Figure an Arduino most matches the "Other" category. To be specific, it isn't an Arduino brand, it is a DigiSpark, but the trouble isn't with the device itself. The problem is with a buzzer. I got ...

Here is the circuit of an Arduino-based Panic Alarm! The wiring is very simple so that even a novice can construct this interesting circuit without any difficulty. Arduino is a family of ...

The base unit houses an Arduino board which polls the buttons to see which is pressed first. The LED on the appropriate buzzer box is illuminated so the players know who got in first.

Our schematic consists on 3 elements which are: Photoresistor (LDR), Piezo Buzzer, 1 – 10 kΩ. The LDR can be connected any way you want because doesn’t have polarity. For resistance you can use from 1 ...

But there are really just the two speeds with the current programming. Inside the cool laser-cut box is an Arduino Uno and a 9V battery, plus a current-limiting resistor and the all-important buzzer.