| Need | Best-fit technology | Example products from this category | Key advantage | Main limitation |
|---|---|---|---|---|
| Walk-through lighting, entry alerts, basic automation | PIR / Passive Infrared | HC-SR501 PIR motion sensor, SR602 PIR sensor module, HC-SR505 mini PIR sensor | PIR sees changes in heat through a pyroelectric element and Fresnel lens, so it is a low-cost fit for motion-triggered lights and alarms. The HC-SR501 gives 3 to 7 meters detection distance with adjustable sensitivity and delay. | PIR does not reliably detect a person sitting still, so it is the wrong choice for desk, couch, bathroom, or bed occupancy. PIR also will not work through glass because glass blocks the 8–14µm IR band it reads. |
| Detecting a seated or sleeping person | 24GHz mmWave presence radar | HLK-LD2410B human presence radar, Ai-Thinker Rd-01 with WiFi and Bluetooth | mmWave presence radar can detect micro-motion like breathing, so it is the right fit when lights must stay on while someone is still. The LD2410B detects both moving and stationary targets. | Higher power draw and more setup than PIR make these poor battery candidates. |
| Hidden install behind glass, plastic, wood, or inside an enclosure | Microwave radar / Doppler radar | HW-M10-A microwave motion sensor, RCWL-0516 microwave radar sensor, RCWL-0515 microwave radar sensor | Microwave and mmWave radar can detect through drywall and glass, which helps with hidden installs. The HW-M10-A specifically penetrates wood, glass, and plastic. | Through-material detection can also create next-room false triggers, so this is a trade-off, not a free upgrade. |
| Battery-powered motion node | Low-power PIR | SR602 PIR sensor module, HC-SR505 mini PIR sensor | PIR modules have far lower quiescent current than radar. SR602 and SR505 fit small, battery-minded builds better than radar boards. | You give up true presence hold; a still person will disappear from detection. |
| Short-range hand-wave control | Gesture sensor | APDS-9960 gesture and RGB sensor, PAJ7620U2 gesture recognition sensor | Good for swipes, proximity, and touchless UI over I2C. | Gesture sensors are for swipes and proximity, not room-scale automation. APDS-9960-class gesture sensing is only about 4–8 inch (10–20cm) range. If you need line-of-sight object distance instead of ambient human motion, use an ultrasonic distance sensor instead. |
For interactive projects, the difference between motion sensing and gesture control prevents the most common category mix-up.
| Product name | Sensor type | Supply voltage | Range | Angle or coverage | Idle or power note | Delay or trigger adjustment | Startup note | Best fit |
|---|---|---|---|---|---|---|---|---|
| HC-SR501 PIR motion sensor | PIR | — | 3 to 7m | — | — | Adjustable sensitivity; adjustable delay 0.3–5 min; two trigger modes (L/H) | Initial 10 to 60 second calibration period | General-purpose adjustable PIR |
| SR602 PIR sensor module | PIR | — | 5m | — | 20µA sleep current | Adjustable output high level time 2.5s to 1 hour | — | Low-power PIR for compact nodes |
| HC-SR505 mini PIR sensor | PIR | — | 3m | — | Low standby current, <60µA | — | — | Ultra-compact PIR |
| D203S PIR motion sensor | PIR | 3–6V | 5m | 120° reaction angle | — | — | — | Native low-voltage PIR build |
| D203B PIR motion sensor | PIR component | 3 to 15V DC | — | 120° detection angle | 5 to 14µm sensitivity | — | — | Component-level PIR integration |
| RCWL-0516 microwave radar sensor | Microwave Doppler radar | 4–28V DC | 7m | 360° sensing angle | 3.2GHz operating frequency | — | — | Wide-coverage radar with broad supply range |
| RCWL-0515 microwave radar sensor | Microwave Doppler radar | — | 12m typical | — | 2.7GHz signal | — | — | Longer typical radar reach |
| RCWL-0513 microwave radar sensor | Microwave radar | 3V to 30V | 15m typical | — | — | Adjustable repeat trigger time | — | Widest-supply RCWL-class option |
| HW-MS03 microwave sensor | Microwave radar | — | 5–9m | — | 2.4GHz to 5.8GHz; 100mA max output current | — | 10 to 30 second startup time | Indoor radar with design caveats |
| HW-M10-A microwave motion sensor | Doppler radar | — | 1m to 30m | — | 10.525GHz; penetrates wood, glass, and plastic | Adjustable delay 3s to 200s | — | Tunable hidden-mount radar |
| HLK-LD2410B human presence radar | 24GHz FMCW presence radar | — | 5m with 0.75m resolution | — | Detects moving and stationary targets | Bluetooth or serial port parameter adjustment | — | Configurable indoor presence sensing |
| Ai-Thinker Rd-01 with WiFi and Bluetooth | 24GHz FMCW presence radar | 3.0V–3.6V | — | — | Supply must provide at least 500mA; detects moving and stationary targets | — | — | Powered wireless presence build |
| Hi-Link LD2450 human presence radar | 24GHz FMCW mmWave radar | — | — | Measures distance, angle, and speed | Ultra-small 15 x 44 mm size | — | — | Wall-mounted tracking-focused radar |
| Hi-Link LD2461 human presence radar | 24GHz mmWave radar | — | 8m moving target range | Angle measurement accuracy 2° | Tracks 5 people simultaneously; current draw up to 400mA | — | — | Multi-person tracking, not low power |
When pairing with modern ESP32 boards, check both supply voltage and logic level instead of assuming every module is natively 3.3V-safe. For more detail on how standard PIR modules behave in Arduino builds, see how standard PIR modules behave in Arduino projects.
| Build priority | Best-fit PIR | Why | Trade-off |
|---|---|---|---|
| Easiest tuning | HC-SR501 PIR motion sensor | Adjustable sensitivity, adjustable delay from 0.3–5 min, and two trigger modes (L/H) make it the right call when tuning matters more than size. It also covers 3 to 7 meters. | Full-size board, plus a 10 to 60 second calibration period at power-up. |
| Low-power battery node | SR602 PIR sensor module | 20µA sleep current and 5m range make it the stronger battery-minded option. Output high level time adjusts from 2.5s to 1 hour. | Sensitivity is not easy to tune; changing it means changing chip resistors. Timing is easier to adjust than sensitivity. |
| Smallest footprint | HC-SR505 mini PIR sensor | The 10x23mm body and <60µA standby current fit very tight enclosures. | Shorter 3m detection distance, so choose it for size, not coverage. It is not a better HC-SR501, just a smaller trade-off. |
| Native low-voltage supply | D203S PIR motion sensor | Runs on 3–6V with 5m range and a 120-degree reaction angle, which simplifies low-voltage controller builds. | Less built-in tuning guidance than the HC-SR501. |
SR505 and SR602 are not “better HC-SR501s.” They are smaller or lower-power trade-offs. If the room must stay occupied while someone sits still, skip all PIR options and move straight to LD2410B-class presence radar instead. For a compact Arduino build, how the SR602 behaves in practice is worth checking before you choose.
If you expect to use RCWL-class radar, ways to wire and stabilize an RCWL-0516 build help set expectations before you start.
| Project | Best-fit product | Why it fits | What to watch for |
|---|---|---|---|
| Arduino or bench prototyping | HC-SR501 PIR motion sensor | The most adjustable PIR in this budget set, with 0.3–5 min delay and L/H trigger modes, so it is the easiest starting point for a human motion sensor for Arduino projects. | Bare sensor modules still need a host such as an Arduino board for automation logic. |
| ESP32 battery node | SR602 PIR sensor module | 20µA sleep current makes it the strongest listed PIR fit for battery-conscious motion nodes. | Confirm logic-level behavior with your exact controller and clone revision. |
| Occupancy sensing in a room | HLK-LD2410B human presence radar | Detects stationary targets and allows Bluetooth or serial adjustment, so it keeps lights or fans on where PIR would time out. | Better suited to always-powered indoor installs than deep-sleep battery builds. |
| Direct lighting or load switching | PIR 5050 LED sensor switch for 12–24V loads, or AC 220V PIR motion switch for mains lighting | The 12–24V switch supports 6A max load current, 8m induction range, and adjustable delay from 1–10 min. The AC switch runs on AC 100–240V with selectable 3s, 45s, or 4min delays and <0.1W standby power. | Most sensor modules only output a logic signal for a relay module input or MOSFET gate; they do not switch mains directly. |
| Hidden install behind non-metal surfaces | HW-M10-A microwave motion sensor | Penetrates wood, glass, and plastic, with adjustable delay from 3s to 200s. | Through-material detection can also catch motion beyond the intended area. For deeper setup detail, see using a microwave radar sensor when hidden mounting matters. |
| Compact enclosure | HC-SR505 mini PIR sensor | 10x23mm size and <60µA standby current make it practical where space is tighter than range needs. | Short 3m detection distance and less room for tuning. |
| Powered wireless presence build | Ai-Thinker Rd-01 presence sensor with WiFi and Bluetooth | 24GHz FMCW sensing for moving and stationary targets, plus onboard wireless capability. | It requires 3.0V–3.6V with at least 500mA supply current, so it is not a tiny battery-node part. |
| Longer-range hidden motion coverage | RCWL-0515 microwave radar sensor | 12m typical sensing range suits broader motion coverage without relying on line of sight. | Radar placement matters because coverage can extend through materials. |
No — PIR detects changes in heat, not stationary presence, while LD2410-class 24GHz presence radar detects moving and stationary targets through micro-motion. If someone will be reading, sleeping, or sitting at a desk, a PIR can time out even though the room is still occupied.
Yes, in many builds, but voltage matters: HC-SR501 often needs a 5V supply while commonly outputting 3.3V, and SR602-style low-voltage PIR modules are the safer native 3.3V route. Some clones can output 5V on the signal pin, so measure first or level-shift before connecting to ESP GPIO.
PIR cannot work through glass because glass blocks the 8–14µm infrared band it reads, while microwave and mmWave radar can detect through drywall and glass. That makes radar useful for hidden installs, but it can also create triggers from the next room.
PIR is the battery-friendly choice, with idle draw around roughly 50–70µA in this class and 20µA on the listed SR602 card. LD2410-class radar draws far more, and the listed Rd-01 requires a supply capable of at least 500mA, so presence radar is the wrong fit for tiny battery nodes.
Most bare modules output a logic signal suitable for a relay module input or MOSFET gate, not for switching mains directly. If you want direct switching, use a dedicated sensor switch such as the 12–24V PIR 5050 LED Sensor Switch or the AC 220V PIR Motion Switch.
PIR modules commonly need about 30–60 seconds of warm-up after power-on, and the HC-SR501 specifically lists an initial 10 to 60 second calibration period. Test code should ignore triggers during that window instead of treating it as a fault.
APDS-9960-class and PAJ7620-class parts are near-field gesture sensors with roughly 4–8 inch (10–20cm) range, while PIR and radar parts are for room motion or presence. Choose gesture parts for swipes and proximity, not for detecting movement across a room.
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