Data Sheet

Project 12 Distance Sensor

This sketch changes which LED is on depending on the amount of light the

phototransistor is getting. Build the circuit and load sketch Distance_Sensor

into Snapino

using the programming instructions in project 3.

Vary the amount of light shining on the phototransistor (Q4) - if the light is

bright then the green LED (D2) will be on, if there is less light then the

yellow LED (D10) will be on, and if there is low light or no light then the

red LED (D1) will be on. This can be used to determine the distance

something is above it, since the object will slowly block out more light the

closer it gets to the phototransistor.

Once programmed, you can use the 9V battery connector to power the

circuit instead of the USB cable, then walk around with it.

Programming Note:

This sketch works by measuring how

much light the phototransistor is getting,

and assigning that value to a variable,

in this case the variable is “Val”. The

Arduino then uses this value to

determine which light to turn on. If the

variable is above a certain value, the

Arduino switches the LED from green

to yellow, and if the value still gets too

high, the Arduino switches the yellow

LED to the red LED.

You can adjust the sensitivity by

changing values 750 and 150 to be

higher or lower.

Use the preceding circuit, but load sketch

Photo_Stop into Snapino

. The LEDs change

colors in a stoplight pattern, with the rate of change

controlled by the phototransistor (Q4). Vary the

amount of light shining on the phototransistor; the

brighter the light, the faster the LEDs change.

Programming Note: This sketch reads the value

from the phototransistor, and uses that value to

change the time delay, causing the stoplight to

switch the LEDs faster or slower.

-23-

Project 13

Photo Stop

SCSNAPINO_Manual_112816.qxp 12/30/16 2:00 PM Page 24