Down-under colleague mrpackethead designed this plug-in module for the Art-Net controller. Sized to fit in the footprint of two existing logic chips, it generates 4 universes of DMX. As boards size is limited, it contains outputs on .1″ pin headers only. Each output is based on a discrete RS-485 driver chip and a high-speed optocoupler.
Yes, the optocouplers may not be needed. But the extra layer of protection isn’t very expensive to include.
A few days ago, I spoke on the phone with a gentleman who installs large-scale Christmas light displays. Apparently his client’s system was hit by lightning. The better part of 40 controllers were destroyed, likely by current traveling up and down the data distribution network.
“I’ve never seen the inside of so many chips! no only were the 485’s blown open but in many cases the PICs and the 74xxx chips that go between the PICs and the optos were also blown open. it was amazing.
They say that when calculating time required for a project, you should make your best estimate and double it.
Then add an order of magnitude.
So an hour becomes two days, a week becomes two months, etc.
This adage certainly holds here.
Not much new to mention today, so I’ve included a picture of the prototype controller.
It’s big – 8.12″ x 4.0″. The end user wanted field-replaceable driver chips, so we picked some chunky DIP parts. This board can drive 16 separate strings, and each string can contain 2048 nodes.
The original design had 2 x LM1117 SMD voltage regulators, one each for the +5 and +3v3 rails. But heat dissipation was a problem – nearly 2 W – they were swapped out for a TO-220 package + heat sink. The ethernet controller (Wiznet W5100) is only available in a .3mm pitch, 80-TQFP package. Getting all those leads soldered in only the proper place takes a steady, steady hand.
Rev2 boards are being manufactured right now, and ought to ship on Monday.