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PCA-80 System Description

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Memory used
Power requirements
Known problems

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 This product was used in the Gondola Wheel in the movie "Mighty Joe Young".


Industrial System

PCA-80 boards contain the power supply, playback speed clock, addressing circuitry and outputs for the first 8 channels.  PBZ-08's plug in as expansion boards - each adding 8 more channels.  These EPROM chasers, like many others, are playback only - that is, once a desired lighting sequence is created and "burned" into Read Only Memory or ROM chips, this board set plays it back, over and over - creating fantastic synchronized displays - all day long

Note: all connections are depluggable.

example 24 channel system - the PCA-80 and two PBZ-08's:


How long can a lighting sequence be?

That depends on the size of the ROM chips used and the user adjustable playback speed.  The standard memory size is 512k. The possible choices are listed in the table below.   The clock circuit that controls playback speed uses a 555 timer pulse-generator configuration.  Clock speed range is 30-580Hz or sequence steps per second with the standard timing components installed.  Of course, different capacitor / resistor combinations may be substituted to obtain an alternate playback speed range.  Please specify when ordering.

The following table shows compatible EPROM chips that may be used, along with an idea of how long a light show would be for a particular size at a particular clock speed setting:

Chip Sequence Steps Playback Time @ 60Hz
2716 2,048 34.1s
27C32 4,096 1m : 8.2s
27C64 8,192 2m : 16.5s
27C128 16,384 4m : 33s
27C256 32,768 9m : 6.1s
27C512 65,536 18m : 12.2s
Design Tip: Finding the ROM size and clock speed combination.
Imagine you have a sign that says "Look Here!". Each letter has a separate wire so it can spell.  There is also a single row or border of lights around the outside of the sign, and every 6th bulb is wired together. We could assign channels 1 - 9 to control each letter respectively including the exclamation mark and channels 10 thru 15 could control the outside border.  Since the widest number of channels used for a peticular section is the nine channels for the letters, choose how fast you would want to see all the letters spell - say from off to on - one letter at a time.  If that is the fastest motion in your program, then use that amount of time divided by nine {nine letters}as your base clock speed.  Speed change effects are achieved by repeating a step multiple times to make the lights appear to move slower.

When designing a lighting sequence that changes speed, pick a base clock speed that will be the fastest any animation can travel, then choose a number of steps or consecutive memory locations in the memory chip where data will repeat, causing a delay and defining the sequences "usual speed". This is effective in creating the illusion of changing speed.

Hang in there folks, working on a way to  explain these details in a clearer fashion.  --necessary, eh?


Power requirements:

The PCA-80 system was designed to carry an encapsulated power supply that fits on the PCA-80 board if another 12volt dc source is not already available.  The Power Gorilla from Cosel USA is a dependable auto ranging power supply that operates the PCA-80 from a 120 or 240vac source with a max input current of 300ma and output current of 900ma @ 12vdc.

Assuming one solid state relay load per output, about 10ma per relay, up to 80 channels may be used using one PCA-80 depending on how many channels are turned on at a time and how long they are turned on during a sequence.
Adding another PCA-80 with the clock and address IC's removed down the line will allow adding more channels, renewing the power load while keeping any additional channels in sync - allowing lighting systems hundreds of channels wide possible. For systems requiring 60 or more channels where many channels are on most of the time, using a heavier external 12vdc supply is recommended and use a  PCA-80-12vdc that has no on-board power supply.


PCA-80/PBZ-08's outputs will directly drive any combination of the following on any output or channel:

  • LED's with a current limiting resistor - usually 570 to 1000 ohms.
  • Low power mechanical relays with a 12vdc coil and reverse blocking diode.
  • Any dc input solid state relay compatible with 12vdc.
  • Low power 12vdc lamps that the total current does not exceed the driver IC capacity - additional heat sink may be required.

All outputs are12vdc positive common and the grounds switched by a ULN2803 or equivalent eight channel darlington transistor array IC.   LED"s and some low power 12vdc lamps may be powered directly from the PCA-80 board if not to exceed 600ma total for those eight channels being on at a time.

How dependable are they:

This board set was designed back in the beginning of 1992 and started being implemented July of that year.  Since that time, there have been around 120 systems using these controller board sets.  Out of that 120:

Four or  five PCA-80 power supplies were replaced and sent back into service.   Two of those, the customers had told me that the neutral was dropped in multi-phase electrical systems.

Two PCA-80's came in for repair where the power input connector soldered to the board pads had got moisture under the connector and "flashed" so that the power traces on the board had - gone away - for about a half an inch. Since then, a marine silicone product is used under that connector.

One PCA-80 board came back with a transistor array integrated circuit - solid state relay driver chip - had failed.

One PCA-80 board came back with an open or failed clock speed adjusting pot.

Problems with PBZ-08's:

Knock on wood - none yet...

 Note: Lighting sequences programmed by LCS are burned into OTP or One Time Programmable Read Only Memories so the program will not be erased.