Home-brewed 24V PSU diagram.

[dimmreaper]

Ok all my Ham friends. My Dad gave me a transformer that pushes 30V @ 16A. So I'm gonna build a PSU around it. I basically using a bunch of voltage regulators to get the job done. And at $.75 a piece, this will cost me next to nothing to build (because I have the transformer already).

Let me know what you guys think. I'm sure their are other voltage regulating circuits for high amperage, but radio shack stocks the ones I'll be using, so I'll just use a bunch of 'em.

 

[Metaxas]

Uhhhh Jeff, that's scary looking. ;D

 

[mark]

u'll have to post if it works.
I wanna know

 

[dimmreaper]

Special thanks to Hoot for pointing out my negleting to add load balancing resistors in my project. I have edited the diagram and re-posted it above.

 

[Metaxas]

I still say it looks scary...make a video tape so that when you plug that puppy in, I wanna see what happens... ;D

P.S. - You know i'm just funnin with ya right... It would cost all of what, may 25 bucks to make that, compared to 150+ for an actual off the shelf 24Volt P/S?

 

[dimmreaper]

Metaxas (Mar 08, 2001 11:39 p.m.):
I still say it looks scary...make a video tape so that when you plug that puppy in, I wanna see what happens... ;D

P.S. - You know i'm just funnin with ya right... It would cost all of what, may 25 bucks to make that, compared to 150+ for an actual off the shelf 24Volt P/S?

Yeah I know your funnin with me.

Not going to get around to building it till I need it. Won't need it till I get my Morgan this summer. But if you want me to tak pictures I will

I might build a smaller, cheaper, 14V 8A PSU for my 72W pelier, with an additional 10V 2A circuit for all my case fans. I'll build this one this month hopefully.

Yeah, it'll be real cheap around $25-30. AFAIK nobody makes an off the shelf model that can hold a candle to this. This thing will be able to handle continuous load of 24V @ 0-14A, that comes to 336W. Although the peltier it will power only draws 24V 11.3A. It'll be super clean and super accurate voltage as well. This is really a special purpose PSU, thats why I couldn't find an off the shelf model anywere. So I decided to build my own.

 

[schmidty]

Hey Jeff,

Where are you finding that rather nice sounding 271W 24v pelt at?

All this talk of powersupply building, and I'm getting an itch ;-) (that is, to build some powersupplies)

And - not that you don't know this, but you'll probably need to get quite a heat sink for all those IC's.

cheers!

 

[HAL6000]

You would be better off only using one 7824 and getting a 2n3055 transistor, TO-3 case is good, to push the current. You would also want a diode to compensate for the voltage drop of the transistor. Feeding the 12v regulator from the regulated 24v will produce a little less heat across it as well. Your 30V AC is going to tunr into 42V DC. That means your going to drop 18V across the regulator. For every 1A of current you pull your going to have to deal with 18W of heat. Your 16A power supply is going to need to disapate 288 watts of heat.

 

[HAL6000]

I thought I'd share this with you guys. This a a variable 40Vdc power supply I made from a 240v to 120v step down transformer. It has to coils on both sides so I placed the input in series and out put in parallel. Giving 30v on the output. It's only rated at 500va. So that's about the same as your transformer. I've also used this regualtor on my 1000va 48 transformer. I do need 2 output transistors to run it full power tho.

 

[dimmreaper]

HAL6000 (Mar 09, 2001 11:13 p.m.):
You would be better off only using one 7824 and getting a 2n3055 transistor, TO-3 case is good, to push the current. You would also want a diode to compensate for the voltage drop of the transistor. Feeding the 12v regulator from the regulated 24v will produce a little less heat across it as well. Your 30V AC is going to tunr into 42V DC. That means your going to drop 18V across the regulator. For every 1A of current you pull your going to have to deal with 18W of heat. Your 16A power supply is going to need to disapate 288 watts of heat.

Funny, I got in this discussion with my Dad earlier today And Hoot also mentioned some of this in an E-mail earlier as well. Another interesting thing to note is that the transformer I'm using is a 440 to 110 step-down transformer, but we tested it and found it pushes 30V under a 16A load with 110V on the primary coil. Whats the deal with putting the diod on the 7824's ground?

My design was a work in progress, that's why I posted it.

Thanks for everyone's input, being an electronics newbie I really appreciate.

 

[HAL6000]

The diode it to compensate for the voltage drop your going to get throught the transistor junction. If you place a diode on the ground og a voltage regulator like that it will cause another .7v from its output.

 

[dimmreaper]

HAL6000 (Mar 10, 2001 05:31 p.m.):
The diode it to compensate for the voltage drop your going to get throught the transistor junction. If you place a diode on the ground og a voltage regulator like that it will cause another .7v from its output.

The output voltage for this project is not *that* critical, as I'm powering a peltier not ICs.

But out-of curiosity, couldn't I just put a variable resistor on the 7824's ground and "fine-tune" it with a multimeter?

 

[HAL6000]

You could use a pot or resistor o nthe ground pin. Giving the peltier max power will deliver max cooling however. A diode is a simple fixed way of bumping up the voltage. I like making power supplies that can deliver lots of power with as few parts and work as I can. I have a 250A 20v power supply I built for a battery charger for my car. I can also start my car off it if I need to.

 

[Metaxas]

So how much would one of you geniuses charge me for builiding a killer P/S?

 

[Hoot]

What voltage? At what current? In what kind of housing? How soon?

Hoot

 

[Metaxas]

12Volt, 400+ watts, I want it in an AT compaitible enclosure, but I want power conditioning built in. With 2 high output fans. And a master switch too.

 

[Hoot]

You can't fit a linear supply capable of 33A at 12V in that area, so you are now looking at a switching supply. I don't do switchers. Too much "blue smoke and mirrors" for my blood. Good Luck finding one that meets your form factor.

Hoot

 

[Metaxas]

Oh heehee, ok, well, thanks anyways.