Datasheet

Light-Sensitive Navigation with Phototransistors • Chapter 6
Robotics with the BOE Shield-Bot • 179
Ambient means ‘existing or present on all sides’ according to Merriam Webster’s dictionary. For
the light level in a room, think about ambient light as the overall level of brightness.
Parts List
(1) phototransistor
(2) jumper wires
(1) resistor, 2 kΩ (red-black-red)
(1) incandescent or fluorescent flashlight or desk lamp
After some testing, and depending on the light conditions in your robotics area, you might
end up replacing the 2 kΩ resistor with one of these resistors, so keep them handy:
(1) resistor, 220 Ω (red-red-brown)
(1) resistor, 470 Ω (yellow-violet-brown)
(1) resistor, 1 kΩ (brown-black-red)
(1) resistor, 4.7 kΩ (yellow-violet-red)
(1) resistor, 10 kΩ (brown-black-orange)
The next drawing will help you tell apart the phototransistor and infrared LED, since they
look similar.
Building the Bright Light Detector
 The schematic and wiring diagram below show a circuit very similar to the ones
in streetlights that turn on automatically at night. The circuit outputs a voltage
that varies depending on how much light shines on the phototransistor. The
Arduino will monitor the voltage level with one of its analog input pins.
Flatter on top
Infrared LED
USE THIS ONE!
Phototransistor
More Rounded Dome