high power Power Supply recommendation?

[Admin]

I need to get a power supply with these bare minimum no exception specs:
45W peak
14W average
7V
3A average
6A peak
under $500
high quality, stable voltage

Sparkfun recommends/sells this (80W, 5A):
http://www.sparkfun.com/commerce/product_info.php?products_id=9291



I'm a bit concerned that it borders my peak current requirement.

Last year I bought another high powered power supply but it just wasn't good enough:
http://www.societyofrobots.com/robotforum/index.php?topic=4410.msg35615#msg35615
It wasn't able to handle peak power, only the average power, resulting in voltage drops.

[Soeren]

Hi,

Did you consider a slightly re-engineered PC-PSU (just changing one feedback resistor should work for most supplies to get the 5V line up to 7V). Even a small PSU will give you ample power.

[Admin]

Did you consider a slightly re-engineered PC-PSU (just changing one feedback resistor should work for most supplies to get the 5V line up to 7V). Even a small PSU will give you ample power.

I've been reading up and not sure what resistor to change. Ideas? I can poke around with a multimeter, but not really sure what I'm looking for . . .

Apparently some have 7V+ outputs, but I may need 6.5V later.

How stable is the output voltage?


notes to self:
http://web2.murraystate.edu/andy.batts/ps/powersupply.htm
http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

[Trumpkin]

On an IDE power connector you can use pin number one (+) and pin number four (-) as a 7v power supply. However I don't reccomend this as I've heard it can be stressful on the psu. Just an idea.....

[Soeren]

Hi,

I've been reading up and not sure what resistor to change. Ideas? I can poke around with a multimeter, but not really sure what I'm looking for . . .

Assuming you have an old(ish) supply  with a TL494, you should have a resistor from +5V out and pin 1 of the TL494 there should be another resistor from pin 1 to ground, as the feedback voltage is realized with a voltage divider (except in those cases where the 5V is compared directly to the reference). the feedback resistor could be replaced with either a larger resistor or a smaller resistor and a trimmer - if you find both resistors, it's easy to calculate the new resistor value.

Apparently some have 7V+ outputs, but I may need 6.5V later.

I don't think so, but if it's the so called "7V trick" (using the 5V as the lower ref. and 12V as the upper ref.) you have heard about, don't do it!
You will have a potentially unstable supply (since your load is not grounded), the max. current is smaller than the current on the +12V line and there's more reasons... Besides, it's impossible to predict how a given supply will handle this unconventional loading.

How stable is the output voltage?

Oh well, PSUs are different beasts, dependant on manufacturer, designer, material quality etc., but raising it from 5V to 7V by means of the feedback circuit alone shouldn't change from the unmodified PSUs stability, unless you intend to load it to the fullest (in which case the inductors/transformers would need a rewind as well).
Your load (6A/45W peak) is peanuts to even the smallest PC PSU.

If you dig into a PSU with a TL494, I'll talk you through, should you need it and with an old PC-unit, it won't cost but a resistor, a bit of solder and a little time.

[TrickyNekro]

You haven't considered building your own did you...It can't be that hard...
A big torroid, some bridges, some PWM..... can't be that hard.... :-P

But I guess you really don't have the time, then....

Look here...
http://www.action-electronics.com/bkpwr.htm


Then again, the supply what needs to power.... :-P
PSU are good but NOISY!!!!
I really don't trust em and prefer some Seal Acid batteries....

Cheers mate!

[mdmedlin]

You could try this site, maybe you can find something that will work:

http://www.coselusa.com/

[Admin]

Tricky, I'm in a situation where money is free and my time is very expensive.

Thanks mdmedlin. I browsed their site, but couldn't find anything between 5V and 12V. I sent them an email to see what they can do for me.

Soeren, if I have no luck buying anything off the shelf, I'll let you know as soon as I obtain an old PSU.

[Admin]

Coselusa just sent me this:

I would like to recommend our
PBA30F-3R3-N power supply, by connecting two units in series, the output
voltage can be set at 6.4V-7.0VDC

It had never occurred to me before that I can put two power supplies in series to double voltage . . . figured crazy ground loops would break something . . .
(3.3V*2=6.6V)

Looking it up, looks like they cost $50 each:
http://www.trcelectronics.com/Cosel/pba30f-3r3-n.shtml
although I may get a higher powered model just for extra wattage:
http://www.trcelectronics.com/Cosel/power-supply-pba.shtml

I'm thinking computer PSUs can be put in series/parallel too for extra crazy high-powered robotic fun

[ceruleanplains]

I have this one:
http://www.mpja.com/prodinfo.asp?number=15950+PS

0-30V @ 20A BENCH POWER SUPPLY 
MFG: MASTECH
P/N: HY3020E
Input: 110 VAC 60Hz
Output: 0-30VDC @ 0-20A
Specifications/Features: Constant Voltage or Current. Enclosed bench supply with LED meters for Volts & Amps. .01% Line / Load regulation (CV) .2% line/load (CC), <1mV RMS ripple. Front binding posts. CE listed.
W: 10-1/4" D:14-1/2" H: 6-1/4” WT: 15

Basically the same price you have.  The 0-10 A version is $100 less. http://www.mpja.com/prodinfo.asp?number=14604+PS

[Admin]

I have this one:
http://www.mpja.com/prodinfo.asp?number=15950+PS

0-30V @ 20A BENCH POWER SUPPLY 
MFG: MASTECH
P/N: HY3020E
Input: 110 VAC 60Hz
Output: 0-30VDC @ 0-20A
Specifications/Features: Constant Voltage or Current. Enclosed bench supply with LED meters for Volts & Amps. .01% Line / Load regulation (CV) .2% line/load (CC), <1mV RMS ripple. Front binding posts. CE listed.
W: 10-1/4" D:14-1/2" H: 6-1/4” WT: 15

Basically the same price you have.  The 0-10 A version is $100 less. http://www.mpja.com/prodinfo.asp?number=14604+PS

I'm unable to find the power rating . . . I suspect its too low for me!