How to get ±10V from dual power supply. - Page 1
Forum section: electronics / testgear

author: Rene
author_rank: Regular Contributor
timestamp: July 21, 2015, 01:27:41 am
content: Hello,I did some research regarding this topic and I think I know how to do this but I wanted to double check with the EEVBlog experts before I do something stupid.Basically, I would like for my power supply to provide me with a voltage ranging from -10 volts to +10 volts (I think this types of power supplies are called bipolar power supply but I am not totally sure).In order to get this from a dual power supply, it looks like all I need to do is to run a wire from the negative terminal from supply one to the positive terminal of supply two (this would be my ground reference). Once that is done, I can use the positive terminal from supply one to get my positive voltage and the negative terminal from supply two to get the negative voltage (see attached picture for connection configuration).Once the connections have been completed, all I would need to do is to set power supply one and two to 5 volts and I should be ok (this should give me ±10V). The thing is that before I turn this puppy on I wanted to verify that I am not going to burn something.Assuming that the solution works, Is this an excellent way of obtaining what I want or is this a hack that will end up introducing all kind of noises? Also, what if power supply one is set to 5 volts and power supply two is set to 10 volts? Would this damage my power supply?Thanks.

author: codeboy2k
author_rank: Super Contributor
timestamp: July 21, 2015, 01:59:23 am
content: The DP832 has channel 2 and channel 3 GND (negative terminals) connected internally.So you want to wire it so that the negative of channel 2 (and thus channel 3's negative too) is still your main ground reference.Your wiring will work as you did it, but it will cause channel 3's GND (negative) to float along with Channel 2's (which in your wiring would be your -10V point)Instead of your way, you should wire it with the negative of channel 2 connected to the positive of channel 1. That is will be the GND (midpoint) reference, and you can still use your channel 3 with the same GND reference.In this configuration, Channel 1 negative is the -10V point and Channel 2 positive is the +10V point.Your second question: if you had one channel at 5V and the other at 10V you would have +5/-10 (or -5/+10 depending on which channel was positive and which was negative). There is no problem with different voltages.See the attached note tooPS: yah, someone just wasn't thinking when they designed it that way

author: dadler
author_rank: Unknown
timestamp: July 21, 2015, 02:01:46 am
content: It won't damage the supply. You can set them to different voltages. You can also turn on tracking, so that a voltage drop on one supply is balanced on the other (e.g. for powering op-amps).If you see common mode noise, you can also tie whichever point you wish to ground (likely the center, which you have chosen as your 0V node), to avoid ground loops etc.

author: JoeB83
author_rank: Regular Contributor
timestamp: July 21, 2015, 09:22:09 am
content: I do a lot of audio & op-amp stuff this way, just as you describe. Use positive from (+) A, bind (-) from A and (+) from B to define ground, and negative from (-) B. I use a tracking power supply so that + and - supplies will be the same magnitude, but a individually programmable power supply works too.Just a bit of advice-you may want to use leads with larger diameter wire & banana plugs so current can flow more freely, instead of proto board wires.Edit: I don't know much about your particular PS, but I'd guess it would work fine, as others have mentioned.Edit two: sorry, it's been a long day.You mention setting power supply one and two to 5V. Perhaps it's an error; but in the eventuality that it's not, it'll only yield +/-5V. Yes, you'll get a total of 10V measured from +terminal on A and -terminal on B, but that doesn't equal +/-10V, only +/-5V.

author: Rene
author_rank: Regular Contributor
timestamp: July 22, 2015, 09:21:42 pm
content: Quote from: codeboy2k on July 21, 2015, 01:59:23 amAh, thanks for the info and the attached document, really helpful and insightful.Thank you to everyone else, really appreciate the help!