OpenDMX

This project consisted in the creation of a USB interface that allows to control DMX-512 (RS485) devices in music shows. There are already some devices like these on the market, but the cheapest is around 50€ plus shipping, while the Martin dongle costs more than 1000€. I really wanted one, but I couldn’t afford those… So I decided to make my own device. The building of a “toy” like this can be trivial for some, and, at the same time, a head-ache for others. I must confess that I found it very simple, considering the accessibility to the products I needed.

Project Status

Progress: 100%
Time Spent: 15 hours
Cost: 30€

Tools Needed

• USB Serial Converter
• Canon/XLR female connector
• IC SN 75176
• 100Ω resistor
• Veroboard
• Box and screws
• Some wires

First steps

I came up with this idea while I surfed the Arduino website. Some people showed, not how to make the bridge between the software and the lights, but how to generate the DMX signal to comunicate directly with the machines, which was not exactly what I intended. I found this PDF in Google. Using only 1 Integrated Circuit, 1 resistor and the Arduino, I could transform it into an authentic DMX Interface. It is actually very simple. The IC is not that expensive and nothing to say about the resistor.

I mounted the circuit on my Diecimila and the protoshield, wired it to a LED PAR 64 DMX device I had here and it worked like a charm! Then I thought I would be japperdising all the functionalities of the Arduino, by using just the RX channel, that is from the FTDI chip. I would be using neither the digital channels, nor the ATMega.

I really needed one simplified circuit that had that USB to Serial converter (the FTDI chip). I discovered that there were an Arduino version that had exactly that. The Arduino USB Serial Converter. PERFECT! The circuit would be like the one on the left.

Assembly

1. Add 2 ‘headers’ to the Serial Converter

This is an important step, as these headers will hold our Serial Converter, so that it doesn’t shake and probably screw up with an
exhaustive use. It is quite simple, provided that you have the necessary tools. I recommend a product that is called “Handy-Hands” which allows you to hold the components, especially for precise solderings.

2. Cut the front part of the box to fit the USB conector and the XLR/Canon connector

In the image, you can see that the USB hole is a little “#%&$(#, as it was made with an x-acto. You should try to make it as clean as possible, using an hobby-drill, like Dremel or similar.

3. Drill the veroboard on the screws place

In the image, it is already drilled and with the screws. Everything shinny!

4. Soldering the Serial Converter to the veroboard

You should do this with maximum care, so you dont melt the FTDI chip, because you run the risk of burning it with the iron high temperature. Use the “handy-hands” to hold the components in place and follow my tips on “How to solder properly” on the Tutorials section.

5. Solder the IC and the resistor

Make shure to reserve some space in the prototype board for the Integrated Circuit and the resistor. Tou can use a IC socket, instead of soldering it directly. That makes it much easier if you need to replace the IC.

6. Wiring it up

6. Set the Canon/XLR in place

Drill a hole and screw the connector.

7. Wire the connector Canon/XLR

Following the schematics, make the necessary connections.

Close the box, and it is done!

Final notes – Software

The software that I recommend you to use is Freestyler. When it asks you what type of interface you have, chose Enttec OpenDMX. Plug in your DMX device and have fun!

FAQ (Frequently Asked Questions)

Does the circuit need an Arduino?
No. The circuit is composed of “USB Serial Converter” (which is a version of the Arduino, with no ATmega, only the USB -> Serial part – has the FTDI chip), the IC 75176 and a resistor.

What is the USB Serial Converter on the list?
It is this one: http://www.arduino.cc/en/Main/MiniUSB
Purchased here: http://www.sparkfun.com/commerce/product_info.php?products_id=8165

When you connect the interface to USB, the PC won’t recognize it, right?
It will recognize, as long as you have the FTDI drivers installed. Those come with the Arduino IDE program, because the chip is the same (FT232R).
Download link: http://www.ftdichip.com/Drivers/D2XX.htm

When you run Freestyler, how does it recognizes the hardware and its port?
You just need to chose the Enttec Open DMX interface.

I have the “Breakout Board for FT232RL USB to Serial”, will it also work, as it has the same chip?
Actually, this is not the same one I used. However, what really matters is the FTDI chip. It should work with no problems.