So i live in a dorm and we have this room that we use for parties. A couple of years ago we bought this REALLY huge sound system (the philosophy being that peoples ears will bleed before the sound system, thus making it last longer than the smaller once we had). This has proven to be true, however the music are louder than it used to be and we have subsequently received some complaints from our neighbors. The loud music seems only to be a problem when people forget to close the doors when they go for a smoke.
So i will put some reed switches on the three doors to detect when they are open, a sound detecting brick to sense how loud the music are. If the music is not loud, the doors can be open without cutting the music, if the music are loud and the door has opened, a display will show a countdown before the music get cut.
And here are my question: How do i cut the music?
I could cut the power supply with some solenoid-relays, but i would imagine that this would stress the two huge amplifiers and reduce their life. Correct me if i am wrong.
A more elegant way would be to cut the music going from the source through the minijack (from the iphone, PC or whatever). But how does one do that? Can i use solenoid relays, without compromising the sound quality? Any other suggestions are welcome.
If the source is a pc, you could connect the arduino to a ps2 port and emulate a keyboard. Then you could assign the mute or even the volume up and down functions to certain "hot-keys" and let the arduino "type" them. This way, you could lower the volume instead of shutting everything down.... Just an idea....
a sound detecting brick to sense how loud the music are is.
That will be a problem. Some one wanted to do a project some time ago in a canteen that would light up a sign saying quite when things got too loud. However, he reported back after six months that he could not find any correlation between the sound readings he was getting and the perceived loudness.
A more elegant way would be to cut the music going from the source through the minijack (from the iphone, PC or whatever). But how does one do that?
In exactly the same way as you would cut the power, with a relay.
If you are clever you can use the relay to switch in a volume control pot or remove it, thus reducing the volume.
Thank you for your answers. People bring their own device for their party, so i can't hack the keyboard (although a very good idea ).
I just went through the sound system again and i can see that i can cut the power for the mixer, thus killing the music without turning the amplifiers of. But i really like the idea of turning down the volume gradually. But what about noise on the line? Can i just us a regular mosfet?
If i just use a regular relay, will that not effect the sound quality?
Put the relay in the main power (But be careful, it's dangerous to mess with main lines. Ask one of your friends from engineering ;)) It won't mess up your sound to much.
But my prediction is: The music get's cut off once, everybody laughs. After the second time, people will get annoyed. The third time the'll plug there sound machine in a normal outlet and keep partying.
I would go for a relay attenuator between the power amplifier and the speaker. But that means that the attenuator has to be able to dissipate some power. Another place would be to place it before the input of the power amplifier but this presupposes that the input i accessible and there will be no ways to bypass the attenuator.
How about using a relay to switch in/out a resistor in each of the input lines (I presume it's stereo)? Sound quality shouldn't be affected when the relay is bypassing the resistors.
You could also get yourself a cheap USB Keyboard, extract the controller and hook it up to the arduino which can then "press" the volume up/down bottons for you by sending some digital signals to the controller which then believes, that buttons are pressed.
Then you can just attach the "keyboard" via usb to every laptop that's brought to your party or maybe with an micro/usb adapter to a tablet or android device (I dont know if this works though. I once connected a USB-Keyboard to my Galaxy S3 with no problems but did not test wheter the "special" keys do also work.
But I think the argument, that people will bypass the music reduction mechanisms somehow is very likely. Maybe you could also create a big sign that displays something like "free round of beer for everybody" when the music is turned down. So everybody will love it
).