ffang@umaxc.weeg.uiowa.edu (Francis Fang) (04/18/91)
First of all, let me thank all of those who replied to my questions regarding IR transmitter control. Your help has been invaluable since I would not be where I am in my project without the info. The following is a number of the replies I have received regarding my question : ------------------------------------------------------------------------------ Date: 15 Apr 91 14:52:36 GMT Could anyone out there tell me where I might be able to buy or get info regarding infra red remote control devices. Specifically, I need info on the coded pulses that are sent. I have tried to "see" the pulses by looking at the output of my remote control on the oscilloscope but all I get are a series of little spikes. This I would have assumed to be the coded pulses but I also found that the waveform on the screen was the same amplitude and frequency no matter what button I press on the IR Trx. Any info at all would be greatly appreciated. Frank. ------------------------------------------------------------------------------ Replies ... ------------------------------------------------------------------------------ From atn@cory.Berkeley.EDU Mon Apr 15 12:05:49 1991 Date: Mon, 15 Apr 91 10:04:52 -0700 From: atn@cory.Berkeley.EDU (Alan Nishioka) To: ffang@umaxc.weeg.uiowa.edu Subject: Re: IR Remote Transmitter Cc: atn@cory.Berkeley.EDU First of all, IR is usually encoded on top of a 40khz carrier which is probably what you are seeing. Radio Shack sells a $4 module that decodes the signal and outputs TTL. It is a very popular receiver (on the net in magazines....) I've been working on making my amiga a universal IR xmitter and controling devices with IR. I have some references (from magazines, sci.electronics) if you are interested (but they are not on this computer and must be uploaded) ------------------------------------------------------------------------------ From fisher@csd4.csd.uwm.edu Mon Apr 15 12:19:18 1991 Date: Mon, 15 Apr 91 12:19:04 -0500 To: ffang@umaxc.weeg.uiowa.edu From: rick@ee.uwm.edu Subject: Re: IR Remote Transmitter Newsgroups: sci.electronics In-Reply-To: <5494@ns-mx.uiowa.edu> Organization: University of Wisconsin - Milwaukee Cc: In article <5494@ns-mx.uiowa.edu> you write: >Could anyone out there tell me where I might be able to buy or get info >regarding infra red remote control devices. Specifically, I need info on the I believe that most IR remote controls use bursts of 40kHz "tones" to prevent interference by the flickering of other environmental light sources. (They use a 40kHz tone detector, so tone-detected = on and tone-not = off.) There's a 40kHz IR transmitter available at Radio Shack, I think... ------------------------------------------------------------------------------ From @RELAY.CS.NET,@tektronix.tek.com:gaulandm@tekig7.map.tek.com Mon Apr 15 18:09:24 1991 Date: Mon, 15 Apr 91 12:24:13 PDT From: Mike Gauland <gaulandm%tekig7.map.tek.com@RELAY.CS.NET> To: ffang@umaxc.weeg.uiowa.edu Subject: Re: IR Remote Transmitter Newsgroups: sci.electronics In-Reply-To: <5494@ns-mx.uiowa.edu> Organization: Tektronix Inc., Beaverton, OR Cc: In article <5494@ns-mx.uiowa.edu> you write: >I have tried to "see" the pulses by looking at the output of my remote >control on the oscilloscope but all I get are a series of little spikes. >This I would have assumed to be the coded pulses but I also found that Tek has a new instrument, the TVC-501 Time-to-Voltage Convertor, that can help you analyze the pulses. The instrument converts pulse width to a proportional voltage, so your scope can show you how the width of the pulses is changing with time. You can actually see the code used for each key, as a pattern of wide and narrow pulses. We have an application note that tells you how to do this; I'll send you a copy if you give me your address. --Mike ------------------------------------------------------------------------------ From ho@s10.csrd.uiuc.edu Tue Apr 16 09:54:02 1991 Date: Tue, 16 Apr 91 09:54:49 CDT From: ho@csrd.uiuc.edu (Samuel W. Ho) To: ffang@umaxc.weeg.uiowa.edu (Francis Fang) Subject: Re: IR Remote Transmitter Well, the most common scheme is to start with a 40kHz pulse train, and modulate the width of the pulse train. This lets you do filtering for 40kHz first thing, so that you don't get trouble with interference from lights and such at 60Hz. Sam Ho ------------------------------------------------------------------------------ From atn@cory.Berkeley.EDU Tue Apr 16 18:07:39 1991 Date: Tue, 16 Apr 91 16:06:31 -0700 From: atn@cory.Berkeley.EDU (Alan Nishioka) To: ffang@umaxc.weeg.uiowa.edu Subject: Re: IR Remote Transmitter Cc: atn@cory.Berkeley.EDU Sorry, I forgot just *who* we are trying to deal with... I guess they don't pay Radio Shack employees enough, so I shouldn't complain. The receiver is an "IR Detector Module" RS part number 276-137 on page 123 of the 1991 catalog. The price is $3.49 and it is usually on the wall with the LEDs (which is usually near the ICs) Some general references: Computers and Electronics, Nov 1983, p.90 Forrest Mims talks IR joysticks (not using 40Khz) Modern Electronics, Feb 1989, pp. 65-69 Mims talks about the Radio Shack receiver. Popular Electronics, Apr 1990, pp.90-1, 102-3, Charles Rakes talks about FM circuits based on the 567 (ie. not 40Khz carrier) Byte, Feb 1987, Build an Infrared Remote Controller, Steve Ciarcia Byte, Mar 1987, Build a Trainable Infrared Master Controller, Steve Ciarcia Modern Electronics, Oct 1990, Power On/Off Remote Controller Apparently Circuit Cellar Ink, Steve Ciarcia's magazine has had IR projects. I haven't seen the magazine. ------------------------------------------------------------------------------ From ptsfa!pacbell!dmturne@PacBell.COM Wed Apr 17 13:59:15 1991 Date: Wed, 17 Apr 91 11:59:02 PDT From: ptsfa!pacbell!dmturne@ns.PacBell.COM To: ffang@umaxc.weeg.uiowa.edu Subject: Re: IR Remote Transmitter Newsgroups: sci.electronics In-Reply-To: <5494@ns-mx.uiowa.edu> Organization: Pacific * Bell, San Ramon, CA Cc: In article <5494@ns-mx.uiowa.edu> you write: >Could anyone out there tell me where I might be able to buy or get info >regarding infra red remote control devices. Specifically, I need info on the >coded pulses that are sent. > >I have tried to "see" the pulses by looking at the output of my remote >control on the oscilloscope but all I get are a series of little spikes. >This I would have assumed to be the coded pulses but I also found that >the waveform on the screen was the same amplitude and frequency no matter >what button I press on the IR Trx. The best source is to get the schematic and repair information from the manufacturer. Many IR remotes use Pulse Position Modulation (PPM). An old National Semiconductor databook tells one way this is done. My RCA TV (I bought the schematics for their mailorder technical bookstore) uses a slightly different method. Both use a pulse or two at a start flag, followed by data pulses. Each bit is defined by a 100 microsecond time period; a pulse within this time is a logical one and the absense of a pulse is a logical zero. ------------------------------------------------------------------------------ From mbd@BRL.MIL Wed Apr 17 15:10:27 1991 Date: Wed, 17 Apr 91 16:00:42 EDT From: Mike Danish (VLD/GSB) <mbd@BRL.MIL> To: ffang@umaxc.weeg.uiowa.edu Subject: reply I have a friend who is in the TV repair business (I am too, part time). He worked and worked and worked on a project to electronically detect the IR signals from various remotes (the easy part circuit-wise) and then using a machine language program on an IBM clone, convert the IR signals to an oscilloscope-like display on the computer screen. He recently succeeded but at this point doesn't want to give out specifics since he's considering perhaps marketing such a device/program to persons in the repair business. It is quite fast and allows comparsion between suspected hand units and known good signals. Byte magazine had a couple of articles on IR two or three years back. I'll let you know the details if they become available. Mike Danish ------------------------------------------------------------------------------ Thanks once more to all those who contributed info. Francis C Fang.