non-geek xmas lights
Love
Tonight I put out the beta version of this year's Christmas lights.
The lights consist of four sets of LED lights, each set a unique
colour: red, yellow, white and blue. Each colour is controlled
separately by a Perl program running on my home computer/server.
Right now they are just doing a binary counter display from
0 to 15. Ultimately I will have an email address collect votes
so that my neighbours can decide what colours are turned on when.
The lights are controlled by my server via parallel port LPT1.
The physical port on the computer connects to a standard
"Centronics" type of cable that attaches at the other end to
a small circuit board of my own design. The circuit board is
just a 74LS373 octal latch and some support circuitry (a
7405 voltage regulator, and just a transistor for the latch
strobe so I didn't need to add another IC). The data outputs
of the 74LS373 are wired directly to an 8 channel opto-isolated
SSR (solid-state relay) array which in turn switches 8 lines
of 115 VAC on and off according to the data input. I'm using
the lowest four lines for my Christmas lights.
(Naturally most of the parts for this are things I had laying
around. I'm proudest of the SSR array since I rescued it
from an industrial scrap bin about 25 years ago. The latch
circuit is something I built almost that long ago for a stage
lighting application that never came to be.)
That's the simple and straight-forward part. The tricky part
was getting the 115 VAC power to the lights. I didn't want to
run four extension cords out the window and since the
circuitry itself is not weatherproof putting it outside was
not an option even if I wanted to run the parallel cable from
my server out the window (which I didn't). I began to think
of ways to do it with only one cable out my window then I had
an epiphany and figured out how to do it with NO cables out
the window.
The puzzle for your amusement is "how did I do this?" Here
are some clues:
1. All four sets are individually controllable -- any
combination of colours is possible
2. One extension cord runs from the exterior electrical
outlet in my driveway to the four sets of lights. This
is sufficient for all four to be individually controlled
with a little creative wiring at the end of the cord (and
no use of cheats like commercial remote control devices).
3. This may be the giveaway clue. The four light sets
connect as two daisy-chains of two sets each. Ie. set
1 plugs into the extension cord and set 2 plugs into the
end of set 1; likewise for sets 3 and 4.
In case it wasn't obvious the receptacle end of the
extension cord is a box and two-outlet receptacle, not
a moulded receptacle. The creative wiring takes place
inside the box.
Oh my look at the time....g'night y'all.
--
Love
May Shai-Hulud clear the path before you.
DT
36 hours, no guesses.
So, how the heck did you manage to pull it off? So to speak...
DT
Nobody in Particular
LEDs emit light when forward biased.
Put a diode in series with the line, and the LED will light up
only when the diode is conducting in the same direction as the LED.
So, in series with the strings, put two diodes in parallel, oppositely
polarized. In series with each diode, put an SSR. A third SSR is
parallel to both diodes ad SSRs to bypass them.
Turn on one SSR, so the diode is switched in. Plug set 1 into the
extension. If it doesn't light up, reverse the plug. Plug set 2
into the end of set 1. If it lights up, reverse the plug.
Turn off that diode, turn on the other one. Now set 2 should light
up. Turn on the bypass SSR. Both sets should light up.
Love
There woulda been a guess if D'on were here.
Diodes. LED xmas light strings only use half the AC cycle.
Some are wired so that half of the lights use one side of
the cycle and the other half the other, but those are
split in the middle to be that way and easy to fix
with some solder and heat shrink tubing.
So I put rectifiers in opposite directions on every second
output of the SSR array and connected them together in pairs:
1 & 2 go to one wire and 3 & 4 to the other. Plug an LED
string into one of those outlets and it will only turn on
when the SSR with the corresponding rectifier is on. Plug
the other LED string in with the opposite polarity (ie. turn
the plug the other way since it's not polarised anyway) and
you control two strings independently with one hot wire and
a neutral. Get a third wire for a second hot and add two
more strings for a total of four on three wires. Naturally
no one would consider the third prong of a three prong outlet
a candidate for that third wire, not even if they were totally
fixated on not putting any cords out their windows. If they
did they'd have to be dang sure they'd isolated it from the
house wiring, including ground, and fused the whole thing
well. But of course no one would do that. They'd create a
custom 3-conductor connector system instead.
http://tinyurl.com/ydoucg/XmasLights/
Counts up votes then changes lights to match every so many
minutes. A vote for no lights is equivalent to a vote for
all lights. Multiple votes from the same subnet are
discarded without feedback so voting more than once every
ten minutes is silly. Also, subnets that vote too often
are simply ignored for a long period since obviously
someone's browser is stuck in "I'm an asshole listen to me"
mode.
Pictures and feedback type stuff will be my weekend project
(along with seeing "Avatar"). I don't think I'll manage a
webcam for it this year, and the above page will go 404 once
I have the email voting system set up.
Love
says...
Heh, damned close.