minimum circuit need to drive a 24VDC motor from 120VAC? Space is a concern and cost is always an issue.

Thanks
Christopher

 

[jbartos]

Comment: A standard branch circuit is 120V, 60Hz, 15A, with #14 AWG CU or #12 AWG AL conductors in the public/house power distribution system. However, you may use a transformer, e.g. 120Vprimary/120Vsecondary single phase with relatively small fuse on its secondary proportional to the transformer VA rating, e.g. 1 ampere to protect very small AWG wires. Also, the secondary winding may have a different voltage e.g. 24V AC that may be rectified.
Suggestion: Visit

http://www.micromo.com/

http://www.micromotor-america.com/

http://www.maxonmotor.com/

http://www.tradesea.com/genesis/ecpjs1.htm#1

http://www.asahi-net.or.jp/~rh5k-isn/LEGO/parts/motors.html

http://www.motorpump.com/mprod1.htm

http://www.osadausa.com/surg/surgical4.html

http://www.shorinternational.com/Micromotors.htm

etc. for more info

 

[andor]

Is there a way to stay away from using a transformer and having a silicon based solution?

 

[nbucska]

Since the 24V motor can't have too high current you may use a series capacitor to drop the voltage folloved by a bridge rectifier. Don't forget fuse !!!
More ? <nbucska@pcperipherals.com>

 

[jbartos]

Suggestions: There are AC to AC converters available. However, they do not provide an electrical isolation since they are galvanically connected between low voltage and high voltage. If this is no problem, not unsafe, then they may be used.

 

The capacitor + bridge is the most elegant! Use it. It's cheap too!

 

[jbartos]

Suggestion/comment to the previous posting. If the safety is not an issue, then it is fine. Otherwise, other means should be considered, e.g. a step-down transformer.

 

[don01]

andor,
jbartos is highlighting an issue when he mentions safety, please use great care direct connecting a 24vdc item to mains supply. Look at it from the future. Would you expect to find a small dc fan hooked up to the biting stuff where it is. If it's really obvious go for it. If not for heavens sake please don't.
An idea which may be a little bit bigger but may help. Try 1/2 wave rectifying with a larger cap after your drop. It may reduce the power youre trying to loose.
Regards Don

 

[jbartos]

Suggestion: The half-wave rectification produces the second harmonic that is fairly dangerous, if it becomes big.