I’m looking around for DC or USB powered thermometers but I can’t seem to find any. Granted, the battery powered ones last many years, but I’m looking to keep my options open. Zigbee devices are preferable. Anyone know?
Like actual thermometer or temperature sensor?
I have so sooo many temperature sensors in my network. Thermostats ($15) plant moisture sensors ($3-$6 from overseas but battery) my window AC unit apparently has several sensors home assistant picked up, a cheap air quality monitor, temp/relay units, and a smart humidifier.
Seems a waste to build dedicated hardware when cheap options just bundle temp sensors willy-nilly.
ESPHome + DHT22 or DSB1820 + ESP32-C6 and a small hobby box plus power supply (old USB phone charger) and you can build your own.
I might do this option, thanks!
I literally just did this over the past few weeks. I bought four ESP32-C3 minis on expansion boards (The expansion boards come with PH2.0mm connectors and built in battery charging management, so that I can add battery power next - already ordered the LiPo batteries. At the moment they’re plugged into USB-C phone chargers) and four SHT-41 temperature and humidity meters. I then installed the espressif development environment and (don’t shoot me, I was under time pressure) vibe-coded the setup for the ESP boards: they broadcast the readings every 10 seconds via mosquitto.
I also bought a barebones raspberry pi and made it subscribe to the mosquitto feeds and write the data to a sqlite database, and created a basic flask website that reads the data from sqlite and shows the graphs and the temperature readings to anyone on my local wifi.
My code is on codeberg - I’d be happy to share the link if any of this is relevant to you.
Discontinued IKEA VINDSTYRKA (Zigbee) or ALPSTUGa (Matter) come to mind.
I’m not sure why you’d NOT want a battery powered one, because as you say, the batteries last years, and a USB powered one would waste much more electricity over time, but I digress.
If you have any mini SoC boards or ESP32 devices laying around, you can get dirt cheap 2-pin external temp sensors. Works on anything with a GPIO pin out that supports simple I/O.
Anything you find that is Zigbee by nature will be battery powered, however, you might be able to find a device with a different purpose that happens to have temp sensors that export data you could monitor.
I do have a Pico sitting around. Maybe I can use it for a thermometer project.
Picos are very bad for battery applications. If you do end up doing this, make sure it is mains-powered like your original thought.
Esp32s, MSP430s, and nRF chips have sleep currents down to around 5uA or less.
Picos have sleep currents of 1-4mA. That is 1000x higher and the battery will only last for a few days instead of a few years.
Thanks for the insight, good to know.
Most of mine are, however plug-in devices also work as repeaters such as my air quality monitor (USB) and smart plugs. I’ve found they really help with dead zones.
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I modded all of my sensors by adding a usb-c port and 5v-3.3v mini converters
Perk is, if done right you can still use battery if needed
I recognize it’s not the answer to your question, but the ZigBee ones I have run on AAA batteries and last about a year on a charge.
With Eneloops, even after a decade they still keep over half their charge capacity. Could probably go 15-20 years per battery in regular trickled use with at most quarterly swaps - I think that’s kinda ideal operation for these guys.
One battery every 15 years, and an annual swap when it drops off my HA is a small price to pay for the flexibility of being able to deploy anywhere with zero infrastructure. I have a dozen sensors and would not want to have to wire each one.
FYI - Stock white charger that came with eneloops did not like how low the voltage gets when they run low in the temperature sensors, so I swapped for the “super pro” charger and it’s significantly better at managing the batteries: https://camelcamelcamel.com/product/B0B2WXJH43
