Need help rectifying 120vAC to 115vDC

Thread Starter


Joined May 7, 2014
Hi, new here. Name is Jordan. My friend told me this would be a great place to seek advice.
I have a 1/8 hp 115vDC Bodine NSH-54RL right angle gearmotor that I am using in a project. I need it to run off 120vAC household current and be able to control the RPM's of the motor.
So far in my research ive found that i need to use a rectifier to convert the AC to DC and a capacitor to 'smooth out the current flow/RPMs'.
I already have an AC speed controller in the form of a fan/light dimmer inline on an extension cord. (can i use this in my project or no?)

So basically i want to learn what kind/size rectifier and capacitor to use.
Would this work as my rectifier?

And how would i control the speed (if i cant use my already made dimmer controller)

Much thanks!



Joined Nov 7, 2013
Should work.

25 amp 600volt are common.

Just connect bridge between dimmer and motor.
No capacitor needed. Although a small value ac rated cap. on the ac terminals will make the bridge happy.

Thread Starter


Joined May 7, 2014
Awesome! Thanks Guys, sorry it took so long to get back to you. Thread update notification emails went into the spam folder for some reason.

Is there a certain way to wire the rectifier? It is a 4 pole device. i would assume 2 are for the AC wires and the other 2 for DC pos / neg wires. Right?

As for the capacitor, do i just wire it across the AC wires before the rectifier?

Would my crude sketch be the correct way to wire it? with the speed controller on the ac side?



Joined Oct 15, 2009
Note..Rectification/smoothing alone will probably NOT be sufficient as you won't get 120VDC.. It will be higher. (DC is approx 1.4 times rectified AC)


Joined Nov 30, 2010
Explanation: If you put a smoothing capacitor in, it will charge to the peak value of the power line, and that's about 170 volts. DC motors don't care much about smooth current, so just leave out the capacitor and you'll get a better approximation of the voltage the motor wants.