using a pt2222 with components salvaged from old VCR

Hi there,

So, I found this PT2222 IC and a some components attached to an old DVD player or VCR. Anyway, I hooked it up to my Arduino and sure enough it worked exataclly as I expected the buttons produced the expected output and the remote did so as well.

What I don’t understand is that LED connected to VDD through the zener diode. Also - in my program it is forever picking up IR results as at the moment I have a program that just sits there and reads any results.

here is the main loop of the program, not much there.

void loop() {
if (irrecv.decode(&results)) {
Serial.println(results.value, HEX);
irrecv.resume(); // Receive the next value
}
}

Hopefully someone with a little more knowledge can tell me what this is all about. I assume somehow that the LED is being used to read IR data but from where?

What I don't understand is that LED connected to VDD through the zener diode.

Which LED?
What Zener diode? None is shown on the schematic.
What circuit are you using for the receiver?

The receiver is in the top right. If I unplug it, the remote (whichever one I use) won't cause anything to be printed to the serial output window. The LED that I am talking about is the white (clear) one on the main board, the arrow is pointing directly at it.

Also, yes you are correct, the circuit diagram doesn't show the zener diode, it is however there in the actual circuit.

Again, the receiver works great, the buttons on the board do as you would expect when pressed however I just don't get that circuit shown in the datasheet which appears to be super close to what is on this board save for the above mentioned zener diode.

Sorry I wasn't more specific, hope that clears up any confusion.

Thanks

I have no idea what you are going on about. If you have questions about a particular circuit, post that circuit.

We need the full circuit and zener part number. How have you arrived at the conclusion that it is a zener?

Weedpharma

OK - forget the part of the image with the actual physical setup in it. Just pretend that the only thing I posted is the snippet from the PT2222 datasheet showing the schematic, the question is what is that supposed to be doing? Forget I ever mentioned a zener diode. that isn't the part of of the circuit that receives the input from the remote.

Just pretend that the only thing I posted is the snippet from the PT2222 datasheet showing the schematic, the question is what is that supposed to be doing?

The schematic shows part of the circuit that transmits an IR code, when you press a button.

" I assume somehow that the LED is being used to read IR data but from where? "

As said by jremington, the LED is an output, not an input. It is being driven by a transistor driven from the IC. Do you see it flash? If so it is not outputting IR unless you are looking at it via a digital camera. It may simply be an activity indicator.

The input is on the small board in top right corner of the picture.

Weedpharma