Q. about connecting two 24 VDC power supplies in parallel - Page 1
Forum section: electronics / beginners

author: fncruz
author_rank: Newbie
timestamp: May 23, 2024, 07:14:03 pm
content: I have a controller that provides about 1/2 Amp to power loop powered devices. This is not enough for me as I need 3+ Amps.If I take a 5Amp 24 VDC power supply can I connect it in parallel?I have some flow meters that provide a analog input to the controller (4-20 mA). If I use the 5 Amp PS to power it and send the return from the flow meter to the controller it will NOT work as it is powered by a different 24 VDC power supply. I think this would require jumping together both DC- or maybe both DC+.Thoughts?Anything dangerous about this?

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 23, 2024, 07:25:23 pm
content: Quote from: fncruz on May 23, 2024, 07:14:03 pmSome power supplies can be conected in parallel (those which have rectifier diodes in series with output).In general, without knowing about both power supplies you can't parallel them, otherwise one of them may burn

author: IanB
author_rank: Super Contributor
timestamp: May 23, 2024, 07:28:19 pm
content: In general, I don't think you can put two regulated 24 V power supplies in parallel. Each of them will independently think they are controlling the 24 V, and will be confused by the other one also trying to control the same 24 V.However, deeper questions arise. You have some transmitting devices or senders (flow meters--how many?), and receiving devices (controllers).I believe 4-20 mA loops can be self-powered (the controller provides the power and the transmitter is passive), or they can be remote powered (the transmitter sends the current and the receiver is passive). There may be a configuration setting to make it work either way.Now, if the controller can supply 500 mA, that would be enough for at least 20 loops. Do you have more than that?If you have lots of flow senders, you might be able to power them all remotely with an external power supply, and put the controllers in passive mode so they just read the current being sent by the flow meters.There are lots of permutations and options here, and you have not provided enough information to provide an accurate answer.If you are in an industrial setting, you should ask a colleague like an instrument technician to advise, someone who is familiar with the specific setup you have. Unless you provide schematics, brand names and model numbers of devices, we are shooting in the dark.

author: pdenisowski
author_rank: Super Contributor
timestamp: May 23, 2024, 07:33:09 pm
content: Can't really comment on your specific application, but most benchtop power supplies can be connected in parallel to increase max output current and in series to increase voltage.Again, speaking only of DC benchtop power supplies

author: BennoG
author_rank: Frequent Contributor
timestamp: May 23, 2024, 08:38:34 pm
content: If you connect only the -24V of the different supply's together then you can use it the way you want.Every signal is then reverenced to those connected -24V and you can use them as inputs for your controller.Benno

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 24, 2024, 04:05:36 pm
content: Quote from: pdenisowski on May 23, 2024, 07:33:09 pmIn this video they are speaking about their own benchtop power supplies, so I wouldn't so sure about all.

author: xvr
author_rank: Frequent Contributor
timestamp: May 24, 2024, 08:01:25 pm
content: Power supply which could be paralleled generally have a something like "load sharing" or "current sharing" in their description. This is a special feature that do not provided for free

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 25, 2024, 12:38:14 pm
content: As written before, it depends on the power supplies used.One trick that may help is to use separate sets of wiring from each power supply to the load. In that case the wiring acts as balancing resistors. The metal mesh enclosed "brick type" power supplies often have a potentiometer to set the output voltage. You can use it so the share the load nearly eaqually (voltage drop over each cable). But there are no guarantees for drift over temperature and aging.But overall, it is a bit messy. Generic purpose power supplies are not very expensive and you are probably better off with just buying a bigger power supply, and use these smaller ones for something else.

author: IanB
author_rank: Super Contributor
timestamp: May 25, 2024, 01:58:21 pm
content: Note, the OP is a drive-by poster who has now asked exactly the same question twice, and has not followed up in either thread.We should not waste our time giving any more responses.https://www.eevblog.com/forum/beginners/hooking-up-two-24-vdc-power-supplies-in-parallel/msg2982944/#msg2982944

author: fncruz
author_rank: Newbie
timestamp: May 28, 2024, 11:12:20 am
content: I have done what you said, connected both DC-, and so far it is working.I am somewhat concerned about any long-term issues but so far I am getting the results I needed.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: May 28, 2024, 12:28:12 pm
content: Good Morning Fncruz, here is a very well done video that may help:https://youtu.be/mJL11UF1arQ