TIME: 9 HOURS
(1) PC board (RadioShack #276-149; $1.99)
(1) Freeduino Really Bare Bones Board Kit .25 Amp (Wulfden Shoppe #RBBBK; $12)
(1) LED 8x8 matrix (SparkFun Electronics #COM-00681; $4.95) [Please note: this is not the same LED used in this project. It is a replacement product with similar specs.]
(1) 180-ohm resistor network (Mouser #652-4116R-1LF-180; $0.58)
(1) JST connector (SparkFun Electronics #PRT-08613; $0.95)
(1) 3.7V LiPo battery (SparkFun Electronics #PRT-00339; $11.95)
1. Assemble the Freeduino Really Bare Bones Board kit. Do not add the “pilot light” LED and the voltage regulator circuit to the Freeduino (e.g., pin D13). Also, forgo adding header pins to any of the Freeduino PCB holes that correspond to the digital and analog I/O pins that will be used in this project (see above wiring schedule).
2. Download our sketchbook code. Upload this code onto your completed Freeduino.
3. Push the 8x8 LED matrix into the PC board. This is a very difficult insertion. Carefully splay the two rows of LED pins apart and push all pins into place. You can hold the LED matrix on the board by bending the dual pin setups together on the underside of the board.
4. Solder short lengths of wire to all of the LED matrix pins that are used in this project.
5. Connect the resistor network to the select matrix pins.
6. Using the above wiring schedule, wire each of the matrix pin wires to their respective Freeduino pin PCB hole. Connect the matrix pins from the resistor network to their respective Freeduino pin PCB holes.
7. Run a short black wire and a short red wire from the JST connector (see the LiPo battery’s connector for proper orientation) to pins 1 (GND) and 2 (+5V), respectively, on the Freeduino.
Check all of your wiring, then recheck your wiring, again. Plug the LiPo battery into the JST connector and check for proper lighting of the LED matrix. If you don’t see the matrix flashing the startup time (e.g., 1200 hours), immediately disconnect the battery and recheck your wiring. Be patient, however, it takes a couple of seconds for the Dot • Watch to start flashing the startup time.
Once the wiring checks out, wait until 12 noon (local time) and plug the battery into the Dot • Watch circuit. Clock watching is now fun, again.single page
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.