We’ve believed of doing a job such as this ourselves as the dehumidifier we ordered on the internet runs the fan 24/7 no matter what the humidity conditions. however it wasn’t that [Davide Gironi] was dissatisfied with the features on his unit. It’s that the dehumidifier controller stopped working so he replaced it with one of his own design. The original humidity sensor was mechanical as well as just broke. He utilized an AVR together with a humidity as well as frost sensor to get the appliance up as well as running again.

A DHT22 humidity sensor is polled by the ATmega8 chip as well as compared to the user-adjustable trimpot value. If it is above that threshold the system is changed on utilizing one of the relays seen in the picture above. The one issue you have to watch out for when utilizing compressor cooled appliances is ice accumulation on the radiator. [Davide] utilizes a thermistor for temperature feedback, changing the compressor off when it gets below 7C as well as turning it back on once again when it is above 12C.

The replacement still utilizes the reservoir sensor as well as sign LEDs. We, however, would suggest utilizing the watchdog timer on the chip to ensure that it is reset if something goes wrong in the code.