Datasheet

Navigating with Infrared Headlights • Chapter 7
Robotics with the BOE Shield-Bot • 217
The TV remote sends messages by flashing the IR LED very fast, at a rate of about 38 kHz
(about 38,000 times per second). The IR receiver only responds to infrared if it’s flashing at
this rate. This prevents infrared from sources like the sun and incandescent lights from
being misinterpreted as messages from the remote. So, to send signals that the IR receiver
can detect, your Arduino will have to flash the IR LED on/off at 38 kHz.
IR Interference: Some fluorescent lights do generate signals that can be detected by the IR
receivers. These lights can cause problems for your BOE Shield-Bot’s infrared headlights. One of
the things you will do in this chapter is develop an infrared interference “sniffer” that you can use
to test the fluorescent lights near your BOE Shield-Bot courses.
The light sensors inside many digital cameras, including some cell phones and webcams, can
all detect infrared light. By looking through a digital camera, we can “see” if an infrared LED
is on or off. These photos show an example with a digital camera and a TV remote. When
you press and hold a button on the remote and point the IR LED into the digital camera’s
lens, it displays the infrared LED as a flashing, bright white light.
IR Receiver
IR LED
A TV remote flashes the IR LED
on/off at ≈38 kHz for certain
periods of time, with periods of
off-time in between.
It makes a different flashing/off
pattern for each key on the
remote.