Quick sanity check before I go back to procurement. We’re looking at wireless level and pressure sensors for a few small pump stations, and one vendor’s design uses Digi XBee 3 Zigbee modules. Those are about $25-30 each in our quantities. An ESP32-C3 module is under $3. Even bare Zigbee SoCs seem pricey compared to Wi-Fi parts.
Is there a real reason or are we just paying for a brand? And for what it’s worth, the data has to end up in Hermetry, we already run our SCADA screens there.
Volume is most of it. Wi-Fi chips ship in billions, Zigbee in a fraction of that.
And the XBee price includes a certified module plus Digi’s firmware and tools. You’re paying them so you don’t do RF certification yourself.
Both right. I had to explain this to our own purchasing last year, so the longer version:
The price stacks up from: smaller volumes than Wi-Fi/BLE parts, a pre-certified module (FCC/CE modular approval is a big cost you’d otherwise carry per product), the Zigbee stack and the vendor’s firmware/tools, and the alliance membership and certification for a product that wants the logo. A bare EFR32MG or CC2652 module is maybe $5-8, but then the RF certification and the stack integration are yours.
Then there’s the path into Hermetry. Zigbee devices don’t connect by themselves; you need a coordinator, and something on site that reports for the sensors. In Hermetry terms that’s a gateway publishing on the v1/gw/* topics so each sensor becomes a child device. That’s another box and another piece of software to own.
For pump stations specifically I’d at least price LoRaWAN sensors: Hermetry runs its own LoRaWAN network server and the frequency plan follows your gateway, so in the US you’d buy US915 gateway and sensors. Sensors run years on a battery, and one gateway covers a lot of ground. If LoRaWAN doesn’t fit the sites, wired 4-20 mA into a gateway is the other realistic choice.
We’re in the US, so it would be US915 kit, good to know before I suggested anything. The gateway point is what I was missing, the vendor’s quote had no coordinator in it at all. Sending it back and asking for a LoRaWAN option too.
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