“An Arduino powered birthday reminder device that’ll wish you happy birthday for 37 years on a single CR2450 (540 mAh) coin cell.
Yes, you read the title correct. Have you ever forgot your birthday? Or what if you can gift to someone you love, a device that’ll wish them on their birthday for 37 times? I kid you not, this simple Arduino powered birthday alarm that runs on a single CR2450 coin cell can wish your loved ones (or yourself) a happy birthday for 37 years, before the battery run out of juice.
Spoiler alert: that 37 years is the result of calculations based on real measurements. In practical, the device will only work for as long as the coin cell live, which as per manufacturers is about 10 to 12 years. Still not bad right?!
I think this is the first time somebody makes a birthday alarm like this, becasue I tried searing for similar projects but found nothing.
I built this as part of the Hackaday Coin Cell Challenge. This birthday alarm thing simply popped into my mind and I started researching how long we can run something on a coin cell. I’ve never used the sleep modes of any microcontrollers before. So I had to learn everything about making MCUs run at insanely low currents and save every bit of energy from a cell. It was a challenge really! I used ATmega168P as the microcontroller (actually I modified an Arduino Nano that has ATmega168P on it by removing all the unwanted components such as the voltage regulator, USB bridge etc.) and used Arduino IDE to develop the firmware.
The time and birthday date can be programmed via serial monitor over USB. Once the time and alarm are set, the MCU goes to sleep. When the current RTC time matches your birthday every year, the LED will flash for a minute and will print a happy birthday message to the serial monitor. The average current consumption is below 2 uA which makes it possible to run it for more than 37 years on a CR2450 (540mAh) Lithium coin cell.
I’ll walk you through how to build this in step by step now.”