Help for audio CD fader start project

Hi guys and girls. Not sure if you can help. I am trying to build a fader start for a dual CD player (Denon 2600) so that when I push a fader up on an audio mixer the CD starts to play. I have had some success with this project so far in that I can remote start each of the players individually, however, when I connect both up to the mixer remote control, pushing up one fader starts both CD players. I suspect it may be a ground issue?
The details. The mixer (Sonifex S1) has outputs for the remotes, sending a signal for each fader movement - mixer details from manual pasted below:

Start Function: This sets whether the Start function is continuous (remains active) or momentary (active for a approximately half a second). Uses Transistor Pull Down Signal Inverters.
Example pin-out
Pin 19: Channel 8 Input 1 Stop
Pin 20: Channel 8 Input 2 Stop
Pin 21: Channel 9 Input 1 Start
Pin 22: Channel 9 Input 2 Start
Pin 23: DGND

I have taken the output of these faders, eg a start pulse and DGND and connected them to a small relay circuit (**broken link removed**), that drives a relay on a 'push button' contact, and the relay starts the CD player. As I said, if just one fader and one relay board are connected - either one - it works great. It even works great with both relay boards are connected to the CD player and I manually close the contacts instead of passing the wires through the mixer. With both relay boards connected to the mixer, depending on how I have the wires connected, one fader start either triggers both relays simultaneously (and starting both CD decks), or each fader only ever controls one relay (and the other is idol).

I have measured and checked the output of the mixer, and in all circumstances the expected output happens when either fader is open - a short contact closure between the start and DGND. Double checked all the wiring etc. and all checks out.

I'm not to clued up on these things, but it could be some kind of earth/ground issue where having both connected somehow the signal, and it is beyond my knowledge how to resolve it.

Bit of a long shot, but if you have any thoughts or ideas on how I could solve this I would be so grateful.

Many thanks,

Andrew.

Have you tried connectung only one relay board to only one channel, and then activate the other channel? i.e. connect relay to channel 1, and then 'fade' on channel 2?

kam1787 said:

Have you tried connectung only one relay board to only one channel, and then activate the other channel? i.e. connect relay to channel 1, and then 'fade' on channel 2?

Click to expand...

Hi there. Yes I have. With just one connected it works as expected. I fade on that channel and the CD works, and when I fade on the other channel nothing happens as expected. All the expected behaviours work when only one relay board is connected, either channel, its just when I connect both that it all starts to go weird!! Then channel 1 fade up, both channel 1 and 2 relays trigger, or channel 1 on and channel 2 relay on etc.

Thanks.

If you connect both relay boards, but only one CD drive, does the other relay get activated?

If you connect only one relay board, can you determine if a pulse exists on the other channel?

Hi there,

kam1787 said:

If you connect both relay boards, but only one CD drive, does the other relay get activated?

Click to expand...

Yes, I disconnected one and both CD players and on the relay side both relays latched when either of the faders were pushed up.

kam1787 said:

If you connect only one relay board, can you determine if a pulse exists on the other channel?

Click to expand...

Yes, just tried. With one relay board connected it fired the fader start perfectly, and there was no measurement on the other fader closure. When opening the fader on the not connected relay board, I can measure the closure independently of the other fader - if that makes sense. I think that it all works fine and everything measures correctly until both relay boards are connected to the mixer.

Thanks.

Sounds like the relay boards are either too sensitive or not well designed. The action of one relay to causing a false trigger in the other.

You could try isolating by connecting a diode [1n4001/2/3/4] in series from the V+ to the board - one diode per board. I suspect that has a small chance of success, so try, after the diode [between the diode and board] connecting a 0.1uF cap and a say 470uF cap from V+ to ground.

The 0.1uF should suppress higher frequency interference, while the 470uF 'buffers' the voltage.

kam1787 said:

Sounds like the relay boards are either too sensitive or not well designed. The action of one relay to causing a false trigger in the other.

You could try isolating by connecting a diode [1n4001/2/3/4] in series from the V+ to the board - one diode per board. I suspect that has a small chance of success, so try, after the diode [between the diode and board] connecting a 0.1uF cap and a say 470uF cap from V+ to ground.

The 0.1uF should suppress higher frequency interference, while the 470uF 'buffers' the voltage.

Click to expand...

Great thanks very much for the advice, I'll try this out and report back.

Thanks,

Andrew.

Did it work?

Sorry for the late reply. It didn't, think you were right about the boards. I ended up getting a different board in the end and that worked a treat. Thanks.