Teach you to design an LED flower that can sense humidity

Material

For this circuit, here are the materials you need. The RGB LED flowers are exclusive to the 21st Century Fashion Kit, but you can use standard RGB LEDs instead if you prefer. You can buy all of the parts listed below at SparkFun.

● 21st Century Fashion Kit

● Arduino Pro 328 - 5V/16MHz

● SparkFun Humidity and Temperature Sensor - SHT15

● Polymer lithium-ion battery - 850 mAh

Circuit

This circuit design (and the associated code) draws heavily on the data in the Bildr tutorial (http://bildr.org/2012/11/sht15-arduino/), which I strongly recommend that you read. The information is very helpful!

In particular, the tutorial mentioned a requirement to place it in a sealed plastic bag with a damp towel (but not touching it) in order to re-hydrate the polymer in the sensor. This was very helpful to me.

The following figure shows the circuit:

The Fritzing diagram makes it almost impossible to tell that the RGB LEDs are separate, but they are, aren't they? The longest pin is ground. The single pin next to the ground pin is red, and the two pins on the other side are first green and then blue.

If you use this flower instead of a standard RGB LED, be very careful as a heat gun can easily melt the petals if you use heatshrink over the connections.

Code

Don't know how to upload code to your Arduino? No problem! It's explained thoroughly in this instructable video. Remember to select the correct board and port for your application.

Copy and paste this code (click here) into the IDE and hit the Upload button.

Once the code is uploaded, open up the Serial Monitor (https://learn.sparkfun.com/tutorials/terminal-basics/arduino-serial-monitor-windows-mac-linux). This will open up a new window with scrolling numbers. The right column is the temperature and the left column is the humidity. Look at your humidity numbers and use them to decide what your ideal humidity is.

The line that says Humidity Threshold is commented out pretty close to the top, take a look at it and adjust it as needed. I set mine to be slightly above ambient humidity because I wanted it to be easy to show. You may want yours to be less sensitive. In the same section you can make changes to how the light reacts to those changes.