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56 lines
1.7 KiB
Markdown
56 lines
1.7 KiB
Markdown
---
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title: Comparing Numbers
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---
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# #18. Comparing Numbers
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<div class="ui segment note">
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<span class="ui ribbon label">Note</span>
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This is a web-version of a tutorial chapter embedded right into the XOD IDE.
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To get a better learning experience we recommend to install the
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<a href="/downloads/">desktop IDE</a> or start the
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<a href="/ide/">browser-based IDE</a>, and you’ll see the same tutorial there.
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</div>
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Now, let's learn how to work with conditionals in XOD.
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We will measure a lightness level, and if the values exceed or are below the
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threshold, we will turn an LED on or off.
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XOD has `greater`-than and `less`-than nodes to do simple
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mathematical comparisons. They are in `xod/core`.
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The left `IN1` and right `IN2` pins receive numbers to compare, and the output
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`OUT` pin returns the comparison result expressed as a boolean value (true or
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false).
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## Test circuit
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<div class="ui segment note">
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<span class="ui ribbon label">Note</span>
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The circuit is the same as for the previous lesson.
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</div>
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[↓ Download as a Fritzing project](./circuit.fzz)
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## How-to
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* Place a `xod/core/less` (or `greater`) node to trigger an action when
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a measured parameter goes under (or over) a threshold value.
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* Use the left pin to link the value measured.
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* Set the threshold as the right pin value.
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* In cases where figuring out the proper threshold is tricky use a value
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from a potentiometer to adjust it dynamically.
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In the example shown, if the `analog-sensor` node (our photoresistor) returns a
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value greater than the threshold, the `greater` node will set the `OUT` pin to
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`true`, and the LED will turn on.
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[Next lesson →](../19-if-else/)
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