Complex PSU wiring help - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: March 27, 2019, 02:57:33 am
content: Hi,A big thanks to anybody who has helped me in the past.I have four meanwell SMPS (two 3.3v & two 15v).For an S-100 project I need to create three voltages +7, +14 and -14 that go in to a 10 position connector (+7, +7, GND, GND, GND, GND, GND, GND, +14, -14).So the two 3.3v supplies dialed up to 3.5v and connected in series and the two 15v supplies dialed down to 14v and connected to create both a positive and a negative voltage.All of the supplies each have 7 screw terminals (L, N, GND, -V, -V, +V, +V).Can someone please help me out with exactly how to wire it all up, a "back of a beer mat" kinda thing?I'm thinking of using ring or spade terminals?I think I "daisy chain" L and N?How do I cable ground, connect the four SMPS grounds together?Thanks again.Richard

author: rthorntn
author_rank: Frequent Contributor
timestamp: March 29, 2019, 01:27:04 pm
content: Just trying to get help on the correct wiring, I will give it a try, is this it?For the +7v:PSU_A positive connects to +7 on the 10 pin connectorPSU_A negative connects to PSU_B positivePSU_B negative connects to GND on the 10 pin connectorFor the +16v & -16v:PSU_C positive connects to +16 on the 10 pin connectorPSU_C negative connects to GND on the 10 pin connectorPSU_C negative connects to PSU_D positivePSU_D negative connects to -16 on the 10 pin connectorPSU_D positive connects to GND on the 10 pin connectorI think that's it but how to populate and chain the 10 pin connectors six ground pins and two +7 pins?Also should all four supplies have their floating grounds connected together?

author: Muny
author_rank: Contributor
timestamp: March 29, 2019, 09:25:56 pm
content: Hi,If I understand what you want correctly:I think that is what you want.Without trying it myself though, I can't guarantee the safety or proper operation of this.Sorry if it looks a little confusing. I will see if I can make it look neater.

author: rthorntn
author_rank: Frequent Contributor
timestamp: March 29, 2019, 11:08:35 pm
content: Quote from: Muny on March 29, 2019, 09:25:56 pmPerfect thanks Muny, would you mind sharing the name of the software that you used to draw this?Would I connect AC earth to each PSU GND then?Also trying to figure out if I should buy anything at Jaycar (or online) to use, for example to neatly split the three PSU negatives going to the six connector ground pins, a bus bar sort of thing?

author: Muny
author_rank: Contributor
timestamp: March 30, 2019, 12:58:41 am
content: Quote from: rthorntn on March 29, 2019, 11:08:35 pmI used KiCAD to produce that drawing:http://kicad-pcb.org/I wouldn't say it's perfect for drawing wiring diagrams (you can't change the colors of certain wires), as it's tailored specifically for circuit schematics. But it does do them pretty nicely.QuoteYes, I believe that is the intended function of these terminals of the power supplies. IIRC (?) they connect to the metal chassis of the supplies. I would consult the datasheets/user manuals for the supplies though.QuoteI've usedthese thingssuccessfully in some projects. Keywords I used were "distribution block." I've seen other designs which would probably work well too.Hope these suggestions helped. Good luck on your project.

author: Bratster
author_rank: Frequent Contributor
timestamp: March 31, 2019, 06:40:47 am
content: One thing to watch out for is if your V- terminal is connected internally to the chassis/earth terminal on the power supplies.If they are connected you won't be able to do what you want.Sent from my Pixel 2 XL using Tapatalk

author: mariush
author_rank: Super Contributor
timestamp: March 31, 2019, 09:25:31 am
content: How much current do you need on those voltages?You may be able to use a classic linear transformer and some linear regulators to save some money.For example, you could use a +/-15v AC transformer with a rectifier and a positive linear regulator for the +14v and a LM337 (or something equivalent) to set the negative voltage to -14v , if the current on -14v is less than 1.5AThe 7v could be a separate SMPS power supply.Alternatively, you could have a transformer with two 9v AC secondary windings and get 7v and 14v after rectification and smoothing. Then if the current is low enough you could use a simple inverting regulator to generate -14v.

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 04, 2019, 11:43:00 pm
content: Thanks everyone.So I already have the power supplies, all Mean Well, two RS-150-3.3 & two LRS-150-15, this is what I'm thinking of doing (because I don't want to modify the IMSAI case in any way).I have a fused & switched IEC socket, I want to mount that into a 120 x 90 x 60mm die-cast aluminium project box that I have, I will bolt the IEC earth pin wire to this box and bolt the box to the bottom of the IMSAI case, the Mean Well supplies will be bolted to the IMSAI case, I was going to connect the grounds of all the Mean Well PSU's to the earth bolt on the project box, is that correct?Thanks again.Richard

author: Bratster
author_rank: Frequent Contributor
timestamp: April 05, 2019, 01:28:23 am
content: Yes, all the earth/chassis grounds should be connected together.Sent from my Pixel 2 XL using Tapatalk