HDMI 5 port switch detecting LED with Arduino

[StealthRT]

Hey all I am wanting to make a project for this HDMI 5 port switch I have. I want to be able, with an Arduino, to detect which of the 5 ports are being used (only 1 can be used at any given time).

My 5 port HDMI switch looks like this:

Ok how about if I used 5 4N25 chips to detect the led being on or off?

One of the LEDs would hook to Pin 1(+) and Pin 2(-). Pin 5 would house a voltage of ~3vdc from a power supply. Pin 4 would be hooked up to the arduino's Analog Pin 0.

So when the LED on the 5 port switch is powered on, it causes the ~3vdc power from the power supply to flow to the arduino where it's read as a voltage value.

Does this seem correct?

 

[ronsimpson]

1) Why do you need to isolate the Arduino? If the Aruduino's ground connects to the HDMI ground then there is no need for the 4N25.
2) If you use the 4N25 add a resistor to the LED side to limit the current.
3) You also need a pull down resistor on "A0".

 

[KeepItSimpleStupid]

I'd do a LITTLE reverse engineering. It looks like a 5V supply in the HDMI thingy. So what's the 3.3 V for
Parallel LEDs get funky. I have done it before. Parallel LED's work reasonably well when the LED voltages are the same with a reduction in intensity.
At least take a pic of the circuit board,
You also need to measure the voltage across the LED, both on and off.
And see what you can discover about the driver.

The output of the OPTO will always show high when presented to the analog input.
You should be able to use a digital input with a pull up resistor. e.g. +3.3..resistor..C..E..GND
An OPTO-FET might be a better choice.

I've been contemplating a more robust LED interface for other projects. It just hasn't got off off the ground. Well, maybe a little

 

[dr pepper]

Stick a ldr on top of the led on the hdmi box with some non light conductive paint, an dchoose a resistor that gives you a reasonable voltage swing when the led is on/off, then use an arduino analogue input, you then dont even need to open the hdmi box.