Step 1: Requirements
- The design must not limit the functionality of the peephole. Thus, the device must be either transparent, or easily removable.
- It must not modify the peephole in any way.
- The design must be low powered, I don't want to have 50 watts of power pumping into my dorm room.
- And of course, since I am a poor college student, it must be low-cost.
Step 2: Parts
- Wall wart: I used a 3.3 volt wall wart to power the entire device.
- Wire: Some small gauge wire, preferably stranded for flexibility and durability.
- Resistor: A proper dropping resistor for the LED.
- Red LED: The most important part of the device, it needs to match the color of HAL's light. I managed to find an LED that matched the color of HAL's eye very well.
- Rubber Stopper: This holds the LED in place inside the peephole.
- Heat Shrink: I always use small gauge heat shrink to insulate the bare wires. You could always use electrical tape instead.