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Goodies in the Mail

While I was traveling, a few goodies arrived in the mail. The most exciting of the bunch are the PCBs for the Backcountry Logger mini version. Pictured here is the mini PCB next to the classic, to give a sense of just how small the mini is. I’ll be assembling the mini prototype sometime in the next few days. Beyond simply being smaller, it also has a few new features, and a completely different battery and power system. Hopefully it works! I think there are going to be some clearance problems around the battery, since I’d thought the battery holder was a pair of end clips, rather than the full-length holder that it is.


Also in this week’s mailbag was the snap-together case for the classic logger. This case was designed using vector drawing software, and the six sides were intended to snap together using beveled tabs on the egde of each piece. It’s a tricky design, because the depth and bevel angle of the tabs must be just right, or else the pieces will be too loose to stay together, or too tight to snap at all. When sizing the pieces, things are complicated further by the need to account for the kerf, which is the thickness of the laser cut. Even when it works as intended, this type of design looks a bit ragged, since the tabs prevent having smooth corners.

I had the case manufactured out of 0.8 mm thick white Derlin by Ponoko. This was my first time using Ponoko, and while the price and quality were good, the speed of the service was pretty slow. It was nine calendar days between when I uploaded the design and when it was acutally cut and shipped. For a simple one-sheet design using in-stock material, I was expecting it to be cut the next business day. My only other laser-cutting experience was with Pololu, which does laser-cutting as a sideline to their main business, and my order from them was cut next day. For a business like Ponoko whose entire premise is custom-cut parts, a nine day lead time seems a bit high. I probably just need to learn to be patient.

As received, the tabs on the case pieces were substantially too big, and the pieces wouldn’t snap together even by applying extreme force. Whether this was because the true kerf was less than advertised, or because my design was flawed, I’m not sure. After half an hour with an exacto knife, I was able to whittle down the tabs and assemble the case you see here. It’s pretty nice, except… where are the buttons? DOH! I guess I should have used tactile switches with a longer plunger, so they’d extend far enough to exit the case. Back to Digikey to order some.

The last mail delivery was some enclosure samples from OKW. These are the enclosures Cesar recommended in an earlier comment, and OKW was kind enough to send me free samples. They look great! I really like the look of the pear-shaped one with green trim, but I think it might be a bit too small to hold the logger mini.

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