0-10v DC Reference Control (volume)

Hi Guys,

Newbie here in both basic electronics and Arduino.

I’m mostly into audio home installation and gears but I’d like to improve my skills and learn more on how I could integrate Arduino in future home automation projects.

Here’s the big picture;

Basically what I want to achieve here might be really easy for you guys but please bear with me as I will do my best to explain myself loud and clear. Thanks!

I acquired an Allen & Heath GR2 Audio Zone Mixer a few months back and would like to control it (Zones, Sources and Volumes) remotely via the RJ45 input on the back of the device. The GR2 is already designed to be controlled via its RJ45 input and a physical remote control (sold separetely). I downloaded the service manual and was able to buit the physical remote myself on a breadboard.

The mixer send a +10Vref dc out on 2 wires of the CAT5 cable (for zone 1 and 2) as a reference signal and must not get more than 100mA load on each of it.

Now… I want to control it with the Arduino and an Iphone app (don’t know which one yet).

The biggest problem I have for now is: How to turn the volume on and off if the Arduino can’t handle 10V?

Physically it’s easy: +10Vref in to 4K7 linear pot to ground.

What would be the easiest way to output (or provide a signal to a digital/mechanical device) 0-10V dc linear from or using the +10Vref provided by the GR2?

Any help will be very appreciated!

Thanks in advance!

Dominic

P.S. I attached a screenshot from the electrical schematic for reference.

The Arduino doesn't have a DAC (no true-analog output) [u]analogWrite()[/u] is [u]PWM[/u] which can "simulate" analog to control the speed of a motor or adjust the apparent brightness of an LED. There are 0-10V light dimmers, and these can usually use 10V PWM, but I don't know about your audio controller.

You can get 10V PWM with a 10V source and a [u]transistor driver[/u]. Just replace the solenoid with a pull-up resistor, maybe 1K, and you can leave-out the diode. The transistor's collector is the 10V PWM output. Almost any NPN transistor will work, since it's low-voltage and low-current.

Note that the transistor will invert so 100% PWM is zero-volts, out and 0% PWM is 10V out. (Easily handled in software.)

PWM can be "converted" to DC with a [u]low-pass filter[/u]. The default PWM frequency is about 500Hz, and you'll want to filter that out. You only have to pass around 1Hz, since the volume can change slowly. So, a simple filter should work very well. However, audio circuits (and your ears) tend to be noise-sensitive so a slight amount of 500Hz PWM could be audible.

You can try it with 5V PWM first to check the noise situation (before you add the transistor). Connect the PWM to the "top" of the existing pot so you can start with the volume at zero and slowly adjust-up the pot to see if you're getting PWM noise. I assume there is a volume control on the amplifiers too. If so, turn that down because a nasty blast of noise could potentially blow a speaker.

If you're not getting noise, and you can turn up the pot all the way to see if PWM controls the volume. (There isn't any PWM noise at zero or 255 because it's off/on with no pulses.) I assume you will get noise, and if so you can experiment with filtering before adding the boost transistor. Or, if you're not getting noise but the PWM isn't adjusting the volume, you can add the filtering to get 0-5VDC.

WoW!!

Thanks guys!

This might be the remedy to today's headache!

I'll post more headache soon!

Thanks again!

Dominic