Me again (the MOSI guy). The pizza oven demo went well so now I’m allowed a “real” first project: 8 sensors around our office, reporting to our Hermetry org. Four are door contacts on the store room, server room and two fire exits, four are temperature in the server room and the kitchen.
Half the internet says Zigbee, half says Wi-Fi. I read that Zigbee is lower power and makes a mesh, but Wi-Fi is everywhere already. Which would you pick for a first project? Ideally something I can’t mess up too badly.
Zigbee’s mesh is more reliable in an office with lots of walls, I’d go Zigbee.
Before picking, which ones can have a power supply? That decides more than the radio does.
The temperature ones can be on USB power, there are sockets nearby. The door contacts have to be battery, nobody will run cables to fire exits.
Then split it, that’s what I’d do as a first project too.
The 4 mains-powered temperature sensors: ESP32 on Wi-Fi, straight to Hermetry over MQTT. No gateway, nothing in between, every sensor is a device you can see connect and disconnect. It’s the shortest path and you learn the topics and payloads on something that’s easy to debug.
The 4 battery door contacts: not Wi-Fi. An ESP32 waking up, joining Wi-Fi and doing a TLS handshake for every door open eats AA cells in weeks. Buy ready-made Zigbee contact sensors (a couple of years on a coin cell), a Zigbee USB coordinator, and run a small bridge on a Pi that reports them as child devices of a gateway. More moving parts, so do it second, once the Wi-Fi ones work.
Emily’s not wrong about the mesh, but with 4 battery contacts there’s no mesh to speak of, battery end devices don’t route. Mains-powered Zigbee devices do.
There’s a decent overview of which way to connect what in the docs, it’s basically this reasoning as a table: Choose how to connect your devices.
Did the Wi-Fi temperature ones this week, all 4 on the board. Zigbee sticks and contacts arriving Monday. The “battery end devices don’t route” bit saved me from buying 4 more contacts to “build the mesh”, which was my actual plan.
Fair point on battery devices not routing, I had mains plugs in mind.
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