The idea for this came about when passing by the Apple Store in Palo Alto, California late one night. After hours, when the store is "asleep," the lighted logos out front pulsate just like the power indicator on a sleeping Mac, and I just about fell over laughing. Unrelated, the following day a friend showed me his new Toyota Yaris, an adorable little economy car whose resemblance to the original "jelly bean" iMac was made even more apparent by the Apple logo decal he'd placed on the back window. The two just screamed to be combined...
Step 1: The Device
- The microcontroller itself. In this case I used a surface-mount PIC10F206 as it's what I had on hand, but just about any simple microcontroller will do provided you have the facilities to program it.
- A white LED. I've made throbbers using both surface-mount and 3mm through-hole varieties.
- A 3 volt lithium coin cell (CR2032 in this case).
- Battery holder.
- Circuit board to contain the components. Since I was using surface-mount parts, I opted to etch something for the occasion. If using through-hole components, the design is simple enough that a small piece of PCB perfboard with wire jumpers is likely sufficient.
- A clear rubber suction cup; pack of six from local hardware store.
- Glue of some sort. Hot-melt glue, silicone adhesive or cyanoacrylate "Krazy Glue" should all work fine.
- Apple logo decal adhered to a clear glass window.
Two components that typically appear in microcontroller and LED projects are conspicuously absent: there's no current-limiting resistor for the LED (the lithium watch battery used is intrinsically limited in current), and there's no decoupling capacitor across the microcontroller's power leads (simply wasn't needed in this noncritical application).