To start things off I’ll go over my build of the MintyBoost kit that I bought from adafruit.com. Despite being tech savvy and loving the latest gizmos, I’m usually not one to buy the latest and greatest phones because I’m cheap (which is why you’ll see me building lots of stuff on this blog instead of buying it). However, when the HTC Thunderbolt came out with the promise of 4G speed and Verizon was offering unlimited data (for a limited time) I decided to be a pioneer. While the phone actually has much better battery life than people give it credit for, it was garbage compared to my Blackberry Curve. So, when I have to go for extended periods of time without a power cord, and I actually may need to use my phone for something important, I carry around this neat little product…
I followed the instructions from Adafruit for the most part, but I did make a few modifications. You’ll noticed that my MintyBoost has a switch. This really isn’t necessary because the IC in the voltage converter supposidly would take years to draw down a set of batteries when nothing is connected, but I wanted a switch, so I put on in.
I picked up a cheap switch from Radio Shack (275-0409) and started thinking of ways to get it mounted in place. I knew it would fit, but I was looking for some kind of small rectangular structure to hold it there opposite the USB, preferably plastic. Then it came to me, the perfect small rectangular things ever made…Legos! They were the perfect height (almost).
They took some slicing and dicing with a Dremel to get the contours to fit right. I trimmed the block bottoms and sides as well as clipping off the bumps. DISCLAIMER: No actual “Legos” were harmed in the making of this MintyBoost. These were a few knock-offs (probably MegaBlocks) that I found in my bin.
I just drilled a few holes and attached the switch with a few tiny wood screws and that assembly was ready. Now that I had a metal piece (the switch body) at the end of my battery pack, I wasn’t comfortable having the poles exposed as they were, so I taped over them with some electrical tape and cut out little discs to cover the metal contacts.
Another benefit of the “Legos” was that there were nice holes already in place for me to route wires through. You can see how I am switching the negative lead of the battery pack. I then screwed the Legos back on and checked the fit in the case. When I was happy I hot-glued the switch assembly to the battery pack.
Now it was time to turn my attention to the business end of the portable power supply, the USB end. The instructions for the Minty Boost say to just cut down all the way through the top of the Altoids tin, but I didn’t think that looked very structuraly sound, or aesthetically pleasing. So, I marked out an “H” shape for some cut locations, and a few more lines for bend locations. I mad the main cuts with a Dremel, but I needed to touch it up a bit with a utility knife on the corners because the Dremel would have over-cut. I then folded the tabs back. The top tab gets folded only to level, while the bottom needs to be folded back against the shell completely. I used some little bits of steel to help me make a nice fold.
I used the supplied foam double-sided tape to mount the battery pack (now with switch assembly glued to it) and the MintyBoost circuit to the floor of the tin. I did take the time to clean everything with rubbing alcohol first. I also added some extra electrical tape to the bottom of the circuit to avoid any potential shorting. The final step was to solder the top tab I had folded up from the tin to the top of the USB connector. This adds a bit more strength.
The USB end looks pretty good, but I did notice that the connector sloped just slightly up. When I checked it out I saw that it was because of this little plastic thing interfering with the bottom of the tin opening. I didn’t feel like pulling tape apart to try to fix it, so it is what it is. Maybe you might want to cut this off on your build.
Once everything was together I gave it a final test. It works! (Yes, I did make sure my voltages were all good before I plugged the phone in, while I was still building my circuit.)
This will be handy for when I’m turning my Thunderbolt into a hand-warmer while using MyTracks to record my snowboard or mountain bike routes. Next step is to make a very low profile, easily packable USB cable to bring along instead of my stock 3ft cable.