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.


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.