Behringer DX2000USB Mixer - "Remote Start" jacks.

[Alan T]

Can anyone point me to a quick info source on "remote start" connections?

My DX2000USB has remote start buttons on each of the stereo channels. I had supposed that these were simple push-to-make switches. However, it appears they are not, because they don't work when the mixer power is off and also when I connect my DVM to them (in continuity check mode) across the remote start jack plug connections I only get a short beep even with teh button held hard down - so clearly there is some kind of logic in there pulsing something.

What I wanted to do was to connect these start buttons to a microcontroller (Arduino) so that I could do some other stuff simultaneosly (for example lighting change) with starting a turntable or whatever. However, when I connect an Arduino interrupt pin (pin 3) to one side of the remote and ground to the other side I get an almost continuous trigger. That seems to be because there are small voltages on the remote start pins all the time (on my DVM I can see 0.2V so I am supposing the peaks will be greater - I don't have a scope available to look closer). I have tried using a more aggressive (1K1) 5V pull up resistor on the Arduino pin, but still have the problem.

There is nothing wrong with my Arduino code - when I disconnect it from the mixer and just use a dupont cable to short ground to pin 3, then I get the expected one-time trigger. Clearly I am not understanding how these remote output connections are supposed to work.

[kmitchell]

It's been a while since I've use this type of signaling but a quick look at the graphic under the jacks reminded me how it works. These are "normally high" +5V output signals that are pulsed to 0V (Ground) for 50 mS each time the Remote Start button is pressed. I don't think holding down the button does anything, since it just triggers the pulse once each time it's pressed. Since there's no +5V when the mixer isn't powered up, these don't do anything without power.

I'd recommend you have the Arduino look for the negative-going (+5v->0V) leading edge of the pulse, otherwise you'll get a false trigger every time you power up the mixer.

[Alan T]

Thanks again. I saw the graphic on the back of the mixer, but the problem I have is that I am not seeing +5v on those sockets. - I think it should be there - but I's not. Very puzzling perhaps I have a faulty mixer.

[Alan T]

Well, as before I have received help from other quarters than Behringer's official "Support" channels (do they actually exist?) and now have an answer to this:

The "track start" outputs are actually open collector outputs. If you want to interface them to a 5V DC logic device such as an Arduino or other 5V Microcontroller - it's very easy but you need to use the right component value for a pull-up resistor. I was using a 1.1K resistor which was too high a value. Here's the step by step for a working solution:

1) Connect a 330ohm resistor between the tip of the "track start" jack to the Arduino's +5V pin (or to its 5V supply if you're not powering it from USB).

2) Choose your Arduino input pin (setup in your code using "pinMode(x,INPUT)" - i.e. do NOT use INPUT_PULLUP). Also connect this pin to Jack plug tip, alongside the resistor.

3) Connect the jack plug ring to one of the Arduino ground pins (or teh ground of the power supply if you're using one.

Now, when you press the track start button you should see a LOW pulse at the input to your Arduino and your code can do whatever it is you want to happen when a button is pressed.

[kmitchell]

Excellent work. Thanks @Alan T for closing the loop and documenting what you got working. This definitely makes the community better. Forum users sometimes find a solution but don't come back and update us on what they found. Thanks again.

[Alan T]

This definitely makes the community better. Forum users sometimes find a solution but don't come back and update us on what they found.

Yes indeed. One of my pet hates is pages of forum discussion with lots of suggested tests or solutions for a problem, but in the end no record of what actually solved the problem.!