How to use lab power supply

[gnd]

Hi.
I have lab PS, which has 3 terminals - (+), (-) and ground. It is adjustable from 0V to 35V, at 5A. Positive and negative rails are floating, and any of them can be connected to ground.

I would like the ground to be at middle point, and get symetrical PS for powering audio op-amps. How shall I connect it to get out of it +/- equal value balanced voltage?

thnx
gnd

 

[CJ]

Is it an earth ground?
Green banana jack cover?
If so, you can not do it.

If they say either rail can be.... then you probably have a single supply with an option for earth ground.

You can either buy or make a dual supply, (see Meta) or re design for a "fake" plus and minus, (the ol 10 K or 100K twin resistor voltage splitter to pin 2 or 3)

Sorry if I spoiled your Friday afternoon.

 

[gnd]

yes. green gnd jack....
It is single supply with ground option.

I know I can buy or make dual, :grin: Thats why I bought this one, I thought it is dual... :? (+), gnd,(-). Great, I thought, just what i need. Well....

Redesign, fake.... Yes, there is hope! Splitter to pin 2 or 3? Which pins do you mean? PS jacks?

I tried faking dual with resistors, and it seems it works fine without load. I just connected same value resistors from ground to both rails, and it came out dual equal value. Is this the proper way to make voltage splitter? But what will happen with load? If I put resistors from (+) and (-) to (gnd), will voltage drift with load? How is it usually with opams, are both rails loaded symetrically, same current through positive and negative?

...

 

[gnd]

BTW, would some circuits like these help?

http://www.headwize.com/projects/opamp_prj.htm , figure 20 and 21, way down at bottom of document.

 

[Guest]

You need one more.

 

[Samuel Groner]

BTW, would some circuits like these help?

Figure 21 would basically work but it's limited with respect to tolerable ground currents. See www.groupdiy.com/index.php?topic=20868 for a better solution.

Nonetheless I'd suggest (in agreement with the previous post) that you get a second unit (or even better a bipolar supply) to make a proper ground. "Hacked" grounds as the above solutions can lead to awkward problems such as intractable oscillations.

Samuel

 

[SonsOfThunder]

Funny that you made the same mistake...

One of the other engineers at work wanted a bipolar supply for prototyping smaller ckts at the bench. We both looked at the description for a new supply at circuitspecialists.com and I ordered the one he wanted for $120, I think. We got it, pulled it out of the box and both said, "Doh!" as we realized our silly mistake as it could be +30V OR -30V...ooops.

I looked online at one of the test equipment places in the bargain bin and found a used, no warranty HP6228B +/-50V@1A dual supply for $95. So we bought that one and returned the first one! They had another one for the same price with slightly different specs. PM me if you are interested and I'll dig up a link.

HTH!
Charlie

 

[gnd]

PM me if you are interested and I'll dig up a link.

Thnx, but it is ok. I will use this one, it will come handy arround the house too.

gnd