Picture of How to Use a Light Dependent Resistor (LDR) Lots of
projects use a Light Dependent Resistor (LDR) to sense light
levels but don't really focus on how they work.  This project
shows you how to use a Light Dependent Resistor (LDR) to sense
light levels, measure those levels with the Arduino and print
the measurements to the Serial port.  Arduino measures Voltages
on pins A0 to A5; but the LDR is a variable resistor (varying
with Light). So we need to convert the varying resistance to a
voltage that the Arduino can measure.  We do that by using the
LDR and a Resistor in a Potential Divider circuit.  Remove these
adsRemove these ads by Signing Up  Step 1: How it Works  Picture
of How it Works The top of the Potential Divider is 5V; the
bottom is at 0V and the middle (connected to A0) is some value
between 5V and 0V that varies as the LDR resistance varies.
Remember the LDR resistance varies with Light so the Voltage at
A0 will too.  If you want to be very precise and technical then
you can work out the