### Your heart beat drives a machine to drop ink at the rate in which it beats.

Classes
Introduction to Physical Computing

We will hook up a heart rate sensor to detect someone's pulse. Once the pulse begins being registered, it will activate a solenoid valve to drop ink at the same rate as the heart beat. This will drip onto a sheet of paper that will make one revolution in 30 seconds. Once the revolution is complete, the solenoid will quit dripping and the person having their pulse read can take the sheet of paper.

Background
Initially we intended to complete this project for our physical computing mid-term but it turned out to be too demanding. In that version of the machine, we tried various ways of detecting a heart beat and finally settling on a pulse rate oximeter. The results however were unreliable. Also, our solenoid valve was causing us some issues due to its large size.

For this version, we are using a heart rate board from Polar and getting very accurate readings. Further we are using a new solenoid with a much smaller diameter thus giving us much more accurate drips.

Audience
Our target audience is really anyone with a pulse.

User Scenario
A person walks up to the machine and places their hands on the metal plates. As board searches for a pulse, the machine reacts to let the user know that it knows there is someone present. Once the pulse is detected, the machine will begin to resonate with the pulse and switch on the motor that rotates a postcard sized sheet. For 30 seconds the machine drips ink at the same rate as the persons heart beat. After that amount of time the motor will shut off and the machine will go silent. The person can then get the slip of paper.

Implementation
The structure is made of metal tubing in order to support the bags of ink and house the machinery. The overall size is not going to be very large, perhaps a footprint of 1m squared at the max.

Conclusion
We have learned a lot about pulse detection and getting accurate drips from a solenoid.