WiFi Humidity Sensor Lasts a Year or More Between Charges

This sensor unit consists of a Wemos D1 mini, a BME280, an XC6206 3.3V LDO, and a single 18650 cell — all housed inside a 3D-printed case.

Jeremy Cook
4 years agoSensors

If you’re going to implement an environmental sensor, you mostly likely don’t want to plug it in, and certainly don’t want to change/charge the battery every few weeks or even months. To make such a sensor, hacker Dave Davenport (AKA “Qball”) used a number of power-saving techniques to keep his running for over a year.

His setup — implemented on two sensor units — uses a Wemos D1 mini board for WiFi communication and to read the temperature and humidity from a BME280 sensor unit. Power is provided by an 18650 cell capable of 3400mAh of charge, and both have been operating for over 12 months with some juice left to spare.

Power tricks used include feeding the Wemos board 3.3V directly to bypass the regulator, and setting a static IP address instead of using DHCP. Cleverly, the BME280 sensors are fed power via a GPIO pin to make sure it’s fully powered down when not needed. With these changes the idle current is around 26µA, or .000026A, and while on-time is a little harder to determine, it’s only functioning for 1-3 seconds at a time.

To keep things nicely packaged, Davenport first experimented with a wooden enclosure, and is now using a 3D-printed case. This is certainly functional, but perhaps not as much fun as this shell-enclosed environmental monitoring station, which implements a few power tricks of its own.

Jeremy Cook
Engineer, maker of random contraptions, love learning about tech. Write for various publications, including Hackster!
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