Hardware

This project necessitates the design of a wearable, wireless ECG unit for real-time performance during dynamic and unpredictable body movement, including contemporary dance. A brief survey of existing technologies for heart rate detection, outlined below, has informed the development of our current prototype.

Requirements and Constraints

  • Low profile, sturdy, sweat resistant, amenable to extreme movement
  • Low cost (<$60)
  • Easy to acquire
  • Rechargeable/replaceable battery with long life (3+ hours)
  • Wireless
  • Wide transmission range (wide enough to cover a large stage)
  • Transmission of the raw ECG waveform

Wearable ECG Unit Prototypes

Prototype 2: Developed with Emmanuel Flety at IRCAM, November 2014

Proto01
Proto02b

This unit consists of:


Rejected Solutions

Before settling on the above hardware, we evaluated a number of other potential solutions which were ultimately rejected as they do not fulfill the requirements and constraints of our project as outlined above.

Polar H7 Bluetooth LE Heart Rate Monitor

71dFGyc02zL._SL1500_

While this unit is reliable, easy to acquire, relatively inexpensive, and transmits its data using a simple protocol (Bluetooth LE), it sends only the heart rate, not the raw ECG signal. Since we are interested in the phase of the signal as well as the variability, access to the raw ECG is important. We also found the short transmission range (10m) of Bluetooth LE and this unit’s susceptibility to occlusion problematic as they would require each dancer to carry a cell phone.

Sparkfun Polar Heart Rate Monitor Interface

08661-01

While this board is intriguing, we decided not to evaluate it as the RMCM01 is no longer manufactured and seems unlikely to be in the future.

Pulse Sensor

earclip_1024x1024

This inexpensive and easy to use device worked relatively well and produced a clear signal which, unlike an ECG, was not susceptible to muscle noise. However, we found that the device had to be positioned carefully with just the right amount of pressure and that it was easily displaced during the execution of fairly modest choreography.

Medical ECGs

While our initial desire was to use medical ECGs, their cost was prohibitive and their reliance on proprietary (and expensive) software made them impractical.

OpenBCI

OpenBCI is a compelling platform and we had a chance to try out an evaluation board, but as it is designed for EEG, it proved to be overkill and cost prohibitive for our purposes.

Future Platforms

A quick search for “Wearable ECG” shows that there is no shortage of interest and many interesting projects under development. While our current prototype meets our needs, we will keep a close watch on the new devices that emerge over the next few months/years.


 

Respiration Sensors

As we are interested in the relationship between breath and heart activity, we have experimented with two different respiration sensors to date.  Both measure the displacement of the chest/ribs/belly during breathing.

BioPak Respiration Belt Transducer

Details: http://www.biopac.com/respiration-recording

biopac

 

Textile Respiration Belt on Tank-top

Developed by Adrian Freed at CNMAT, August 2014

respiration_shirt