Hi everyone,
I'm trying to set up an e-textil project involving a PulseSensor (http://pulsesensor.com/) and a lilypad. My problem is the following :
The pulse sensor gives its best output when powered at 3.3v and when analogReference(EXTERNAL)is enabled.
The problem is that I can't figure out how to use the aref pin on the lilypad. It seems to be somewhere when you look at the schematics, but it's linked to other pins so if any one of you guys would clarify the situation regarding that issue, it would be wonderful !
I tried using the pulsesensor at 5v. It works (not as well, but it could be enough) except that when I power it externally (AAA battery) vs from usb, it doesn't anymore. My guess is that :
- when powered from usb, the sensor receives precisely 5.05V.
- when powered from battery, it receives 4.90/4.95V.
Since in that case the analog reference is internal, my guess is that it is set to 5v and that's why it doesn't work when I'm running at 4.90.
I'm new to electronics and arduino so please excuse me if I misunderstood everything about how to get it working 
link to the project : http://www.twitter.com/LetHitBeat