Infrared is frequency of light that are not visible to eyes which have range of wavelength like visible light. The process of infrared data transmission especially the kind which is used in old standard television remotes it is a rather simple wireless communication protocol which uses near-infrared light. Infrared communication transceiver (receiver + transmitter) in both devices which want to communicate. Infrared communication is playing important role due to polarity of laptops, mobile devices and another wireless electronic gadgets. Infrared communication is light of sight transmission. It is sensitive for fog and another environment condition.
In order to transmit data, this is light that has a wavelength that is just below the visible light spectrum. In other words, the human eye can’t quite see it. If you want to transmit with iolite you can do it with one of these IR LEDs. It is just like any other regular LED diode except you cannot see the light.
In the myths this is the same diode that can be found in the front of this remote control. In fact any remote or IR transmitter will have some permutation or this IR LED. When you transmit and receive ion you do so in a flooded environment everything from the lights in your ceiling the Sun or even the screen you are watching could be outputting some form of IR light. However this IR light will be present in random wavelengths and have no particular structure. This is why 38 kilohertz was chosen for the frequency of commercial IR transmission to operate on.
There are two types of infrared light:
- Far infrared
Far infrared wave are thermal that is why we feel warm in sunlight and fire. Near-infrared waves are not thermal at all even not visible to human eyes. Near-infrared are used in TV remotes.
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Infrared remote work:
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 article 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.
Now to further explain the process of IR transmission I will use this remote control as an example. Let’s take it apart to see the components inside the components that you see here are typical for most IR remotes.
When you take off the back cover of the control you can see that there is really just one part visible a printed circuit board that can change the electronics and the battery contacts. The main microchip is packaged in what is known as a 20 pin dual in line package or a dip.
Next to it you will also find a transistor several resistors and of course the IR emitter diode. On the circuit board you will also find a plastic film which houses the contacts and wires for each individual button and the silicone buttons themselves. When a button is pressed on the remote very sample the on/off button a small metallic pad is lowered onto two contacts located on the plastic film directly under the button. This sends a signal to the integrated circuit board at the front of the remote control each individual button sends a different signal then a small pre-programmed microchip recognizes the signal as coming from the on/off button and encodes it into a series of electrical impulses sort of like Morse code. These impulses are then carried to the IR emitting diode at the front of the device where they are admitted as impulses of IR light. In the receiving device in our case this DVD player this whole process is essentially repeated in Reverse. The IR receiver diode picks up the incoming IR impulses and converts them back into their original electric signal. This signal is then carried to the circuitry of the DVD player and is recognized as the on/off button being pressed on the remote. We can draw a simple graph to show the sequence of an IR signal the y-axis shows the voltage and the x-axis will show the time. We can take the voltage as the direct voltage being passed to the IR LED. It can be either on or off if we take the on button example.
The LED is held on for 24 milliseconds then held off the eight milliseconds and then on again for 10. However we mentioned before that there is a lot of background IR radiation therefore the IR signal actually looks like this it is modulated at 38 kilohertz. This means that every time the light is on instead of being constantly on it flashes at 38,000 times a second. The IR diode and the DVD player then only picks up IR signals that are pulsing at a rate from 38 kilohertz therefore cancelling out all background radiation
Advantages of infrared communication:
Due to short range of communication it is secure. It is quite inexpensive in term of wireless transmission media.
Disadvantages of infrared communication:
It can be used for short range of communication. Infrared wave transmission cannot pass through obstruction like walls buildings etc.
Infrared light is an electromagnetic wave characterized primarily by its wavelength the light spectrum is divided into segments or spectral bands visible light also called white light ranges from 0.4 to 0.8 micrometers. White light is mainly emitted by the sun it can be reflected absorbed or transmitted by a body. When white light hits an object some wavelengths are absorbed and others are reflected. The wavelengths that are reflected determine the color of the object as we see it light whose wavelengths are between 0.8 and 50 micrometers is infrared light which is invisible to the naked eye only. Some animals such as snakes can see infrared radiation which is proportional to the temperature of the body being observed. Anybody with a temperature higher than absolute zero kelvins or minus 273 degrees Celsius emits thermal radiation by day and night. The higher the body’s temperature the closer this radiation will be to the white light segment for example when a blacksmith heats a piece of iron until it is white hot. We see it as white because it is emitting radiation at all wavelengths in the visible spectrum this relationship between radiation and temperature is described by Planck’s law which is used to calculate the intensity of thermal radiation or radiance this law applies to black bodies theoretical bodies that absorb all wavelengths and emit a flux depending on their temperature for a given spectral band radiance can then be used to determine how effectively a body emits radiation for a given temperature. This is called emissivity ranging from 0 to 1 emissivity compares the radiance of the body with the radiance of a black body. The closer the emissivity of the body is to one the closer its radiance is to that of a black body if its emissivity is 0.5. It emits half the radiation of a black body a body’s emissivity depends on its physical properties for example skin has an emissivity of 0.98 whereas polished metal bodies like aluminum have emissivity values that may be less than 0.1. These are infrared mirrors if the emissivity value of the body is known the emissivity can be used to calibrate infrared devices the body’s thermal radiation can then be captured to determine the body’s temperature known for enabling us to see by night infrared light is now used in many fields such as industry defense and remote fever detection.
The infrared sensors actually come in two packs as we can see one is the Rx and one is the TX also they come in various packages size like this is the 5 mm package and this is the 3 mm package. They differ in size they are not up to scale as visible over here but still we can manage to see at least.
Now we can see that there are color differences between the Rx and TX. Now basically Rx and TX as they say the receiving and the transmitting LEDs the transmitter actually transmit Ray’s in infrared spectrum and the RX is designed to receive. Those IR spectrum rays as we can see that the IR receiver is more darker in color and the transmitter is like a transparent. Similarly the another package that is available in market here we have the transmitter in slightly blue shaded color while the receiver is completely transparent so this was how an IR transmitter receiver pair looks like.
Working principle of Infrared Sensor:
Let us move forward to the working principle of an IR sensor now as just we said that an IF LED that is a transmitter can actually transmit in infrared spectrum in the infrared spectrum whenever a voltage is given between its terminals. It is just a diode but it emits Ray’s whenever a specific voltage is given between its two terminals that is a cathode and the anode. So we have a transmitter that we saw over here a receiver as we saw and the principle actually behind the working of an IR sensor is the reflectivity of by an object now whenever we have any object in front of a transmitter the object tends to reflect the risk that is coming from the IR sensor to back to the IR sensor so actually you by using this principle we can like use this IR transmitter receiver pair for detecting objects and how do we do that whenever a ray that is reflected by an object is received by the receiver. It generates a voltage level across its terminal and this voltage level depends upon the intensity of the light that is reflected by the object we will further discuss about what intensity level and what voltage level we mean over here. So let us move forward to our first example where we have a transmitter and a receiver placed side-by-side now we can see that the IR transmitter it’s transmitting within a limited range and it goes to a certain distance actually IR transmitters are not so powerful that it can traverse great distances but still it can manage at least a few centimeters for detection purpose. We also have a receiver over here this is actually a very sensitive type of receiver not a common type of receiver. Now as there is no object present over here so there is no reflection and that is where no object has been detected also the output between the terminals of the receiver. IR LED will be like zero volt now we move towards an another example where we have the object present in front of the IR transmitter here we can see that the Rays have been reflected and some of the Rays can be captured by the IR receiver. Now this will in turn generate some voltage and we will have an object detected though it may not give the accurate distance of the object but still it can manage to give the desired output that is detecting an object in its vicinity. Now let us move to an another example here actually we can see whenever there is a brighter object like a completely white screen it reflects more of the race whenever we have a black screen it reflects very much less than the previous one it reflects but still the quantity is too less to be detected by the IR receiver that means if a brighter screen is there it will reflect more if a darker screen is there it will reflect less in the IR range. So using this principle actually we can make a line follower which will track a bright line or a black line depending upon whatever we want suppose we want a black line then we will program it that whenever the IR receiver will receive the most lesser amount of the Rays that means the lower voltages it will follow there only suppose we want the eye our robotic vehicle to track a brighter line that is a white line then we will have larger voltages across the receiver so we will be getting the brighter rays and following it with a larger voltages across the terminals the voltage levels can be compared with comparators or various other techniques of using microcontrollers etc so this was how the IR sensor works.