My mother needs twice a day an alarm set to 3 minutes. Instead of always configuring the alarm on a phone or egg cooker to 3 minutes, I decided to make a simple alarm box, which triggers at a fixed time of 3 minutes.

The usage should be as simple as just turning it on and off. That's why this simple project was born. The user interface is very simple and exists of a switch, LED and piezo buzzer.

The base of this project is an Attiny13 from Atmel. Only 2 outputs are used for now, so there are some extra I/Os available for future expansion.

The alarm is powered by a 9V block battery.

After powering up, the following steps happen:

• Beep once at start, LED goes on
• After 1 minute, beep once and flash the LED once
• After 2 minutes, beep once and flash LED twice
• At the end (3 minutes), the pieze beeps and LED flashes forever until you power it off.

The code is written with WinAVR becase of the compact flash size of the ATtiny13. Fuse bits are: LF=0x6A; HF=0xFF, Lock=0xFF