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Issue #1, February 1996
As an engineer I love to solve problems. What I'm not as good at is letting
the world know when I've developed a solution. As entertainment professionals,
you need to know that solutions to problems exist, and how to find them. Doug
Fleenor Design's niche is DMX512. You are probably familiar with our main line
products: our Splitters, Combiners, and Converters. We are constantly developing
products for particular applications. Some of these may be of use to you or your
customers. It is our goal to inform clients of new advancements. As a small
company we do not have the resources to prepare, print, and mail data sheets on
each new design, or twist on an existing product. Instead we will prepare a
monthly FAX of interesting developments in the DMX512 world. Some of the
information will relate to our products, some to DMX512 in general. We hope
these newsletters will be a valuable resource to you and hope you will save them
in a file or binder for future reference.
Interesting Fact Of The Month:
A common transmitter/receiver chip (integrated circuit) for DMX512 is the
'75176'. Two versions are made: the 75176A and 75176B. The data sheets are
almost identical, and either will work. My experience is that the 'B' is more
rugged. When replacing this chip, specify the 75176B. An even more rugged chip
is the MAX483E. This chip is only made by Maxim and may be harder to find. Maxim
claims it is protected against Electro-Static Discharge (ESD) up to 15,000
volts! We use the '483' in our Enhanced Splitter (model 125E). The '483' is slew
rate limited which Maxim claims reduces errors caused by improperly terminated
lines. One warning however: the '483' is pin compatible with the 75176 but is
not an identical part. It may require additional power supply bypassing or other
modifications to the circuit.
USITT:
Doug Fleenor Design will be involved in two events at USITT, both sponsored by
ESTA. A dealer training session is scheduled for Friday morning, March 15th, and
that afternoon we have a part in the session "DMX Isn't Just for Dimmers
Anymore".
New Product:
We are now making a DMX512 to Analog 0-10 converter. The unit converts any
consecutive 24 DMX channels to 0 to 10 volt output. The starting address is
selected by an easy to read (and set) three digit push-wheel switch. The switch
is mounted on the front panel along with power, signal, and output 1 mimic
indicators. The DMX in and through connectors and the female DB-25 output
connector are located on the back panel. All connectors feature gold plated
contacts. The output pinouts are easy to remember with the pin number equaling
the channel number, pin 25 being common. The DMX512 input is optically isolated
from the outputs and is protected against miswiring up to 120 volts. The
(defeatable) hold feature holds the last look indefinitely upon loss of DMX. A
test feature allows bringing any output to full by setting the front panel
switch to 601 - 624. The unit is housed in the same 1.6" x 5.6" x
9.0" (hwd) chassis as our three output splitter. A 19" rack adapter is
available. Suggested list is $650.00.
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