Wiring a WH-8040 humidity controller to your incubator

Wiring a WH-8040 humidity controller to your incubator to see the humidity in real time.

I recommend reading this article on installing a STC-1000 temperature controller first. I installed my humidity controller directly on top of my STC-1000 with zip ties as seen in the picture below. Wiring the WH-8040 humidity controller to the incubator is extremely easy, much easier than the STC-1000 temperature controller was. In this instance, the controller is used only to monitor the humidity inside the incubator, not to actually control it.

WH8040 humidity controller

Wire the WH-8040 humidity controller to your incubator using the following wiring diagram:

WH-8040 humidity controller

You will have to supply a power cord for the controller. I used an inexpensive extension cord and cut off the female end. The hot wire from the power cord connects to 3 on the back of the unit.  The neutral wire from the power cord connects to slot 4.  The neutral wire on the extension cord will have a white stripe, writing, or ribbing on the insulation.  The WH8040 humidity controller has 2 probes that it uses to calculate the humidity inside the incubator; a temperature probe which connects to slots 8 and 9, and another probe that connects to slots 5, 6, and 7.  Poke holes in the incubator to insert the probes. I installed mine on opposite ends of the incubator.


Because the humidity controller is only being used to observe what the humidity is inside the incubator and not to actually control any humidifier, there is no need to program it.

Although, after installing the controller I did decide to put it to use since I discovered the humidity in the incubator was far lower than expected, even after all the improvements I had done. So be sure to read this article on how I am controlling humidity in an incubator and what parts it took to accomplish it. HINT: you probably know I am cheap and like to invent and fabricate things, so you also know it wasn’t very expensive.

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