Remote controlled LED


Posted on Sep 10, 2012    11321

The remote control transmits encoded signals. Each time a key is pressed, the relevant code is transmitted, usually repeating it many times to ensure reception. This encoded signals travels over a radio or infrared-light beam, to eventually get captured by the receiver. The receiver includes a sensitive circuit capable to transform those weak radio-clicks or infrared flashes in an electric signals with only two logic levels, zero and ones. The logic levels appear as train pulses relfecting the original code: they conneot be used directly, as the need to be decoded in order to determine which key was origianally pressed.


Remote controlled LED
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Remote controls are easy to get as spare parts for TV sets and gate openers. The fall in two categories, infrared (TV, HiFi, VCR, DVD) and radio frequency (gate openers, alarms). The former can be found in supermarkets also as "universal" remotes, capable of emulating almost all of known codes. Receivers are specialized integrated circuits or miniature modules. They usually require just a 5V power supply to work, with three or more pins. Apart power supply, the extra pins can carry test signal, separate power lines, aerial input for RF (radio frequency) receivers, or be just NC (not connected) pins. The output signal is a logic pulse train consisting of zeroes and ones, ready for the decoding stage. nce again, we start from the LED flasher circuit from our previous articles in this mini-course; we are going to add an infrared receiver IC, a TSOP1836. This integrated circuit manufactured by Temic/Vishay is very simple to use, as its only three pins must connect to the positive power supply (+5V), negative (GND), and remote control decoder (OUT). The receiver's output connects to Nutchip's remote control decoder input, namely the REMOTE pin (pin 6). The manufacturer specifies a pull-up resistor to keep this output positive when no signal are received: the REMOTE input integrates this resistor therefore it is no longer necessary to add it externally. A decoder is integrate inside Nutchips, its input connected to REMOTE pin (pin 6). It is suitable for decoding either RF or infrared signals, and can recognize up to 8 different key strokes. You can cselect which 6 keys to decode among the many a remote control can offer. Keystrokes (identified by key1, key2,... key8) can be inserted into truth tables, as they were real keys connected to Nutchips inputs.

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