stuart wrote: > Humm, but I can't find what I'm thinking of (using a 74CH00 chip, > half as a monostable multi vibrator operating at 40KHz and the other > half to help gate the signal).
That might be because the modulation required by some devices may be more sophisticated than simple asynchronous amplitude modulation. Some devices may require frequency or phase modulation, or AM that is synchronous with the carrier wave. Although according to: http://www.linux.org/docs/ldp/howto/Infrared-HOWTO/infrared-howto-c-lirc-irda.html "The IrDA Physical Layer is totally incompatible with the DASK modulation used in IR remote controls." I assume the D in DASK stands for digital. Amplitude-shift keying (ASK) is described here: http://en.wikipedia.org/wiki/Amplitude-shift_keying and in its simplest form would be achievable with the circuit you describe. This site: http://www.zen22142.zen.co.uk/Circuits/Interface/mod_det.htm which has a schematic for building an IR receiver for use with a scope for observing remote control signals (most likely overkill, and with a decent scope you'd do fine with a photodiode or a phototransistor and a few components), also backs up the idea that the modulation is simple AM. That site also has a pile of remote control extender circuits: http://www.zen22142.zen.co.uk/Circuits/Interface/rce.htm which could be adapted for use with a PC. > Instead I found things like: > http://www.lirc.org/improved_transmitter.html > ...which need each pulse controlled as you said above. And half of that circuit is just trying to achieve creating a power source for the LEDs from the serial port. If you wired up a power supply, you could probably do it with half the components. > ...I'd search the hifi-remote.com web site. Chances are very good > that someone has already captured the codes you are interested in and > published them... Agreed. I wouldn't recommend using a scope to reverse engineer the actual codes. I was just suggesting using it to verify that the general signal characteristics, such as modulation frequency and type, match between the original remote and the simulated remote. -Tom ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Mvpmc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/mvpmc-users mvpmc wiki: http://mvpmc.wikispaces.com/
