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If a PIR sensor turns off your office lights while you are sitting still, an Infineon radar project can provide a more responsive motion signal for that space. It connects a BGT60LTR11AIP radar board to a PSoC6 microcontroller, then publishes target states to Home Assistant over MQTT. It is a hands-on maker build—not a finished, whole-room presence sensor—and still needs wiring, firmware, MQTT setup, and careful placement.
What radar changes—and what it does not
A passive infrared (PIR) sensor detects changes in infrared radiation as a person moves through its sensing zones. That makes PIR useful, inexpensive, and relatively easy to constrain, but a seated person typing intermittently or reading may not create enough movement to keep it triggered.
Doppler radar detects movement from changes in reflected radio waves. In the Infineon project, small movements in the sensor’s detection area may keep a target signal active when a PIR would time out. That is not the same as reliably detecting a completely motionless person: this board provides simple target and phase/direction-style signals, not the distance, zones, or stationary-person tracking associated with more advanced mmWave systems. The project author reported that their radar continued recognizing a seated desk user where an infrared sensor had repeatedly switched off a light; that is an account of one setup, not a controlled comparison. Read the project account.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchRadar can also detect unwanted movement, including beyond the intended area, and its behavior depends on placement, materials, and reflections. PIR is often the better choice when low power, simplicity, and a defined field of view matter more than continued detection of a mostly stationary occupant.
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What you need
- Radar board: Infineon S2GO-RADAR-BGT60LTR11, a Shield2Go evaluation board built around the XENSIV BGT60LTR11AIP radar sensor and integrated antenna. See the Infineon board page and user manual.
- Controller: Infineon CY8CPROTO-062-4343W PSoC6 Prototyping Kit, with a MicroPython setup compatible with the project.
- Connections and enclosure: USB cable, suitable power, and the correct Shield2Go connector arrangement or jumper wires. A 3D-printed housing is optional; the project includes printable parts.
- Network and software: A working Home Assistant installation, an MQTT broker, Home Assistant’s MQTT integration, MicroPython on the PSoC6, and a MicroPython MQTT client such as
umqtt.simple.
The radar board is an evaluation module, not a consumer-ready sensor. Expect to handle controller wiring, software, calibration, and enclosure decisions. Pin names and electrical behavior should be checked against the board revision and schematic before wiring; do not treat example GPIO assignments as universal.
Prepare Home Assistant and MQTT
Home Assistant needs to connect to a broker that the PSoC6 can also reach. The Home Assistant MQTT integration guide describes broker setup and discovery. For many Home Assistant OS installations, the official Mosquitto Broker app is the simplest route. Home Assistant Container or Core users typically manage a broker separately. On segmented or remote networks, check DNS or IP reachability, firewall rules, and broker authentication. Do not expose an unsecured MQTT broker directly to the public internet.
MQTT discovery lets the device describe its entities to Home Assistant rather than requiring each sensor to be configured by hand. The default discovery prefix is homeassistant, and a binary-sensor configuration topic follows the general pattern homeassistant/binary_sensor/<node_id>/<object_id>/config. Its JSON payload needs a stable unique_id, a state_topic, and appropriate component and device metadata. Consult the current MQTT discovery documentation and MQTT binary sensor documentation when shaping the payload.
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesDiscovery configuration and sensor state are separate messages: discovery tells Home Assistant what the entity is; state messages tell it whether the target is on or off. Retain discovery configuration or resend it when Home Assistant announces its MQTT birth, so entities can be recreated after a restart. Give each board and entity a stable, sufficiently unique identifier; the original example’s two-hex-character suffix can collide in a multi-device deployment. Use a separate application namespace for ordinary state topics, and add availability information so Home Assistant can distinguish an offline device from a sensor reporting no target.
Read the radar signals and publish entities
Define the entities
The project exposes two binary sensors: target detected, and a phase/direction signal described as target approaching. The target entity is the useful starting point for occupancy-oriented automations; use Home Assistant’s motion device class if representing it as a motion detector. The direction signal is auxiliary and may not fit a standard device class. It is meaningful only while a target is detected, so mark it unavailable when no target is present rather than presenting it as a dependable entry event. The original project follows that approach. See the project’s implementation.
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- Security : The motion sensor light bulb will turn on automatically when you enter the detection range and then turn off after left, you won’t be stumbling around in the dark. (NOTE: when you find that the radar sensor light bulb is on the first time it is turned on during the day, please do not worry, as this is the self check initiated by the LED light bulb program. After about 2 seconds, the light bulb will automatically turn off)
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Include manufacturer, model, firmware version, and a stable device identifier in device metadata. A device identifier should be represented in the format expected by the current discovery schema; check the current binary sensor documentation rather than copying an older payload unchanged. For a deployment with several entities, Home Assistant’s device discovery approach can avoid repeating device metadata.
Keep topic names and IDs consistent
Use one state-topic base for runtime messages and distinct discovery topics. For example, a target sensor might be configured with a state topic such as smarthome/radar/<device_id>/target, while its discovery configuration is published to homeassistant/binary_sensor/<device_id>/target/config. The exact device ID must be unique and stable across restarts. Each entity also needs its own unique ID. Verify that the topic in the discovery payload exactly matches the topic used by the publishing code.
A binary sensor accepts ON and OFF by default; publish those values unless the discovery payload explicitly defines different payload strings. Retained state can make the latest value available immediately after a subscriber reconnects, but a retained ON can be misleading if a device disappears while the target is detected. Use availability and a Last Will strategy to communicate loss of connection, and decide deliberately whether state retention is appropriate. See the MQTT binary sensor options.
Read GPIO inputs safely
The tutorial combines two digital GPIO inputs for target and direction. Its sample constructor accepts pin arguments but then hardcodes pin names internally, so it should not be treated as reusable wiring code without correction. Pass the selected pins through to the input objects, and confirm the PSoC6 pin mapping and radar board’s electrical behavior against the board manual.
Polarity and pull configuration depend on the wiring and board output. Verify whether each signal is active-high or active-low and whether the input needs an internal pull-up or pull-down before setting inversion in firmware. A mistaken polarity can make a sensor look permanently active or inactive. The original code’s pin hardcoding and short device ID are reasons to validate the example before scaling it beyond one bench setup.
Rank #3
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Handle reconnects instead of assuming a permanent connection
Wi-Fi loss, broker restart, or a Home Assistant restart can interrupt publication. Reconnect Wi-Fi before MQTT, catch connection errors, and ensure the loop continues to service the chosen MQTT client’s keepalive. The project describes periodic client.ping() calls with its MicroPython MQTT implementation; whether that is needed depends on the library version, keepalive settings, and code, not on a universal Mosquitto rule. On reconnect, republish discovery when required and update availability. A Last Will can let the broker publish an offline state if the device drops unexpectedly.
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After the device publishes valid discovery configuration, check Home Assistant’s device and entity lists for the radar device. Then confirm that the target entity changes when a person enters and leaves its detection area, and inspect the direction entity only while a target is present. If the device does not appear, work through the transport and discovery path in order:
- Confirm the MQTT integration is connected to the intended broker and the microcontroller can reach that broker.
- Check broker credentials and any firewall, DNS, or network-segmentation rules.
- Inspect the published discovery topic: it must use the configured prefix and a valid binary-sensor path.
- Validate that the payload is valid JSON and includes a component definition, stable unique ID, and state topic.
- Confirm that the device actually publishes discovery and that it is retained or resent after Home Assistant restarts.
- Use broker or Home Assistant MQTT logs to verify the discovery message arrives.
If the entity exists but stays unknown, check that a state message has been sent, the state topic matches exactly, and the payload is ON or OFF as configured. Home Assistant cannot update the binary sensor until it receives a matching state message, as explained in the MQTT binary sensor documentation.
Build an automation that tolerates gaps
A raw radar transition should not necessarily switch a light immediately. Use an occupancy helper or an automation with a delay so brief signal gaps do not cause distracting light changes. For example, turn an office light on when the target is detected, then turn it off only after the target has remained off for a suitable interval. Set that interval from observation in the actual room rather than treating one delay as correct for every installation.
For higher confidence, combine the radar signal with a door contact or PIR: a door opening or PIR movement can establish that someone entered, while radar can help maintain the occupied state as the person sits at a desk. This adds logic and another sensor, but can reduce false activation from movement outside the intended zone. Other uses include occupancy-based heating or ventilation control, provided the automation’s consequences and delay are appropriate for the space.
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- 【Precise Radar Detection — A Reliable Camping Companion】Unlike traditional PIR motion sensors that rely on heat and struggle in harsh conditions, Letwesaf radar motion alarm system uses advanced 24GHz millimeter-wave radar to detect real movement. Smart filtering reduces false alerts from wind, sunlight, leaves, or brush. This camping alarm can detect motion through tent, bushes, and light obstacles with consistent accuracy, helping reveal hidden threats even in total darkness for dependable outdoor security.
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Home Assistant can expose entities through other ecosystems, but discovery of an MQTT entity alone does not guarantee identical HomeKit, Google Home, or Matter behavior. The bridge or integration and supported entity type determine what is exposed.
Measure desk occupancy without calling it work time
The History Stats integration can calculate how long an entity held a chosen state over a period. A time-based sensor can use the discovered target entity and the on state for a daily total. In configuration, select the actual entity ID shown in Home Assistant rather than copying a placeholder: discovery names and generated IDs can differ.
The resulting value is the duration that the sensor reported its target state. It is not proof of continuous work: it can include breaks, another person, or a chair left in the detection area. Treat it as an occupancy estimate, not a productivity measure.
Test placement, false detections, and recovery
Test the assembled sensor in its intended room and enclosure. Record false-on and false-off events separately; a subjective impression that it “works” will not reveal whether a light stays on for passersby or turns off during quiet work.
- Try a seated person reading, typing, and moving a mouse, then an empty chair.
- Check a person walking past the room and a person in an adjacent room; repeat with the door open and closed.
- Test likely environmental sources of movement, such as fans, curtains, pets, or moving plants.
- Try the intended mounting angle, distance, sensitivity and hold-time settings, and enclosure. Material and geometry affect behavior; do not assume a plastic cover is transparent to the sensor in every installation.
- Power-cycle the controller and restart Home Assistant and the broker to verify discovery, state, and availability recover as intended.
- Disconnect Wi-Fi briefly and confirm the device reconnects and republishes what Home Assistant needs.
If the sensor stays on, check whether the radar hold-time setting is high, the target remains in range, movement or vibration is being detected, the firmware ever publishes OFF, or GPIO polarity is inverted. Also check delays in the Home Assistant automation itself. If it sees an adjacent room, adjust orientation and mounting position and repeat the test; the nominal pattern cannot account for every wall, door, furniture arrangement, or reflection.
When this DIY build is the right choice
The Infineon build suits a technically capable Home Assistant user who wants a local, privacy-preserving desk or single-zone experiment and is comfortable maintaining firmware and MQTT. It is less suitable when the requirement is a finished battery-powered product, reliable multi-person distinction, precise room zoning, or safety-critical occupancy detection.
A finished mmWave presence sensor may be a better fit when quick installation, an enclosure, zone tuning, or reduced firmware work matters most. Check its local Home Assistant integration, cloud dependence, power needs, zone support, firmware policy, and performance through the intended mounting surface before choosing. Another option is an ESPHome-based design if a supported component or usable interface exists for the specific radar module; native support for this Infineon board should not be assumed. For many homes, combining a PIR for quick motion with radar for continued occupancy is a practical compromise.
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