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I need to Power an RPi from a +24VDC industrial power supply. The RPi is mounted in a DIN-rail mounting box, in which there is plenty of space. The +24VDC is quite reliable and does not vary by more than about 0.1A depending on loading.

I've looked at DC-DC converters, and it's looking like a 15w supply would be needed to give +5VDC and a max of 3A (so seems ideal) but I can only find PCB mouting types, which isn't ideal, as I need the solution to not be making a new PCB or requiring too much soldering.

There are a fair few DC-DC converters available on ebay, but I really need something that is fairly standardised. If it could be something with screw terminals for the +24VDC, and an output that you can then connect to the header to power the RPi directly, (as I believe that's possible.. you don't have to use the USB micro B port do you?) that would be ideal.

I've also seen a reference to a UBEC, no idea what it is. Would that be appropriate?

Any and all suggestions or ideas would be welcome.

Many thanks!

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    This seems to be a shopping question. ANY switch mode supply (which accepts 24V) >1A would run the Pi, slightly more if peripherals are connected.
    – Milliways
    Commented Dec 11, 2017 at 10:52
  • I'd go for a UBEC. Simply for the flexibility on input voltage.
    – joan
    Commented Dec 11, 2017 at 12:13
  • The input voltage will be completely fixed at +24vdc, so input flexibility isn't an issue. It being an off-the-shelf solution matters more..
    – David_R
    Commented Dec 11, 2017 at 12:46
  • You may wish to check out the "Pololu 5V, 2.5A Step-Down Voltage Regulator D24V25F5", amazon.com/Pololu-Step-Down-Voltage-Regulator-D24V25F5/dp/… or pololu.com/product/2850.
    – bstipe
    Commented Dec 12, 2017 at 5:09

5 Answers 5

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I realize this is an old post, but most of these answers are either unhelpful or flat out wrong. If you are in an industrial environment that uses DIN rail then you definitely want a DIN rail mounted DC/DC converter. They are very commonly available building blocks for industrial systems. And 24v is just about the most standard industrial DC voltage so just about anything made to go on a DIN rail should be able to take in 24v. Look at this digikey search that returns several very solid options. This one for example is likely a great fit from a reputable manufacturer: enter image description here

And no you don't need to use microUSB to get 5v into the RPI, the headers have a 5v input line ( just make sure you don't power the 5v header AND the microUSB at the same time ). You also need to make really sure the connections going to the header are 5v with correct polarity as these pins bypass the usual USB niceties (which is perfectly fine so long as you make sure you are putting in 5v).

As for UBECs -- I wouldn't recommend anything that is labelled as UBEC. These are essentially the same thing as a DC/DC but usually wrapped in a package more appropriate for RC toys and certainly not rated for an industrial environment.

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  • The question seems to be " If it could be something with screw terminals for the +24VDC, and an output that you can then connect to the header to power the RPi directly," So the 24v is already there, so half of the answer can be redacted. And as opinion, please leave them at home.
    – Mats Karlsson
    Commented Oct 12, 2020 at 11:05
  • Right, that's what my answer says. These units take in 24v via terminal block connections (very similar to screw terminals but spring loaded). And output 5v to the same type of connections. Plus they are from a well known brand that has good margin on the design and is rated for the environment. I'm honestly not sure sure what you mean about the opinion.
    – eceforge
    Commented Oct 18, 2020 at 0:40
  • For anybody still not a 100% sure what this means. The depicted device converts 24V DC to 5V DC.
    – Christiaan Westerbeek
    Commented Feb 4, 2022 at 20:34
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You are looking for the wrong solution. A DC-DC converter not only gives a lower voltage but also has galvanic separation. They are also very expensive compared to a simple regulator. All you need is a 5volt regulator, but because your input voltage is high you should look for a switching 5V regulator. They come in 3 pin through hole like a TO-220 case but then a bit bigger.

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UBEC is just a step-down DC-DC voltage converter (Universal Battery Elimination Circuit) for flying aircraft models.

They can be switching or linear mode. If you are want to use this, make sure it is switching mode one. Otherwise you need to dissipate great power on 24V/3A (about 57W). I doubt that any linear regulator will survive this.

There are a lot of switching DC-DC step-down modules ready to use. The only problem is, that many of them are overrated on eBay by the max current they can deliver. Most of them 2A output max (even if it's written 3A or 4A), especially the cheap models. All of them need appropriate cooling with 3A output. Check if then can handle 24V input (I think you need some voltage durability reserve, at least 24V + 10-15%, e.g. 26-28V input). Or they even can catch fire.

You can connect 5V directly to the expansion header, but then you shouldn't connect any power supply through USB.

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I will recommend this, (https://www.robotshop.com/ca/en/5v-3a-step-down-voltage-regulator.html)

5V, 3A Step-down Voltage Regulator

As for the output (from this very regulator), please use the Micro USB male connector, as I have seen, directly connecting 5 volts to the motherboard of Raspberry pi can go wrong or get shorted and fry U3 regulator IC on the Raspberry pi. Details about Micro USB connectors are available on the net.

USB DIY Connector Shell (type Micro-B Plug)

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You can use a 24v switching power supply with 12v 5v entry so you can plug raspberry and also 12v equipments ....

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