I am thinking of building a simple remote control. It'll learn certain commands from different remotes, then when buttons are pushed it'll transmit those IR commands.
After doing some reading I found two things; a) Remote commands are a set of binary commands coupled with an address to differentiate devices. b) That the remotes don't simply transmit 0s and 1s, but instead they are analog waves of 0s and 1s with a modulation of 38 or 40 kHz.
Now I did find receivers that have built-in demodulation (like TSOP38238 and TSOP-1140) or a receiver controller like (SIS-2). But can't find ones with a transmitter. So I'm assuming i'll have to build one myself, probably with an LM555 chip or something.
I'll using an arduino with it. The arduino will transmit the codes to the emitter and record the codes from the detector.
i'm not looking for schematics on how to build these, but I'd rather not have to build a modulator for transmitting the IR signal, if there is something I can hook directly to digital output of the arduino it would be great.
So unless i've misunderstood how IR remotes work, I'd be grateful if someone can point out some components I can use with an arduino to build such a device.
40kHz is a cycle length of 25microseconds.
As long as you don't want to do too much at the same time, it is quite easy to do the modulation in software using direct port manipulation and "delayMicroseconds".
Useful to have a scope or frequency counter on hand to verify your software.
Or you could use one of the IR remote libraries.
Also, Project 28 in '30 Arduino Projects for the Evil Genius' uses it - pretty much exactly what you are trying to do - record then playback using one of upto 10 'memory' slots.
You can get the source code for free for my project here: http://www.arduinoevilgenius.com click downloads tab and get all the sketches in a zip.
That the remotes don't simply transmit 0s and 1s, but instead they are analog waves of 0s and 1s with a modulation of 38 or 40 kHz.
Not sure where the word analogue comes in, it is all digital 0's and 1's sent on the back of much faster digital 0's and 1's. Analogue means continuously varying quantity and there is non of that going on.
Thanks for the info. I was under the impression that the 0s and 1s needed to be modulated with a sine wave carrier frequency. Seems like I was wrong. It's actually a digital carrier of 0s and 1s at a 40khz frequency.
As usual I over think these things. Thanks for the heads up on the book and the library. As AWOL mentioned, it can be done by software.