The initial intention is to create a control system for interior space conditions. A space has temperature around 20-25°C and humidity percentage of 50-60%. Assuming that this system reads the temperatures and the humidity percentage. If the conditions are good, then, the users can be informed by the LCD screen and also by the green LED.If the conditions are different, then for extra safety, the air quality sensor is put into operation. This sensor can sense gases like NH3, benzene, smoke, alcohol, Co2 among some other gases. In this case, the user can be informed by the LCD screen, the red LED  and also by the buzzer, if something wrong happened.

Concept diagram

BoM (Bill of materials)

  1. 1 x Arduino Uno
  2. 1 x Breadboard
  3. 1 x MQ sensor    
  4. 1 x DHT11 sensor
  5. 1 x 5mm Led: Red
  6. 1 x 5mm Led: Green
  7. 3 x 220 ohm resistor
  8. 1 x LCD Screen
  9. 1 x 10k ohm potentiometer
  10. 1 x Buzzer
  11. 24 x Jump wires

Schematic  Diagram
Code Diagram
Code Text


For the MQ sensor:

  1. Check the operation of the sensor with Serial Monitor and the dht11.Read command
  2. With the use of a lighter we can find the value sensorThres  in order to create
    the condition:if (analogSensor > sensorThres)

For the DHT11 sensor:

  1. Check the operation of the sensor with the If  command and the Serial Monitor
  2. With this sensor, the normal temperature is around  20*C  and humidity 60%

Indication_”Temperature and Humidity
Indication_”Perfect Condition”
Indication_”Potential Threat”

Next Steps

In the future, to further improve the results, the system could
recover the average temperature based on the seasons,
as it is possible that the indoor spaces have significant differences in winter and summer.
In addition, one more light sensor would result in faster detection of a potential fire.