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PIR motion sensor for ProbeHarbor

An HC-SR501 PIR sensor reports motion in the garage, shed or workshop to ProbeHarbor, with an RGB LED that glows green when quiet, red on motion and blue if Wi-Fi or ProbeHarbor is unreachable.

Starter25 min115200 baud

For ProbeHarbor, open-source freeze and flood monitoring for garages, workshops, attics and crawlspaces, with live charts and alerts. This board sends its readings to a ProbeHarbor device; create one at probeharbor.dev.

Board

ESP32

3V3

GND

CMD

CLK

Fig. 1. Pins this project uses on the ESP32-DevKitC V4, 38 pin. USB connector at the bottom.

Wiring

From	To board	Note
PIR VCC	5V	The HC-SR501 needs 4.5 V or more; it has its own 3.3 V regulator
PIR OUT	GPIO 27	Its output is 3.3 V when high, safe for the ESP32 as it is
PIR GND	GND
RGB red	GPIO 25	Through 220 Ω
RGB green	GPIO 26	Through 220 Ω
RGB blue	GPIO 33	Through 220 Ω
RGB common leg (the longest)	GND	For a common-anode LED: to 3V3, and set COMMON_ANODE to true

Tested on this board

Not run on this board yet. Treat the wiring and code as a first draft.

Firmware, Arduino sketch for ESP32 Dev Module

// PIR motion to ProbeHarbor: an HC-SR501 reports motion to a ProbeHarbor push
// device, and an RGB LED shows what is happening.
// Green: quiet. Red: motion. Blue: Wi-Fi or ProbeHarbor trouble. Green blinking: PIR warming up.
#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>

// ---- Your settings ----
const char* WIFI_SSID = "your-wifi";
const char* WIFI_PASS = "your-password";
// ProbeHarbor: Dashboard, Devices, add a push device, copy its ingest address.
const char* INGEST_URL = "https://probeharbor.dev/api/ingest/YOUR_DEVICE_KEY";
// ProbeHarbor reads a true/false value whose name contains "motion" as a motion sensor.
const char* SENSOR_KEY = "motion1";
const unsigned long HEARTBEAT_MS = 5UL * 60UL * 1000UL;  // re-send the state every 5 minutes
const unsigned long MIN_GAP_MS = 10UL * 1000UL;          // never post more often than this
const unsigned long WARMUP_MS = 60UL * 1000UL;           // the HC-SR501 settles for about a minute

// ---- Pins ----
const int PIR_PIN = 27;
const int LED_R = 25, LED_G = 26, LED_B = 33;
const bool COMMON_ANODE = false;  // true if the LED's long leg goes to 3V3 instead of GND

// Root certificates for probeharbor.dev: Google Trust Services R1 and R4, and
// Let's Encrypt ISRG X1 and X2. Cloudflare issues the site's certificate from one of these.
const char* ROOT_CAS = R"PEM(
-----BEGIN CERTIFICATE-----
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)PEM";

bool motion = false;          // debounced PIR state
int sentState = -1;           // last state ProbeHarbor accepted
unsigned long lastPost = 0, changedAt = 0, retryAfterMs = 0;
bool trouble = false;

void setColor(uint8_t r, uint8_t g, uint8_t b) {
  if (COMMON_ANODE) { r = 255 - r; g = 255 - g; b = 255 - b; }
  analogWrite(LED_R, r);
  analogWrite(LED_G, g);
  analogWrite(LED_B, b);
}

// Returns the HTTP status, or a negative number if the request never got an answer.
int postMotion(bool on) {
  WiFiClientSecure tls;
  tls.setCACert(ROOT_CAS);
  HTTPClient http;
  const char* keep[] = {"Retry-After"};
  http.collectHeaders(keep, 1);
  if (!http.begin(tls, INGEST_URL)) return -1;
  http.addHeader("Content-Type", "application/json");
  char body[64];
  snprintf(body, sizeof(body), "{\"%s\":%s}", SENSOR_KEY, on ? "true" : "false");
  const int code = http.POST(body);
  if (code == 429) retryAfterMs = 1000UL * (unsigned long)max(10L, http.header("Retry-After").toInt());
  http.end();
  return code;
}

void setup() {
  Serial.begin(115200);
  pinMode(PIR_PIN, INPUT);  // the HC-SR501 drives its output high and low itself
  pinMode(LED_R, OUTPUT);
  pinMode(LED_G, OUTPUT);
  pinMode(LED_B, OUTPUT);
  setColor(0, 0, 80);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  while (WiFi.status() != WL_CONNECTED) delay(250);
  Serial.printf("wifi ok %s\n", WiFi.localIP().toString().c_str());
}

void loop() {
  const unsigned long now = millis();

  // Debounce: the PIR output has to hold a new level for 200 ms.
  const bool raw = digitalRead(PIR_PIN) == HIGH;
  static bool lastRaw = false;
  static unsigned long rawSince = 0;
  if (raw != lastRaw) { lastRaw = raw; rawSince = now; }
  if (raw != motion && now - rawSince >= 200) {
    motion = raw;
    changedAt = now;
    Serial.printf("motion = %d\n", motion ? 1 : 0);
  }

  const bool warming = now < WARMUP_MS;
  if (warming) setColor(0, (now / 300) % 2 ? 60 : 0, 0);
  else if (trouble) setColor(0, 0, 160);
  else if (motion) setColor(200, 0, 0);
  else setColor(0, 60, 0);
  if (warming) return;

  if (WiFi.status() != WL_CONNECTED) {
    trouble = true;
    static unsigned long lastTry = 0;
    if (now - lastTry > 10000) { lastTry = now; WiFi.reconnect(); }
    return;
  }

  const bool changed = (int)motion != sentState;
  const bool heartbeat = now - lastPost >= HEARTBEAT_MS;
  const unsigned long gap = retryAfterMs ? retryAfterMs : MIN_GAP_MS;
  if ((changed || heartbeat) && (lastPost == 0 || now - lastPost >= gap)) {
    lastPost = now;
    retryAfterMs = 0;
    const int code = postMotion(motion);
    trouble = code < 200 || code >= 300;
    if (!trouble) sentState = motion;
    Serial.printf("posted %s %s\n", motion ? "motion" : "quiet", trouble ? "FAILED" : "ok");
    if (trouble) Serial.printf("ProbeHarbor answered HTTP %d\n", code);
  }
}

3V3

GND

3V3

RST

GND

Fig. 1. Pins this project uses on the ESP32-S3-DevKitC-1, 44 pin. USB connector at the bottom.

Wiring

From	To board	Note
PIR VCC	5V	The HC-SR501 needs 4.5 V or more; it has its own 3.3 V regulator
PIR OUT	GPIO 4	Its output is 3.3 V when high, safe for the ESP32 as it is
PIR GND	GND
RGB red	GPIO 5	Through 220 Ω
RGB green	GPIO 6	Through 220 Ω
RGB blue	GPIO 7	Through 220 Ω
RGB common leg (the longest)	GND	For a common-anode LED: to 3V3, and set COMMON_ANODE to true

Tested on this board

Not run on this board yet. Treat the wiring and code as a first draft.

Firmware, Arduino sketch for ESP32S3 Dev Module

// PIR motion to ProbeHarbor: an HC-SR501 reports motion to a ProbeHarbor push
// device, and an RGB LED shows what is happening.
// Green: quiet. Red: motion. Blue: Wi-Fi or ProbeHarbor trouble. Green blinking: PIR warming up.
#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>

// ---- Your settings ----
const char* WIFI_SSID = "your-wifi";
const char* WIFI_PASS = "your-password";
// ProbeHarbor: Dashboard, Devices, add a push device, copy its ingest address.
const char* INGEST_URL = "https://probeharbor.dev/api/ingest/YOUR_DEVICE_KEY";
// ProbeHarbor reads a true/false value whose name contains "motion" as a motion sensor.
const char* SENSOR_KEY = "motion1";
const unsigned long HEARTBEAT_MS = 5UL * 60UL * 1000UL;  // re-send the state every 5 minutes
const unsigned long MIN_GAP_MS = 10UL * 1000UL;          // never post more often than this
const unsigned long WARMUP_MS = 60UL * 1000UL;           // the HC-SR501 settles for about a minute

// ---- Pins ----
const int PIR_PIN = 4;
const int LED_R = 5, LED_G = 6, LED_B = 7;
const bool COMMON_ANODE = false;  // true if the LED's long leg goes to 3V3 instead of GND

// Root certificates for probeharbor.dev: Google Trust Services R1 and R4, and
// Let's Encrypt ISRG X1 and X2. Cloudflare issues the site's certificate from one of these.
const char* ROOT_CAS = R"PEM(
-----BEGIN CERTIFICATE-----
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-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
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)PEM";

bool motion = false;          // debounced PIR state
int sentState = -1;           // last state ProbeHarbor accepted
unsigned long lastPost = 0, changedAt = 0, retryAfterMs = 0;
bool trouble = false;

void setColor(uint8_t r, uint8_t g, uint8_t b) {
  if (COMMON_ANODE) { r = 255 - r; g = 255 - g; b = 255 - b; }
  analogWrite(LED_R, r);
  analogWrite(LED_G, g);
  analogWrite(LED_B, b);
}

// Returns the HTTP status, or a negative number if the request never got an answer.
int postMotion(bool on) {
  WiFiClientSecure tls;
  tls.setCACert(ROOT_CAS);
  HTTPClient http;
  const char* keep[] = {"Retry-After"};
  http.collectHeaders(keep, 1);
  if (!http.begin(tls, INGEST_URL)) return -1;
  http.addHeader("Content-Type", "application/json");
  char body[64];
  snprintf(body, sizeof(body), "{\"%s\":%s}", SENSOR_KEY, on ? "true" : "false");
  const int code = http.POST(body);
  if (code == 429) retryAfterMs = 1000UL * (unsigned long)max(10L, http.header("Retry-After").toInt());
  http.end();
  return code;
}

void setup() {
  Serial.begin(115200);
  pinMode(PIR_PIN, INPUT);  // the HC-SR501 drives its output high and low itself
  pinMode(LED_R, OUTPUT);
  pinMode(LED_G, OUTPUT);
  pinMode(LED_B, OUTPUT);
  setColor(0, 0, 80);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  while (WiFi.status() != WL_CONNECTED) delay(250);
  Serial.printf("wifi ok %s\n", WiFi.localIP().toString().c_str());
}

void loop() {
  const unsigned long now = millis();

  // Debounce: the PIR output has to hold a new level for 200 ms.
  const bool raw = digitalRead(PIR_PIN) == HIGH;
  static bool lastRaw = false;
  static unsigned long rawSince = 0;
  if (raw != lastRaw) { lastRaw = raw; rawSince = now; }
  if (raw != motion && now - rawSince >= 200) {
    motion = raw;
    changedAt = now;
    Serial.printf("motion = %d\n", motion ? 1 : 0);
  }

  const bool warming = now < WARMUP_MS;
  if (warming) setColor(0, (now / 300) % 2 ? 60 : 0, 0);
  else if (trouble) setColor(0, 0, 160);
  else if (motion) setColor(200, 0, 0);
  else setColor(0, 60, 0);
  if (warming) return;

  if (WiFi.status() != WL_CONNECTED) {
    trouble = true;
    static unsigned long lastTry = 0;
    if (now - lastTry > 10000) { lastTry = now; WiFi.reconnect(); }
    return;
  }

  const bool changed = (int)motion != sentState;
  const bool heartbeat = now - lastPost >= HEARTBEAT_MS;
  const unsigned long gap = retryAfterMs ? retryAfterMs : MIN_GAP_MS;
  if ((changed || heartbeat) && (lastPost == 0 || now - lastPost >= gap)) {
    lastPost = now;
    retryAfterMs = 0;
    const int code = postMotion(motion);
    trouble = code < 200 || code >= 300;
    if (!trouble) sentState = motion;
    Serial.printf("posted %s %s\n", motion ? "motion" : "quiet", trouble ? "FAILED" : "ok");
    if (trouble) Serial.printf("ProbeHarbor answered HTTP %d\n", code);
  }
}

GND

3V3

GND

RST

GND

Fig. 1. Pins this project uses on the ESP32-C3-DevKitM-1, 30 pin. USB connector at the bottom.

Wiring

From	To board	Note
PIR VCC	5V	The HC-SR501 needs 4.5 V or more; it has its own 3.3 V regulator
PIR OUT	GPIO 4	Its output is 3.3 V when high, safe for the ESP32 as it is
PIR GND	GND
RGB red	GPIO 5	Through 220 Ω
RGB green	GPIO 6	Through 220 Ω
RGB blue	GPIO 7	Through 220 Ω
RGB common leg (the longest)	GND	For a common-anode LED: to 3V3, and set COMMON_ANODE to true

Tested on this board

Not run on this board yet. Treat the wiring and code as a first draft.

Firmware, Arduino sketch for ESP32C3 Dev Module

// PIR motion to ProbeHarbor: an HC-SR501 reports motion to a ProbeHarbor push
// device, and an RGB LED shows what is happening.
// Green: quiet. Red: motion. Blue: Wi-Fi or ProbeHarbor trouble. Green blinking: PIR warming up.
#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>

// ---- Your settings ----
const char* WIFI_SSID = "your-wifi";
const char* WIFI_PASS = "your-password";
// ProbeHarbor: Dashboard, Devices, add a push device, copy its ingest address.
const char* INGEST_URL = "https://probeharbor.dev/api/ingest/YOUR_DEVICE_KEY";
// ProbeHarbor reads a true/false value whose name contains "motion" as a motion sensor.
const char* SENSOR_KEY = "motion1";
const unsigned long HEARTBEAT_MS = 5UL * 60UL * 1000UL;  // re-send the state every 5 minutes
const unsigned long MIN_GAP_MS = 10UL * 1000UL;          // never post more often than this
const unsigned long WARMUP_MS = 60UL * 1000UL;           // the HC-SR501 settles for about a minute

// ---- Pins ----
const int PIR_PIN = 4;
const int LED_R = 5, LED_G = 6, LED_B = 7;
const bool COMMON_ANODE = false;  // true if the LED's long leg goes to 3V3 instead of GND

// Root certificates for probeharbor.dev: Google Trust Services R1 and R4, and
// Let's Encrypt ISRG X1 and X2. Cloudflare issues the site's certificate from one of these.
const char* ROOT_CAS = R"PEM(
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zj0EAwMDaAAwZQIwe3lORlCEwkSHRhtFcP9Ymd70/aTSVaYgLXTWNLxBo1BfASdW
tL4ndQavEi51mI38AjEAi/V3bNTIZargCyzuFJ0nN6T5U6VR5CmD1/iQMVtCnwr1
/q4AaOeMSQ+2b1tbFfLn
-----END CERTIFICATE-----
)PEM";

bool motion = false;          // debounced PIR state
int sentState = -1;           // last state ProbeHarbor accepted
unsigned long lastPost = 0, changedAt = 0, retryAfterMs = 0;
bool trouble = false;

void setColor(uint8_t r, uint8_t g, uint8_t b) {
  if (COMMON_ANODE) { r = 255 - r; g = 255 - g; b = 255 - b; }
  analogWrite(LED_R, r);
  analogWrite(LED_G, g);
  analogWrite(LED_B, b);
}

// Returns the HTTP status, or a negative number if the request never got an answer.
int postMotion(bool on) {
  WiFiClientSecure tls;
  tls.setCACert(ROOT_CAS);
  HTTPClient http;
  const char* keep[] = {"Retry-After"};
  http.collectHeaders(keep, 1);
  if (!http.begin(tls, INGEST_URL)) return -1;
  http.addHeader("Content-Type", "application/json");
  char body[64];
  snprintf(body, sizeof(body), "{\"%s\":%s}", SENSOR_KEY, on ? "true" : "false");
  const int code = http.POST(body);
  if (code == 429) retryAfterMs = 1000UL * (unsigned long)max(10L, http.header("Retry-After").toInt());
  http.end();
  return code;
}

void setup() {
  Serial.begin(115200);
  pinMode(PIR_PIN, INPUT);  // the HC-SR501 drives its output high and low itself
  pinMode(LED_R, OUTPUT);
  pinMode(LED_G, OUTPUT);
  pinMode(LED_B, OUTPUT);
  setColor(0, 0, 80);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  while (WiFi.status() != WL_CONNECTED) delay(250);
  Serial.printf("wifi ok %s\n", WiFi.localIP().toString().c_str());
}

void loop() {
  const unsigned long now = millis();

  // Debounce: the PIR output has to hold a new level for 200 ms.
  const bool raw = digitalRead(PIR_PIN) == HIGH;
  static bool lastRaw = false;
  static unsigned long rawSince = 0;
  if (raw != lastRaw) { lastRaw = raw; rawSince = now; }
  if (raw != motion && now - rawSince >= 200) {
    motion = raw;
    changedAt = now;
    Serial.printf("motion = %d\n", motion ? 1 : 0);
  }

  const bool warming = now < WARMUP_MS;
  if (warming) setColor(0, (now / 300) % 2 ? 60 : 0, 0);
  else if (trouble) setColor(0, 0, 160);
  else if (motion) setColor(200, 0, 0);
  else setColor(0, 60, 0);
  if (warming) return;

  if (WiFi.status() != WL_CONNECTED) {
    trouble = true;
    static unsigned long lastTry = 0;
    if (now - lastTry > 10000) { lastTry = now; WiFi.reconnect(); }
    return;
  }

  const bool changed = (int)motion != sentState;
  const bool heartbeat = now - lastPost >= HEARTBEAT_MS;
  const unsigned long gap = retryAfterMs ? retryAfterMs : MIN_GAP_MS;
  if ((changed || heartbeat) && (lastPost == 0 || now - lastPost >= gap)) {
    lastPost = now;
    retryAfterMs = 0;
    const int code = postMotion(motion);
    trouble = code < 200 || code >= 300;
    if (!trouble) sentState = motion;
    Serial.printf("posted %s %s\n", motion ? "motion" : "quiet", trouble ? "FAILED" : "ok");
    if (trouble) Serial.printf("ProbeHarbor answered HTTP %d\n", code);
  }
}

Parts

Quantity	Part	Where to buy
1×	ESP32 dev board	Buy at Amazon
1×	HC-SR501 PIR motion sensor
1×	RGB LED, common cathode or common anode (or three single LEDs)
3×	220 Ω resistors, one per LED colour
8×	Jumper wires

Amazon buy links may include an Associates tag, and this site may earn a commission from qualifying Amazon purchases at no extra cost to you. Adafruit links are direct.

Libraries

WiFi (built in), HTTPClient (built in)

Load it

In the Arduino IDE, install the esp32 board package and pick the board named above the sketch.
Paste the sketch, choose the board's port and upload. Hold BOOT if the upload stalls at Connecting.
Close the IDE's serial monitor, then open the bench here to watch the output.

Field notes

In ProbeHarbor, add a push device and paste its ingest address into INGEST_URL. The sketch sends {"motion1": true} or false: ProbeHarbor files a true/false value whose name contains motion as a motion sensor, shown as MOTION or CLEAR.
It posts when motion starts and stops, and again every 5 minutes so ProbeHarbor knows the sensor is alive. Posts are at least 10 seconds apart, well inside ProbeHarbor's 60 a minute, and if ProbeHarbor answers 429 it waits as long as asked.
The HC-SR501 has two orange trimmers. Sx sets sensitivity, roughly 3 to 7 metres. Tx sets how long the output stays high after motion, from about 3 seconds to about 5 minutes: turn it fully anticlockwise for the shortest time, so ProbeHarbor sees each visit separately.
Set the jumper to H (repeat trigger): the output then stays high as long as something keeps moving, instead of dropping out mid-visit. L gives one fixed pulse per trigger.
After power-up the sensor needs about a minute to settle and may trigger on its own. The LED blinks green during that minute and nothing is sent.
Which leg is common? On most 5 mm RGB LEDs it is the longest. If green shows as everything-but-green, you have a common-anode LED: set COMMON_ANODE to true and move the common leg to 3V3.
PIR sensors see warm moving bodies, so heaters, sunlight on a wall or a draught from a vent can trigger them. Point it away from windows and heat sources.

Not tested yet

Not tested on hardware or with ProbeHarbor yet. Compiles for every board listed with Arduino-ESP32 core 3.3.12.

Open the bench at 115200 baud

Community builds

Loading build reports from people who made this.

Built it? Send a build report with your board and what the serial port printed. Working reports become the "Tested on this board" entries above.