Building a Power Supply

[xairflyer]

I want to build a 24v 10A Power supply for my hobbycnc board, I was wondering what level of smoothing would be required. i.e could I just use a bridge rectifier and large smoothing cap or would I need to clean it up further.

[MrBean]

That's all I used. I don't know if you need to do any more than that. But mines working fine.

Regards Terry.....

[HobbyCNC]

Originally Posted by xairflyer I want to build a 24v 10A Power supply for my hobbycnc board, I was wondering what level of smoothing would be required. i.e could I just use a bridge rectifier and large smoothing cap or would I need to clean it up further.

Use @2,000uF per amp on the cap..50VDC rated minimum. usually 15-25,000uF is fine

Dave Rigotti

[stevec]

Hello,

I just purchased the hobbycnc 3 axis package with the 80oz steppers. I am rounding up last minute parts and need a transformer for the kit. Hobbycnc recommends a 30vac - 10amp one that cost $59.99!

Is there a common place I could salvage one from to save the cash. I have a couple of old c-band (big dish) positioners that have larger transformers in them to run the motor at 24 volts for positioning of the dish but don't know the amps or how to find out (no markings on them). Could I use them somehow? How critical is the voltage/amps and what happens if I use one that to big or to small and could I use two smaller ones to make one (say two 24volt 5 amps each)?

Could I use a transformer from a computer power supply just to get started. I also have a couple of these.
Any advise here would be great, I don't want to cheapen the build just make it less costly.

Sorry for all the questions, I could really use some easy to understand help.

Steve

[Al_The_Man]

That is only 300va that you need, so it would not have to be a very large one, I assume the transformers you have are square laminated type? If so the VA can be approximated from the size of the laminated core, if you post that I may be able to give you and idea what the VA is of the ones you have.
Al

[stevec]

Hi Al,

Thanks for taking the time to help me out.

Below are photos of two different units, 3 views each. I checked unit #1 with a volt meter and got 39.5 volts using the green and red wires and 26.3 volts using the red w/yellow strip and green wire.

I haven't checked unit number #2 for voltage yet, as the wires are not as easy to get to but will check it out if you want. These two units do the same thing which is to power an actuator that moves a satellite dish (big c-band) .The motor of the actuator on the dish was a 36 volt motor.I said 24 volt motor in my first post and that was wrong.

Steve

[Al_The_Man]

You did not include the dimensions of the laminations but they look at least like 1kva
Al

[stevec]

Ok, great....... I think.
Does this mean one will work?

Steve

[Al_The_Man]

I would guess that those have more than enough rating based on your first post values.
Al

[Al_The_Man]

I plugged in the numbers based on a 24vac transformer with load of 10amps, for a ripple of 2.5% the capacitor should be 36,000µfd. VA would be 430va at max current, or 288va with 50% duty cycle (Current).
Al