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TV, VCR, Cable, etc remote control IR signals

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kinarfi

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what type of signal do remote control unit put out? I know it's an IR signal that if you point it at your web cam, you can see the output flickering, but what is the signal, is it a square wave, pwm signal, is it a coded pulse, what frequency? just a few details would interesting to know,
Thanks
Kinarfi
 
There are different codes that modulate the ultrasonic carrier frequency. There are many carrier frequencies. The codes are Philips, NEC, Sony and others. Look up which one you want to use.
 
Maybe we have a remote communication error here, the remotes I'm asking about have the Led in the front, so no ultrasonics, I think, I assume your suggesting I google my question and you have supplied enough answer to give my something to google, codes for Philips, NEC, Sony, and here's the answer https://www.remotecentral.com/features/irdisp3.htm
Thanks, now if I could just read them some how. maybe I'll put a scope across the out put and see if I can decipher it.
My goal is to get my RCA digital to analog converter box to operate from my Hitachi TV remote. RCA has a list of #s with 3 digits and and Hitachi has a list of #s with 2 digits, hope that doesn't mean anything, as the digits are for preprogrammed codes, I think
 
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Maybe we have a remote communication error here, the remotes I'm asking about have the Led in the front, so no ultrasonics
The carrier for the IR remote control codes is an ultrasonic frequency of about 38kHz. The IR LED turns on and off at about 38KHz with the codes. An IR receiver IC is manufactured to the correct ultrasonic carrier frequency and has the code as its output. Then you need a smart IC to figure out what the codes are.
 
It's interesting to connect a phototransistor circuit to the input of an oscilloscope and look at the output of a remote. For a simple remote, you can see the difference in the various pulses for each button pressed. National makes (used to make) IC sets for transmitter and receiver. It all used to be ultrasonic, but when IR LED remotes took over, the general specifications remained the same (40KHz pulse trains) but light was used rather than "sound".
 
Phillips use amongst others rc5, and sony ppm (pulse position modulation).
The handset transmits data as bursts of 37 or 40 kc's, a burst for a 1 and silence for a zero for rc5, whereas ppm transmits a start pulse, then the position of the second pulse in time denotes the value of the transmitted number.
In the receiving end there is a infra red pin diode and an amp with a 37-40 kc's filter, the reason for the toneburst at 37 kc is to reduce the effect of interference from fluorescent lighting, sunlight etc.
 
Phillips use amongst others rc5, and sony ppm (pulse position modulation).
The handset transmits data as bursts of 37 or 40 kc's, a burst for a 1 and silence for a zero for rc5, whereas ppm transmits a start pulse, then the position of the second pulse in time denotes the value of the transmitted number.
In the receiving end there is a infra red pin diode and an amp with a 37-40 kc's filter, the reason for the toneburst at 37 kc is to reduce the effect of interference from fluorescent lighting, sunlight etc.

Sorry, but that is completely incorrect on pretty well all counts.

Philips RC5 uses Manchester coding, the zeros and ones are carried by the transitions from high to low, and low to high - NOT the pulses themselves.

Sony SIRC's uses three different width pulses to signify a start pulse (the longest one) and ones or zeros, it's a pulse WIDTH scheme. SIRC's is explained in my PIC tutorials.

The reasons for the different systems, and the slightly 'obscure' way they work is due to the limitations of the IR (or radio) systems used - the pulses coming out of the receiver aren't the same width as the pulses supplied to the transmitter, so you can't use a simple timing scheme like RS232.
 
I stand corrected, I think I oversimplified things there.
I've written code to decode phillips rc5 so I understand the system, but it was a while back.
 
i used a code like this to read pulse trains

if(port=0){
for pos=1to99{
while (port=1) {onbit(pos)++; delayms1}
while (port=0) {offbit(pos)++; delayms1}
}
}
that told me what exactly came out of my remote, that code is just example, it may need editing, it may be inverted on the port, an i forget exact delay time i used, maybe 100us, but from that i was able to compress the values into a few bytes and plot all my buttons,

thats before i knew what my remote type fell under
 
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i used a code like this to read pulse trains

if(port=0){
for pos=1to99{
while (port=1) {onbit(pos)++; delayms1}
while (port=0) {offbit(pos)++; delayms1}
}
}
that told me what exactly came out of my remote, that code is just example, it may need editing, it may be inverted on the port, an i forget exact delay time i used, maybe 100us, but from that i was able to compress the values into a few bytes and plot all my buttons,

thats before i knew what my remote type fell under

No need to be that clever (I did the same though, using DOS on a 386 laptop a LONG!! time ago) - simply use the free audio software Audacity, and record the output from an IR receiver IC.

Or if you have a PICKit2, use the logic analyser tool that comes with it - this does give a nicer result, but only for a short recording time.

In both cases you can reasonably accurately measure the width and spacing of the pulses, it doesn't need to be that accurate, because the pulses aren't the same as transmitted anyway.
 
Hi,

I had used a IR diode detector and scope. I was able to see the various parts of the signals and figure out the codes for each button of several remotes. What i found was that the carrier frequency varied from around 20kHz to about 110kHz and the codes themselves were pretty varied.
 
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