Advice on filtering / regenerating digital signals
Advice on filtering / regenerating digital signals
(OP)
Hi,
I'm designing a LED matrix for Outdoor VMS of a considerable size (about 5meters).
There are about 16 matrix. From matrix to matrix are traveling signals, like clock, data out, latch enable etc.
What is the best circuit to amplify / regenerate signals? And about noise filtering (I did see (in a commercial product) some inductors in series with the signals. Is this the best way?
Thanks in advance for the help.
Joaquim
I'm designing a LED matrix for Outdoor VMS of a considerable size (about 5meters).
There are about 16 matrix. From matrix to matrix are traveling signals, like clock, data out, latch enable etc.
What is the best circuit to amplify / regenerate signals? And about noise filtering (I did see (in a commercial product) some inductors in series with the signals. Is this the best way?
Thanks in advance for the help.
Joaquim





RE: Advice on filtering / regenerating digital signals
TTFN
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RE: Advice on filtering / regenerating digital signals
Filtering data and clock signals does not sound like a good idea. But, if the array is up to 5 m, you may need to run - say - a 12 V signal and use galvanic isolation. Either optocouplers or transformers. A differential mode system (think RS485) will probably also work.
The reason is that a large LED matrix consumes lots of power and if you use the same common for power and control signals, you will have severe ground shift problems.
Do not try to use 3.3 or 5 V signals with same ground as the power. You will be very sorry if you do that.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Advice on filtering / regenerating digital signals
In my prototype sometimes I have one missing pulse causing the matrix to show the chars incorrectly. I had check (with scope) the signals. The level is correct, but the signals have some noise. The VMS will be in open field. I'm looking for a way to improve the design. Maybe I have to redesign the PCB using a star topology to connect the ground.
Thanks for the feedback
Joaquim
RE: Advice on filtering / regenerating digital signals
If that's the case, I would highly recommend changing your design to something a little more distributed. A small processor per module connected by RS-485, Ethernet, etc. to a larger control system is a much more tractable design. This removes the need for synchronous clocks and long distance comm issues.
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Advice on filtering / regenerating digital signals
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Advice on filtering / regenerating digital signals
In the factory floor we have some large metal working machines... Maybe they are the source of noise...
The RS485 approach is a good one. Small processor for each board (addressable) and a master controller for the entire VMS? I have 3 rows of 16 boards, so 48 nodes are no problem
for modern RS485 drivers right?
Tks
Joaquim
RE: Advice on filtering / regenerating digital signals
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Advice on filtering / regenerating digital signals
If you aren't running video image rates then even a slow data rate is fast enough.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Advice on filtering / regenerating digital signals