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Delay with Large Displays


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I am evaluating a large scale animated lighting system for an Australian organization and would to hear from anyone using a large number of channels using LOR or similar products.

My issue is this - whilst the customer specification calls for 400 individually controllable channels, the animation sequence also calls for the ability to switch large numbers of these channels - sometimes all of them - nearly simultaneously (by simultaneously I mean within one 100msec event timeslot ; for example a 200msec would be unsatisfactory to my client). And my worry is how to get so much data transmitted in a very short time???

There are two ways I can see to do this...

The first (and my least preferred) option is to custom make the equipment and software, using something like the theatrical "DMX512" protocol. This protocol, using RS485 transmission standards, sends sequential "brightness" bytes in channel # order. At 115200 from the serial port of a PC (converted from RS232 to RS485 with a suitable converter), this would allow all 400 channels to be transmitted in around 50msec (at approx 100usec per word). Great, as this is < 100msec!

But I'd prefer to use existing technology if possible, so I am leaning towards the LOR solution. I have seen other posts refer to LOR's ability to address 3000+ channels (240 device addresses x 16 channels per device), so I have no doubt it would cope with the number of channels. But how fast is it? With this kind of addressing scheme I'd imagine they must be transmitting 2 or 3 bytes per event (one to identify the card, one for the channel, one for the brightness) so I am concerned that it could not control 400 channels simultaneously - all within one tenth of a second and repeated every tenth of a second!

Are there any large-scale users of the LOR system with 400 or more channels that can either confirm my concerns, or put my mind to rest, as I would much rather not have to build or design anything from scratch.

Warm regards,
Ralph Parkhurst,
Parkhurst and Associates,
Melbourne, Australia.

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LOR can DEF do what you want it to do. Check out www.amazingchristmas.com darryl is using over channels for this display. I am sure that dan at LOR can anser ANY questions you have.

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Ralph,

The answer is a maybe! It does depend on a couple of things. LOR can run at 115200 (out of the box) and with the compression that it uses, the best case is tht we must transmit about 1/3 byte per channel for a command. So in the best case we are many times faster than you need.

However in the worst case (very rare and very unlikely) we would not be able to keep up... If you can send an email to dan@lightorama.com and explain what you want/need to do every 1/10 second on those channels then I can tell you if it will work or not.

We have a customer with 600 channels, with a 1/10 second grid who was running at 57600 (max speed of our wireless)... There were not problems.

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Not to hijack the thread, Dan. But I am sequencing with sections with events quite a bit shorter than 1/10 of a second. Am I safe to think that if it works in "view animation" it should probably work with lights?

I actually get a bit of lag in one section, but figured it was my beater of a computer.

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Dave Sanderson wrote:

Not to hijack the thread, Dan. But I am sequencing with sections with events quite a bit shorter than 1/10 of a second. Am I safe to think that if it works in "view animation" it should probably work with lights?

I actually get a bit of lag in one section, but figured it was my beater of a computer.
I would not be concerned. Darryl Brown has places in some of his sequences set to a 1/100 second grid with 200+ channels... It does not fall behind.
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Many thanks to those who have replied. To be honest I hadn't even thought of compression techniques - And no doubt I have made some technical assumptions when when voicing my concerns that can be put to rest with some expert knowledge.

I have sent you an email Dan, as suggested, giving you a bit more detail.

Thanks,
Ralph.

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