DMX - Pixel board with stepdown regulator

David_AVD

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I have been thinking of designing a new board with DMX input and one SPI (pixel) output. It would also have an on-board DC-DC converter. This would allow you to push 24V + DMX around the yard, daisy chain style (looping in and out of each element). The pixel string / strip would be 5V / 12V and the on-board regulator would convert from the incoming 24V and greatly reduce the voltage losses in the cable.

I know some say "DMX - SPI is a dead duck", but I don't agree. It comes down to topology. Ethernet would require the data cables to be "home run", whereas DMX can be daisy chained. I am thinking that this board would be useful for things like mini trees where you only have 50 pixels max.

Now, as to the question of an isolated DMX input, I think for a daisy chain situation, the extra parts cost would be hard to justify. Maybe the board can be offered in isolated and non-isolated versions.

So, what's the interest factor here?
 

dmoore

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I'm in - this sounds a bit like a version 2.0 of the TP3244. I think, like you, that there is a need for a distributed DMX to SPI board.
 

David_AVD

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So, I was thinking of:

  • 24Vdc power input with polyswitch protection
  • Selectable 5Vdc / 12Vdc pixel power
  • Non-isolated DMX input
  • 5 pin pluggable "Phoenix" connector for power + DMX
  • 4 pin pluggable "Phoenix" connector for pixel string
  • Optional RJ45 for power + DMX
  • ICSP header for firmware upgrades

The power + DMX via RJ45 option could be used where you have display elements spread out and daisy chaining the power + DMX isn't suitable. A central power + DMX splitter could be made too.
 

fasteddy

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Definetly not a dead duck, It comes down to choices, some want DMX others want E1.31 and I want both
 

David_AVD

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So, given the proposed specs / features, tell me what types of elements you might use this new board for. That way I can possibly tune the specs to make it better / more useful for all.
 

neilric99

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good job David,

I could use 4 of this type of board for my light poles with stars.

David_AVD said:
So, I was thinking of:


  • 24Vdc power input with polyswitch protection
  • Selectable 5Vdc / 12Vdc pixel power
  • Non-isolated DMX input
  • 5 pin pluggable "Phoenix" connector for power + DMX
  • 4 pin pluggable "Phoenix" connector for pixel string
  • Optional RJ45 for power + DMX
  • ICSP header for firmware upgrades
The power + DMX via RJ45 option could be used where you have display elements spread out and daisy chaining the power + DMX isn't suitable. A central power + DMX splitter could be made too.
 

David_AVD

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Getting the right balance of cost, size and current output for the step down regulator section is tricky. For example, a 50 x WS2801 string draws approx 3 Amps @ 5V. One common type of regulator is rated for 3A, but I'd like a bit of headroom. The board's own circuitry needs power too, so using 50 x WS2801 pixels with a 3A regulator is really not a good idea. Higher current regulators are available, but for more $$ of course.

So, how many pixels would people envisage using with a board like this? Keep in mind this board is meant for smaller "pockets" of pixels (mini trees, etc), not large runs.
 

chilloutdocdoc

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I see 50 being a good number, and personally what I would use it for.

We have yet to see some $$ numbers. Even if they're ball-park (within $10 one way or the other) maybe it would help some gauge interest?
 

mrpackethead

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David_AVD said:
.... Ethernet would require the data cables to be "home run", whereas DMX can be daisy chained. I am thinking that this board would be useful for things like mini trees where you only have 50 pixels max.


Interesting that this same argument got applied about 20 years ago, when 10baseT came along and challenged 10base2...
 

David_AVD

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David_AVD said:
.... Ethernet would require the data cables to be "home run", whereas DMX can be daisy chained. I am thinking that this board would be useful for things like mini trees where you only have 50 pixels max.
mrpackethead said:
Interesting that this same argument got applied about 20 years ago, when 10baseT came along and challenged 10base2...
I can see what you mean, but it's not quite the same comparison IMO as the scales of data and cost are different.
 
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