Yamaha trigger output + Elk 924

[mikei-ma]

I'm running into a roadblock trying to use the trigger from my Yamaha RX-A3000. I have it set to trigger high when the receiver goes on, so it throws a constant 12v across the line when the yamaha is on and nothing when it is off (I have tested it and it throws 12v). I purchased an ELK-924 sensitive relay to facilitate my external relay. The 924 requires a secondary power supply so I put 12v on the power side and hooked up the yamaha via a standard 1/8 mono plug to bare wire and hooked the + trigger on the board to the +12v trigger output and it turns the LED on the relay on faintly (at all times) but doesn't trigger when I turn the yamaha on. The instructions say I can use EITHER a + or - trigger (but doesn't show both) If I add the - from the trigger it triggers the relay, even when the yamaha is off (which says I have a ground). When I measure voltage from the yamaha it's ZERO (+/- .001v) when the yamaha is off, but if I hook the positive to the - trigger on the relay it does nothing when the yamaha is off or on.

The Yamaha trigger is supposed to throw 12v 15mA when on, so that is more than enough to trigger the sensitive relay requirement of 1.2mA

Stumped in MA
Mike

 

[mikei-ma]

Figured it out. Join the grounds from the power supply and trigger - it works. But now my amplifier 'pops' because I'm "plugging it in" when it's on. I suppose the best way is to open the amplifier case and connect the relay to the on/of switch rather than the power. Another project time estimate blown.

 

[gatchel]

You could also use an optocoupler to trigger the relay. This would allow you to isolate the two power sources and use the 12vdc power for the Elk relay also as its own trigger through the optocoupler.

 

[mikei-ma]

My EE skills are DIY so I'm not fully understanding the optocoupler schematics I've researched on the net. Am I understanding that I can use an optocoupler instead of the elk relay? Wire the 12v trigger output on one side and the power amplifier power on the other?

 

[gatchel]

I would use the optocoupler to trigger the elk relay since you already have the relay. You would need a Photo Transistor Optocoupler.

I have used MOC3010 in the past but that is a triac output. You would want a transistor output. Maybe others with more recent Opto experience can add to the discussion.


...Now that I think about it you may be better using a solid state relay that falls within your allowable current availability from the amp. That would eliminate one step in the process.
Look here:
http://www.crydom.com/en/Products/Catalog/e_l.pdf

Most have an input current of less than 15mA.