diff --git a/usermods/photoresistor_sensor_mqtt_v1/README.md b/usermods/photoresistor_sensor_mqtt_v1/README.md
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+# Photoresister sensor with MQTT
+
+This simple usermod allows attaching a photoresistor sensor like the KY-018 and publish the readings in percentage over MQTT. The frequency of MQTT messages can be modified, and there is a threshold value that can be set so that significant changes in the readings can be published immediately instead of waiting for the next update. This was found to be a good compromise between spamming MQTT messages and delayed updates.
+
+I also found it useful to limit the frequency of analog pin reads because otherwise the board hangs.
+
+This usermod has only been tested with the KY-018 sensor though should work for any other analog pin sensor. Note that this does not control the LED strip directly, it only publishes MQTT readings for use with other integrations like Home Assistant.
+
+## Installation
+
+Copy and replace the file `usermod.cpp` in wled00 directory.
diff --git a/usermods/photoresistor_sensor_mqtt_v1/usermod.cpp b/usermods/photoresistor_sensor_mqtt_v1/usermod.cpp
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+#include "wled.h"
+/*
+ * This v1 usermod file allows you to add own functionality to WLED more easily
+ * See: https://github.com/Aircoookie/WLED/wiki/Add-own-functionality
+ * EEPROM bytes 2750+ are reserved for your custom use case. (if you extend #define EEPSIZE in const.h)
+ * If you just need 8 bytes, use 2551-2559 (you do not need to increase EEPSIZE)
+ * 
+ * Consider the v2 usermod API if you need a more advanced feature set!
+ */
+
+//Use userVar0 and userVar1 (API calls &U0=,&U1=, uint16_t)
+
+const int LIGHT_PIN = A0; // define analog pin
+const long UPDATE_MS = 30000; // Upper threshold between mqtt messages
+const char MQTT_TOPIC[] = "/light"; // MQTT topic for sensor values
+const int CHANGE_THRESHOLD = 5; // Change threshold in percentage to send before UPDATE_MS
+
+// variables
+long lastTime = 0;
+long timeDiff = 0;
+long readTime = 0;
+int lightValue = 0; 
+float lightPercentage = 0;
+float lastPercentage = 0;
+
+//gets called once at boot. Do all initialization that doesn't depend on network here
+void userSetup()
+{
+  pinMode(LIGHT_PIN, INPUT);
+}
+
+//gets called every time WiFi is (re-)connected. Initialize own network interfaces here
+void userConnected()
+{
+
+}
+
+void publishMqtt(float state)
+{
+  //Check if MQTT Connected, otherwise it will crash the 8266
+  if (mqtt != nullptr){
+    char subuf[38];
+    strcpy(subuf, mqttDeviceTopic);
+    strcat(subuf, MQTT_TOPIC);
+    mqtt->publish(subuf, 0, true, String(state).c_str());
+  }
+}
+
+//loop. You can use "if (WLED_CONNECTED)" to check for successful connection
+void userLoop()
+{
+   // Read only every 500ms, otherwise it causes the board to hang
+  if (millis() - readTime > 500)
+  {
+    readTime = millis();
+    timeDiff = millis() - lastTime;
+    
+    // Convert value to percentage
+    lightValue = analogRead(LIGHT_PIN);
+    lightPercentage = ((float)lightValue * -1 + 1024)/(float)1024 *100;
+    
+    // Send MQTT message on significant change or after UPDATE_MS
+    if (abs(lightPercentage - lastPercentage) > CHANGE_THRESHOLD || timeDiff > UPDATE_MS) 
+    {
+      publishMqtt(lightPercentage);
+      lastTime = millis();
+      lastPercentage = lightPercentage;
+    }
+  }
+}