# DC Power Supply Help needed, Not Rocketry related.

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##### Well-Known Member
I need to get back to processing brass for reloading. I have these DC gear motors. I need to build a power supply, I am doing an LC choke filter from 230 VAC. The motors only need 180V DC to run. I want to make the power supply variable voltage and I know that can be done with a transistor and a potentiometer, but I must have killed the brain cells that previously held that memory.

I have a bridge rectifier good for 25 amps, and some caps good up to 250V (300V surge) I should be able to get the transistor for free and I have pots.

What I need to know is the remainder of the circuit. And if it is easy set up the bias to limit the output to 180V max.

Rb is just a bleeder resistor so I don't kill myself with a charged cap.

TIA!

#### jderimig

I need to get back to processing brass for reloading. I have these DC gear motors. I need to build a power supply, I am doing an LC choke filter from 230 VAC. The motors only need 180V DC to run. I want to make the power supply variable voltage and I know that can be done with a transistor and a potentiometer, but I must have killed the brain cells that previously held that memory.

I have a bridge rectifier good for 25 amps, and some caps good up to 250V (300V surge) I should be able to get the transistor for free and I have pots.

What I need to know is the remainder of the circuit. And if it is easy set up the bias to limit the output to 180V max.

Rb is just a bleeder resistor so I don't kill myself with a charged cap.

TIA!
Your caps need to be rated for at least 325v if you are rectifying a 230AC source.

In any event, high voltage DC motors are typically driven using a switching (PWM) DC source not a linear DC output. Not cheap or easy for DIY unless you know how to PWM mosfets with microcontrollers.

I have heard of people going cheap with a light dimmer circuit on the input but I suspect that will not be reliable.

Your best bet is to find a used KB or equivalent motor controller. You may find one on ebay once in a while for about $100. Google is your friend. Edit: Here's one new for$89 https://www.kb-controls.com/product...5408E50.qscstrfrnt05?productId=9&categoryId=3

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#### sandman

##### Well-Known Member
Your caps need to be rated for at least 325v if you are rectifying a 230AC source.

In any event, high voltage DC motors are typically driven using a switching (PWM) DC source not a linear DC output. Not cheap or easy for DIY unless you know how to PWM mosfets with microcontrollers.

I have heard of people going cheap with a light dimmer circuit on the input but I suspect that will not be reliable.

Your best bet is to find a used KB or equivalent motor controller. You may find one on ebay once in a while for about $100. Google is your friend. Edit: Here's one new for$89 https://www.kb-controls.com/product...5408E50.qscstrfrnt05?productId=9&categoryId=3
I have several very large autotransformer lighting dimmer (circa 1960' era) in 20, 30 and 60 amp. That would eliminate the potentiameter control. These are mechanical units with a moving brish and designed to be encased in an enclosure.

The problem is getting them to you. They are heavy as all get out!

About 40 lbs for a 20 or 30 amp and about 65 lbs for a 60 amp.

They are all single phase so that may pose a problem.

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##### Well-Known Member
I have several very large autotransformer lighting dimmer (circa 1960' era) in 20, 30 and 60 amp. That would eliminate the potentiameter control. These are mechanical units with a moving brish and designed to be encased in an enclosure.
SWEET!!!

The problem is getting them to you. They are heavy as all get out!
Not so much a problem I am in Detroit area almost every month. Send me a PM on what city you are in if you do not mind and how much you want for one of the 20 amp models.

They are all single phase so that may pose a problem.
Single phase is no problem my shop has 400 amp 230 volt single phase service.

PM sent.