Set up a Wireless Endpoint to Control and Monitor Humidity

Mold is a big issue in boat cabins, sheds, basements and other enclosed spaces where moisture is high.  Keeping boat cabins free of moisture is a particular challenge.  Even boats with integrated HVAC systems are not easy to automate or monitor and most boat AC systems will only work while the boat is in the water.  Solutions range from low tech moisture absorbing products to small heating elements or even incandescent light bulbs.  For boats that have a mains power source a small electric heater can be an effective way to control humidity.

SAFETY NOTE: Most electric heaters are not safe enough to be left unattended. Small oil-filled radiant or ceramic heaters are a safer option and manufacturer’s guidelines should be followed.

This tutorial shows you how to use a Wireless Endpoint to monitor and control humidity using a small heater.  Note that a dehumidifier is also an option so long as it can be switched off and on using the power source and  can be drained easily.

Project Components

The following steps assume you have performed initial setup of your Gamma gateway and Wireless Endpoints as described in the tutorial Initial Setup of Wireless Endpoints with Temperature and Humidity Monitoring as an Example.

Step 1 – Setup the Gamma and Wireless Endpoints to Control Humidity

Since it is possible to control humidity by switching a heater or dehumidifier on and off a wireless endpoint can be used to power a heater on and off using a PowerSwitchTail II. The Endpoint wiring to control the PowerSwitchTail is as follows.  In this configuration the internal latching relay switches the 5 volt power.  Note that is is possible to alternatively connect the +ve to the DO.

Endpoint powerswitchtail wiring

In this particular tutorial the Endpoint is connected as Endpoint B (note that in the setup tutorial Endpoint A was used).  The rules and actions to control the humidity are as follows:

Humidity Control Rules

Variable 6 is the humidity value and Variable 47 is being used as the humidity set point.  A widget is used to set the value of Variable 47 and hence the humidity. Variable 7 controls the relay and DO. A value of 0 represents off and 1 represents on.  Variable 5 is the temperature in tenths of Kelvin.  301 Kelvin is approximately 82F and is used to limit the temperature in the cabin as this demo was performed in Spring with temperatures naturally well below this value.

Step 2 – Log and Monitor Humidity

Following steps outlined in the setup tutorial it is possible to set up a dashboard that looks like this:

Cabin Humidity Dashboard


Note the rapid drop in humidity from 60% to 40% when the system turned the heater on and the subsequent control of the humidity at the set point of 40%.