Sensors and connectivity

A project log for Entropy Wheel Heat Recovery Ventilator

Rotating perforated disk counter-flow heat exchanger maintains indoor temperature while exchanging fresh outdoor air.

bryan-williamsBryan Williams 08/19/2014 at 20:090 Comments

This project was something I began working on before the Hackaday Prize was announced, and sensors and connectivity were always part of the plan. At the very least, temperature and relative humidity need to be measured as condensation can be a problem without a drain to send it to. In certain circumstances, shutting down fresh air input to function as exhaust only would allow it to function as a ventilator but drawing fresh air into the home through the normal leakage points. For R&D purposes, the temperature sensors allow me to estimate efficiency and understand how things are working. Pressure sensors can detect other situations: filter blockage and fan speed compensation (if I find a BLDC fan solution) and also wind/venturi effect compensation -- or weather prediction via barometric pressure.

Other thoughts would be passive IR motion detection/presence sensing and perhaps LED lighting to go with it. Options of nightlight level or full 10W LED lamp at about 800 lumens.

Connectivity to the unit itself will be via low-cost, long-range, low bit rate Nordic Semiconductor 2.4GHz NRF24L01+ modules. The Cypress PSOC 4 I an eyeing as the embedded processor has just 32KB of program FLASH and 4KB RAM, so Wifi would be hard pressed to fit and overkill for the application. Since I have plans for many nodes constrained by minimum cost & minimum power, collecting sensor data I think would be best served by a bridge device with Ethernet or Wifi connectivity, be it Arduino, Raspberry Pi, BeagleBone Black, etc. Optimally, integration into a whole-house automation & alarm system would be the final goal.

With the sensor package and wide range of potential usage preferences, the short packet exchanged would carry sensor readings from the heat exchanger and also carry configuration information to the embedded controller. Example configuration would specify things like motion activation activities (fan on, light/nightlight on), timed auto turn-off, scheduled activation, filter alarms (timed or back pressure-based), and whatever else I can think of. Spooky noises mode Easter egg?