This traffic light model is designed to accommodate six 5mm LEDs, and can be wired to work with the Chibi Clip, a programmable circuit board available at Chibitronics.com. The chip clips on to the model, and once programmed, will operate the lights.
Students can program the Chibi Chip using block or text code, as described at chibitronics.com. It allows for multiple challenges, from a simple flashing yellow light, to full operation of all 6 lights on two sides.
• The base is intentionally off-center to account for the weight of the Chibi Clip when attached.
• You'll want to stuff something inside after the lights are installed to prevent "internal light bleeding", since that can make it look like an LED is on when it is off. I just used a rolled up tissue, but anything opaque will do.
Here's a video demo that includes the wiring diagram: