: Designing digital clocks using LCD or LED displays is a common introductory project. For example, a Digital Countdown Timer can be built using three control buttons to set minutes and seconds, with an alarm triggered upon reaching zero.

: Use an IR receiver (like the TSOP1738) connected to one of the interrupt pins.

Use a DS18B20 digital temperature sensor on a 1-Wire bus. This is easier and teaches bit-banging serial protocols.

: An EP51-style programmer allows you to read, write, and debug both the and AT89S51 series. Components