How to calibrate the sensors for the Interactive Wall Kit

Learn how to calibrate the sensors for the Interactive Wall Kit

If the sensors on your interactive wall are not working as expected, you might need to calibrate them. This is especially the case if you’ve decided to use either shorter or longer cables than the 5m long ones that are included in the Interactive Wall Kit. Before starting to calibrate your sensors, make sure you have everything set up correctly and all the cables are connected. If you need help with setting up the Electrode Shield, have a look at the How to set up the Electrode Shield tutorial.

Step 1 Explore the sensors with Grapher

The best way to start calibrating your sensors is by using the Grapher sketch. The Grapher allows you to visually see what is happening when you are touching the sensors. To install the sketch, follow the Touch Board + Grapher tutorial.

Step 2 Changing the settings

If the Grapher shows you that the sensors are not responding at all, then have a look at the code you are using. First, try changing the threshold values of the MPR121. In the “Touch_MP3_IWK” code, you can find them on line 109 and 110. You need the setTouchThreshold value to be twice as a large as the setReleaseThreshold value. The default values are 40 and 20, respectively. Try setting them to 20 and 10 and test the results with the Grapher.

If you are using a code that has “MPR121.restoreSavedThresholds();”, you can set the thresholds value with the Grapher in the bar mode instead.

Step 3 Changing FFI

If adjusting the thresholds aren’t helping, you can try changing the FFI value in the code. This is for the first filter and you can change how many samples are being measured. Try changing the filter to one of the following values:

FFI_6, FFI_10, FFI_18, FFI_34

You can check your settings by running the Grapher again.

Step 4 Sensor design

The design of the sensor also influences performance. Depending on how you have designed your interactive wall, it’s worth having a read through our Electric Paint Sensor Design Rules of Thumb tutorial.

Sensor Design Painted Sensors Conductive Paint Paper Squares