The Interro is an Arduino-based 8-player contestant lockout system designed as an open source kit. It’s meant to allow school kids to play trivia games, both extracurricularly and in class. It’s meant to be significantly cheaper than existing commercial solutions, which cost upwards of several hundred dollars.
- Cost – As a kit for schools, cost had to be at a minimum.
- Easy to build – The kit was meant to be built by amateurs, so it couldn’t be too difficult.
- Easy to hack – People had to be able to modify the system and expand it.
- Concept. I’ve been toying with the idea for the system since high school, and refining my ideas over that time.
- Parts Selection. I went with the Arduino platform as a base to allow hackability, and went standard 3.5mm stereo cables to connect the buzzers to the controller, and a USB power adapter to power the unit. Standard, easily-obtained parts in case they break and have to be replaced.
- Circuit Board Design. I laid out the PCB in EAGLE with an eye towards easy of assembly.
- Programming. The firmware was of my own design, using standard Arduino libraries to allow people to customize the system easily.
- Over-reliance on Arduino libraries – One major issue involved the dimming of indicator LEDs when the buzzer was inactive. Turns out that the code I’d written was calling the Arduino pinMode function repeatedly, which seems to flip the pin to an input and then to an output when it’s run. This was tricky to track down, though easily resolved when found.
- Cost tradeoffs – A perennial battle in Engineering, keeping the costs low either removes desired features or impacts reliability (using lower quality parts). Hitting the price target while maintaining quality is an ongoing challenge with this project, which is part of the reason it isn’t done yet.