How to power several devices from an emergency battery pack.

Recently (actually almost one month ago :), I had to power several devices (three different units) using one of those battery packs with an USB output (http://papermint-designs.com/community/node/289). The easiest way to do that is to power a USB hub with your battery pack and then use the hub to provide power to all other devices. That will work OK as far as the current needed by your devices fits the output of the USB hub (around 100 mA).

The drawback of that solution is size, and in my case I had to use an already bulky HMDI to VGA converter so I tried to build simple adaptors to reduce size. My first attempt was a quick and dirty board to test if my battery can drive all the devices I had to use. Here is the first result

USB Power Adapter. Top sideUSB Power Adapter. Top side

USB Power Adapter. Bottom sideUSB Power Adapter. Bottom side

As you can see the board can be smaller but my intention was to add a third connector just there. The output USB connectors are positioned vertical as the whole thing will be a quite thick sandwich. I had to put some hot glue around the USB connectors to give them some consistence. However the final result was still too bulky

USB Power Adapter. Full connectionUSB Power Adapter. Full connection

Better than using an USB hub, but still too bulky. So, for my second try, I got rid of the LED and switch and solder together two USB connectors (male and female) and added a barrel connector directly over the connectors pins. This is the result:

USB Power Adapter take 2USB Power Adapter take 2

I also put a bit of hot glue in between the two connectors to make the rig stronger and some electrical tape around it.

USB Power Adapter take 2. FinalUSB Power Adapter take 2. Final

Another advantage of this new adapter is the need for just two wires with the right size. A picture of the final result.

USB Power Adapter take 2. Final setupUSB Power Adapter take 2. Final setup

Which is a lot smaller than the previous solution. I used this adaptor with my BeagleBoard as well as with my Raspberry Pi just plugging different cables on the USB female output of the converter. Specifically for these two boards I could forget about the USB female and solder two more wires directly on the male USB connector (the one connected to the battery). Then plug these wires on the expansion headers of the board to power them up. That will produce an even smaller setup.

For my project I had to power three devices. At the end it was not possible to power the three of them from just one battery, at least not from any of the batteries I had available at that time, so I ended up using two batteries. One powering the computer and the other one powering the HMI to VGA converter plus the display, and I had to use a USB cable to power the display so the double USB connector worked better than the two additional wires.

However, for the final picoFlamingo HW I will probably go for the USB connector plus wired to minimise the size.

CU
The picoFlamingo Team