In this lab you will build a circuit with one LED, one 10KΩ resistor, one 330Ω resistor and one photo resistor. You will then write a program for the Arduino using the Scratch for Arduino language. The program will turn the LED on when photo resistor is in the dark. This is the way street lights work, they have a photo resistor and are programmed to turn on automatically when it gets dark. The photoresistor has two leads of equal length. It is shown below:
You will need the following parts:
- 1 LED with two leads of any color. (NOT the white LED with 4 leads)
- 1 330Ω resistor
- 1 10KΩ resistor
- 1 photo resistor
- 6 jumper wires (the color of the wires doesn't matter, but you may find it convenient to use the same colors in the wiring diagram below) Connect the parts as shown below. Note that the direction of the resistors and jumper wires don't matter, but the LED must be connected in the correct direction.
Test your circuit by using your hand to create a shadow over the photoresistor. A shadow should decrease the the value of the Analog0 sensor. You can see the value of Analog0 in the sensors display shown below.
One finished program used the following blocks:
- 1 forever loop block
- 1 digital on block
- 1 digital off block
- 1 if/else block
- 1 less than operator block
- 1 value of sensor Analog0 block
Choose File | Save and name your project something like NightLight. Save your project to your My Projects folder and click Ok.
Have your teacher or a TA verify that you have a working program. Then, submit your finished program by uploading the NightLight.sb file to Google classroom. You should be able to find it in My Documents | Scratch Projects. If you worked with a partner, each partner should submit a copy of the finished program to Google classroom.