building my own IR receiver ...

electron

Administrator
Staff member
Since the soldering bug bit me, I have been looking for another very useful project I can put together, and found some simple shematics which show how to build your own IR receiver interface.

http://www.lirc.org/receivers.html
http://lnx.manoweb.com/lirc/
http://www.casemodgod.com/htpc_ir_receiver1.htm

There isn't much to it, and the last URL even gives me most of the Radioshack part numbers, so I am hoping you guys can help me with a few simple questions.

1) RadioShack carries the 276-640 IR receiver, mentioned in the last url, but the LIRC site mentions that this one has some issues. I don't see any other IR receivers on the RadioShack site, and RS is the only store in my area which carries these type of parts. Should I give it a try or look for something else?

2) I also can't find any voltage regular on the RS site which is close in specifications to the ones mentioned in the schematics (one site mentions "5V 100mA TO-92 78L05", another mentions "Voltage Regulator NTE 977").

Is there anything else I am missing? I am planning on running a script to deal with the input, I don't think it should be too hard as these receivers work with LIRC, Girder, etc. ...

In case you are wondering why I want to build one of these:
  • automatically switch the amp/tv to the correct input depending on the remote used. I.e. if I start using my MCE remote, I want it to automatically switch to the HTPC input, and adjust the audio as well. This should be even more WAF friendly than the current macros I have in place.
  • follow-me-tv: when I start the good night sequence, automatically turn the tv on in the bedroom, and tune in to the channel I was watching in the living room.
  • control all my HA equipment (garage door, camera, etc.) by adding a 'fake' remote to my universal remote. I will just pick a set of IR codes I don't use right now (i.e. a Denon receiver), so I can send IR codes without controlling my actual A/V equipment.
I am sure there is much more that can be done, but it's a start.
 

Guy Lavoie

Active Member
If the Radio Shack model is all that's immediately available and doesn't cost too much, I'd give that a try. You can always replace the receiver with a better one later. The TSOP1738 is what the Ocelot uses.
 

electron

Administrator
Staff member
Around $15 in parts, but I have some of the parts already (the resistor, Serial connector, the soldering board). The RS part was around $4 if I am not mistaken, so I guess I am just going to give it a try.

Any idea about what RadioShack voltage regulator I can use ?
 

smee

Senior Member
Digikey is your friend. You don't need to rely on Radio Shack. ;)

If your serial port spits out high enough voltage, you should be able to use the 7805 that Radio Shack sells: 276-1770.
The 78L05 is much smaller (TO-92, the size of the transistors you've been buying). The 7805 may not be very efficient, but it shouldn't matter too much. If your serial port doesn't spit out enough voltage, the 7805 may not deliver 5 volts.

If you want, I can toss a 78L05 in the mail. If I can find them, I should have 100 or so around here.

I've given up on using serial and parallel IR receivers and transmitters (that is, the ones that are driven by timing from the PC). Even in the short run, I haven't found them to be particularly reliable (even using the DLLs that people say work well in XP - they work much better under 98). They are making the PC do all of the work (catching incoming 1s and 0s and rebuilding timing).

I've been much happier with dedicated units (like the USB-UIRT). In those boxes, they are doing all the work and transmitting final data to the PC. All of the timing-dependent work is done in a microntroller, offboard from the PC.
 

electron

Administrator
Staff member
I have had a PCIR before, and it was junk (parallel based tho), but I was hoping that this one would do the job since there isn't much to it, and all I want to do is receive commands. Do you think this is a bad idea? I really don't want to invest in a USB-UIRT as I have an Ocelot.
 

AutomatedOutlet

Senior Member
These are the kinds of IR receivers we'll have in later this week:

Tube kind (http://www.buffaloelectronics.com/p-ir350.htm)

Jbox type (http://www.buffaloelectronics.com/p-ir250.htm)
 

smee

Senior Member
It's cheap enough, so I'd go ahead and try it if you want. Functionally, though, they work exactly the same way whether they use the serial or the parallel ports. The device is not returning serial data to the PC, just toggling a pin on and off. The PC is looking at one pin of the port and seeing when it goes from 1 to 0 and 0 to 1 (and counting while it's doing it).

Doesn't the Ocelot have an IR in?
 

electron

Administrator
Staff member
hmm, so I would have to use Girder or LIRC to process these commands? I was hoping a simple serial port script would do the job.

As for the Ocelot IR in, it is meant to be used for IR learning, it only recognizes about 1 command / second, so many IR commands tend to get dropped, I already tried that route and had no luck. Guy can explain this one better tho.
 

smee

Senior Member
electron said:
hmm, so I would have to use Girder or LIRC to process these commands? I was hoping a simple serial port script would do the job.
No such luck on the simple script.
 

electron

Administrator
Staff member
ok, I do have Girder, so I guess I will have to start using it again. That's assuming I can get everything else to work, this project is starting to sound like a bad idea already lol.
 

Guy Lavoie

Active Member
That's right, the Ocelot's IR in just samples the bit stream for one second and then tries for the closest match with the codes in memory. Because it is designed for learning and replaying codes, it has no idea of how long an actual code is or if it contains part of a repeat, noise, or whatever. This is different from a conventional IR controlled device which has a native code set and recognizes each bit of its protocol as soon as it is received.
 

electron

Administrator
Staff member
Long time ago, I bought a parallel version of the PCIR, am wondering if I can reuse some of those parts, including the IR receiver. I will have to dig it up.

Question, I have a Pinnacle PCTV receiver, hooked up to my MCE box, using Girder, and it works without any issues. Is this the same type of dumb receiver?

extreceiver_small.jpg
 

smee

Senior Member
The Pinnacle receiver looks like it's probably the same thing. Can't tell for sure.

The parallel PCIR does not use the same kind of IR receiver, as far as I know. The ones used in the designs you posted above use a receiver that removes the 38kHz carrier from the signal and just returns an on or off. I think the PCIR uses a receiver that detects and passes on everything (just something that detects IR).
 
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