Flexible Dehydrator project using rotary encoder and i2c 1602 LCD for settting temperature and reporting status.


This is a dehydrator project sketch for building (food) dehydrators. In the sketch most effort is put in the schema, this is the main source of information of the build. The breadboard + PCB are not complete.

Please be aware that there are risks involved when you switch 220v with solid state relays, there are no fuses in the sketch. Work safe or atleast use lower voltage heaters...


Using a rotary encoder it is possible to set a temperature between 25-75 degrees ( this can be modified in code ). When the switch of the rotary encoder is pressed then the program wil go in: "on" mode, this turns on the relays for the fans and starts to check the temperature and moisture using a KY-015 Sensor ( DHT11). Temperature and Moisture is displayed on the LCD and when the temperature is lower than the set temperature then the relay for the Heater will be turned on.

If the heater is turned of then there will be a counter which will make sure there is a timeout of about 10 seconds before the heater can be turned on again, this is to avoid quick switching.

2 x 0.47uF Capacitors are used on the CLK and DT pins to the ground for the rotary encoder, this removes debouncing and makes it possible to smoothly set the temperature.

Key components used:

  • Solid State Relay : Omron G3MB-202P 2A ( can be switched by arduino without external power )
  • PTC (Air) Heater Element : 100-300W
  • Arduino Uno
  • Perf / prototype board
  • KY-040 Rotary encoder
  • KY-015 Temp + Moist sensor
  • 1602 16x2 HD44780 Character LCD /w IIC/I2C Serial Interface
  • 60mm fans for airflow
  • skilled woodworker / case builder

Everything related to the build will be available on Github, see the external link for the github repository and feel free to give advice or comments.