what are the best privacy-friendly occupancy sensors for offices without cameras?
dd_Growth 2026-10-08 11:10:31 556 Views3 Replies For offices, mmWave sensors are good. They can detect stationary occupants better than PIR sensors.
PIR is an affordable and simple, but may miss people sitting still.
mmWave is better for presence detection. mmWave may detect movement through open doorways.
Ultrasonic sensor is also another camera-free option, though room conditions can affect performance.
For privacy, process sensor data locally when possible. Store occupancy status instead of individual movement histories. Test false triggers from adjacent rooms before deployment.
Check each sensor's detection range, sensitivity, and interface. When evaluating occupancy sensors, engineers should confirm specifications in the datasheet and use platforms such as Unikeyic to check availability and alternatives.
Which controller will you use: ESP32, Arduino, or a building-management system?
love.forcircuits Thanks for the detailed reply, really helpful.
I'm still in the research/prototyping stage and haven't locked in a controller yet (likely ESP32 for flexibility). My target use case is a shared / co-working style office: I need to detect whether individual seats or desks are occupied, so people can quickly see which spots are free, ideally fed into a simple dashboard.
I was originally looking at mmWave - 80GHz Liquid Level Detection Sensor（https://www.dfrobot.com/product-2959.html）,
but I've since realized that one (SEN0676) is an 80GHz liquid-level sensor — not for people. So I wanted to ask your team directly:
Which DFRobot sensor would you recommend for seat-level presence detection in an open-plan co-working space?
From what I can tell, the C4002 (SEN0691) looks like the right fit — it detects stationary occupants (someone sitting/typing) and lets me set the detection range so I can limit it to a specific desk and ignore people walking in the aisle or at adjacent seats. Before I buy a few for testing:
1. Is the C4002 indeed the recommended model for this, or would you suggest something else?
2. For seat-level coverage, do you recommend one sensor per desk, or can one C4002 reliably cover a small cluster of 2–4 desks with the range tuning?
3. How bad are false triggers from adjacent desks / passersby in an open office, and how tunable is that in practice?
Appreciate the guidance.
hi，for office occupancy where people sit still, go with mmWave, not PIR. PIR only fires on movement, so a person working at a desk reads as "empty" once they stop moving. An mmWave presence sensor holds the "occupied" state even when the person is still - which is exactly what office occupancy wants. And neither uses a camera, so both stay privacy-friendly.
As for "reliable" - that's hard to vouch for from listings alone; I'd check the product's review/wiki and test one in a real desk corner before committing.
Jason.Miao 