Tansy Peplau, HCIM
Zahra Ashktorab, HCIM





Heartbeat Sweater from Zahra A on Vimeo.


In this class, we have been looking at innovative ways to interact with the environment. How can we utilize what's available to us to convey our emotions or to communicate with people? One aspect of our emotions which is often hidden is our heartbeat. In our project we aim to translate our heartbeat in a potential mode of communication. If we communicate our heartbeat to others by visibly displaying its rhythm on our clothing, what kind of effect can that have on human communication? We aim to create a wearable item that displays the heartbeat.


  • Pulse sensor (which consists of an IR sesnor and emitter)
  • Breadboard
  • Arduino Uno
  • Wires and resistors (82, 10, 47, and 51 ohms),
  • A sweater,
  • LEDs (16)
  • Yarn for covering LEDs on sweater
  • Perfboard

photo (4).JPGLED-red.jpgMKSP11-2.jpgPulse Sensor, LED, and Arduino Board

Background Research

Traditionally, in a doctor's office, a physician follows your heartbeat by listening for it through a stethoscope. Another way that heartbeat can be detected is through the use of infrared emission and detection. When your heart beats, it is pumping blood throughout your arteries, thus changing the blood volume inside the tip of your finger. By emitting a IR light onto your finger you can detect the reflected emitted light by using a photo-resister to measure the heartbeat. In our project, we aimed to do exactly that. The sensor that we used (pictured above) consists of a emitter and detecter. Pictured below, is an image from a similar project that shows the reflection and detection process.

This is not our image. Taken from http://www.instructables.com/id/Microcontroller-measures-heart-rate-through-finger/
This is not our image. Taken from http://www.instructables.com/id/Microcontroller-measures-heart-rate-through-finger/

Project Description

Choosing an Appropriate Pulse Sensor

Our project depended on the ability to get a readable signal from the pulse sensor and for the LEDs to react to it. We tried a combination of different sensors before deciding on the pulse sensor that we have listed in our tools. Below, we have pictured the combination of the different sensors and emitters that we used.

external image 13325553100.jpgexternal image 00241-02.jpg
Other IR Sensors and Emitters Used

Because a user is constantly in contact with the hardware of this project, we needed to choose a sensor that would be easy to hold. While we could alter the hardware above so that it would be connected, the pulse sensor that we settled on fit snugly around the finger and seemed the most appropriate form of sensor to use.

Setting up LEDs
The LEDs are arranged on a perfboard along with resistors in the shape of a heart to represent the data picked up from the IR sensor. There are 8 sets in parallel of 2 LEDs in series. Each set of 2 LEDs in series requires 56 ohm resistance, but since we didn't have exactly that, we alternated combining (47 ohm + 10 ohm) resistors or (51 ohm + 10 ohm) resistors. We then sewed the LED perfboard setup into the shirt with the wires poking through and coming down through the sleeve.

Image of the Soldering Process

Final Product

Yarn was an appropriate medium, because the LEDs conveniently poked through it.


The wiring includes the LEDs and perfboard, the arduino, and the breadboard.



Though the goal of this project seemed simple, our biggest challenge was working with IR sensors and emitters. We tried several different types of emitters and all of them seemed to act differently. Additionally, they seemed to send different signals in different environments. The signals sent from the IR sensors range from 0 to 1023. At one point a signal was sent in the range (200-300), while at another point in time, in the same exact state the signal would range between (1020-1023). This proved to be an extremely frustrating challenge to overcome. Most of the resources that we found measures the difference between the last signal and the current signal. If a certain allotted amount of time had passed and the threshold was greater than or equal to a certain threshold, that was translated to a heartbeat. We experimented with the thresholds to find the most appropriate one with our sensor and setup, but even then the signals were unstable. Through all of our efforts, we experienced a definitive change between the signals when the finger was placed between the emitter and detector. Though the fluctuation was unstable, there was always a fluctuation in signals sent from the pulse sensor. This shows that this method of detecting heart rate is valid, but is dependent on stable and appropriate hardware.

Secondly, the instability of our sweater continued when we switched from the USB cable to a 9V battery. This is still an issue in which we are trying to solve. We utilized the multi-meter to make sure that the same amount of voltage was flowing through the components when it was connected to the USB cable as well as when it was connected to the battery. Our measurements showed that it was the same amount of voltage. When our heartbeat sensor was functional with the USB cable, its sensitivity was decreased when connected to the 9 Volt battery. The behavior change was quite challenging and for the purposes of our demo, we connected the Arduino to the cable.

Future Work

There is a great amount of potential in combining wearable items and technology in creating innovative interesting products. For our project, we chose to work on heartbeat and LEDs. However, we could easily apply temperature sensors and other available sensors and find interesting ways of expressing those results. Though the usefulness of such applications is questionable, communicating with someone whose heartbeat is visibly expressed on their shirt could change the mode of the communication, causing people to be friendlier when they realize that we (people, humans, etc.) are all the one in the same, as we all have a beating heart.