Overview
The 4tronix dew heater controller is available in both 2-channel and 4-channel versions. Apart from the number of channels, they are identical in operation – in fact they use the same PCB and the same code on the internal microcontroller.
Each channel is fully variable from completely Off to permanently On. The positions in between are managed using PWM (Pulse Width Modulation), which is a method of reducing the overall power usage, while keeping the voltage level the same. Basically, it provides power at the input voltage for a certain percentage of the time, with the power off for the rest of the time during each period. Each PWM period is only about 2ms, so you won’t see any fluctuating values.
There is an indicator LED on each channel to give some indication of the power selected. If the indicator LED is Off, then there is no power being provided to the dew heater. If it is On solidly, then the full input voltage is being provided to the heater. In between, the LED flashes. A slow flash indicates little power and a fast flash (up to 30 Hz) indicates more power. Note that the flashing of the LED is not the same as the PWM values on the heater outputs.
The Dew Heater Controller can operate happily from about 7V up to about 15V. The driver for each channel is rated at over 4A, but do not use all 4 channels at 4A – other parts of the circuit won’t cope.
The power is supplied via a 5.5mm DC Jack, with centre Positive. There is a reverse polarity protection circuit inside, just in case you get it wrong.