■ FIGURE 9. DMX I/O Board.
A friend showed me a cute trick that creates a logarithmic
curve: you simply square the value and then divide it by
256. Doing this makes the LED brightness output much
more appealing. The math for this trick is wrapped up in a
method called .ezlog() that is part of the BAM object. For
you advanced users, there is also a method to read a
value from a table which allows you to map the DMX
input value to an output value as desired.
IF THREE IS GOOD,
FOUR MUST BE BETTER!
My original design (see the
prototype in Figure 9) was oriented
toward RGB lighting control and
as I was building it, a post in the
Propeller forum vis-à-vis stepper
motors got me thinking: If I added
one more channel, I could control a
unipolar stepper motor with the
TIP125 outputs. Then, I thought:
Why not add servo headers on the
outputs, as well? So, for those of you
who purchase the PCB or kit through
Gadget Gangster (recommended;
see BOM), you’ll get the four-channel
version which gives you more
options for outputs. Of course, if you
want to roll you own I’ve included
the four-channel files in the PCB
download at www.nutsvolts.com so
you can use them as you please.
Okay, then, how about adding a
little DMX to your holiday lighting
arsenal? It could be a lot of fun and
really make the neighbors jealous!
Until next time — and next year! —
here’s to spinning and winning with
the Propeller. NV
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