Anyone built a homebrew lirc IR receiver?

I've been using an IRman for years but recently bought a Sky Navigator remote to use with my mythbox, the reason being was that it had a keyboard which I thought would be useful. Anyways, the remote and IRman don't get on so I looked for a replacement. The IRman uses lirc anyway so I thought I'd build the 'homebrew' serial receiver.

I had all bar one of the components hanging around so I stuck a TSOP1738 on a recent CPC order and decided to build one.

The details are here:

http://www.lirc.org/receivers.html

Schematic is here:

Code:

---

IC1 = TSOP 1738
+-----------------------+ 3                           R1 (4k7)
|               data -> +--------------------------------+------------o DCD
|                       |                 _______        | 
|      ______________   |                | 78L05 |      | |   D1 (1N4148)
|     /                 |    +-----+-----|OUT  IN|--+   | |
|    (                  | 2  |     | +   |__GND__|  |    |      | /|
|     \______________ + +----+   -----       |      +----+------|< |--o RTS
|                       |        -----       | IC2              | \|
|                       | 1        |         |
|                     - +----------+---------+------------------------o GND
+-----------------------+      C1 (4.7µF)

---

To put it bluntly, it doesn't work. The serial port of every machine I have at home (7 or 8, must try harder) is seemingly unable to supply the voltage under load resulting in just over 3V going into the TSOP, not enough, the minimum is 4.5V. So, I decide to power it off the internal 5v rail via one of the molex's. The reg finally puts out a good 5V but this then shows up another problem, the data line is then tied high at 10V (the TSOP is running at 5 remember) and it melts the bugger (good job i bought a few).

Am I being an idiot, or is this design ill-conceived? Given this circuit is basically a reg, a cap, a diode and a resistor, it should work fine.... and they do, in isolation. Just bringing it all together seems to be the problem.

I've built that same circit, and had the same issues, I gave up and picked up a cheap PC remote setup off Ebay that works with lirc, after searching, I can't find the same setup, but I did find someone who's selling pre-made recievers for a decent price.

http://cgi.ebay.com/Serial-Infrared-Remo...1QQcmdZViewItem

I must admit I too had problem building my own, I just splashed out and bought a USB-UIRT and it has functioned perfectly all the time I have had it, it also has a pretty powerful IR transmitter, which comes in handy when automating things via the HTPC. It also handles cable TV boxes etc...

Cheers

Cris.

It doesn't look very clever, that chip is a TTL/cmos device and is being exposed directly to RS232 voltages. I went to the site and there is a more comprehensive version of that circuit which uses transistors to buffer/protect the chip from these voltages, you might want to consider using that - or get a max232 and a couple of caps and use that.

All the ebay ones are based upon a design by a guy called Igor Cesko. I've got two good TSOPs left and all the bits to build so I'll probably give it a go first.

Well, I doff my cap to Mr. Cesko, he certainly knows what he's doing. Just got to program all my key events into MythTV now.

Quote:
It doesn't look very clever, that chip is a TTL/cmos device and is being exposed directly to RS232 voltages. I went to the site and there is a more comprehensive version of that circuit which uses transistors to buffer/protect the chip from these voltages, you might want to consider using that - or get a max232 and a couple of caps and use that.

No. There is regulator to regulate RTS down to +5V as a power supply. DCD is an input to the PC. So it's all legit. Although it's not really to the standard PCs almost always will understand +5v/0V instead of proper TTL.

Personally I built a UIR for my MythTV but that requires a PIC programmer. After quite a few years it went a bit flaky though and I ended up buying a Microsoft MCE remote and USB receiver which works just fine under Linux.