The development of the previous two prototypes — a glove and a wristband — provided valuable insights into the requirements for wearable technologies giving autonomic feedback, leading to the construction of this third version. It uses a Polar chest strap to detect a users pulse and translate it instantaneous into vibrations on a users wrist. It also is the first functional prototype providing possibilities for continuous, shared autonomic feedback between two people, albeit only across a short distance.
The image below gives an impression of the overall appearance of the prototype and the belt, that is used to get a users HR.
The actual components involved can be seen in this circuit diagram, and include the transistor-based motor circuitry mentioned in the post about the previous prototype. With it in place, constant and reliable control of the vibration motor at various intensities is possible.
The great benefit of using an ECG-type sensor to measure heart rate is its low level of invasiveness: Apart from putting the belt on, there is little action required by users, and next to no constraints are placed on their natural pattern of interaction. Battery-life is extensive and the sensor starts its transmission only once the pads are connected to the skin.
From a technical point-of-view the only downside to this solution is that a special receiver is needed to decode the signal sent by the chest strap. This has several consequences: (1) while it enables remote transmission of HR signals, its range is limited to about 1.5 meters, and thus is unable to form an adequate broadcasting mechanism on its own. Instead, an additional component is needed to get the data from the microcontroller across further distances. Furthermore, (2) the receiver hardware itself is difficult to obtain and rather expensive. I have summed up relevant information and alternative solutions over in this post, also giving a general overview over DIY-solutions for monitoring a person’s HR that I have investigated.
Despite its limitations, it has potentially all the functional components needed to start experimenting: (1) Reliable detection of HR activity, (2) reliable transmission of HR activity to a wristband unit, (3) reliable generation of vibro-tactile feedback. With these constraints met, the next steps will consist of conducting informal tests with shared autonomic feedback, in addition to variation in HR feedback to various arousal-inducing stimuli. Results will be documented and published on this blog.