The contest comes to an end and I am tying up some loose ends - one of them the power supply.

The Sniffing Trinket is intended for indoor air quality monitoring and with this in mind as well as the knowledge that USB plugs are a common sight everywhere these days, a USB port or wall plug is probably the first choice for the power supply (come on, even most cars now have a USB power supply).

However, as this is not truly EDC and there might be situations where you want to monitor the air quality and you don't have a USB power supply, there is also an alternative battery power option.

Instead of designing my own solution I decided to go with a module you can buy pretty cheap: Just put "5V USB step up" into ebay or alibaba or any other site and you get those modules for about 1 Euro (1.5$) in single quantity delivered. You can't build something like that cheaper yourself. These modules take anywhere from 1V to 5V input and put out 5V with up to 600mA - perfect to power your little gadget. I haven't tested them properly but I suspect (from my own painfull experience with step-up converters) that they are not that efficient - but they should be good enough to power the SniffingTrinket for a couple of hours from 2 AA batteries. Additionally, the modules are small, about the size of a USB connector. So here is how to build one:

You need

• A cheap chinese USB 5V step up converter module
• A battery holder for 2 AA cells (+batteries, obviously)
• As I used a holder that conveniently outputs to a 9V clip I needed a matching clip for connection, otherwise some wire

Construction is pretty simple. Just solder the red wire from the battery clip to the + pad on the step up converter board and the black wire to the - pad (if you just use wires, connect them to the battery holder with the correct polarity). Connect the clip to the battery holder. Put in the batteries. I additionally glued down the step up converter board to the battery holder.

You can now connect the SniffingTrinket via a USB cable. I only have very long and stiff ones (therefore you can't see the whole cable), but you can get a smaller, more flexible one.

Alternatively, you can also desolder the bulky full size USB connector from the converter board, cut the board a little bit and run you own wires to the Trinket.

Congratulations, you can now monitor the air quality in the mines of Moria!