# AC and DC power supply

## Main Question or Discussion Point

Hello people!

I've been absent from this forum for quite a while. But now I return with questions regarding a little project I have to do.

So basically I have to make a AC and DC power supply. I need 24 V AC output and 0-30 V DC power supply.

I have a transformer(I think its 220V/24V) which i plan on using to build such power supply

I have some circuits in mind, but I have no clue how to use 24V AC safely from transformer. So basically I would have to combine 2 different designs for DC and AC. I found some projects for 0-30 V variable but they don't cover AC supply.

Can anybody give me some references or schematics or pointers on how I can make such power supply?

Thanks

## Answers and Replies

Related Electrical Engineering News on Phys.org
Integral
Staff Emeritus
Science Advisor
Gold Member
Just fuse the 24VAC. Get the fuse rating from the transformer specs.

You will have to jump through some hoops to get 30VDC from a 24VAC signal. It will not be as easy as just using a rectifier and regulators.

Well i figure if 24V AC is a effective value and the amplitude of the sine wave I am rectifying is $24\cdot \sqrt{2}$ then that comes to about 33.94 V sine wave amplitude. If i rectify that I should get enough voltage for DC.

So a fuse will do a trick? Ok, im gone shoppin!

jim hardy
Science Advisor
Gold Member
2019 Award
Dearly Missed
You'll notice poor regulation at high DC output

but you should be able to get your 30 volts at not much current, maybe even 32 or 33
because the transformer is rated 24 volts at substantial current, probably makes 25 or 26 at zero current

reason regulation is bad is this:
With capacitor filter the current is delivered in big gulps near sinewave peak, so voltage drop along transformer's resistance is more than you'd expect. So peaks get 'flattened' as current goes up.

We learn best by doing and figuring out the complications that arise along the way ...

Experiment with a choke(inductive) input filter if you can - regulation will be better but voltage a bit lower...

old jim