xod/docs/tutorial/18-comparisons/README.md

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Comparing Numbers

#18. Comparing Numbers

Note This is a web-version of a tutorial chapter embedded right into the XOD IDE. To get a better learning experience we recommend to install the desktop IDE or start the browser-based IDE, and you’ll see the same tutorial there.

Now, let's learn how to work with conditionals in XOD.

We will measure a lightness level, and if the values exceed or are below the threshold, we will turn an LED on or off.

XOD has greater-than and less-than nodes to do simple mathematical comparisons. They are in xod/core.

The left IN1 and right IN2 pins receive numbers to compare, and the output OUT pin returns the comparison result expressed as a boolean value (true or false).

Test circuit

Note The circuit is the same as for the previous lesson.

↓ Download as a Fritzing project

How-to

• Place a xod/core/less (or greater) node to trigger an action when a measured parameter goes under (or over) a threshold value.
• Use the left pin to link the value measured.
• Set the threshold as the right pin value.
• In cases where figuring out the proper threshold is tricky use a value from a potentiometer to adjust it dynamically.

In the example shown, if the analog-input node (our photoresistor) returns a value greater than the threshold, the greater node will set the OUT pin to true, and the LED will turn on.

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