diff --git a/ampel-firmware/co2_sensor.cpp b/ampel-firmware/co2_sensor.cpp
index 436b36b06f85da4a5c031c5d02a8eb31f3b66276..05c4ffc736a0b3b636632e2b1452fde25cfe641d 100644
--- a/ampel-firmware/co2_sensor.cpp
+++ b/ampel-firmware/co2_sensor.cpp
@@ -31,6 +31,17 @@ namespace sensor {
     Serial.println(co2);
   }
 
+  void setTimer(int32_t timestep) {
+    if (timestep >= 2 && timestep <= 1800) {
+      Serial.print(F("Setting Measurement Interval to : "));
+      Serial.print(timestep);
+      Serial.println("s.");
+      sensor::scd30.setMeasurementInterval(timestep);
+      config::measurement_timestep = timestep;
+      led_effects::showKITTWheel(color::green, 1);
+    }
+  }
+
   void initialize() {
 #if defined(ESP8266)
     Wire.begin(12, 14);  // ESP8266 - D6, D5;
@@ -76,6 +87,7 @@ namespace sensor {
     Serial.println(config::auto_calibrate_sensor ? "ON." : "OFF.");
 
     sensor_commands::defineCallback("co2", setCO2forDebugging);
+    sensor_commands::defineCallback("timer", setTimer);
   }
 
   //NOTE: should timer deviation be used to adjust measurement_timestep?
diff --git a/ampel-firmware/mqtt.cpp b/ampel-firmware/mqtt.cpp
index 62c597ea82c577179c0814b70d00620df6d04de6..6427647d256696a54fba5b1098ad0205de119218 100644
--- a/ampel-firmware/mqtt.cpp
+++ b/ampel-firmware/mqtt.cpp
@@ -55,20 +55,6 @@ namespace mqtt {
     }
   }
 
-  //TODO: Move all those setters to a separate class, which could be used by Serial/MQTT/WebServer
-  void setTimer(String messageString) {
-    messageString.replace("timer ", "");
-    int timestep = messageString.toInt();
-    if (timestep >= 2 && timestep <= 1800) {
-      Serial.print(F("Setting Measurement Interval to : "));
-      Serial.print(timestep);
-      Serial.println("s.");
-      sensor::scd30.setMeasurementInterval(messageString.toInt());
-      config::measurement_timestep = messageString.toInt();
-      led_effects::showKITTWheel(color::green, 1);
-    }
-  }
-
   void setMQTTinterval(String messageString) {
     messageString.replace("mqtt ", "");
     config::sending_interval = messageString.toInt();
@@ -101,13 +87,6 @@ namespace mqtt {
     }
   }
 
-  void setCO2forDebugging(String messageString) {
-    Serial.print(F("DEBUG. Setting CO2 to "));
-    messageString.replace("co2 ", "");
-    sensor::co2 = messageString.toInt();
-    Serial.println(sensor::co2);
-  }
-
   void sendInfoAboutLocalNetwork() {
     char info_topic[60]; // Should be enough for "CO2sensors/ESPd03cc5/info"
     snprintf(info_topic, sizeof(info_topic), "%s/info", publish_topic.c_str());
@@ -146,11 +125,7 @@ namespace mqtt {
 
     //TODO: Move this logic to a separate class, which could be used by Serial/MQTT/WebServer
 
-    if (messageString.startsWith("co2 ")) {
-      setCO2forDebugging(messageString);
-    } else if (messageString.startsWith("timer ")) {
-      setTimer(messageString);
-    } else if (messageString == "calibrate") {
+    if (messageString == "calibrate") {
       sensor::startCalibrationProcess();
     } else if (messageString.startsWith("calibrate ")) {
       calibrateSensorToSpecificPPM(messageString);
diff --git a/ampel-firmware/sensor_commands.cpp b/ampel-firmware/sensor_commands.cpp
index 868f37ec30a9c91936c4a8d4305324452e681715..fd04e47280c42a2eea6605409905e49cbb34f4bf 100644
--- a/ampel-firmware/sensor_commands.cpp
+++ b/ampel-firmware/sensor_commands.cpp
@@ -5,8 +5,6 @@ namespace sensor_commands {
   const uint8_t MAX_COMMAND_SIZE = 30;
 
   uint8_t callbacks_count = 0;
-// A callback contains both a function and a pointer to arbitrary data
-// that will be passed as argument to the function.
   struct Callback {
     Callback(const char *s = 0, void (*f)(int32_t) = 0) :
         name(s), function(f) {
diff --git a/ampel-firmware/sensor_commands.h b/ampel-firmware/sensor_commands.h
index cecbcf37a74f3f9d7163e6048a1618f9b58071e5..11d06aecd42cf9ca9f3704067583d592a5e4adce 100644
--- a/ampel-firmware/sensor_commands.h
+++ b/ampel-firmware/sensor_commands.h
@@ -7,5 +7,6 @@
 
 namespace sensor_commands {
   void run(const char *command);
+  //TODO: Add defineIntCallback?
   void defineCallback(const char *command, void (*f)(int32_t));
 }