# 0-30 v Variable DC Power supply!!!!

Discussion in 'The Projects Forum' started by farhan89, Mar 28, 2010.

1. ### farhan89 Thread Starter Member

Feb 13, 2010
34
0
Hello All,
I want to make a 0-30v DC Power supply. I want separate pot for 0 to +30v and s separate pot for 0 to -30 V .

I also want high current in output approx 15-20 Amps

Is it possible ????

If yes then kindly send me the schematic for this power supply i would be very thankful to you guys

Thanks!

Bye and Take care!

2. ### dsp_redux Active Member

Apr 11, 2009
182
5
Regulated or Unregulated? Linear or Switching? Do you have anymore details? Do you know how much a transformer meeting your first requirement costs? What is your budget?

3. ### farhan89 Thread Starter Member

Feb 13, 2010
34
0
Regulated,
Linear or Switching ???
Can u define what is linear and what is switching ??

don't worry about the budget, but the transformer and the whole circuit should be installed in the 14*14 CM box

4. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
$\frac{{2x30voltsx20amps}}{{efficiency}}\quad = \quad 2KW$

is one big SOB.

Perhaps Bill Marsden will lend you his welder.

5. ### farhan89 Thread Starter Member

Feb 13, 2010
34
0
@^
Didn't got u?????

6. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
You probably won't be able to build a linear power supply in a 5.5" x 5.5" box, unless you can have the box be a couple of feet tall.

You will have a very hard time even making a switching power supply of that size.

7. ### russ_hensel Distinguished Member

Jan 11, 2009
820
47
It is a do able project, size aside. But from the thread so far I think the op, farhan89, is way over his head.

8. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
Actually there was a nice 15amp variac for sale on our E__y this week.
That would be the way to go, feeding a standard bridge/rectifier smoothing condenser farm.

A pair of these fed from a 1:1 two Kilowatt isolation transformer would suffice.

They would just about all fit into the 5 foot by 5 foot box as well.

Otherwise a pair of lorry batteries and a compound emitter follower with darlington-triple output stages would also do this job.

9. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
15-20 amps is a lot of current, you actually want twice that, each at 30V. That is going to be largish.

10. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Our OP wants it in a 14cm by 14cm box, or about 5.5" by 5.5".

That is about the size of my 250 Watt ATX form factor power supply.

Our OP wants 8x that much power output, and for it to be adjustable.

That's a mighty tall order.

11. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
I've been trying to figure out how to do something similar, dual 24V at 6A using switching regulators. Near as I can figure I'm going to have to make a box, with at least 8" X 8" X 8", and that will still be too small, what with controls, displays, AC power in and whatnot.

The regulator isn't the issue, though you need to figure a heat sink design, the problem is the base DC converters. I was planning on using two switchers that output 24V at 6.5A. These are about as small as you can get.

My power supply modules measure 1.4" X 3.7" X 6.7". I believe this is as small as I can get them. In your case, with the extra amps, it will be bigger. If you go the traditional transformer / capacitor route it will be much bigger, since both components are basically huge.

So instead of setting a size limit (which is unrealistic), start from a design and try to figure out how big a case will be to hold everything. If you go with transformers and caps it will be well over 1' square, by a large margin. If you can find some switchers for the basic DC power that will likely set the limits on your case size.

If you were to try to do something with care batteries as the source (a bad idea) it would take 6 big batteries.

12. ### farhan89 Thread Starter Member

Feb 13, 2010
34
0
Ok
Just provide me the schematic of the circuit , i will make a box by my self according the size of the Circuit.

Thanks Guys!

13. ### Audioguru New Member

Dec 20, 2007
9,411
896
But we are not a free design service for such a complicated high power project. Its transistors must be able to dissipate up to 2000W of heat unless the circuit has a complicated high power switching converter.

If you find and build a circuit or design it yourself then have a problem with how it works then we might help you fix it.

Apr 2, 2009
8,788
771
LMAOF
Good One.

15. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,788
771
OK... Do you need my paypal address.
It's going to cost you USD 500.00.

I have one working schematic

16. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
One problem that you may have is a source of mains power for such a hefty supply.

Since we do not know where you are located, we have no idea what mains supply you have.

In the States, a typical wall outlet has 120VAC 60Hz power that is limited to 15A current. That is 1.8KW, and is not enough power for a project like you are considering - even if the supply were 100% efficient, which is impossible.

17. ### farhan89 Thread Starter Member

Feb 13, 2010
34
0
@^^: I live in pakistan and we have 220VAC 50 HZ voltage

OK guys So provide me the schematic of -30-0-+30 vairaible power supply with 10Amp constant current?

So now it's easy or it would cost more?????

18. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
First, show us your access to 2 10A 28VAC transformers. I suspect they will be fairly hard to get.

That or qty 2 10A 35V switching power supplies.

19. ### farhan89 Thread Starter Member

Feb 13, 2010
34
0
What you all say on this

It's for +30 v , what additions should be made for -ve 30 volts????

20. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,788
771
Then U can use the same circuit in opposite polarity

Last edited: Mar 30, 2010