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Old 29th Oct 2019, 12:17 pm   #1
Max Ripple
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Default Infra red remote control receiver

I'm trying to find a replacement for a failed device,it's one of those integrated receiver/demodulator jobbies,ubiquitous to any remote controlled device it seems?
There are a variety of replacements available of course,but how to determine what carrier frequency was employed by the original device eludes me.
I have the original (functional)remote control,but I have been unable to establish what carrier frequency it's sending.
I could just plump for the most common 38Kh type I guess,but it would be interesting to come up with a test method,which could be useful for other projects too?
Any input appreciated,thanks.
Nick
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Old 29th Oct 2019, 12:38 pm   #2
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Default Re: Infra red remote control receiver

With the aid of a frequency counter or 'scope, would it not be possible to measure the frequency of the working control, subject to it's o/p being of sufficient level to drive the counter or scope of course. I've never tried to do this, and the I.R. tester I have only gives a 'go/no go' indication via LRDs.
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Old 29th Oct 2019, 12:48 pm   #3
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Default Re: Infra red remote control receiver

Are you talking infra-red or ultrasonic here?

Talking about 'measuring carrier frequencies" makes sense in the context of Ultrasonic, and is relatively easy - measuring the frequency of non-visible IR light's not so easy!
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Old 29th Oct 2019, 1:47 pm   #4
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Default Re: Infra red remote control receiver

Put a 'scope across the IR diode.
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Old 29th Oct 2019, 7:25 pm   #5
Max Ripple
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Default Re: Infra red remote control receiver

Thanks for the replies.
It's a common infra red system,with standard operation.
Ie,the actual remote control keystrokes create data that modulates a carrier wave,this then in turn modulates the ir light beam.
Instruments(mine at least!)seem only able to display the composite signal,and it's tricky to distinguise between the components of the signal.
Info on the machine that uses the device seems to be unobtainable,as that would be the easy route to establish the spec.
I probably should get out more,but it's one of those nagging techo questions that keep coming back to haunt!
Nick

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Old 29th Oct 2019, 7:40 pm   #6
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Default Re: Infra red remote control receiver

Maybe look what chip and what crystal the transmitter use.
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Old 30th Oct 2019, 2:20 am   #7
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Default Re: Infra red remote control receiver

Is there not a part number on the IR receiver?
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Old 30th Oct 2019, 6:50 pm   #8
Max Ripple
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Default Re: Infra red remote control receiver

No luck tracing the control chip (D62A804125K)but the associated crystal is 3.64Mhz.I'm wondering if that is stepped down in decades within the chip,as is usually the case,the ir signal carrier frequency could be 36Khz?
The only identifying numbers on the ir receiver are "143D0004".
Thanks for your interest.
Nick
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Old 30th Oct 2019, 8:17 pm   #9
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Default Re: Infra red remote control receiver

Quote:
Originally Posted by G6Tanuki View Post
Are you talking infra-red or ultrasonic here?

Talking about 'measuring carrier frequencies" makes sense in the context of Ultrasonic, and is relatively easy - measuring the frequency of non-visible IR light's not so easy!
In infra-red remote control systems the infra red beam is interrupted at a fixed ultrasonic frequency, typically 30Khz to 60Khz - this is often referred to in this context as the 'carrier' frequency. The (much slower) serial data 'modulates' the high frequency pulsed carrier by turning it on and off.

The reason for the use of a 'carrier' is to enable the receiver to look out for something more distinctive than the simple presence or absence of infrared light, since there are many potential sources of infrared light, not least conventional light bulbs. One of the jobs the I/R receiver module does is to remove the 'carrier' leaving only the low-frequency data to be passed on to whatever will be decoding it - usually a microprocessor.

Integrated receiver / demodulator devices like the ones described in post #1 are nominally 'tuned to', or sensitive to, a particular I/R carrier frequency, and it is this property (of the original receiver device) that the OP needs to be able to determine.

One way is to open up the remote and scope the signals it sends to the I/R LED. The shortest cycles observed will be at the frequency of the I/R carrier, so it should be possible to work out the I/R carrier frequency from the length of one 'carrier' cycle.
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Old 1st Nov 2019, 12:07 pm   #10
Max Ripple
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Default Re: Infra red remote control receiver

The mention of ultrasonic signals in relation to remote control,conjures up reminiscence of the early tv remote controls that utilised that system,and images of channel changes etc, when you rattled your key's!
But of course,it means that the frequencies employed were in the ultrasonic waveband,and some critters(eg bat's)can hear up to 150khz!!!
Bang&Olufsen developed an ultrasonic remote control system during the 'seventies,that was,and still is,for fans of vintage equipment,quite robust.
The system employ's piezo elements to transmit and receive the acoustic carrier,which is modulated by the keystroke data.
The infra red system(only the light beam is at ir frequency of course) was developed as remote controls became more complex.As with digital sampling,the higher the carrier frequency of the composite transmission,the more robust the operation.
Again,with B&O systems they employ 455kh rather then the common 38khz for the carrier frequency,although I understand that they employ Bluetooth rf technology in their current products remote control systems,as do also Sky.
There seem to be remote control tester's that analyse the output of vehicle remote control keyfob's,but not for common or garden versions?
Thanks again for your interest.
Nick

Last edited by Max Ripple; 1st Nov 2019 at 12:08 pm. Reason: spelling and grammar
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Old 1st Nov 2019, 9:40 pm   #11
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Default Re: Infra red remote control receiver

When I was playing with Grundig CTVs, the first ones with rem com used the TP7. Condenser L/S, a tapped coil giving 7 discrete frequencies.
There next model, the TP12had (I think) four frequencies, but these were chopped into pieces and mixed up so that a train of the four were sequenced. eg, ABCA -- ABCA repeated. (*) Anyway, this produced 12 commands. This was followed by the TP16, now however with infra red signals. These used the same coding and frequencies as the TP12, but with four more commands.
At the time, the cost of a TP12 was horrendous (100+ i think) whereas the TP16 was around 30, with non OEM replacements about 15 max.
I bought these cheaper ones, cut the track to ensure only the first 12 programmes, removed the condenser microphone from the TV set, and tagged in an infra red diode and a couple of resistors. Now I could sell the sets and still make enough s to keep me happy.
(*) That explanation is probably way off, but I do have the books somewhere upstairs should I need to KNOW for certain.
Les
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Old 2nd Nov 2019, 11:37 am   #12
Max Ripple
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Default Re: Infra red remote control receiver

Ah yes,happy day's.Quite tricky to get those funny flat batteries though I remember?The system worked well though.I had one of the small portables as a workshop monitor.
Nick
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Old 2nd Nov 2019, 9:40 pm   #13
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Default Re: Infra red remote control receiver

Oh no Nick. The ones with the flat batteries (6K7?) were another generation on. Single frequency I think, but various pulses of length and sequence. i think that was the stage when everybody started to use essentially the same system. TP200, TP300, TP400 and another, TP380?? which was used in an add on remote for the 2X4 super videos, V2000 system. There were plenty of those going cheap, so I bought a few and used the innards when I got a badly worn TP350. Another money saver.
Les.
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Old 4th Nov 2019, 6:34 pm   #14
Max Ripple
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Default Re: Infra red remote control receiver

Necessity the mother of adventure indeed?I too have kept loads of old bit's n bob's,as you never know?
As to the ir problem,I've used a Vishay TSOP4438 receiver/demod device,and all is now functional.
An interesting project,and thanks to all the interested parties here too.
It's left me wondering about cobbling together some sort of ir remote control tester,in case this problem crops up again?
Nick
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Old 4th Nov 2019, 7:14 pm   #15
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Default Re: Infra red remote control receiver

The most effective I/R analysing tool I know is an Arduino running the third-party 'I/R library', which can show the protocol type being used (Example: NEC, RC5 / RC6 or 'Manchester'), the codes being transmitted and the durations of the mark and space signals of the transmission, just in case the format is one not recognised by the library.

However this works in conjunction with an I/R module of the type which has been discussed here, so the one thing the tool can't tell you is what the high 'carrier' frequency is, because the I/R module removes that and outputs only the original low-frequency data.
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Old 5th Nov 2019, 11:03 am   #16
Max Ripple
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Default Re: Infra red remote control receiver

Indeed,and that seems to be a useful option too.However,as you say,it still doesn't help with identifying the carrier frequency.
I've found over the years,that remote controls can send spurious data due to worn keyboards etc.I used to have a keyfob ir detector that was a useful go/no go tester,but as with using your 'phone camera,it only indicates the presence of the ir beam.Operating a "streaming" command such as volume will make the beam blink of course if data is also being transmitted.
I wonder about some sort of "broadband" remote control tester,that could separate and analyse the various components of the signal?
Food for thought?
Nick

Last edited by Max Ripple; 5th Nov 2019 at 11:10 am. Reason: grammer
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Old 5th Nov 2019, 12:00 pm   #17
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Default Re: Infra red remote control receiver

Some LCR testers have a remote control function. I have never seen a bare PCB one with this function though. I bought one without realizing it also does remotes as the function only adds pennies to the price.
These test the IR LED by default as the receiver is built in.
The top line is the ID of the remote itself and the bottom line changes according to the button you have pressed.
It is basically a full all buttons go/no go test for any IR remote.
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Old 5th Nov 2019, 4:06 pm   #18
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Default Re: Infra red remote control receiver

Quote:
Originally Posted by Max Ripple View Post
It's left me wondering about cobbling together some sort of ir remote control tester,in case this problem crops up again?
You've probably already got one! Most digital cameras can see infra-red. Put your mobile phone in self-portrait mode, aim a remote at it, and you should see a bright flash coming from the end of the remote when you press one of the buttons.
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Old 7th Nov 2019, 9:54 am   #19
Max Ripple
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Default Re: Infra red remote control receiver

What a useful piece of kit(TC1),and laughably cheap too.Thanks for the link.
It's worth getting one for the tool kit,as it will be good for testing remote controls to show that they are "active",ie sending data rather than just ir?
My original problem was that I had a faulty unidentifiable remote control receiver device,fitted in a machine with seemingly(so far?)no technical info available.I needed to establish what remote control carrier frequency was in use,in order to fit an appropriate replacement.I winged it,and plumped for a common 38Khz device,and happily, it works!!
If I come up with a better tester,I'll let you all know of course
Nick
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Old 7th Nov 2019, 3:28 pm   #20
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Default Re: Infra red remote control receiver

The TC1 sure does show the pulse trains on the screen.
The IR is obviously working if the display shows something.
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