I want to make a cluster of BeagleBones, so I was pondering how to power them. I wanted a unit that would provide 5 volts at least 1 amp per BeagleBone.

Power requirements

The BeagleBone takes DC power from a plug with the following specifications, taken from the recommended peripherals page.

The power adapter needs to provide 5V over a 5.5mm outer diameter and 2.1mm inner diameter barrel connector. A barrel connector length of 9.5mm is more than sufficient. The currently recommended supply current is at least 1.2A (or 6W), but at least 2A (or 10W) is recommended if you are going to connect up anything over the USB. The actual power consumption will vary greatly with changes on the USB load.

BeagleBoard recommends accomplishing this with a Digi-Key-supplied PHIHONG USA PSC12R-050.

Approaches I don't want

I could just use a bunch of the recommended power supplies, similar to what Matt at Liquidware did, but that seems messy and expensive.

Standard PC power supply

I could just use a standard PC power supply, but that would be heavy and quite inefficient.

USB

Powering the BeagleBones over USB might work.

The USB specification requires devices to power up under 100mA (~500mW) and the USB hub circuit on the BeagleBoard-xM may consume around 100mA itself. Modification is required to the kernel to avoid powering up this section of the board until sufficient current is confirmed by the software. In practice, most host machines will provide sufficient power, despite this violation of the specification. You should consider your power requirements before attempting to utilize USB to power your BeagleBoard or BeagleBoard-xM.

If it does, it would substantially increase power consumption; Revision 0.0 of the BeagleBone Rev A5 System Reference Manual (February 2, 2012) analyzes the "power consumption of the board in ... various scenarios" in this table.

Table of power usage indicating that plugging in the only USB cable
  uses about three-halves the power of plugging in only the DC cable

I tried it anyway to be sure, and I couldn't connect.

What I wanted and made

I really wanted something like the recommended power supply except with several barrel connectors coming out of it. So I bought a 5V 40W power supply and a bunch of plugs.

If you're reading this, remind me to add pictures here.

Right now, I just have the beaglebones, switch and power supply inside of a pizza box, taped in place so they don't move.

If you're reading this, remind me to add pictures here.

If I get more, I might mount the BeagleBones right on top of each other by making a little post and just soldering some wires to it.