Principles of infrared communication & Infrared Remote Control
Infrared is an invisible light to the naked eye, with a wavelength of approximately 950nm. Infrared light however 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 is similar to the principals of Morse code using long and short pulses. A long pulse of 1.2ms is represented a digital 1 and a short pulse of 0.6ms is represented as a logic 0. There is a 0.6ms pause between each pulse.
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.
This means that , the sensors will only recognise a 1 or 0 pulse, when the infrared source is sending bursts 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 a second!
To gain some immunity from ambient light sources, the IR sensors ‘trigger’ only when a 32KHz-40KHz modulated IR signal is sent. The sensors used in the IR-CF are PNA4620M-ND from Panasonic (or similar component) that has a centre frequency of around 38KHz.
The sensors used in the IRCF360TM and IRCFLTM are PNA4620M-ND from Panasonic (or similar component), which has a centre frequency of 38Khz. The sensitivity of these sensors is dependent on the modulated frequency. The frequency bandwidths are very narrow. A few Khz too low or too high reduces the sensitivity dramatically, as depicted in the graph below.
The SIRC infrared signal is made up of a 12-bit packet, which is split into a 7-byte button code and a 5-byte device code. The button code represents the actual button pressed on the remote control. There is a 2.4ms ‘start bit’ between each packet, which is used to synchronize the sensors.
The device code determines which remote control device is being address; such as video, television, CD, Amplifier, SAT, etc.
IRCF360TM and IRCFL are equipped with an on-board infrared remote controlled receiver and transmitter, so that it is possible to control robots or other electronic projects using a standard TV remote control that can transmit Sony SIRC (12-bit version). The protocol used with IR Control Freak is the 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: