Some History:

Back at the end of November of 2005 I watched an internet video of a house that had a large number of flashing lights synchronized to music, and challenged me to figure out how he did it.  At the same time my wife who loves Christmas lights saw the video and told me to do it.  So I went forward and came up with the current design, not really knowing how the other guy made his display work. 

Just recently I found a Google search string that got me to information regarding the above mentioned lighting display.  The creator of the display, Carson Williams of Mason Ohio built up the display on his home using a commercial lighting system made by a company called “Light-O-Rama” and set the standard for how I developed my system and the quality of the display needed.  There are a number of adventurous people out around the US that have built up advanced lighting displays.

This is my story:

My interface is 100% home grown.  It uses a digital music technology called MIDI (Musical Instrument Digital Interface) to control the sequencing of the lights and the playing of audio files.   I chose this method because this is a very stable and defined interface with a lot of existing MIDI hardware and software around at affordable prices.

The design idea is simple; use the MIDI Note On and Note Off commands to control a number of solid state relays.  The MIDI interface can communicate with up to 16 channels (or devices), and each channel can control up to 127 notes.  I wanted a design that was modular and supported the incremental addition of light control, the basic specifications follow: 

Basic Specification:

• 20 Light Channels/PCB
• PCB Addressable to MIDI Channel 00, 01, 02, or 03
• Code Addressable to any of 16 Channels
• PCB Note addressable in 2 ranges allowing up to 40 light channels per MIDI channel used.
• Maximum number of Light Channels addressable using hardware is 160 (8 PCB x 20 Light Channels)
• Maximum number of Light Channels addressable using Code and Hardware is 1920 (96 Controllers - hahahah)
• Each PCB can switch a total of 64 AMPS @ 120VAC.  Split between 4 individual AC circuits rated at 16AMPs MAX and 5 AMP MAX per Light Channel.  7000 Watts Max
• The PCB allows for a mix of 5 AMP and/or 2 AMP Solid State Relays.

After doing the initial design requirements and researching component availability and specifications, I set out to develop the Light Controller.  As I have a lot of experience working with the Zilog Z8 products and a large library of functions that I have developed over the years, I chose to work with what I knew for a fast design project (ya right).

The final design uses 3 Zilog microcontollers, each with custom firmware to control the particular controllers function.  Using the Zilog Z8 products had some limitations, the biggest being CPU clock speed which limited the number of instructions that can be processed between MIDI data sequences.  That and the number of I/O bits needed caused me to separate the functions into 3 areas:

• MIDI Interface
• Display Control
• Light Control

- The MIDI Interface takes incoming MIDI data, Decodes the channel number, converts the data from Serial to Parallel, and if the channel matches the current hardware address, passes the note on/off data to the other 2 processors. 

- The Display Controller is an optional part and not needed but adds lots of user information during the operation of the Light Controller.  I initially built this into the design to help debug and trouble shoot the hardware as I got tired of looking at Logic analyzer traces and counting timing data on the color scope.  It also adds real ‘bling bling’ to the finished product.

- The Light Controller takes the same data as the Display Controller and controls the 20 solid state relays. 

Once the hardware was designed I set out to writing the code to control the first of the 3 controllers, the MIDI Interface.  During that time I built up the prototype hardware.  As getting a PCB made from an untested and changing design is outside my budget I hand soldered the prototype.  It was built in 2 parts, the logic hardware and the power switching hardware.  As with all software UARTS, timing is critical, so I spent a number of evenings developing code that worked properly with the fast 32Kbs data stream.  The current code revision is rock solid, never misses a sequence.

I next focused on the Display Controller code.  It was rather simple to develop as I have used this technology in past projects so libraries all ready exist for the basic display functions.  Other than displaying an initial sequence of start up messages, the displays purpose is to show the note (light) number and an on or off indication.  This was very useful in the final debug of the MIDI Interface code and the Light Controller code.  The hardware for this part of the design can be left out but is worth the investment in parts just to see the data ‘flying’ by on the display when valid MIDI data is received, again ‘Bling-Bling’.

The Light Controller code was developed after a few days of thinking about how best to do the task of tracking which light is on, which is off and how to act when new light on/off values are received. 

From concept to working prototype, I spent about 1 month of evenings in my home lab before I was ready to try putting the prototype into use.  I then hung short light strings all over the lab and went about setting the lights to the music.

• WindowsXP based computer
• Cubasis Audio/MIDI software
• 2 Channel Audio/MIDI Interface
• 3 20 Channel Light Controllers for a Total of 60 Channels
• mini-MIDI-Keyboard
• Low Power PLL FM transmitter for remote audio

Each Light Controller is mounted in a metal enclosure with the following specifications: 

• 20 Light Channel Control
• MIDI Channel Addressable
• MIDI Note (light) base selection
• MIDI Through port
• 2 20 AMP AC inputs with Circuit Breaker protection
• Fuse protection on each Light Channel
• 5 and/or 2 AMP solid state relay per channel
• Vacuum Florescent 2 line x 24 character display
• Manual light control on 4 channels (useful when you want some lights on but don’t want to run the whole display
• Dual Fan forced air cooling (needed with high current loads)
• Logic Level Output 5 Volt TTL) for each light channel

 The pictures below show some of the detail about the finished models.  I found that I had 4 traces wrong in the final PCB after having them made.  It turned out that this was the results of a mistake I made about 4 months earlier.  The schematic capture software that I use did not have the Zilog CPUs in it's library, so I had to creat the part.  In doing this, I misslabeled 4 pins on the 44 pin PLCC part.  It was an easy fix ond only took a few hours to figure out what I did wrong.