This one is a very simple but cool project, something that I would recommend to anyone who is interested into DIY electronics, gadgets and learning new stuff in general. It is definitely one of those projects that don’t require too much time but you can learn a lot by making it and also earn a lot of credit by sharing it with your friends and family.
Below you can see a final product. It’s a heart shaped, touch sensitive, keychain for your loved ones. On the front side there is a smiley face drawing that has eyes and mouth. Eyes have two red LEDs that will start to pulse once you touch the keychain or place you finger on the smiley face (see it in action below)
On the back side there is a battery holder for coin cell battery, microcontroller (MCU) and four passives to support the MCU and front LEDs.
Components that you will need for this project
PIC12LF1822 Microcontroller, the brain behind our device
CR2016 for providing power to our device
4.7uF capacitor, two 200 Ohm resistors and 2 RED LEDs. All with footprint 0603 (imperial)
Detailed BoM is attached with rest of the source files.
Let’s see how this thing actually works
We want to detect when someone is interacting with our keychain and when that happens we will turn on the LEDs to signify something like “I love you”, “I miss you” or anything else that you want. Since this is a keychain first, it has to look and feel nice. Putting a tactile button would sure make our life easy but it would also make device bulky and ugly, and we don’t want that. So instead of using a tactile button, we are going to use touch sensor aka cap sense. Basically same thing that you have in phones touch screen, payment terminals and etc.
Read More: LED HEART KEYCHAIN