Now, do you remember those 20 light sets of lights ?
and a certain website - computerchristmas.com ?
Put the two together and what do you have ?

A crazy idea for an 8ft tree made out of lights that is sequenced by a computer and fits over the water feature in the front garden.

So, how does one arrange the lights?  Obviously in strings, but how many?  There are eight sides to the water feature & four different colours, = 32 lines (channels).  Parallel ports have 8 data lines and a PC can have a maximum of 3 parallel ports, that's only 24 lines.  But parallel ports also have 4 control lines so these will have to be put to use if I am going to use 24 strings of lights.

Back to computerchristmas.com as there is an explanation of how to use the control line outputs from the parallel port there.  I chose to use three of the control lines plus the eight data lines from each of the three ports, this gave me the 32 lines I needed plus one spare.  Also on this website is a "How to" describing a 320 line controller driven from one parallel port.  I did think about building the 320 port controller,  but that's for a later development I'm thinking of.  (No I'm not giving away any hints yet, so there ! )

To get 32 lines of data from the garage to the front garden I was going to need some multicore cable, at least 33 cores.  Back to the internet & Maplin, no not a holiday camp, a Hobby Electronics retailer.  After some searching, the best I could do was a real of 12 core alarm cable from which I cut three lengths giving me 36 cores.

Once again I used the ULN2083 to interface to the PC.  Four of these chips were fitted on a small piece of stripboard and mounted inside the PC on a standard expansion card bracket.

Then the 36 way cable run to the front garden and into a box with the 32 opto-isolators & thyristors also mounted on stripboard.  I had to use the thyristors because the current in the 20 light sets was a little to much for the opto-isolators.

Another little problem that reared it's ugly head during testing, was that each time a channel switched on, the fuse bulb would momentarily glow very bright.  The reason being that the fuse bulbs are a different wattage to the rest of the bulbs in each string.  The solution was to pass a little less current through the string of lights by adding another bulb in series with the existing 20.  So each string now has 21 bulbs in it.    Sorted !    I hope.

History Index

Messages from
     The Grinch (2011)
No Change
     (Dec. 2010)
Trees Grow !
     (Dec. 2009)
2008 Display
     (Dec. 2008)
Planning for 2008 !
     (Early 2008)
Here we go !
     (Nov. 2007)
The Big Change !!!
     (2007)
The Night Before
     Light-up (Dec. 2006)
The Tungsten Tree
     (Feb - Nov. 2006)
The Second move
     (Dec. 2005)
Who put that there ?
     (Aug. 2005)
Back in business
     (Dec. 2004)
Click Click Click
     (Dec. 2003)
Rope Lights
     (Dec. 2002)
The Move
     (Dec. 2001)
More Silicon Chips
     (Dec. 2000)
The Next Few Years
     & Chips
The Bug was biting
     (1993 on)
Early Married Life
     (1981 on)
A logical development
     (Dec. 1973 ish)
In the Beginning
     (Dec. 1962)