The Controller
Let's start off with some pictures:
LPT Interface + 56 of the 64 SSR's.
Wired Up for the 2004 Display...
 
Click to enlarge these photos!
Pictures From 2003's Setup....
 
Click to enlarge these photos!
Video of the Controller
working
(1.4MB Windows Media Video)
So how it's all work then?
In a nutshell:
1. Computer runs custom software I wrote. Everytime I
light needs to be changed it sends data out to the LPT parallel
port.
2. The controller connected to the LPT port is basically
converts the 8bit LPT port to a 64bit output. Now since parallel
ports only output 8bit data, the actual data for all 64bits
has to be sent out using multiple writes in an address/data
scheme. There's more info about how it works here.
3. Each one of these 64 "output" bits
is connected to a single SSR circuit. So when the bit
= 1, the SSR turns the lights on. When the bit = 0,
the lights turn off.
4. The SSR is connected between the "string
of lights" on the secondary (low voltage) side
of the transformer.
The software also has network / IP
support, so I can use a Laptop with wireless networking (or any
networked PC really) to remotely control it. The other easier
option is to just use Windows XP Remote Desktop Ability. This
works well, providing your controller PC is fast enough.
  
Solid State Relay (SSR) Circuit
Click here to view information about the "Solid
State Relay" circuit that does the actual ON/OFF switching for
each channel of lights.
Other Interesting Facts:
- Switching of the lights is done on the low voltage side of
the transformer.
- Each channel/circuit on the controller is numbered, and the
list on the wall says what each number/circuit matches up to.
(eg Channel 37 = Front Gutter, RED segment)
- Yes... it took ages and ages to connect up!
- The computer
is a Pentium III 500Mhz, 192MB RAM,etc running Windows XP.
This is a bit of an overkill for the job, however it's the
oldest, working PC I had working this year :)
- XP Remote
Desktop ability to a Laptop via Wireless Networking means
the light control PC can be fully remoted controlled....from
across the road, or down the street :)
- The controller/electronics took longer than I can remember
to build! Many weekends, nights, and afternoons spent on various
aspects of it! I do NOT want to have to build another one any
time soon!!! :-D
- The powerboards shown are NOT overloaded - remember low voltage
light sets don't take much current to run.
- All the
lights draw ~1500W of 240V power total, according to (big)
UPS i used to measure the load with.
- Each transformer averages about 40-45W on the 240V side when
at full load. IF the lights are off, (secondary side open)
then this drops to around 9W
- Switching the lights on the low voltage secondary side has
presented no problems so far. Infact, response time is better
since the transformer doesn't have to warm up. Most sets have
no problems a cool 50hz strobe light effect!
- The board holding all the transformers wieghs a tonne :)
The transformers & powerboards are left on the board, and everything
is packed up together. This saves so much time not having to
mess around connecting power up again.
Photo during testing
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