Author Topic: Need help understanding DMX protical and devices  (Read 746 times)

Offline blk69

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Need help understanding DMX protical and devices
« on: October 06, 2017, 04:36:22 PM »
Hello, looking for someone to point me in the right direction.  Was successful in running my first Christmas show last year, ws2801 pixels, Xlights, Ras Pi, ver 3, Falcon Pi hat.  Have some standard LED lights would like to add to the show, just have them turn off and on with a simple relay.  My Pi Hat has a DMX port, thought this would be a good place to start. 

Found this on Amazon, says for DMX

Would prefer to use something like this, more relays and cheaper.  But not DMX.

Hoping someone could point me to some literature on DMX controller, how they work and such.  Ideally, would like to have 4 or so 8 relay boards on this DMX channel.  Would like X lights to control them (on/off).  Is this possible and if so, why isn't everyone doing this?  Have basic soldering skills, could build myself if not to crazy.  Any help greatly appreciated.  Cannot use the GIDO pins on the PI as Pi Hat is connected to them.

Offline AAH

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Re: Need help understanding DMX protical and devices
« Reply #1 on: October 06, 2017, 04:56:10 PM »
  DMX is easy but there may be an easier option if you are committed to using relays rather than dimming the lights. I make a 2801DC15 and 2801DC30 which connect up the same as your 2801 pixels and with that you can turn your relays on and off. The only thing is that you would need to put diodes across the coils of the relays to prevent the spikes from the back EMF damaging the mosfet.
  If your leds are low voltage (under 35V) then you could drive them directly from the 2801DC boards with a suitably sized power supply. That would give you the option of dimming them rather than just turning them on and off.

Offline tbone321

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Re: Need help understanding DMX protical and devices
« Reply #2 on: October 06, 2017, 05:42:23 PM »
You might be better off looking for a DMX SSR controller.  Mechanical relays are not the best idea for controlling lights in a show type environment because being mechanical devices, they do wear out and are really not all that much cheaper than a SSR.  Where relays are needed in most cases with inductive loads, incandescent lamps and LED's work well with SSR's and then you can dim as well as on and off.


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