Flashes of Panic

Two evenings ago, I sat down with a soldering iron and made one of these. If it’s not immediately clear what this is, it’s a tiny circuit which allows you to hook two AA batteries to a USB jack and thereby charge anything which can be charged that way—most iPods, for example, but also, as it happens, my new phone. The whole thing fits in the tin from Altoids gum.

I’m interested in this because it may allow me to reduce the number of wall-wart chargers I take with me when I travel. AA batteries are almost as easy to find as cigarettes, at home and abroad, and they aren’t subject to unusual voltage or AC issues. Based on a post Steve Frank made last week, I’m wondering if my phone, which is supposedly an “unlocked, tri-band” phone, might be usable in Japan (albeit with a different number) if I get a pre-paid SIM or something like that.

I’ve never done soldering of this type before, but the instructions linked a few helpful pages, and I got the hang of it. My previous metal-joining experience was some years ago, hanging around the Smithsonian’s Folklife Festival, where the museum exhibit staff were doing demos. Things were quiet, so they invited me behind the protective glass, put a mask on me, and showed me how to weld. I had the two slugs of steel I joined on my bureau for several years; I may still have them kicking around somewhere.

Soldering with a pressed circuit board is nothing like that; every component has a socket, some number of metallic collars around holes in the PCB. You run the component’s contacts through the holes, flip the board, then solder from the bottom. After you’ve heated both the collar and the contact for a second or two with the iron, you touch the wire of solder to the joint. It becomes a drop of metallic liquid, and if you’ve done it right, some kind of capillary action sucks the drop into the hole, cementing the contact in its socket and joining the component semi-permanently with the board.

I got out the multimeter I got for Christmas and checked input and output voltage, and it appears to be working as advertised. It doesn’t charge my phone yet, but there’s a particular resistor with two different options, and I may need to re-solder it in the other option to get my phone to like it. I also need better wire cutters so I can trim the excess contact wire from the back of the board; right now, it doesn’t sit down close enough to fit in the tin.

Update, 5/7: Thinking through the changes, I realized that the laptop should be sufficient for charging the phone; the battery pack is going to be most useful for charging an iPod on a lengthy plane trip. So the excess leads are clipped, and the PCB is stuck down in the tin; no more soldering on this one. Maybe I’ll try another one for the phone, for fun, someday.

Now Playing: Block from Uninvited, Like the Clouds by The Church

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