|Note from the author (== Plons): It has been a while since I used DHE-editor to create webpages. I did some family webpages with the free version of this editor. You can find this free version at http://www.dynamic-html-editor.com/en/download.asp|
But since this webtool generates much nicer webpages than the archaic ones I used to publish, I purchased a licence to allow me to use it for personal and professional use.
This page shows my first steps with this new tool ..... uh .... toy :-)
Large fontsize huh ? I use it as it's more comfortable for me AND for collegues from the same age-group.
|24 button IR controller|
|On this page you will find all the information you need to build your own Led-light controller.|
I reverse-engineered the protocol because I like this remote, but the implementation of the actual controller (the power-module) did not give the result I needed for my application.
|Opening up this remote would destroy it, so I had to come up with a non-invasive way to measure the carrier frequency.|
I took a 680uH inductor, connected it to the oscilloscope, pushed a button and found:
|Yes, but it uses the current transients in the IR-diode, so put the inductor like shown above, and press a button.|
|An inductor to measure the IR-carrier ?|
|The oscillations you see in this picture are so-called parasitic oscillations: the inductor has some parasitic capacitance and so does the probe. The transients in the current through the IR-led are picked up and make the circuit oscillate.|
But that is not what we are looking for.
When the current is turned on, there is a sudden change in magnetic field. But also when the current goes off: so the time of two oscillations reveals the IR-carrier frequency. The measured time is a tad more than 25 us: appr. 26us. That comes down to a 39 kHz carrier. A 40 kHz IR receiver (like the TSOP1740) will work fine, although it's slightly off.
|Okay, we know now what carrier we're dealing with, so time to hook up the logic analyzer.|
The w i d e picture is a screen-cut from what the Intronix Logic Analyzer picked up from the TSOP1740
The application software is very powerfull, and it was a piece of cake to measure the intervals. Counting 32 bit in a row is a different story.
With notes on a sketchbook I used my PCB-design program SprintLayout to draw the complete pattern, and exported it to a pdf.
A .png file for this webpage and the .pdf as a downloadable link
|AHA ! 40 kHz ? Nope, 39 kHz is the correct number. The 40 was my first rough estimate. But I am too lazy to correct it in the files and exported docs.|