---
title: A Radar That Sees You Sitting Still
description: Why mmWave radar beats a motion sensor for someone sitting still, how the Everything Presence Pro pairs two radars with a PIR, and ceiling vs wall mounting.
image: https://willcurran.com/hubfs/will-curran-brand/radar-that-sees-you-sitting-still-cover-nolane.png
---

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# A Radar That Sees You Sitting Still

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Will Curran Jul 24, 2026 · 6 min read

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![An abstract dark scene: a small sensor at the top sends orange radar arcs down toward the outline of a seated figure at a desk, next to the title A radar that sees you sitting still.](https://willcurran.com/hs-fs/hubfs/will-curran-brand/radar-that-sees-you-sitting-still-cover-nolane.png?width=1600&height=900&name=radar-that-sees-you-sitting-still-cover-nolane.png)

My thermostat's room sensor once decided I was in my office for about half a day after I had left, and it kept turning a light back on in an empty room. The motion sensor in the same room had the opposite problem: sit still at the desk long enough and it turned the lights off on me. The fix was a sensor that can see someone breathing. I now run three Everything Presence Pro units, and the one in my office is the one this post is about.

## Motion sensors see movement, not people

A PIR motion sensor reads changes in heat across its view. Walk in and it fires at once. Sit and type for twenty minutes and, as far as it can tell, the room is empty. So every automation built on plain motion is a bet on the off-delay. Make it short and the lights go out while you work. Make it long and everything stays on long after you leave.

mmWave radar changes the bet. It sees very small movement, down to a chest rising and falling, so a still person stays a person.

## Two radars and a PIR in one box

The Everything Presence Pro does not pick one sensor. It stacks three, plus temperature, humidity and light:

- **A static presence radar** (DFRobot SEN0609, up to 25 m). The vendor describes it as optimized for detecting very still people over long periods.
- **A tracking radar** (HiLink LD2450, up to 6 m). It reports X/Y positions for up to three people, which is what makes zones possible.
- **A PIR** (Panasonic, 12 m) for the instant "someone just walked in" trigger.

The sensor combines all three into one occupancy output, and the vendor recommends that output for most automations. The PIR gives you speed, and the static radar gives you the hold. It runs ESPHome on an ESP32 and shows up in Home Assistant with no cloud account, powered over PoE or USB-C. They were about $94 each before import duties, and they were backordered for months.

## Ceiling or wall: decide before you drill

I bought the ceiling mounts along with the sensors, and the most useful thing I learned before mounting anything was that the two radars want different things.

The tracking radar is built for a wall. It maps people on a flat plane in front of it, so mounted at chest height and aimed across a room it covers most of that room. Point it straight down from a ceiling and the useful tracking area shrinks to roughly 2 m around the sensor, because everyone is nearly underneath it. That figure comes from people testing it on the Home Assistant forum, not from the spec sheet.

The static radar and the PIR do not care as much. Pointing down, they are excellent at one job: telling you that somebody is at the desk directly below.

![Top-down comparison of tracking radar coverage in the same synthetic 6 by 6 metre room. Left: a sensor on the wall at about chest height covers a wide fan reaching about 6 metres across the room, narrowing at the sides. Right: a sensor on the ceiling pointing down covers only a circle about 2 metres in radius around it, centred over one desk. A note says the static radar and the PIR are not shown and both work well pointing down.](https://willcurran.com/hs-fs/hubfs/will-curran-brand/radar-that-sees-you-sitting-still-coverage.png?width=1440&height=1192&name=radar-that-sees-you-sitting-still-coverage.png)

So the choice depends on the question you are asking the room:

- **"Is someone at this one desk?"** Ceiling, directly over the chair. A small tracking area is fine because you only care about one spot.
- **"Where in the room is someone?"** Wall, about chest height, aimed across the room. You need that for more than one zone.

## How I actually use it

My office is set up with two zones: one for the desk and one for the rest of the room. The desk zone drives the things that only matter while I work, like the fan. The lights follow either zone and only start their off sequence when both are clear. The zones are drawn so they don't overlap, so the room zone goes clear the moment I sit down. Without the "either zone" rule, sitting down would have turned the lights off.

The office unit replaced both old sensors in that room as a trigger: the thermostat's occupancy sensor for the desk and the motion sensor for the lights.

## The parts that were not magic

**A ghost held the room.** Right after setup, one zone read "occupied" around the clock. The tracking radar was reporting a target that never moved, and its position never lined up with where I actually was. It was a solid object near the sensor, not a person. An exclusion zone over that spot fixed it. I checked by sitting at the desk while the other zone read clear and nothing turned off. The lesson: look at the raw target positions before you blame your automation.

**Radar still blinks.** The desk zone kept dropping to clear for a minute or two at a time while I sat there. Real departures were much longer than that. Whatever turns things off has to wait well past the blinks, and a short off-delay sits right on top of them.

**Moving air counts as motion.** A fan pushing air across a zone produces ghost targets of its own. This is a documented problem with these sensors, and the fix is an exclusion zone or a tighter zone.

## Read the manual. Really.

I have my assistant help with Home Assistant work, and early on its knowledge of this sensor turned out to be secondhand, not the vendor's documentation. I sent it the full docs. It paid off a couple of weeks later, at a firmware update. I had assumed an update meant redrawing my zones. The vendor's notes for that update said the zones would carry over. The release notes also named the crash the update targets.

Spec sheets tell you what a sensor can do. The manual tells you how it behaves when things change.

## If you are about to try this

- **Decide the question first.** One desk means ceiling. Zones across a room mean wall.
- **Use the combined occupancy output** for on and off, not the tracking radar alone. Tracking is for deciding where someone is.
- **Watch raw target positions for a day** before trusting a zone. Anything that never moves is furniture.
- **Mask fans, windows and doorways** with exclusion zones from the start.
- **Set off-delays from what you see**, longer than the sensor's short blinks and shorter than a real trip out of the room.

## Build it yourself

What it does: turns things on the moment someone walks in, keeps them on while that person sits completely still, and turns them off soon after they actually leave. The parts:

- **A multi-sensor mmWave presence sensor** with a static radar, a tracking radar and a PIR. The Everything Presence Pro is the one I use.
- **PoE or a USB-C supply**, and a ceiling or wall mount depending on the question above.
- **Home Assistant with ESPHome**, plus the vendor's zone tool to draw detection and exclusion zones.

How the pieces fit: the sensor publishes occupancy, per-zone presence and target positions to Home Assistant. Automations turn things on from occupancy or a zone and turn them off only after every zone that matters has been clear for a set time.

Give this to your AIHelp me set up an mmWave presence sensor in Home Assistant for \[room\], so \[devices\] turn on when someone enters, stay on while they sit still, and turn off soon after they leave. The sensor is \[model\], with \[list its radars and PIR\]. First, read the vendor's documentation end to end and tell me which outputs to use for on and off. Ask whether I care about one spot (like a desk) or where someone is in the room, then recommend a ceiling or wall mount and explain what that does to the tracking range. Help me plan the zones and exclusion zones, and list common false-trigger sources to mask, like fans, windows, doorways and fixed objects. Before writing any automation, have me log the raw target positions and zone states for a day, then pick off-delays from that data. If zones are mutually exclusive, make sure the off logic waits until all relevant zones are clear.

If you have found a better way to tame fan ghosts, I would like to hear about it.

Filed under [Home](https://willcurran.com/blog/tag/home)

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Will Curran

I spent sixteen years building one company, and I have been in the event industry since 2007. These days I write about the technology I actually use — trucks, radios, home infrastructure, and the tools that survive past the first invoice.

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