The MintyBoost is an open-source, small form-factor, USB charger which runs on AA batteries – and lets you charge your mobile phone, tablet or other USB device, without the need for mains power or a computer.  It was designed by one of the leading proponents of the open-source hardware movement, LadyAda – aka MIT Engineering graduate: Limor Fried

All the details of the circuit can be found on the project’s web-site.

You can build it entirely on your own, or you can buy it in kit form. I chose the latter – and bought my kit from a French company Alpha Crucis (who seemed pretty good) – but lots of other places sell the kits. If you’re in the US, then you can buy directly from Adafruit Industries.

The kit takes it’s name from the fact that it was designed to fit into an empty tin of Altoids chewing gum. Given that you can’t (easily) buy Altoids gum in the UK (and given that, by all accounts it’s not actually very nice anyway) – I decided to buy on of the “replica” Altoids gum tins that are now quite widely available. Again, I bought mine from Alpha Crucis: but again other vendors are available.

Actually soldering the board is pretty trivial. I’d say that even if you’ve never soldered before, you could probably manage to put it together: especially if you follow the very comprehensive set of instructions on LadyAda’s website. There are even some tutorials on how to solder: ideal for anyone contemplating their first electronics project.

Once you’ve built the circuit – you need to fit it into the housing. The project’s website suggest you to make two cuts down the front of the Altoids tin with some tinsnips – and then to break out the flap, and put the USB connection into the space. This design seemed a bit inelegant to me: I really didn’t like the idea of having to slice through the edge of the tin (weakening it): so my humble addition to the canon, is to suggest a modification to the way that the circuit fits into the tin – by fitting the USB connector through a window cut out of the side of the tin.

I did this with a cutting disc on my dremmel, and a cylindrical grinder to extend the slot to the correct width.  This worked pretty well – though it did leave some rather rough & sharp edges.

To fix that, I first hand-filed the edges of the window (also taking the opportunity to square off the corners).  I then sanded the whole thing off with some 240-grit wet & dry paper – and finally finished off with a cotton polishing pad on the dremmel.

I didn’t have any polishing compound to hand – so I used a bit of toothpaste (well, it is called a Mintyboost, after all!). 🙂

I think that this modification worked really well: and it’s not really much more difficult to do (providing that you have the right tools). One thing to note though, is that in my tin, the USB connector is at the maximum height it could be, to still permit the tin to close properly. So if you’re going to try this method, then you do need to be sure to measure-up carefully first.

The finished case looks really good – and it should definitely be stronger than it would’ve been in the original design. (It also has less sharp edges – so it’s safer to handle too: which is a bonus).

A gallery of images from my build can be found here.

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