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Issue #217 August 2008
3rd Place Microchip 2007 Design Contest
The DMX Portal
Obtain Lighting Control Via Ethernet
by Matt Ernst
Ready to build your own DMX lighting controller? Matt’s design enables him to remotely control up to 512 channels through an IP-based network or directly interface them to embedded systems with a serial connection. It is perfect for distributed lighting systems where low-cost Ethernet wiring is a better option than RS-485 wiring.
Start | DMX Protocol | Advantages of the DMX Portal | Hardware | Firmware | Work with the W5100 | Command Interfaces | Software Interfaces | Future Developments | Sources & PDF
The DMX Portal is a self-contained lighting control unit that you can use to control moving lights or special effects equipped with a DMX interface (see Photo 1). The project provides a low-cost, flexible way to interface embedded systems with DMX devices, and to allow DMX control to be distributed over long distances using Ethernet.
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| Photo 1—The DMX Portal is a compact lighting control unit. It’s designed around a WIZnet 5100 Ethernet controller and a Microchip Technology PIC18F4620. The WIZnet development board is secured to the right side of the PIC development board. The five-pin XLR connector and RS-485 level converter are on the add-on board behind the PIC development board. |
Most programmable lighting is designed for stage performances. Stand-alone lighting boards are the most common playback controllers/programming interfaces used in these applications. The programming interface provided by the lighting boards is implemented via slider controls and buttons similar to an audio mixer. This type of interface is most appropriate for stage performances that change frequently or need to be adjusted on the fly. In applications such as permanent installations or automated applications, the programming doesn’t need to change frequently, but the applications usually require the lighting controller to be controlled from another system instead of through physical controls. For this reason, the DMX Portal does not have a physical programming interface. Instead it offers RS-232 and Ethernet communication interfaces and two different protocols, which allow it to be used in a variety of different applications.
The system has an effects engine to automatically generate timed fades with simple commands. It also allows user-defined scenes to be saved and recalled when a command or digital trigger is received. These features enable the DMX Portal to fit into a variety of applications, ranging from a simple virtual lighting board emulated on a PC to a self-contained lighting control unit in an embedded system.
To keep project costs down, I built the DMX Portal around a Microchip Technology PIC18F4620 microcontroller and a WIZnet W5100 Ethernet interface. The complete system costs less than $50, making it extremely cost-effective in comparison to other DMX controllers.
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