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Products > Infrared Control Freak - 360 degree Proximity Sensor >

Principles of Infrared Remote Control

Principles of infrared communication & Infrared Remote ControlInfrared is an invisible light to the naked eye, with a wavelength of approximately 950nm. Infrared lighthowever can be detected with one of the modern digital cameras that have night vision functionality.

Digital Infrared messages are create by transmitting short and long pulses of infrared light. The code issimilar to the principals of Morse code using long and short pulses. A long pulse of 1.2ms is representeda digital 1 and a short pulse of 0.6ms is represented as a logic 0. There is a 0.6ms pause between eachpulse.

To gain some immunity from natural Infrared light (e.g. sunlight) or ambient light sources, the IR sensors‘trigger’ only when a 32khz-40khz modulated IR signal is sent.

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This means that , the sensors will only recognise a 1 or 0 pulse, when the infrared source is sendingbursts of Infrared light at a frequency of 32Khz – 40Khz. If we use the formulae [seconds=1/frequency],we see that the pulse width is 31,25– 25.0 uS (microseconds). Remember that uS is one millionth of asecond!

To gain some immunity from ambient light sources, the IR sensors ‘trigger’ only when a 32KHz-40KHzmodulated IR signal is sent. The sensors used in the IR-CF are PNA4620M-ND from Panasonic (orsimilar component) that has a centre frequency of around 38KHz.

The sensors used in the IRCF360TM and IRCFLTM are PNA4620M-ND from Panasonic (or similarcomponent), which has a centre frequency of 38Khz. The sensitivity of these sensors is dependent onthe modulated frequency. The frequency bandwidths are very narrow. A few Khz too low or too highreduces the sensitivity dramatically, as depicted in the graph below.

Sending Sony 12-BIT SIRC standard IR packages

The SIRC infrared signal is made up of a 12-bit packet, which is split into a 7-byte button code and a5-byte device code. The button code represents the actual button pressed on the remote control. Thereis a 2.4ms ‘start bit’ between each packet, which is used to synchronize the sensors.

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Start BUTTON CODE DEVICE CODE

S B1 B2 B3 B4 B5 B6 B6 D1 D2 D3 D4 D5

2.4ms 1.2 mS or 0.6mS 1.2 mS or 0.6mS

The device code determines which remote control device is being address; such as video, television, CD,Amplifier, SAT, etc.

Infrared Remote Control within the IR Control Freak Modules

IRCF360TM and IRCFL are equipped with an on-board infrared remote controlled receiver andtransmitter, so that it is possible to control robots or other electronic projects using a standard TVremote control that can transmit Sony SIRC (12-bit version). The protocol used with IR Control Freak isthe Sony format known as SIRC.

A remote control feature enables inter-robot communication and Robot Gaming such as tag, zapping,Robot team communication, etc.

Buy using coded IR messages; you can transmit signals to other robots. For example:

It is possible to determine whether your robot opponent is a friend or foe You could also configure a unique ID for each robot and robot team, allowing your robot tocommunicate between team members and sending a 'tag' or ‘zap’ code to the other opponentteam. For example, ten ‘zaps’ to sent and acknowldeged by component robot could mean, "yourit!"Simple communication to other swarm robots signalling that food has been located

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