Powering from 12 volt

[cchisholm]

I have created a couple platforms for my 3d printers that house pi's (RPb+ on one and RP2 on the other.) , a lcd screen, and a 12v 30a power supply. I am able to run the printer and lcd screen from the p/s, but still have to run another wire in (cell charger wall wart) for the pi. Anybody got any safe ideas how I van get my power from the p/s. I'm sure I will need some sort of step down but cobbling a micro usb cable seems pretty kludgy

Edit: Changed mini to micro above

[drgeoff]

Without a step down you will produce a dead RPi. A switching type regulator would be best. Many are available eg from eBay.

Note that the RPi's power socket is micro-USB, not mini.

[mikerr]

Something like this should work fine:

DC-DC Supply Power Converter Buck Module 12V to 5V 3A Mini USB Output Power Adapter Car

http://www.amazon.co.uk/dp/B00E5VH1OI/

[joan]

I have a somewhat similar set-up. A 12V supply for a car reversing screen also feeds into a 5V UBEC to power the Pi.

[JimmyN]

How about a car USB charger, they can handle 12~14V input and have a 5V output and I'm sure you can find one with a miniUSB plug. Look at the specs on it to make sure it's at least 1 amp output. Cut the cigarette lighter plug off the end and connect the red/black to the 12V source.

[jwatte]

A slightly less bulky option is a 5A voltage regulator, preferrably a switching one to avoid a massive heat sink.

I've used both of these, they both work great:

https://www.pololu.com/product/2850

http://www.digikey.com/product-detail/e ... ND/2259781

Note that the second one "only" puts out 1.5A, so if you're going to load a RPi 2 with USB devies and load it to the max, it may not be enough. I haven't run into that problem. However, I power it with a 2S LiPo battery, and it cuts off power if input goes below 7V, so I have to keep the battery well charged. Not a problem for your 12V situation.

[cchisholm]

Wow!!!! A lot of good suggestions. I ended up ordering a device similar to what mikerr suggested. I had originally said mini usb in my post, but actually I needed a micro and they are available as well.
Also, these will handle both 12v and 24v input and my other printer is a 24v supply.


I was concerned about trying to attach a micro usb to the other suggested devices (not as good with small things as I once was).

thank you all.