IR help

[Deanuth]

Hi, i'm just getting in to pic programming and i am trying to created a basic IR reciever and emitter, i have the diodes and photo transistors but they pick up some ambient light aswell, i need to use some sort of modulation to allow them to comunicate only with each other, but i do not know where to start.

Any help here would be great!!!

 

[breyno2]

Are you using C, BASIC or assembler?

 

[Nigel Goodwin]

Check my PIC tutorials, and use IR receiver IC's!.

 

[3v0]

Like Nigel said using a receiver will make you project much easier and even more important more reliable.

I like the Vishay TSOP parts.

 

[Sceadwian]

Modulating the IR can be very simple as all you do is set a timer to toggle the IR pin at the desired modulation frequency and then turn the timer on and off, detection is pretty complicated for a beginner. There's a link bellow this post for a simple single opamp bandpass filter that only requires a couple capacitors and three resistors. If you're not familiar with basic analog opamp circuits get yourself one of the Vishay modules, all the work is done for you though you're limited in carrier frequency selection. Baud rates are generally limited to 9600 or so.

 

[Deanuth]

Thanks for all the replies, i'm using the assembler software which came with my PIC flashing board. do the vishay have a matching transmitter?, or is it pretty simple to make one?

 

[Deanuth]

Ok, i can get my hands on some of the vishay recievers, should i pick any frequency in particular?, any more info on how these things work would be great.

 

[3v0]

Ok, i can get my hands on some of the vishay recievers, should i pick any frequency in particular?, any more info on how these things work would be great.

When the reciever see the correct frequency IR is goes from high to low and stays low as long as the frequency is present. The rest of the time it is low. The code you will use/write is all about timing the low and/or high pulses. As Sceadwian mentioned the PICs timers are handy for this.

When I started playing with IR I used an old VCR remote control to test my reciever. The codes and freq for most remotes can be found on the net.

TSOP1100 that will accept frequencys from 33-57kHz. This is handy if you want to use a remote and do not know or care what the frequency is. I order 4 of these a month ago but now they are marked as obsolete. Perhaps Sharp or others makes these wide range recievers.

For actual projects you can choose any frequency if you are building a TX RX pair.

Nigel's tutorial on IR is a good place to start.

There are links to datasheets for the Vishay Recievers on Mouser's site and many other places.

 

[Deanuth]

Well i've ordered some 36khz recievers, so i am going to be after code examples etc so i can set an emitter up.