RCWL-0516 + Battery Enclosure by Michaelo

Last crawled date: 3 years, 1 month ago

Home Security with an inexpensive Microwave Radar Sensor
This project includes a 3d printed enclosure for the RCWL-0516 Microwave Radar Sensor and one 18650 3.2 volt LiFeP04 battery. The enclosure also includes enough room for an ESP32 to provide communication via WiFi or BLE...
Basic Operation
When the sensor detects intrusion it wakes the ESP32 from deep sleep, the ESP32 in turn can either analyze the situation further or fires up the WiFi or BLE and send the appropriate data... Once done it returns to deep sleep reducing the current consumption greatly...
Battery Choice (updated 27/02/2018)
The ESP32 will operate from 2.3v to 3.6v and as the RCWL-0516 appears operate reliably down to ~3.0 volts. Charging the LiFEP04 to 3.6 volts should allow approximately 28 days of operation, during which time the battery will discharge at 0.010 volts per day, increasing to 0.025 volts as the voltage nears the minimum 3.055 volt cutoff.
Testing: 02/02/2018 - 28/02/2018
After some initial testing with a single LiFePO4 battery charged to 3.6 volts (to allow for connection to a 3.3 volt microcontroller), it appeared that 28 days was possible for a battery charged to 3.6 volt. If however, we use a 5 volt tolerant microcontroller, we can charge the LiFePO4 to 4.2 volts (max safe charge) extending the period between charges.
Conclusion:
In real world testing I have determined that the minimum working voltage for reliable operation is approximately 3.1 volts (the sensor will continue to operate down to 3.0 volts or less, however, the intruder must pass close to the detector for reliable detection).
Basically unless your prepared to change/charge batteries every couple of weeks it is best to power the devices from the mains using a small USB type power supply. The only option is to find a method to reduce the quiescent current even further and this normally requires a passive sensor such as a PIR or possibly a microphone...