xod/docs/tutorial/17-ldr/README.md

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Reading lightness

#17. Reading lightness

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.

Let’s introduce a new sensor to measure an ambient light level. A photoresistor (aka light dependent resistor or LDR) would do a great job of measuring the parameter. However, there is a small problem: we do not have a photoresistor node in XOD.

Yet, we have basic nodes for working with the digital and analog ports of the Arduino. A photoresistor is a pretty primitive device, and all we need to do is read its value from the analog port on the Arduino. To do so, we will use an analog-sensor node.

It is a low-level node that reads an analog port of Arduino directly and outputs the value measured in 0–1 range where 0 corresponds to 0 volts (value of 0 in the Arduino native language) and 1 corresponds to the power voltage (usually 5 or 3.3 volts; value of 1023 in C++).

Test circuit

↓ Download as a Fritzing project

Try to create a device as shown above, cover the photoresistor with your hand, and watch how the brightness of the LED changes.

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