HC-SR501 PIR
Also known as: SR501 · PIR motion sensor · Presence & motion
Still shipped by the million: a dollar of instant motion detection. The 2026 pattern is PIR + mmWave together — PIR for instant lights-on, radar for lights-off when you're still.
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At a glance
⚑ flag an error| Measures | motion |
|---|---|
| Accuracy | Classic passive-infrared motion; fast trigger, no static detection |
| Interface | GPIO (digital out + retrigger/time potentiometers) |
| Supply | 4.5–20 V (onboard LDO) |
| Battery-viable | Yes (deep-sleep friendly) |
| ESPHome | Generic ESPHome component (adc/gpio) — binary_sensor (gpio) |
| Typical price | $1-2 (street, varies) |
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Which one do I buy?
PIR sees *motion*, mmWave sees *presence*. If your lights turn off while you read a book, you wanted mmWave (or both).
Clone check
Medium clone risk. All are clones; quality varies batch to batch — buy a few, keep the good ones.
Good for
Gotchas to know
- Mount it away from the ESP32's antenna: Wi-Fi bursts false-trigger PIRs wired too close.
- Runs on 3.3 V only via the bypass-the-LDO hack (feed 3.3 V to the pin after the regulator).
- The big dome is slow and wide; the AM312 is the compact alternative.
Wiring it up
Simple wiring: one data GPIO on any ESP32 dev board.