Pages: [1]   Go Down
Author Topic: Dual Voltage Supply +/- 15V  (Read 534 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 0
Posts: 32
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I'm working on a circuit with about 6 op-amps and need a dual supply.  I was told I could use two +15V supplies to create both rails.  The circuit that was given to me is attached...

I don't think I did anything wrong when I assembled it, however, it's remotely possible that I did err somewhere.  It's not like it's that difficult to make, which is why I don't think I screwed up!

My problem is, I'm measuring +30V from the positive terminal to the common, and -15V from the negative to the common.  Why am I measuring +30V?

I, stupidly, heat-shrinked the cables and connection points so I haven't wanted to rip it open and ruin all of my work yet!

Thanks for any advice!



* Dual Power Supply.jpg (91.69 KB, 699x326 - viewed 40 times.)
Logged

Left Coast, CA (USA)
Offline Offline
Brattain Member
*****
Karma: 361
Posts: 17262
Measurement changes behavior
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I'm working on a circuit with about 6 op-amps and need a dual supply.  I was told I could use two +15V supplies to create both rails.  The circuit that was given to me is attached...

 Your drawing has no errors or flaws, assuming each supply has isolated outputs with no connection to input ground or common.

I don't think I did anything wrong when I assembled it, however, it's remotely possible that I did err somewhere.  It's not like it's that difficult to make, which is why I don't think I screwed up!

My problem is, I'm measuring +30V from the positive terminal to the common, and -15V from the negative to the common.  Why am I measuring +30V?

Not sure, but are those measurements being taken with anything being wired up to the output voltages?


What voltage do you read if measured between the +15 terminal and the -15 terminal without anything connected to the output terminals except your voltmeter ?

I, stupidly, heat-shrinked the cables and connection points so I haven't wanted to rip it open and ruin all of my work yet!

Well you must be the very first person in all of history to do something like that, NOT!  smiley-grin

Thanks for any advice!

Just continue your troubleshooting adventure, there is always a logical explaination once it is all figured out. Electronics seldom operates in mysterious ways. Software however is a whole different ballgame. smiley-grin
Lefty


Logged

Offline Offline
Jr. Member
**
Karma: 0
Posts: 83
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

If its wired correctly, the two possibilities I can think are either first power supply is 30V or you are measuring the voltage between + and - instead of common.
Logged

Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 46
Posts: 2865
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

If you make a simple diagram of the measurements I think you will find out that one of your power supplies is not what you think it is. The telling measurement is to measure the voltage from the -15 V point to to the + 30V point and see what that measurement is. (-15) + (+30) = ?)...

Doc
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Offline Offline
Newbie
*
Karma: 0
Posts: 32
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I screwed up twice!

Once when I messed up when building the thing, and secondly when I read the voltages.  I was actually getting -30V.  The problem was, when I made the jumpers to extend the shielded cable, I mixed up my colors!

So I wasn't actually referencing the + and - to ground.

Got it all squared away!  Thanks to you guys for letting me know that the theory was correct and that it was my error.
Logged

Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 46
Posts: 2865
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Somedays it just doesn't pay to get out of bed... IMO and In My Direct Experience...

Doc
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Pages: [1]   Go Up
Jump to: