Everything About Infra-red

[Canyouknott]

Hey me again LOL...

I need help understanding how Infra-red works (Couldn't find any good explanations on the internet).. Lets say you want to press a button sending a IR signal out to the device that is gonna receive and lets say the device just turns on a LED or light (Something simple so I just get the concept). What components will be used in this basic circuit? Does the infared signal just complete the circuit on the so called device like a transistor (E.g on a transistor when the base pin is more then .7V (I pretty sure) it will allow the current to flow through the other two pins)????

Thanks (I haven't learned anything at all about IR so please keep it simple and don't judge haha )


-Pete

 

[Ian Rogers]

There is a complex signal involved... IR is normally embedded onto a 38Khz signal... If you look at Nigel's tutorial on IR you will be much the wiser.... As you know Nigel is a Sony TV man so there is a bias on SIRC!!!



I have also converted this tutorial to C so if C is more understandable.... The link is in my signature..

I know this is more than you want, but IR is data transfer!!

 

[audioguru]

IR is light energy at a frequency that is invisible because it is below a red color. It can be sent from an IR Light emitting Diode (LED), from the sun or from anything that is hot.
An IR receiver can be an IR diode (it needs an amplifier), an IR Photo-transistor or an IR receiver integrated circuit that is usually used.

To avoid interference from the sun or from anything that is hot then the IR is pulsed at a frequency around 38kHz and an IR receiver integrated circuit is most sensitive at that frequency. Most IR receiver ICs have an automatic-gain-control that reduces the sensitivity when there is continuous IR pulsing which is produced by compact fluorescent light bulbs and fluorescent tube lights.

 

[Ian Rogers]

Whoops I may have gone too far!!! Just as a switch... Normally opto couplers do the job.. Look at the datasheet as it has the basic circuitry you need..

 

[Canyouknott]

IR is light energy at a frequency that is invisible because it is below a red color. It can be sent from an IR Light emitting Diode (LED), from the sun or from anything that is hot.
An IR receiver can be an IR diode (it needs an amplifier), an IR Photo-transistor or an IR receiver integrated circuit that is usually used.

To avoid interference from the sun or from anything that is hot then the IR is pulsed at a frequency around 38kHz and an IR receiver integrated circuit is most sensitive at that frequency. Most IR receiver ICs have an automatic-gain-control that reduces the sensitivity when there is continuous IR pulsing which is produced by compact fluorescent light bulbs and fluorescent tube lights.

How do you change the frequency of which the IR outputs? Is the frequency just rapid pulses or something

 

[Canyouknott]

The idea of learning how this stuff works etc.. Is to some attempt to make a simple IR Robot which follows command through a simple button or so..... Like RC Car or something, I believe this would be fun as

 

[crutschow]

...................
I need help understanding how Infra-red works (Couldn't find any good explanations on the internet).. Lets say you want to press a button sending a IR signal out to the device that is gonna receive and lets say the device just turns on a LED or light (Something simple so I just get the concept). What components will be used in this basic circuit? Does the infared signal just complete the circuit on the so called device like a transistor (E.g on a transistor when the base pin is more then .7V (I pretty sure) it will allow the current to flow through the other two pins)????

The simplest approach would be to use an IR LED to generate the IR signal and a photo-transistor to receive the signal.
If the received signal is of sufficiently high intensity, then the photo-transistor will turn on.
The photo-transistor can then drive another transistor (since the photo-transistor's output current is generally small) to amplify the signal sufficiently to light an LED or whatever else you may want to switch.
Of course this ignores the effects of any sources of interference, as mentioned on the other posts, from other external light sources.

 

[Canyouknott]

Is this concept basically correct?

 

[Canyouknott]

Oh so you are meaning like this using the Photo-transistor
?

 

[Canyouknott]

Is this the correct use of an Amplifier ??? (Haven't used one before haha)

 

[audioguru]

Many opamps do not work if an input is at the power supply voltage like in your circuit. Also, when there is no light then the voltage at the (-) input is not defined so the transistor and LED might never turn off.
I biased the (-) input of the opamp at half the supply voltage and added a collector resistor and an emitter resistor so that the (+) input never gets near the supply voltage or near 0V.
I added a power supply bypass capacitor so that the opamp does not oscillate.