Hi everyone,

Just a quicky that for once requires a simple yes or no answer!

I have an RS bench PSU that has 2 terminals that give a fixed 5v and 0v, and 3 terminals that provide a variable 0 to 15v+ a 0v and a 0 to 15v-.

I have used it for years and just come upon a circuit that would be easier to build if I could common both 0v connections on the breadboard, would this do any harm?

Thanks for looking.................Al

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No.

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Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

I'll go ahead and screw up a simple thread... why not??

[EDIT] Ok... I thought you were telling him that it wasn't a good idea to do it. Then I read the reply again. My bad.

 

Many thanks Eric, just wanted to be sure, so I didn't make that smoke the wife hates again! hehehehe

Regards............Al

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If you really want to double check, bung a 100ma fuse between both 0v lines on the power supply and run it like that for a while - if the fuse blows then you know you probably can't.

Other thing to do would be to measure the continuity between both 0v posts and if its less than 1/2 ohm or so you should be fine.

Gut feeling would be you should be able to do it without any problems.

 

Other thing to do would be to measure the continuity between both 0v posts and if its less than 1/2 ohm or so you should be fine.

Gut feeling would be you should be able to do it without any problems.[/quote]


Just tried the meter across both 0v terminals and there seems to be no direct connection at all even on the M ohm scale!

..........Al

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I would have assumed that the ground for the +5 was connected to the chassis (and earth ground if there's a grounded cord) and that the variable supply's common floated and that it was an option to connect the common to the chassis. Didn't the unit come with an instruction book and schematic? If not, can't you get one?

Dean

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Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

 

Turn the power supply ON, set the +- variable to say 10V, and use your voltmeter to measure the voltage between the two 0V terminals. Do this on both the AC and DC ranges of the meter. If you measure next to nothing, it it safe to connect them together.

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hi Henry,
It it makes you feel any better, I also misread it.!
Had to quickly edit it from Yes to No.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Hi Al,
You said you wanted a 'Yes or No' answer... you didnt ask how to check it out.

In my experience where a bench top PSU has a separate 0V for the different voltage outputs,
they are usually isolated from each other.. [the 0V's that is]

And unless marked with a 'chassis' connection symbol, the 0V's are also ground free.
Its very easy to check this out using a DMM.

Dont forget to add a medium sized electrolytic, say 220uF and a 0.1uF at the connection point on your breadboard,
for each psu supply wire.

The type of smoke you want to avoid is the smoke with the 'dark brown smell'

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Hi guys,

You were all right about the PSU being OK to common up.

Just tried it and it seems fine!

BTW I measured from all the posts and the only ones that had a PD between them were the ones that were supposed to, as Eric said.

Thanks for the input, yet another question successfully answered

Al

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