# LED on MAX300102 does not light up

**URL:** <https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789>\
**Category:** Sensors\
**Created:** [March 25, 2026, 10:09am UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789 "2026-03-25T10:09:57Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![byte\_bandit](https://avatars.discourse-cdn.com/v4/letter/b/bbce88/32.png) [@byte\_bandit](https://forum.arduino.cc/u/byte_bandit)\
**Post date:** [March 25, 2026, 10:09am UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/1 "2026-03-25T10:09:57Z")

</div>

i'm having a similar problem as what was previously discussed here:

> [@MAX30102 was not found. Please check wiring/power](https://forum.arduino.cc/t/max30102-was-not-found-please-check-wiring-power/1410654):
>
> I’m new to robotics. I’m using a MAX30102 (black) heart rate sensor with an Arduino Uno and testing it with the SparkFun library’s Example 5. The wiring seems fine, but the sensor’s LED doesn’t turn on, and the serial monitor keeps saying: "Initializing... MAX30102 was not found. Please check wiring/power." What should I do to fix this? I have bought the sensor from [here](https://store.roboticsbd.com/sensors/2303-max30102-heart-rate-and-pulse-oximeter-sensor-module-robotics-bangladesh.html?srsltid=AfmBOooyAZxake4s0K4IryjcNIVZIu-l_d7jWRKN1Hszh-25TQKO2lfG) Here is the Schematic diagram: (Everything else is connected the same way, except I used the 3.3V pin on the Arduino inste…

I tried doing what was written there, but still nothing works.

---

<div class="post-metadata">

**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\
**Post date:** [March 25, 2026, 10:31am UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/2 "2026-03-25T10:31:31Z")

</div>

Have you tried the I2C scanner sketch?  
Do you have the same **exact** set-up as @zarin12027, same parts and wiring?

---

<div class="post-metadata">

**Author:** ![byte\_bandit](https://avatars.discourse-cdn.com/v4/letter/b/bbce88/32.png) [@byte\_bandit](https://forum.arduino.cc/u/byte_bandit)\
**Post date:** [March 25, 2026, 10:51am UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/3 "2026-03-25T10:51:08Z")

</div>

yes but still could not light up

 ![image](https://europe1.discourse-cdn.com/arduino/original/4X/1/b/f/1bf870e87d6bef271db6e2675708a0a4ee560eab.jpeg)  
 ![image](https://europe1.discourse-cdn.com/arduino/original/4X/0/3/6/03623ae64e9ba104e2d4f0b03bf4bd8baaedef48.jpeg)

---

<div class="post-metadata">

**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\
**Post date:** [March 25, 2026, 11:33am UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/4 "2026-03-25T11:33:09Z")

</div>

> [@byte\_bandit](#):
>
> yes

Does not look like it, that is not an Uno and it looks like you have other things connected.

Please provide information on the components you are using and a diagram showing how they are connected.  
Also post the code you are using, use code tags \<_CODE_/\>

---

<div class="post-metadata">

**Author:** ![byte\_bandit](https://avatars.discourse-cdn.com/v4/letter/b/bbce88/32.png) [@byte\_bandit](https://forum.arduino.cc/u/byte_bandit)\
**Post date:** [March 25, 2026, 11:36am UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/5 "2026-03-25T11:36:27Z")

</div>

![image](https://europe1.discourse-cdn.com/arduino/original/4X/d/a/8/da882fad83981fbd99926a8bc5402c4777c3d03e.jpeg)

```arduino
#include <WiFi.h>
#include <WebServer.h>
#include <Wire.h>
#include "MAX30100_PulseOximeter.h"
#include <OneWire.h>
#include <DallasTemperature.h>
#include <DHT.h> // Adafruit library

// Pin Definitions
#define DHTPIN 4
#define DHTTYPE DHT11
#define DS18B20 5
#define BUZZER_PIN 2 // CHANGED: Moved from 13 to 2
#define REPORTING_PERIOD_MS 1000

// Health Thresholds
const float TEMP_HIGH = 38.0;
const float TEMP_LOW = 35.0;
const float BPM_HIGH = 120.0;
const float BPM_LOW = 50.0;
const float SPO2_LOW = 90.0;

float temperature, humidity, BPM, SpO2, bodytemperature;

const char* ssid = "Project123";  
const char* password = "Password123"; 

DHT dht_sensor(DHTPIN, DHTTYPE); 
PulseOximeter pox;
uint32_t tsLastReport = 0;
OneWire oneWire(DS18B20);
DallasTemperature sensors(&oneWire);

WebServer server(80);              

// Heartbeat sound (short chirp)
void onBeatDetected() {
  digitalWrite(BUZZER_PIN, HIGH);
  delay(20); 
  digitalWrite(BUZZER_PIN, LOW);
}
 
void setup() {
  Serial.begin(115200);
  pinMode(BUZZER_PIN, OUTPUT); 
  
  // --- STARTUP BEEP ---
  // Confirms the buzzer is working on Pin 2 immediately
  digitalWrite(BUZZER_PIN, HIGH);
  delay(200);
  digitalWrite(BUZZER_PIN, LOW);

  dht_sensor.begin(); 
  sensors.begin();

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  
  server.on("/", handle_OnConnect);
  server.onNotFound(handle_NotFound);
  server.begin();

  if (!pox.begin()) {
    Serial.println("Pox Error - Skipping...");
  } else {
    pox.setOnBeatDetectedCallback(onBeatDetected);
  }
  
  pox.setIRLedCurrent(MAX30100_LED_CURR_7_6MA);
}

void loop() {
  server.handleClient();
  pox.update();
  
  // Read Sensors
  sensors.requestTemperatures();
  temperature = dht_sensor.readTemperature(); 
  humidity = dht_sensor.readHumidity();       
  BPM = pox.getHeartRate();
  SpO2 = pox.getSpO2();
  bodytemperature = sensors.getTempCByIndex(0);

  // --- ALARM LOGIC ---
  bool isEmergency = false;

  // Check for abnormal vitals
  // Only trigger if sensor values are "active" (above 10) to prevent false alarms when disconnected
  if (SpO2 > 10 && SpO2 < SPO2_LOW) isEmergency = true;
  if (bodytemperature > 10 && (bodytemperature > TEMP_HIGH || bodytemperature < TEMP_LOW)) isEmergency = true;
  if (BPM > 10 && (BPM > BPM_HIGH || BPM < BPM_LOW)) isEmergency = true;

  if (isEmergency) {
    digitalWrite(BUZZER_PIN, HIGH); // Alarm stays ON
  } else {
    // Pin remains LOW (unless chirping in the onBeatDetected callback)
  }

  if (millis() - tsLastReport > REPORTING_PERIOD_MS) {
    tsLastReport = millis();
    Serial.print("BPM: "); Serial.print(BPM);
    Serial.print(" | SpO2: "); Serial.print(SpO2);
    Serial.print(" | BodyTemp: "); Serial.println(bodytemperature);
  }
}

void handle_OnConnect() {
  server.send(200, "text/html", SendHTML()); 
}

void handle_NotFound(){
  server.send(404, "text/plain", "Not found");
}

String SendHTML(){
  String ptr = "<!DOCTYPE html><html><head><meta name='viewport' content='width=device-width, initial-scale=1.0'>";
  ptr +="<style>body{font-family:sans-serif; text-align:center; background:#f0f2f5;}";
  ptr +=".card{background:white; padding:15px; margin:10px auto; border-radius:12px; width:85%; max-width:400px; box-shadow:0 4px 6px rgba(0,0,0,0.1);}";
  ptr +="h1{color:#1a73e8;} .val{font-size:32px; font-weight:bold; color:#d93025;}</style></head><body>";
  ptr +="<h1>Patient Monitor</h1>";
  ptr +="<div class='card'><div>Body Temp</div><div class='val'>" + String(bodytemperature, 1) + " &deg;C</div></div>";
  ptr +="<div class='card'><div>Heart Rate</div><div class='val'>" + String((int)BPM) + " BPM</div></div>";
  ptr +="<div class='card'><div>SpO2</div><div class='val'>" + String((int)SpO2) + " %</div></div>";
  ptr +="<div class='card' style='font-size:14px; color:#555;'>Room: " + String(temperature, 1) + "C | " + String(humidity, 0) + "%</div>";
  ptr +="</body></html>";
  return ptr;
}

```

---

<div class="post-metadata">

**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\
**Post date:** [March 25, 2026, 11:58am UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/6 "2026-03-25T11:58:10Z")

</div>

Looks like you have a breadboard with the split power rails.  
You need to connect them with small wire connections like this

 ![image](https://europe1.discourse-cdn.com/arduino/original/4X/c/c/b/ccb2c33acf20e770c7177be7ed1240458244ac7f.jpeg)

---

<div class="post-metadata">

**Author:** ![byte\_bandit](https://avatars.discourse-cdn.com/v4/letter/b/bbce88/32.png) [@byte\_bandit](https://forum.arduino.cc/u/byte_bandit)\
**Post date:** [March 25, 2026, 12:27pm UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/7 "2026-03-25T12:27:16Z")

</div>

still max300102 LED did not light up. the code run successful but not reading for the heart beat rate and the oxygen level. Any solution for that problem?

---

<div class="post-metadata">

**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\
**Post date:** [March 25, 2026, 12:35pm UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/8 "2026-03-25T12:35:58Z")

</div>

zarin12027 used the MAX30105 library. Try the code zarin12027 used

---

<div class="post-metadata">

**Author:** ![byte\_bandit](https://avatars.discourse-cdn.com/v4/letter/b/bbce88/32.png) [@byte\_bandit](https://forum.arduino.cc/u/byte_bandit)\
**Post date:** [March 25, 2026, 12:45pm UTC](https://forum.arduino.cc/t/led-on-max300102-does-not-light-up/1447789/9 "2026-03-25T12:45:03Z")

</div>

i just run the code the max300102 LED light up now. Thank you