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I have an electrical control box that needs 48v, 12v, and 5v to power stepper motors, sensors, and microcontrollers, respecitvely. All power items will be mounted on a DIN rail right next to each other. Is it better to have an AC-DC power supply for each output voltage, or one larger 48v supply and use DC-DC converters to get the lower voltages needed? It's cheaper to get seperate power supplies, so if there aren't going to be any negative effects I'd like to go that route. Thanks!

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  • \$\begingroup\$ No real issues with either. \$\endgroup\$
    – DKNguyen
    Mar 3, 2021 at 3:33

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Both works, however, the separate AC/DC supply is a bit better.

  • AC/DC power supplies are dirt cheap.
  • There are plenty of AC/DC that can be rail mounted, DC/DC is more difficult to find.
  • You will have overall fewer conversion losses.

Where it is debatable is the 12V -> 5V where you can have a 2$ small converter onboard if you want to save some space, assuming 5V requires low current.

You need to connect all the negative to a common line.

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  • \$\begingroup\$ Thanks. I plan on having a nema c19 plug that goes from the wall to the control box, so they'll share the ground. Does it matter if the mains connections on the power supplies are in series or parallel? \$\endgroup\$
    – jackson
    Mar 3, 2021 at 3:52
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    \$\begingroup\$ I was referring to the ground of the DC side as AC/DC is isolated, so you need to connect the negative terminal of the DC side of all power supply together. Can you give more detail about your question series/parallel, you mean the input, output, current sharing? \$\endgroup\$
    – Damien
    Mar 3, 2021 at 4:01
  • \$\begingroup\$ Ah, yeah the DC negatives will all go to a common bus bar. On the AC side, I mean can I daisy chain the wiring, say, to the 48v supply, then to the 12v, and 5v, or should I split the mains wiring once it enters the box and run seperate wires to each supply? Using short jumpers to carry the mains power between the supplies will help keep the wire clutter down. \$\endgroup\$
    – jackson
    Mar 3, 2021 at 4:05
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    \$\begingroup\$ Just to make clear, when you talk about daisy-chain, they are still in parallel, meaning they get 230VAC ( or 110VAC) each right? You cannot put them in series, but you can daisy chain the cabling as long as you pay attention to be within the current limits and that your company doesn't have specific requirements against that. \$\endgroup\$
    – Damien
    Mar 3, 2021 at 4:17
  • \$\begingroup\$ @jackson C19 is an IEC standard, part of IEC 60320. It's not a NEMA standard. \$\endgroup\$
    – Hearth
    Mar 3, 2021 at 4:49
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Parallel is better because it improves the reliability. For your logic, you want that independent so you can continue to monitor systems like motor position and fluid levels even if you have a major failure that causes one of the other supplies to completely fail. This also allows you to have some sort of logic level fault detection for the other circuits that can help with troubleshooting during failures.

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