Rules off Ground and Earth - Page 1
Forum section: electronics / projects

author: GGMM
author_rank: Frequent Contributor
timestamp: July 08, 2023, 08:52:56 am
content: Hello,Good morning,I am currently building a 0-30V 0-3A power supply based on a kit.see here:https://www.paulvdiyblogs.net/2015/05/tuning-030v-dc-with-03a-psu-diy-kit.htmlsome modifications are made (power for the ci's!)I will also add in this box a fixed 12v power supply ( will also be used for the display) and also a fixed 5v output based on a regulator from the 12v.The metal case will be basic connected to the earth (green/ yellow wire) of the mains cord.Now I wanted to know the rules for the "-" power supplies.Connect them together with a direct connection to the chassis (thus to the earth)?no connection and floating ground?I have heard of "soft" connection, that is with a resistance or capacitor.Attention, the power supply adjustment having a V/A display requires a little special cabling. (see image)See also my post here but no answer at this time:https://groups.io/g/HBTE/topic/homebrew_power_supply/99852161?p=,,,20,0,0,0::recentpostdate/sticky,,,20,2,0,99852161,previd%3D1688745234944938384,nextid%3D1642844033607435268&previd=1688745234944938384&nextid=1642844033607435268Thank you for your answers

author: Benta
author_rank: Super Contributor
timestamp: July 08, 2023, 10:16:48 am
content: Your protective earth (PE) to chassis is good.Leave the outputs floating, both negative and positive and add PE banana socket to the front panel. Then you're completely flexible and can use any of the outputs earthed or floating as necessary.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 08, 2023, 10:24:24 am
content: Connecting PE and secondary GND is optional. By default, don't do it; the supply will be more useful without such connection, e.g., allowing you to connect multiple supplies in series. You can add a separate PE socket/post if you wish.Instead of fully open circuit, a capacitor can be used for EMC in switch mode supplies. This linear supply won't need it.

author: GGMM
author_rank: Frequent Contributor
timestamp: July 08, 2023, 12:34:49 pm
content: Thank's for your answersso i can do that (see picture)cdt

author: Siwastaja
author_rank: Super Contributor
timestamp: July 08, 2023, 12:42:25 pm
content: Yes, you can.

author: GGMM
author_rank: Frequent Contributor
timestamp: July 30, 2023, 09:45:03 am
content: Hello,I’m almost finished building, but I have a little doubt.In fact as said there are 3 outputs, the variable 0-30v coming from a first module, and a 12v from the other module (the 5v being derived with a regulator).If temporarily I want to connect the "grounds" of these 2 power supplies, (via lugs and wire) will it be necessary to do it in point B or D of theshunt? (See picture before)I want to avoid "burning" the display.Thank you for returning.cdt

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: July 30, 2023, 10:10:17 am
content: B

author: GGMM
author_rank: Frequent Contributor
timestamp: July 31, 2023, 03:22:11 pm
content: Hello,So, after several hours of work on the plate and assembly, I finally finished my power supply. 3 outputs 5v, 12v and a 0-25v variable with current limiter.Given the time spent on and the various parts purchases, this may not be worth the effort compared to any done or used purchase on some sites. Well, the pleasure is in having done it with his hands. lol.

author: Someone
author_rank: Super Contributor
timestamp: July 31, 2023, 10:26:44 pm
content: Quote from: Roehrenonkel on July 30, 2023, 10:10:17 amI disagree, then current may flow back through a different path to earth which won't be picked up by the current shunt.

author: GGMM
author_rank: Frequent Contributor
timestamp: August 01, 2023, 07:20:51 am
content: Hello Someone,I think you may be right. If I switch connector that connects the 2 grounds of the power supplies, the power overload light comes on fugitively. It’s actually a bit odd that the current measurement is done on the ground leg. I do not know if we can modify and rather measure it on the part +.Anyway, for now, I only use it with floating ground.cdt

author: Terry Bites
author_rank: Super Contributor
timestamp: August 02, 2023, 03:26:20 pm
content: Ideally and sensibly your supplies need float independently of each other. That gives you full flexibility and frees you from short to earth worries.