Light Sensor Challenges

Light sensors are used to detect the level of brightness and produce an output signal representative of the amount of light detected. The LEDs on the micro:bit board can also act as an input by detecting ambient light. MakeCode includes a "light level" block in the 'Input' category that reads the light value detected by the LED screen. This value ranges from 0 (dark) to 255 (bright).

Challenge #1: Showing light level

Objective.

Pressing button A displays the numerical value of the ambient light intensity. Pressing button B displays the light intensity graphically. Pressing buttons A and B simultaneously turns off the screen.

Code description.

The proposal is to create three different programs, each triggered by pressing a specific button or combination of buttons.

Pressing button A will display the numerical value of the light intensity. The "show number" block will be used, with the "light level" block inserted as the value to be displayed.

Pressing button B will light up the necessary LEDs to graphically display the light level value. The "plot bar graph of ... up to ..." block, found in the LED section, will be used. First, insert the "light level" block, and then replace the default value in the second field with 255, which is the maximum value detected by the light sensor.

Finally, pressing buttons A and B simultaneously will be used to clear and turn off the LED display.

Extra activity

Create code that turns on all the LEDs on the micro:bit panel when button A is pressed and turns them off when button B is pressed, but prevents them from turning on if the light sensor value is greater than 175.

Challenge #2: Twilight Switch 

When the light intensity falls below a predetermined, pre-set illumination level, the twilight switch turns on the lighting. Conversely, if the light intensity exceeds the preset level, the switches turn off the lighting.

Objective.

Create a program that measures the current light level using the micro:bit's light sensor. Then, check if the value is below 50; if so, turn on all the LEDs on the board at maximum intensity.

Code description.

We suggest using the ‘forever’ event, which is in the ‘Basic’ category. This block allows the code entered to be executed during all the program. An "if... then... else" condition will be introduced to check whether the value is above or below the threshold—set to 50 in this instance. If the value "light level", from the 'Input' category,  is less than 50, the LED intensity will be set to the maximum using the "set brightness to 255" block in the 'Led' category. If the value is greater than 50, the "clear screen" block will be used to turn off all the LEDs.

The code would look like this; its operation can be verified by varying the intensity in the board simulator.

Information extracted and translated from catedu.