Detect SPDIF signal from a squeezebox

Other Hardware Sensors
1

Hi, I've just ordered my first Arduino so I'm very new to this.
Today it hit me, I should be able to build sensor that detects when there is a signal from one or more of my squeezebox duets and let the Arduino turn on/off a relay for the power to my amplifier.
All the digital SPDIF contacts are free at my squeezeboxes, so my question is what kind of sensor do I use to detect if there is signal from SPDIF contact?

2

Please post some links or a schematic or some code. I'm an electronic technician but I don't know what you're talking about.
If you post a schematic (photo of hand drawn schematic is fine) then we can discuss it further.

3

Hi, what I have are 3 pcs Squeezeboxes each one connected to the amplifier with RCA contacts. The squeezeboxes are turn on with a remote or via a phone and when one are turned on I want the power to the amplifier turned on autmaticaly.
What I thought I do is:
The Squeezeboxes also have SPDIF contact (that I don't use now) and connect a sensor to that contact to detect when a signal is comming. This signal should only come when the squeezebox are on. So then when a signal is detected I let the Arduino turn on a relay that controls the power to the amplifier.
The problem is I don't know what kind of sensor to use to detect that SPDIF signal (I do NOT need to decode it or anything like that).

Hope you understand what I mean.

4

Please list your project objectives:
1-
2-
3

5

1 - Have a sensor that detects signal or no signal from the SPDIF contact.
2 - Have Arduino control a relay that turns on/off the power to my amplifier.
3 - When I have signal from the SPDIF contact then the power to the amplifier turns on.

My problem is the sensor, what to use?

6

We need to know the type of connector used for SPDIF on your squeezbox.
Can you post a photo of the connector or a link to a web page showing a photo of the connector ?
Is it a stereo audio jack (3.5 mm) ? or XLR or what ?

Here is a link to a decoder to convert the SPDIF to audio which the arduino can detect easily.

Once you have this device, detecting the audio is a simple interface to the arduino analog pins using a 1 uF capacitor and two 10k ohm resistors wired as a voltage divider. The program to detect the audio will monitor the left and right audio channels from the RCA red and white connectors and look for voltage transistions (high to low , low to high etc) or possibly an RC Low Pass filter to convert the audio signal to a voltage. Another option is to use a sound detector circuit with a current limiting resistor (100k ohm)
between the audio out from the conveter box and the audo in from the sound detector from Sparkfun. The microphone would need to be removed from the board and replaced with a resistor.

This is the easiest approach since the sound detector outputs a binary (HIGH/LOW ) signal to indicate the presence of sound as well as an analog voltage to indicate the amplitude of the sound. The arduino can monitor the analog signal for variation as well as the digital signal for status. Using these two devices together reduces the solution to primarily software. The relay to turn on the amplifier can be one of several types:

or

http://www.ebay.com/itm/IG1NC-210D-Solid-State-Relay-10A-Output-0-220VAC-1pcs-/360614748118

7

Hi.

Sorry for bringing up an old thread, but I have a pretty easy solution to this problem

I used an osciliscope to analyze the signal from an S/PDIF (SPDIF) output on my soundMate (cheap airPlay reciever) and it seems like the signal is between 0-1V which makes it hard for the arduino to read.

However, since it is between 0-1V even though the sound on my Iphone (airPlay) is at 0%, my reciver won't stop outputting data until I pause the sound, which makes it perfect to interface with the arduino thorugh an analog input.

The spdif has three outputs, one is GND, one is 5V and the last one is signal.
Connect it in the following order
SPDIF GND --> Arduino GND
SPDIF signal --> Analog input on arduino

For me, when the music is paused, the analog line drops to somewhere between 0 and 1, and when I play the music, it goes up to 200-300 which makes it very easy to determine if there is music on or not by just using an if-statment, for examble:

if (threshold < value){

digitalWrite(relayPin, LOW)

}

Hope that this helped someone, since I had a hard time finding an answer my self.