Since several days I try to successfully send IR commands to my Denon AVR3806.
I used the library from Ken Shirriff to capture and send the IR command. The Denon protocol is supported, so I used the sendRaw function.
The same approach sending commands to my Samsung TV worked. So the LED works and also the sketch.
I am using a transistor to amplify the PWR signal. So PWR pin 3 is connected through resistor to the Basis and the LED is directly connected between 5V and the collector of the transistor.
Anyway my meter just shows about 2.5mA. My suspicion is that the signal is too weak for the denon although I put the LED directly in front of the IR receiver of my Denon.
I am really stuck and don't know how to proceed or even what to try.
Any help is highly appreciated.
Grumpy_Mike:
You sure your LED is still OK? What limits the LED current?
Reading PWM current with a normal meter will not usually be accurate.
I am not sure whether my LED is still working correctly. Before I posted I successfully tried to switch my Samsung TV which worked. How can I determine whether it is still working correctly? It seems that I do not see it blinking with my mobile camera. But, as I said, it still switches my TV???
With respect to resistor: My current circuit has no resistor, since I thought that due to my measurements I won't need. I also tried the circuit with 100 Ohm resistor.
What puzzles me is that there are so many circuits in the internet, with resistors directly hooked to PWM, some are stating that PWM does not provide enough current....
The reasion why you see so many circuits with IR diodes and no resistors is because people are idiots and have not got a clue about exactly what they are doing.
You measurements do not measure the peak current, at best it only measures the average but usually it will measure much less. I said that meters are not designed to make measurements on this sort of waveform.
Depending on the modulation you may not see it blink on a camara. If it still switches your TV then I guess it is still OK but the led will probbly have lost some brightness due to having no resistor, so put one in immediately. A 50R one should do or two 100Rs in parallel.
The 'marks' on the DENON protocol are 275 uSecs, which is one of the shortest out there.
IR receivers can distort the timings by 100->200 uSecs.
IRremote measures to +/- 50 uSecs, which puts you at another big disadvantage and is probably one of your main issues. There are a few protocols like that.
Mike is correct about the direct connection. To stay within specs you should have a resistor in series with the IR LED of at least 75 Ohms (or 100R is a more common value). Range will be limited.
We posted a blog about driving IR LEds directly from Arduino pins which explains some of the findings.
Let me know, if you cannot make any progress & I will try to help.
