James Lewis Puts a Nordic nRF7002 Design Kit to Work Making a Dehumidifier Smart

Triggering an MQTT event every time the dehumidifier's tank full light goes on, this smart upgrade needs no warranty voiding.

Hackster contributor and self-proclaimed "Bald Engineer" James Lewis has designed a handy gadget for getting smart home notifications out of very-much-not-smart appliances like dehumidifiers — by detecting when a warning LED lights up.

"My goal is to turn [a] normal dehumidifier into an Internet Thing," Lewis explains of the project. "I want to know when its fill light is on, so I can 'unfill' it. Using a Nordic microcontroller and their Wi-Fi 6 chip, I will detect when it is full and then send a message to my phone."

A microcontroller and a photoresistor can turn even the most disconnected of appliances into a smart appliance, as James Lewis demonstrated. (📹: Element14 Presents)

There's no shortage of "smart" dehumidifiers out there, though most limit easy interactivity to a proprietary app. If you've got one with no connectivity at all, though, a drop-in notification upgrade is a major quality-of-life improvement — and rather than having to mess about with its inner workings, Lewis's solution is a much simpler: detecting when the existing on-board notification LED lights up.

Having initially tried to build a detector around the Seeed Studio XIAO BLE nRF52840 but running into a lack of RAM, Lewis turned to the official Nordic nRF7002 Design Kit. To this, Lewis added a simple photoresistor and a 3D-printed case — positioning the photoresistor over the dehumidifier's LED and having it fire off an MQTT message when it lights up, triggering an alert that the dehumidifier needs emptying.

More details on the project are available on the element14 Community site, and in the video embedded above.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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