Electronics Let hit beat

Let hit beat project

I often go during the weekends to a festival in Montreal called the piknic electronic. Basically a bunch of people enjoying good music (well, depending on your tastes) in front of the St Laurent and a beautiful skyline.

I was looking for a project that would lead me to play around with LEDs and the lilypad so I began thinking of a way to display the emotion felt when you are dancing and reacting to the music. Thus came the idea of a sweatshirt with embedded leds that would react to the wearer’s cardiac rhythm (I was strongly influenced by this project).

How to measure the cardiac rythm ?

A quick visit to my local electronics-for-hobbyist shop and I ended up buying a pulse sensor amped (see bottom of the page for references). The first thing to figure out was how to get a led blinking according to my pulse. I was very glad to find out that the “hello world” of the pulse sensor library was about…getting a led to blink according to the pulse value.


The (not as dirty as it would seem) sock under my finger is nothing else than an attempt at making a wristband to hold the sensor.

I then began to plan how to embed the leds in the sweatshirt, and what quantities would be needed. Since I’m such a bad drawer, I got some help from my laptop (I know, it’s a shame to do such a thing 😉 )


Next step : prototyping with the actual lilypad. I had some issues because the pulse sensor works best with a 3.3v input voltage re-fed to the aref pin in order to set REFERENCE(external) in the code. Unfortunately the aref pin is linked to the vcc on the lilypad, so I couldn’t use. The consequence is measure too sensible to noise for my taste.


Next step : sewing the leds on the back of the sweatshirt. The leds are from the lilypad collection, so they are specially made to be sewn and are washable. I used conductive thread. Disclosure : it was a real pain in the *** to sew the 20 leds together.


I wanted to be able to use the lilypad again on other projects, so I connected the pins I needed to magnetic snap buttons, and sewed the other end to the conductive threads.


Here is the final result.


And that’s it ! I will reboot this project soon (I hope) in order to improve it. The sensor wasn’t stable enough without the aref pin used so I’m going to use an arduino pro mini next time. Plus since I use 3 pins to turn on the leds, I always have a little delay for the middle rows of the heart, I don’t really know why but I sure don’t like it. So next version will be built with EL wire instead of Leds.

Stay tuned for more !

The parts :

  • 1 lilypad arduino 328
  • 1 lilypad power supply
  • 1 pulse sensor amped
  • 6 magnetic snaps
  • 20 sewable leds
  • conductive thread


    1. Unfortunately I think I broke the sensor tinkering with it but I’m planning on ordering/making a new one so I will as soon as it’s done !

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