LED controlled circuit for volume.

[DAR-HD]

Hello everyone, I'm a newbie on here, and have a question that I can't figure out and would appreciate any help you can send my way.

I've been asked by a friend to see if I could come up with some sort of LED indicator box for one of our local churches. The purpose of this box is to alert the sound box operator at the back of the church to turn on the music and then to turn it up or down as requested by the director who will be in the front of the church. Now, the church is already wired for sound & such, so we have an XLR (3 wire) connector at the front of the church that they would like to use to connect the director's controller to. Then on the other end of that XLR cable (at the back) connect the indicator box so that the director can control the indicators.

So, here is what I'm thinking, but I'm not sure if I can do. For power, I would like to use a 120vac to 12vdc wall wart. on the indicator box.

I would like to be able to put a toggle switch (or pushbutton) on the controller box as well as some sort of switch or potentiometer for the volume command. So that when the director wants the music to start, they press the "start" switch (toggle, pushbutton, etc) and say LED #1 on the indicator box will fire. At that point the sound guy will turn the music on.

Then if the director wants to increase or decrease the volume they can then turn the pot up/down to turn the LED's for sound up or down on. It would be awesome to have a bank of LED's (vertically) on the indicator box that correlate to the volume - so if the director wants higher volume he turns a pot and the leds start to light up 1 after another depending on how high he turns the pot or the LED's will go off (top to bottom) as he turns the pot down. However, that might be two complex, so if I could just fire two different LED's (blinking LED's) from a momentary switch of some sort that would also work.

The thing I'm having problems with is that it is a three wire cable (XLR cable has to be used). So I was thinking of using wire # 1 as my power to both switches (from the indicator box), and use wire # 2 as my ground/return for switch #1 and wire # 3 as my volume up/down command (variable power from a pot or divider of some sort back to a comparator??).

Do you guys have any ideas?

 

[Reloadron]

Maybe think about the use of a LM3914 LED dot/bar driver chip. The front end has a pot controlling a voltage to the back end and display driver. That is a common plus 1 wire. The remaining wire could be a que? You would need a wall wart for power on both ends though. Maybe a single power supply and a LED bar scheme to say when to turn on? Anyway, if you want the fancier display I would be thinking of incorporating a LM3914 in the scheme.

Ron

 

[DAR-HD]

Well, having an "ON/OFF" LED is important, so I wonder if it is possible to fire two more LED's then?? I could put in a flashing LED for volume up and another for volume down, but with only three wires, I'm not sure if I can fire those two LED's...

 

[Reloadron]

From a simple standpoint you could use three wires. You could have a single LED illuminate for turn on music. A single switch would take care of that. Then use a pair of LEDs (green & red) for raise / lower. You set them up bipolar and use a DPDT momentary rocker switch to reverse polarity to the pair.

When you mentioned multiple I suggested using a LM3914. This is the data sheet. You drive it with a simple circuit like the attached. When the switch is turned on one or two LEDs would light. As the pot is increased the remaining 8 LEDs would light sequentially. Run the 3914 off the 12 volt wall wart and add a simple LM7805 regulator to get the 5 volts that will run to the front.

Ron