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Controller Images
DMX Dimmer

In the middle of December 2005, Mary emailed me a video of Carson Williams house in Ohio which had lights and decorations that turned off and on in sync with TransSiberian Orchestra's "Wizards in Winter".  All I could say was "wow".  Much to my surprise, she gave me two years to come up with a similar exhibition!  Being hooked, it did not take much convincing to start in on this new project.

I found two websites that dealt with computer operated Christmas lights.  ComputerChristmas  is aimed toward the user who wishes to build his own hardware and either write his own software, or use one of the free programs available.  PlanetChristmas is a larger website covering more areas.  There seems to be less specific details on how to build controllers.  There are also areas there dealing with commercial hardware and software.

The originator of ComputerChristmas, Hill Robertson developed a controller that ran off the parallel printer port of a typical PC.  Using Basic, he could turn on/off up to 320 circuits.  Peter Olson came along with a different design that could control up to 1024 circuits off the parallel printer port.  While the hardware was fairly simple to construct, getting the lights to turn on and off in sync with music was a little more of a challenge.  Darryl Quinn wrote a program in Visual Basic, named Comet, that tied the media player to the output of data to both the Hill-320 and Olson-595, as well as several other controllers.  Comet was a free download - even the source code is available for those caring to dive into it.  It is no longer available with the advent of Vixen.  In February of 2005, K.C. Oakes released the beta version of Vixen.  K.C. has continually improved Vixen over the course of 2006 and into 2007, creating an amazing piece of free software.  At this time it will only run under Windows

So what makes up the components needed for a computer Christmas light display?  For most all displays you need a PC.  Vixen prefers Windows XP.  The computer needs a parallel printer port - a USB to parallel port converter will not work.  Next you need a controller.  As mentioned, for a DIY person, either the Hill-320 or Olson-595 are the two most common controllers, although the PIC based Renard is becoming popular.  There is a chat based website dealing with the Renard. I personally chose the Olson-595.  While 320 channels is a lot, if you start combining channels to perform dimming you can eat up channels in a hurry.  The output of the controller is low voltage/low current dc (0 to +5v), so we need a way to change that to control the 120vac typical of Christmas lights.  Using a SSR or triac is the common method.  Depending on the current requirements, you can use an encapsulated triac (solid state relay or SSR) that accepts +5vdc to turn on loads up to 3 amps, or for heavier loads you can use discrete triacs with opto-isolators.  Of course you need your lights to turn on and off and lastly you need control software to run on your PC to do the actual work.

As noted, I choose the Olson-595 design for my controller.  The schematic of my design can be found here.  Basically the design is a series of 74HC595 serial shift registers with parallel outputs that are daisy chained together.  Data is output on data pin 0 of the parallel printer port.  The outputted data is clocked in by the *Strobe pin of the printer port.  Once all the data has been clocked out, it is loaded to the parallel side of the 74HC595 by a third signal of the printer port.  The data will remain on the parallel side until new data is loaded in.  It is the parallel output of the 74HC595 that controls the triacs and thus the lights.  My design has 256 outputs.  The first 128 are used as simple on/off functions.  The last 128 are combined into 16 groups of 8 bits - this gives me 16 analog outputs with a range of 0-10 vdc in 256 steps.  The analog outputs will typically control dimmers allowing the fading in and out of lights rather than just off/on functions.  As seen in the images, the signals from my IBM Thinkpad's parallel port are less than perfect digital signals (which are typically 0 or +5 vdc).  Because of this there is a 1.8kV pull up resistor (R1, R2) on the two control lines.  On each output of the printer port used, there are also a pair of inverting Schmitt triggers (U1) to clean up the incoming signal.  The parallel output of the 74HC595s go to a DB9 connector on the back panel to control the triacs.  The parallel output of each 74HC595 also goes to the input of a 74HC573 buffer, whose output then feeds a LED.  As seen in the images, there is an LED for each of the 256 outputs allowing me to see what output is active.  A R2R resistor ladder makes up the digital to analog converter for the last 128 outputs.  The output of each ladder is 0 to +5 vdc.  This is fed to an op amp which doubles the range to 0 to +10 vdc.  On the far right of the schematic is a ten pin connector.  This connector has two functions: 1) it allows me to expand my controller by daisy chaining another controller to the current controller giving me even more outputs.  2) A couple of the signals present on this connector would allow an appropriate program read in values from a remote console, allowing real time programming of a show.  Vixen's capabilities appear to make this not necessary.
MAJOR RETHINK ON THE CONTROLLER - I have decided that I want dimming on all my lights.  The layout my wife and I have come up with has 209 channels.  This is too many to do with at 595 (8 channels x 209 dimmable channels = 1672 on off channels), the limit seems to be about 1000 channels for a single 595.  A few people started preaching DMX - taking a look, I was impressed with DMX.  Up to 512 dimmable channels from one output.  Vixen has a DMX plug-in, so that was not a problem.  I found a design that explained the DMX protocol and went to work on a MicroChip 16F877 version.  I am pleased to say that I have a working model that has 24 channels off of one 16F877.  The design is relatively cheap.  The most expensive part is the USB to DMX converter at $70.  I am still adding to and tweaking the software (March 19, 2007) - a final version should be ready in a couple of months.  I already have a PCB laid out that is less than 16 square inches.

Power Control and Triacs
It would be easy to get carried away with desiring tens of thousands of lights for a show, but a quick look at the power required will bring us back to reality.  The standard string of Christmas lights (100 mini-lights) draws ~.3 amps.  The maximum number of strings you should plug into one after the other is 3, so this would give us ~1 amp.  Now multiply that times 128 channels and you would be using 128 amps or 14.7kW.  In that most receptacles circuits are fused at 15 amps, the average house could not power the 38,400 lights we dreamed about.

The Olson-595 only outputs 0 or 5 vdc, so how do we control 115vac with 5 vdc?  The use of a triac will allow us to do just that.  As noted in the intro, there are two ways to buy triacs - discrete and in complete packages (SSR).  I picked up 50 such SSRs off eBay for $75.  They are rated up to 3A - more than I will need.  Having just finished my controller (early February 2006), I am just starting to build my power control units.  I envision them to be quad plastic boxes (blue boxes from Lowe's Home Improvement store) used for holding 4 light switches or 4 receptacles.  There is a tab between the top and bottom of a standard receptacle that when broken off allows you to apply separate power to each half of the receptacle.  It is my hope that there will be enough room in the blue box to mount 8 of the SSRs in the bottom, each controlling one half of a receptacle.  A single 9 conductor cable from a DB9 on the controller will go to a blue box.  This cable would contain ground and signals for the 8 SSRs.  Once I finalize on a design I will post it here.

My dimmer design is also not yet finalized.  It also will be posted here once completed.

At this point it is my intention to use Vixen - it's free and appears to be headed in the right direction.

Christmas Lights
A week or so before Christmas 2005, Lowe's placed their Christmas lights on sale for 50% off.  We picked up a couple thousand.  Then after Christmas, Lowe's placed their lights on sale for 75% off!  All toll we ended up with about 12,000 lights.  If you have not purchased lights, after Christmas is the prime time.  I understand that Home Depot, Wal-Mart, Sam's Club and Target also drop the prices on their lights after Christmas.  While most Christmas lights are still incandescent, LED Christmas lights are available.  The advantages of them are lower current, almost indestructible and a variety of really pure colors.  The cons of LED Christmas lights (as of Christmas 2005) is they are several times more expensive that incandescent lights.  I read of one person being annoyed that they flickered on and off at 60 Hz and they could see it - most people can not seen such a high rate of flicker.

To see what our display will look like, we intend to build a model of our house and sailboat.   We will add LEDs to the model to represent the lights we will place on the real thing and program away.  This way we can get an idea of what we are doing without having to set up the actual lights outside.  The town where we keep , our 41' sailboat, holds a boat parade the first weekend in December.  Our intention this year is to deck out with a Christmas light show that will run prior and after the parade - we have too good of a seat to participate in the parade!

Most towns have noise ordnances - our city states that music from loud speakers cannot be audible for more than 50' from the speaker.  Besides, playing the same group of songs over and over for weeks would not endear you to your neighbors.  The answer others have come up with is to broadcast your music on your own FM transmitter.  This must be a low power broadcast - typically limited to just a couple hundred feet.  Otherwise the FCC will be paying you a visit and shutting you down.  Computer Christmas recently (early February 2006) had a thread on modifying really low power transmitters to be just a low power transmitter.  Planet Christmas has had a couple of threads in early 2006 making recommendations for commercially available transmitters.  Ramsey Electronics seems to be a top seller of FM transmitters.

No one seems to be concerned with copyright violations with music they are using.  I have the feeling that being a small public free display, that most music houses would see such use as not worth bothering with.  Just an opinion - not a legal opinion.

A sign in the yard would indicate the FM frequency viewers would need to tune their car radios to in order to hear the music.

Light Displays
This will be another developing section. 

Items we have under design are 10 3' trees made of 3 plastic rods such as used to hold up tomatoes plants.  The three rods would be joined at the top to form a pyramid, with a 4th rod cut up and secured between the legs to hold the right shape.  Three sets of lights (one yellow, one red, one green) will be wrapped around the tree - each string controlled separately. 

Icicle lights on the eve of the house - can't get much simpler.

A 16' tall tree made of a pole mounted in the ground with numerous strings of lights going from a ~10' diameter ring around the tree to the top of the pole.  Each set of light would be controlled separately.  A look at Carson's video will give you an idea of the endless possibilities there!

There will not be any letters spelling out words - the wife is not in favor of such and peace in the world starts at peace at home!

Web lights on bushes - another simple lighting idea

Where from here?
This is just my beginning into Christmas lighting synchronized to music.  Where it will end I am not sure - but we plan on having fun doing it.  If you are not having fun doing something - then you need to find something else to do!

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This page was last modified: 01/22/14
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