The light sensor add-on can be used to measure overall light level nearby. The add-on is actually made up of three light sensors which you can see in the photo below.
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Front of light sensor, showing the three light sensors
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Back of the light sensor, showing the i2c connectors, microcontroller and the rest of the circuitry
===== Set Up =====
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The light sensor is designed to attach to one of the two attachment points on each of Marty's feet - the front or the back.
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An empty slot on Marty's foot where the sensor can be mounted
==== Installing the Sensor ====
**Step 1: Decide where to mount the sensor, and ensure you have a free cable**
You may need to unscrew and disconnect an existing sensor to make space for the light sensor. Alternatively mount it at the back of the foot instead.
**Step 2: Connect the cable to the light sensor**
Connect the black i2c cable to either socket on the light sensor - it doesn't matter which one
**Step 3: Fix the light sensor board to Marty**
Use two M3 nuts and bolts to firmly fix the light sensor to the foot.
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The light sensor connected and screwed into place on Marty's foot
==== Checking and Configuring the Sensor ====
When you are connected to your Marty from the Marty the Robot v2 app, select **Configure** then **Add-ons** to get to the Add-on configuration screen.
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The light sensor in the add-on list
Your light sensor should be shown in the list of addons. It will have a default name like "AddOn_I2CB_28" unless you have previously given it a name.
There is no need to rename the sensor unless you have more than one
===== Using with Marty Blocks =====
The light sensor can be read using the " light sensor <1/2/3>" block under Sensing.
If you only have one light sensor, it doesn't matter if you select the left or right option. If you have two light sensors you must name them ''%%LeftLightSensor%%'' and ''%%RightLightSensor%%'' in the add-on configuration screen for them to be identified correctly.
The block will always return a positive number, with a higher number meaning more light.
Try shining the torch from a mobile phone on the senor and see what happens!
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Click the checkbox next to the light sensor to see a live display of the sensor value