IR Remote Control Issues

[Kamikaze47]

Ok, here's what i've done since the description in my original post:

- Changed the LED's resistor to 10 ohm
- Removed one transistor, turning on and off PWM to control the LED
- Changed the frequency to 38kHz
- Changed the duty cycle to 25%
- Improved the timing using TMR0 for timing instead of PAUSEUS

The end result is an improvement, but not spectacular. The range is improved, however I still need to point the LED pretty much directly at the TV for it to work - Whereas i can point my normal TV remote anywhere in the room and it will work (even pointing directly away from the TV).

Perhaps I need some kind of diffusing material in front of the LED? I'm not sure what to use tho. Or maybe I need to get an LED with a better viweing angle, but i'm not sure that this is the case, unless my tv's remote has a 360 degree viewing angle - lol. I assume that my tvs remote is simply powerful enough to bounce off the walls and eventually find its way to the tv no matter what direction i point it.

[keithdoxey]

Looking at the schematic again, I dont think you are getting enough drive to the transistors.

Either change the transistors to PNP types and invert your gating signal or put the transistors where the LED is and the LED where the transistors are so that the transistors are sinking current rather than sourcing it.

You may also need to reduce the value of the base resistors to get more drive.

[ardhuru]

Perhaps I need some kind of diffusing material in front of the LED? I'm not sure what to use tho. Or maybe I need to get an LED with a better viweing angle, but i'm not sure that this is the case, unless my tv's remote has a 360 degree viewing angle - lol. I assume that my tvs remote is simply powerful enough to bounce off the walls and eventually find its way to the tv no matter what direction i point it.

I dont think any external diffusing material would help. A lot of remotes have the LED body itself sticking out of the remote. You're right about the signal bouncing off objects; IR does tend to reflect well, although the signal strength must be dropping signaificantly after every refelction.

I suspect now its just a matter of getting the frequency and/or duty cycle right. You could also try 2 LEDs in series, pointing in a slightly divergent manner to give you a wider coverage.

Regards,

Anand

[dhouston]

Are you sending single or multiple copies of the IR? Most of the receivers need to see multiple copies to set their AGC and receive threshold so most protocols send more than a single copy.

[Kamikaze47]

Excellent! Working perfectly now

Switching the transistor and LED around so that the transistor is sinking current, and changing the bias resistor to 1k did the trick (Thanks keithdoxey and ardhuru)

It now has pretty much the same range and capability as my regular TV remote.

Thanks very much to all for your help.

My next step is to get it working with my Receiver. Getting that working should be much smoother now tho. I can actually change the PWM frequency on the fly by writing to the appropriate registers, so even if my other equipment works on different frequencies it shouldn't be a problem.