General Purpose Controller

 The Gemini General Purpose Controller is an intelligent control unit designed to convert computer commands from either the Hercules Central Processor or the Cygnus Manual Panel to low voltage device control signals suitable for handling a wide variety of projection devices used in planetarium presentations. Slide projectors, special effects, and slue zooms are some of the devices that can be controlled by this unit through the appropriate device interfaces.

Each Gemini has four device control ports. Each device control port can be configured by means of front panel settings to supply the appropriate control signals for any of the following devices:

Slide Projectors - By means of the Castor Slide Projector Interface, the Gemini can smoothly fade the lamp from any level to any other level at any rate from 0 to 999 seconds, flash the lamp at practically any frequency, and even combine the two for a unique flash-fade effect. The projector power can be cycled automatically, so that the projector fan runs only when it is needed. This leads to a reduced ambient noise level as well as extending the time between projector servicing.   Slide trays can be moved accurately forward or reverse to any slide position for a random access capability.

Special Effects - Through use of the Pollux Special Effect Interface, lamp control for special effects is as comprehensive as that of slide projectors. Automatic fan cycling insures that the projector is cooled when needed and quiet when not. Two auxiliary switchable motor control functions provide ample control opportunity. Home position sensing guarantees that an effect motion will be in the right place at the right time.

Three types of Dubhe Multiplexed Special Effect Interfaces provide simpler special effect interface capabilities for those on a budget.

Slue Zooms - Position accuracy is maximized through the use of the DC Motor Position Interface. The Gemini actually tracks the position of any slue zoom motion to insure that the image always winds up where you want it.  Variable speed control allows you to control how fast it gets there. Almost any existing positioning mechanism can be modified to operate in this mode.

In addition to the four device control ports, each Gemini includes eight dry contact switch closures to trigger other effects!

  Future viability of the product is ensured due to the ability of the Gemini to accept software upgrades from the host computer by means of the communications network serial port.




 General Purpose Controller Specifications


Desktop enclosure: 7.29" wide x 2.52" high x 10.00" deep.
Rack mount enclosure: 19.00" wide x 3.5" high x 11.50"deep.


Selectable 100-120 VAC / 220-240 VAC, 50/60 Hertz, 10 Watts max.


16 characters x 2 line LCD display with backlight.


RUN/STOP/RESET for local projector control.
SET/NEXT/PREV to set Gemini configuration.


One RS-485 full duplex multi-drop, two connectors allow multiple device daisy chain.


Four low voltage device control ports, each able to supply control signals for operation of a slide projector, special effect, or slue-zoom.

LAMP CONTROL:                           

101 programmable intensity levels. Accurate length ramps from current intensity to any other intensity in 0 to 999 seconds in one-second intervals. Integral Flash effect capability provides additional effects. Lamp failure sensing with Castor and Pollux.

POWER CONTROL:                        

Programmable or automatic on any projector command for Castor, Pollux, and type DF Dubhe.

SLIDE TRAY CONTROL:               

Forward, reverse, and random access capabilities. Tray "home" sensing and tray motion sensing on compatible projectors.

SLUE ZOOM CONTROL:               

100 programmable motor rates, 245 programmable positions.

SWITCH CLOSURES:                     

Eight SPDT light duty switch closures. Rated load (resistive): 0.5A at 125VAC, 1A at 30VDC.  Lower rating for inductive loads.


  • DB-9 male and DB-9 female for system communication.
  • DB-9 female,  (4) for device control ports.
  • DB-25 male for switch closures 

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-  PO Box 486 - 347 Bigler Road  -  Bigler, PA 16825  -  (814) 857-5420  -