50th Anniversary nanoKenbak-1
A few years ago, I saw the "Digirule 2", a programmable ruler-type device made with SMD components and thought "That would be really cool if it functioned just like a Kenbak-1." I also was just getting interested in surface mount technology. So I converted my pc board design from my µKenbak-1 and took a stab at creating an SMD device.
I'd like to say it a was a quick and easy task, but the project spanned a couple years, several revisions, and fumbling around with solder rework stations and eventually my own reflow oven. I guess that's the reason I'm in the hobby - the trial and error, problems and solutions, and of course buying really cool workshop gear.
The nanoKenbak-1 has the same ATMEGA328p programming from Mark Wilson as the µKenbak-1 (and the new full-size version). It also has a DS3231 real-time clock chip so it can be used as a fun binary/BCD clock on your desk.
It is kind of a power-hungry device. Because of that, I am powering it with an LIR2032 coin cell that recharges from the micro USB port. Fully charged, the battery will power the device for a bit more than four hours. Plenty of time to fill the 256 bytes with your own application! It includes a MCP73831T charge management controller, so you can leave it plugged into a USB power source continuously.
You'll notice a smaller battery on the back of the board. This provides power to the DS3231 chip to maintain the correct time, even when powered off.
Like the nanoKenbak-1? I suggest you follow the Kenbak-1 Google group.