if you look at the top of your remote-control unit you will see there is a small plastic LED that is the light emitting diode which emits the infrared radiation now take a look at your TV or DVD receiver somewhere on the front there is a small infrared light detector this detector will convert the infrared light signal into an electric signal the focus of this video is to explain what goes in the infrared radiation that travels from the remote to your TV all the buttons that you see in a remote control are connected through an electronic circuit to a microprocessor so anytime you press a button the microprocessor will generate a binary signal or a binary code that is associated with that button new pressed so for example the code associated with volume up could be something like this channel down would be a different set of one and zeros and so forth for all other options in the remote control keypad all the binary command codes will have the same number of bits in this example it is six bits as you see here bit zero correspond to low-voltage while bit one is the high voltage and this takes the full duration of the bit in reality the binary code that is transmitted is slightly different than the simple binary code I presented here bit zero is represented by high voltage in the first half of the bit duration followed by low voltage in the next half of the bit duration and mid one is simply the reverse of that the first half is a low voltage and the second half is the high voltage this kind of Winery coding is called Manchester coding applying Manchester coding to volume up code that we saw previously bit zero will be high voltage followed by low voltage bit one will be the opposite with zero one more time bit zero and you get the idea another modification done on the binary code before it gets transmitted is to modulate the binary code with a 36 kilohertz signal that is the frequency career you see here so instead of having high level voltage you have a train of parcels at 36 kilohertz so why the binary code is being modulated well because sunlight include infrared light that can interfere with the binary code so modulation makes the infrared light signal becomes more robust to sunlight interference now in addition to controlling TV you may want to control other devices such as TV box a DVD player and probably a Playstation in order to do that the IR signal needs to also indicate which system the command is intended to so beside the command control the IR signal include an address code that specify the device to control and this one consists of five bits in addition to the address and command bits the infrared light signal include a start bid to indicate the start of the frame and the field bit which is actually part of the command bits we also have a control bit which toggles to either 0 or 1 every time a remote control button is pressed there are many types of protocol that are being used in remote control in this video I showed you the RC 5 protocol which was first introduced by Philips so that's it for my tutorial on infrared remote control
