special IR signal

Hello folks,

I’m trying since weeks, but i cannot decode a special IR signal.
It’s a signal of a RC-car transponder for lap counting.

So the transponder pulses allways the same signal automatically which is just an id/number.

With an oscilloscope at the ir-sender electrics it looks easy.

But: i cant get manage to read the ir input at arduino with IRremote- oder IRlib dumps; these pulses/spaces are not the values i am expecting.

Oh and BTW: i tried several TSOP IR receiver from 33-56khz…
Where’s my fault?

Thanks in advance.

Where's my fault?

Not providing enough detail.

With an oscilloscope at the ir-sender electrics it looks easy.

I don't see the trace posted here, or a detailed description of it.

these pulses/spaces are not the values i am expecting.

I'm a Lancastrian; your Jedi mind-tricks don't work on me.

okok: here's what i get with arduino (positiv pulse/negativ space): 100 -1900 200 -1950 250 -2800 150 -1400 150 -3850 300 -2000 350 -3850 150 -1200 150 -150 100 -3800 150 -150 100 -2450 300 -4100 150 -2200 300 -3450 300 -2000 300 -3250 300 -2250 250 -3700 150 -1200 300 -2800 150 -1950 300 -4000 300 -1600 250 -4450 300 -1400 300 -4200 300 -1700 300 -1900 300 -2800 300 -1250 300 -3700 250 -2050 300 -3900 300 -1050 150 -4000 300 -2600 300 -4100 400 -1950 350 -3400 400 -1900 400 -3150 400 -2150 150 -150 100 -3550 400 -950 400 -2700 400 -1700 150 -4150 350

the oscilloscope looks like: http://download.unixfrickler.de/arduino/osc.bmp

I'm realy noobie, so i'll try to provide as much information you need and i would not think of....

Thanks for the picture.

It seems that a high frequency is used, and without further modulation. I think the base frequency could be 80kHz.

Did you use a scanning sketch for those numbers ? Are those microseconds ? Can you give a link to the scanning sketch that you used ? And tell us if you used a receiver module or just a bare diode for those numbers.

If those numbers are microseconds, then I can't match those number with the picture. I think something is wrong with reading the pulses in the Arduino.

Step 'h' in this page shows a modulated signal : http://jumpjack.wordpress.com/2008/05/22/remote-control-3-editing-waveform/


This is the Sketch i used: https://github.com/shirriff/Arduino-IRremote/blob/master/examples/IRrecvDump/IRrecvDump.ino

Yes, that's also my problem matching these two data dumps.

Sadly, access to the oscilloscope is very complicated for me ( a friend sometimes at work ), but i have this: http://download.unixfrickler.de/arduino/osc-long.bmp

And i used IR receiver Vishay TSOP312(33-56)

And i used IR receiver Vishay TSOP312(33-56)

That is your problem. That chip demodulates the signal so the numbers you are seeing is the length of time each burst of IR is giving you. It is way higher than the IR signal you have therefore it is giving you the best numbers it can, which in a nonsense given the high modulation frequency.

Note there is no such thing as a TSOP312(33-56), you can have a TSOP31256 or a TSOP31240 or a TSOP31238 and so on. So what one are you using?

TSOP312(33-56) means, i used different IR receiver from TSOP31233, TSOP31236, TSAP31238, TSOP31256.

The data generally looks always that way and i can't match it. The posted data was from the 38khz receiver.

I couldn't get a 40khz ...sold out at my store. I hoped 38 would be common enough to cover that range...but i may misunderstand this.....


i see.....nobody answers, so i did something basically wrong. May anyone help despite my noobness?

Thanks and happy new year !

Well one answer that you did get, was the the carrier frequency seems to be 80kHz.

If I were you I'd investigate the manufacturers of the RC timing equipment and see what the frequency is. There's no reason why their transponder should work with a receiver from another manufacturer: just becasue 38kHz is common in the world of TV remotes, it's very possible that in the RC world they settled on a diffeent frequency.


Thank you !

So.....80khz IR receiver...where do i get these? Cannot find any in my common stores.

Schoofseggl: is it possible to use 40khz receviers because 80khz is multiple?

I'm not sure; I doubt it, but others may know for sure.

s it possible to use 40khz receviers because 80khz is multiple?

No. If you look at the data sheet you will see there is a band pass filter in it. Also look at Figure 5. Frequency Dependence of Responsivity, and you will see it drops off very sharply.


Sorry for the re-edit…you’ve been really fast in answering this time :open_mouth:

Shortly after i’ve written my question, i came to the conclusion it wan’t work.

So i can’t get a 80khz IR receiver…do i have to use a photo diode or how can i receive this 80khz signal?

Why don't you do what I suggested a few replies above, and contact the makers of the transmitter and get the matching receiver?

Three suggestions for you...

A: Try this sketch which will give better timings than IRremote which is +/- 50 uSecs. (although you can alter this in the library). Post back the output. Air Conditioners: Recording long Infrared Remote control signals with Arduino Of course, if it is a non-standard modulation it wont help much.

B: Try using the sketch/setup in this post. It should be able to capture the signal, if you follow the instructions carefully. However, it was only tested up to 56kHz. Poor maker’s Infrared receiver

C: Finally, use this circuit with your oscilloscope and you should get a clear picture of the signal. ‘Silver bullet’ – the Oscilloscope Infrared Receiver

If it turns out to be 80kHz, it should still be possible to send it using arduino & IRremote/IRLib using the sendRAW function - provided you manage to capture the signal, of course.

Kudos on the Silver Bullet there, AnalyisIR. I just breadboarded that. At the 500us as you suggested, easy to see the spaces and marks as in your photo. Then separated the peaks in the block at 25us and easy to measure the carrier frequency.

My supplier has BNCs with rubber boots: I'll see if I can get the LED and resistor inside there.



Thank you very much for those hints....I'll try them as soon as i have all components ready. BTW: i only got ld 274-3 here as diode....are these ok as well?

BTW: i only got ld 274-3 here as diode…are these ok as well?

It is eol but looks pretty good.

FYI: It is a diode - but better referred to as an Infrared emitter or IR LED.

Sooo, after all i did built up the poor maker's ir receiver.

A quick test with a usual IR remote....36khz for it....ok seems to work.

Sadly it shows nothing for my special transponder/ir emitter .....

Can i modify the sketch anywhere to maybe approach it anyhow?

Next the modified sketch for long signals....


I just reviewed your oscilloscope trace & assuming that the probe was right on the IR emitter LED....

...it looks like this could be an unmodulated signal(?). Photo of the circuit?

Can you confirm again where the probe was & maybe capture another one right at the IR emitter.

What type of scope were you using? Could you also capture a trace at the poor makers receiver (LED) as well.