Summary Instructions Update: I am working on a LoverHearth v2 with Neopixels and a Adafruit Gemma The LoverHeart is just a simple wearable for times when you and your boyfriend/girlfriend want to get noticed in crowded places at warm summer night. It can be used as a necklace bracelet or you can stitch it to a tshirt or cap. They dont light up untill another one is close to it. Also for battery save there is a switch on the side where top is closed and the bottom is open. On later stages I am thinking of using NeoPixel and Gemma from AdaFruit for fancier lighting effects and quality use but you can keep it simple and don't use them. *more information avaliable on the pdf file Circuit: a. Infrared Heart Beat transmitter: Heartbeat transmitter is a simple 555 timer circuit. I had two options to decide for circuit; One of them is to use IR receiver commonly used in remote controllers which works 38kHz. The other is to use IR diode or IR transistor. In the first case use 38kHz clock and 1 Hz for the second case. For the calculation of 555 circuit values I use the tools below: http://houseofjeff.com/555-tim... https://en.wikipedia.org/wiki/... Adafruit Circuit Playground iOS application b. Heart Beat Light Circuit When “Lover Heart” sees IR light of the other “Lover Heart” it just convert invisible light to visible LED light.