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Littlebits humidity indicator

by alexpikkert

Published on November 12, 2015

Do you have a room where you think the humidity is too high?
Put a moisture absorber in the room and keep an eye on the relative humidity with this Littlebits humidity indicator. It uses the KY015-DHT11 humidity sensor.

Duration: 3 hrs.

How To Make It


The humidity sensor I used the KY015 sensor board from Robotlinking, with the DHT11 humidity and temperature sensor on it. The pin-layout is a little different from the connections on the protobit so I had to make some wiring to connect this board properly. The sensor worked OK in a prototype setup with an Arduino UNO and a Duemilanove, but on the Littlebits Arduino Leonardo it refused to start indicating after a power down. I had to connect an additional resistor of 10 kOhm between the signal output of the sensor and the GND connection. Funny enough this is deviating from the sensor documentation, showing a resistor connected to VCC.... But it works !
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The sensor connected to the proto bit

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Th complete indicator

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The proto bit with the sensor connection.


The Arduino program

I used the original INO file and changed it to be used with Littlebits. The program normally stores the data from the humidity and the temperature in an array, and shows the values on the serial monitor of the connected computer.
I only used the array part for the humidity (stored in dat[0]) to activate the number bit, the RGB LED and the Cloudbit. I used the serial monitor only for testing. I connected the Cloudbit to output 9 of the Arduino instead of connecting it to the number bit. The only reason was that it fitted nicely on just one mounting board.....

You could change the program and connect a second number bit to the Arduino for an indication of the temperature.  

There is a warning RGB LED connected to the Arduino that lights up when the humidity reaches the level of 50% or more.

The Cloudbit sends the level to my smartphone.  Now I can really check if the moisture absorber is working !

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