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[touchtobegin]

I am setting up a small disco with some moving lights.  I have a Crestron control system that I wanted to use to stop DMX data from making its way to the moving lights.  The idea is that during normal operation the moving lights are in sound-to-light mode but when the owner of the system is in the room, he can pick up his touch panel and take control of the moving lights.  The current setup has a NSI rs232 to dmx interface for control, a Doug Fleenor splitter, and the Crestron system.

Interface --> Splitter  --> Moving Light Line Pins 2 + 3 into Crestron Relay --> Moving Light Chain.

The problem, is that even when the data line is simply wired to the relays, the moving lights think there is data.  Maybe its just garbage on the line from the relays them selves.  Whatever the reason, its causing me grief.  Are there any known devices available that can act as a remote controllable dmx kill switch?

Thanks in advance.

Joe

[DMX512]

My assumption (and yours, I guess) is that if the movers dont have DMX512 data coming their way they "fallback" to sound to light mode.  If that is the case, then what you are trying to do should work, so the devil is, as ever, in the detail.

You have read the rants about DMX512 termination, haven't you - 'cos my money says thats where it's all coming unglued.  You have got a terminator at the end of the DMX512 run haven't you.....?  I thought not

The relay: use a DPDT relay.  Wire the commons of the two poles to the movers A and B inputs, the normally open contacts to NSI A and B outputs, which is probably exactly what you've already done.  Now wire a 120R resistor across the normally closed contacts.  That provides the bus termination when you dont have a desk connected.  Energise the relay to give control to the NSI interface.

That will work, and when the relay is open the DMX512 bus will be silent.  Note that everything will probably "glitch" as you connect and disconnect through the relay,as the switching is not syncronous with the data.  This shouldn't be a problem of any magnitude, but if it is you need a fancier (and thus more expensive)  solution.

Some movers with sound to light and other self-running modes are cleverer than others, and the DMX512 bus isn't actually a daisy cahin, althopugh it looks like and is wired that way, but a point to point link between each device, and the first one in the chain can generate control info for the rest, so they behave as a single collection of fixtures, rather than a bunch of fixtures doing their own thing.

Let us know how you get on!

[touchtobegin]

My assumption (and yours, I guess) is that if the movers dont have DMX512 data coming their way they "fallback" to sound to light mode

Correct.

You have got a terminator at the end of the DMX512 run haven't you.....?  I thought not

Actually I did ;-)

the normally open contacts to NSI A and B outputs, which is probably exactly what you've already done.  Now wire a 120R resistor across the normally closed contacts.  That provides the bus termination when you dont have a desk connected.  Energise the relay to give control to the NSI interface.

The lines I'm breaking are post splitter, and the run is not very long at all.  I find it works well without termination.

Some movers with sound to light and other self-running modes are cleverer than others, and the DMX512 bus isn't actually a daisy cahin, althopugh it looks like and is wired that way, but a point to point link between each device, and the first one in the chain can generate control info for the rest, so they behave as a single collection of fixtures, rather than a bunch of fixtures doing their own thing.

There are 4 VRX scanners with one master and all set to 'super sound light show'.  They look pretty good!


I am finding though, that there must be leakage on the Crestron solid state relays, enough to confuse the moving lights.  I'm thinking of throwing in opto-isolators on the two lines I need to cut off.  I can kill power to those with the relays, achieving the desired results.

Thanks for the advice!  I'll post how it works out.

[DMX512]

...I am finding though, that there must be leakage on the Crestron solid state relays, enough to confuse the moving lights.

Arrgh - you're using SSRs not real electromechanical relays?  I wouldn't have thought they were at all adequate, you need something with metal contacts and air gap seperation.