My daughter likes buttons. She's learning letters. I was bored over winter break and had these parts laying around... so I built her a "Button Box" based around an Arduino. Open source, hackable ...

The Arduino UNO R4 boasts a 3x performance increase over the UNO R3 and , in addition, SRAM has been upgraded from 2kB to 32kB, and flash memory from 32kB to 256kB to support more complex projects.

The Arduino Uno-compatible board has an MCS-51 (often called 8051 instead) instead of the usual ATmega328P/ATmega168. Specifically, [ElectroBoy] uses the AT89S52 .

But if you can push your button while your yellow LED is lit, ... Inside the cool laser-cut box is an Arduino Uno and a 9V battery, plus a current-limiting resistor and the all-important buzzer.

To build this project, all you need is three main components: an Arduino Uno, a 16x2 LCD, and a push button. You can connect everything to a breadboard to keep it simple.

The Arduino UNO R4 Minima and the Arduino UNO R4 WiFi. But apart from the obvious wireless connectivity hinted by the name what other differences do the microcontrollers have.