External PSU to power a Raspberry PI

[AtomAlex]

I am planning to build a little server-cluster out of 10 Raspberry PI B+. Since I don't want to buy a USB-Connector to power each of them, I was thinking of using a PSU instead. I've been searching the internet for a while now and came across this one:

Mean Well MW SP-75-5
https://cdn-reichelt.de/documents/daten ... _75_XX.pdf

DC-Voltage: 5 V
Rated Current: 15 Amps
Rated Power: 75 Watts

I was wondering if i could use this PSU to power all 10 Raspberry PIs (I'm kind of new to this and I'm not too sure if I paid attention to all the important aspects ...)

Thanks for your help in advance

[mahjongg]

Yes, you can, but adjust to 5.0 V precisely (or to 5.1V if you want to compensate for cable losses).

Be very careful with your wiring, especially the polarity, and use wire that has no significant drop at say 1A.

Also be sure nothing shorts, as 15A will blow up your wiring instantly!

Not the PI itself, but UB devices need precise voltage of 5V +- 5% (4.75 to 5.25V).

Voltages above 6V (+- 5%) will trigger a protection mechanism in the PI that shorts the 5V rail, so make sure your unloaded PSU doesn't output any higher than say 5.5V

[AtomAlex]

Allright, so all I need to do is connect each RPI to the output of the PSU right ? Is there anything that I should put in between the devices to protect it from getting damaged ?

[davidcoton]

Each Pi will protect itself, as long as the power is supplied to the micro-USB connector. It is a false economy to not but the connectors and leads -- you will need some alternative (for example to make connections via the unprotected gpio 5V pins). You could fuse each lead at say 1.5A, this will protect the wiring but not the Pi (electronics blow faster than fuses). If you are really concerned you will need an electronic current limit for each Pi (pronounced "expensive", and you'll probably need find them ready made). Also a single power supply means one fault will take down the whole cluster -- if you want fault tolerance, a USB PSU for each Pi is ideal, although the mains distribution will be quite bulky.