Disturba il segnale! Ecco come costruire rapidamente un apparecchio per disturbare i segnali dei telecomandi.Nostra sorella ci rompe in continuazione perché non vuole vedere Yu-Gi-Oh? Il fratellino più piccolo continua a fregarci il telecomando? Nostra madre vuole a tutti i costi passare da CSI Miami a Beautiful? Diciamo basta!E' venuto il momento di costruirci un offuscatore di telecomandi, che manda in confusione il sistema a infrarossi fino al punto in cui la nostra vittima non potrà più cambiare canale.Un'innocua scatoletta posizionata nel punto giusto e qualunque tentativo di passare da un canale TV a un altro via infrared remote control will have no effetto.Il device used to capture infrared television will be completely blinded by such a large amount of false signals that can no longer distinguish the real signal from noise. And 'as we drive as if someone had bet him in a flash flash and then pretended to see there headlights of another car coming. Virtually impossible!
:: Ingredients::
least three infrared LED
a BC548 PNP transistor or equivalent
a BC547 NPN transistor or equivalent
a resistance of 100 ohm resistor 1 Kohm
a resistance of 100 ohm resistor 150
Kohm 10 Kohm trimmer
a
a 10-nF ceramic capacitor capacitor electronic
1 nF / 16 V 4.5 V
a stack
All resistors are 1 / 4 Watt. The trimmer can be replaced by a potentiometer, and if we really want to overdo it, an expensive multi-turn to adjust the frequency of our On the issue exactly led infrared remote control.The true cost very little, a few cents, so it is advisable to take new. The other components are cheap, but we can also easily recover from an old TV.
: At work! :: The procedure is simple. We observe the following schedule ...
... and build the obfuscation on a remote base multihole, welding components as we think we're better neighbors to each other. They are so few that there is no risk of making mistakes. Beware of transistors, which are not equal. One is a PNP and an NPN another, then you first need to look good connections at the base, collector and all'emittore.
: Calibration:: Remote controls for televisions operate at a frequency range is quite similar, but not always the same. The coded signal that comes from the remote control has a frequency range from 30 to 50 KHz, depending on model and brand. The operating principle of our jammer is to generate pulse trains totally meaningless to the same frequency as the remote control that we normally use. So the receiver, even if it is informed signals of the true remote control, no longer able to decode it in the middle are all the impulses generated by our device, which are disturbances sufficient to confuse and thus to block the infrared receiver TV.La the first thing to do is see if our circuit work. Not being able to see with the naked eye if the LEDs come on or not, just because they emit only infrared light, we use a digital camera or a webcam, or simply placed in our room the phone. LEDs pointing towards the goal we will see them on, because the sensor of digital cameras is also sensitive to infrared. Especially with the phone, usually devoid of quality filters, we will see a light most intense.
Authority is satisfied that the circuit works, we calibrate the frequency. So we've put the trimmer or a strength that we can change the value using a small screwdriver. More accurate is the trimmer, or more laps we can do in moving from low frequency, it is easier to hold down the right frequency. This is the most critical step to design our. We must turn the obfuscator, then press a button on the TV remote control that gives a continuous type, for example, the volume or change channels in sequence, and then turn the trimmer very slowly until you find the point where the selection function the remote control does not work anymore (the channels not more or change the volume rises or falls). On older TV will be easier, because the encodings are less sophisticated. On most modern TV can meet more difficulties, because over time have been introduced to encode the signal that seek to minimize the influence of disturbances esterni.Ecco the circuit before ...
... and after welding ...
:: A little 'more than theory: The majority of infrared remote controls of the equipment we use at home, from TV to the VCR, lamps fans, air conditioners from the stereo, and so on, they emit a carrier signal wave square to 36 or 38 KHz. This means that if it were emitted in continuous oscillation between the state 0 and 1 was about 36/38 thousand times secondo.I useful signals are pulse trains that are issued in series, the majority of cases simply by turning the carrier signal. The amount of information that can be transmitted with this system is approximately 1000 or 2000 bits per secondo.Le encodings are the most diverse and depend on the make and model of the device we are using. This means that the remote firing trains of bits with different meanings, which are then decoded by the microcontroller of the receiver, according to a table stored by the manufacturer.
:: RC5 and Philips: A very widespread in the coding control projects infrared è la RC5 della Philips. Sfrutta una frequenza di 36 KHz e invia dei treni di impulsi fatti da 5 bit di indirizzo e 6 di comando (7 nella codifica estesa RC5X).Il protocollo usa una modulazione bifase, chiamata Manchester, sulla frequenza portante di impulsi infrarossi a 36 KHz. Tutti i bit hanno una uguale ampiezza pari a 1.778 millesecondi, di cui la metà è riempita di impulsi del carrier a 36 KHz e l'altra metà è tenuta a 0. I bit a 1 hanno la prima metà a zero e la seconda piena di impulsi del carrier, mentre i bit a 0 hanno la prima metà piena di impulsi e la seconda metà a zero.Così facendo si diminuisce il consumo della batteria del telecomando di 1/3 o 1/4 rispetto a una codifica a impulsi continui.Il protocollo invia treni of bits in the following sequence: two bits of
both start at 1 (RC5X in the start bit is one)
a toggle bit, which is inverted every time you press a button. In this way the receiver can distinguish between a key and repeatedly pressing a button pressed continuously
five bits from most significant to least significant, which form the address of the IR device to control
six control bits, always with the most significant bit at the beginning (in RC5X are 7) In total, therefore, 14 bits for a total duration of 25 ms, each command sent.
:: The IR command table: In the standard Philips RD5 there is room for everyone. Indeed, there is more than a place for everyone. So, having multiple addresses for devices similar or identical (for example, two VCRs stacked on each other) we will not have problems with the same remote control them separately.
article taken from Standard Bus # HackerJournal 109.Secondo the provisions of this article is HJ open source for use on the web, but copyright to stampa.Trascritto in digital form by David Micheletto (http://micke84 . altervista.org) For further information, questions or concerns, please write to standardbus [at] gmail [dot] com
