Gemini Stepper Interface User’s Manual

Installation

To make the best use of your Gemini Stepper Interface (GSI) you will likely want to attach a piece of velcro to its back and then also attach a mating piece of velcro onto one of your tripod legs or onto the tripod head. This way you can simply stick the GSI onto the mount, cable it up, and be ready to use the GSI as quickly as possible. In this document however, the components are shown simply laying on a table for clarity.

Interfacing to the Gemini

The GSI is interfaced to the Gemini using the two provided patch cords. One is a sixteen-inch long, eight-conductor modular patch cable with RJ45 plugs on each end. This patch cord will be referred to as the control patch cord henceforth.

The other patch cord is a two-conductor, 24 AWG patch cord with a 2.1mm power plug on one end and a four-position circular DIN connector on the other end. This patch cord will be referred to as the power patch cord henceforth.

Figure 1: Standard patch cords that come with the GSI

One end of the control patch cable is inserted into the Gemini’s feature port; the other end plugs into the RJ45 socket on the GSI. Either end of the control patch cord can be inserted into either the Gemini’s feature port or the RJ45 socket on the GSI. This cable is safely attached in either direction.

Attach the other patch cord by plugging the four position circular DIN connector into the power out socket of the Gemini; the other end plugs into the 2.1mm power socket of the GSI.

Interfacing to the Focusing Unit

You interface your focusing unit to the GSI using the female DB9 connector on the end of the GSI. The GSI unit is pin-for-pin compatible with Robofocus motors, so if you are using a Robofocus motor, then just plug it into the GSI and start using your GSI. Otherwise, you can build an adapter cable to go to your stepper motor using the following cabling diagram:

Table 1: Motor Wiring Table

Usage

Operation

Pressing the Menu button for more than a second scrolls a choice of centering speeds, hand controller mode and focusing mode through the display. This is known as the Quick Menu. Releasing the Menu button while scrolling through the Quick Menu selects what is displayed.

You change focus using the hand controller by putting it into Focus Mode. To put the hand controller into Focus Mode, select Focusing from the Quick Menu. This menu item is only available if the adapter board is connected. While in Focus Mode, the DEC buttons move focus in and out, and the RA buttons toggle between fast and slow focusing.

To disengage from the Focus Mode, press the Menu button.

Adjustment

There are several jumpers on the GSI that can be used to change the behavior of the GSI. These jumpers are described in this section.

Direction

The direction that the motor turns for focus in and focus out can be reversed using this jumper. When the jumper is to the left, the direction the motor turns for focus in and out is the default direction. When the jumper is to the right, the direction the motor turns for focus in and out is the reverse of normal.

Speed

The speed for fast, medium and slow can be set to one of four different ranges using this jumper. Revolutions per minute are based upon a 1.8 º per step motor. The jumper position one is labeled on the silkscreen and positions two, three and four are to the right of position one respectively.

Table 2: Stepper Motor Speed Settings

Motor Power

The GSI uses a low drop-out voltage regulator that drops the output voltage from your Gemini down to the 12VDC needed by the your stepper motor. If you are supplying your Gemini with 12VDC or less, then you can bypass this regulator using the motor power jumper. If it is in the down position so that the jumper is closest to the 12V on the silkscreen, then the low dropout voltage regulator will be bypassed. Usually this jumper will be in the position that does not bypass the low dropout voltage regulator.

Half/Full

When this jumper is to the left (towards the FULL lettering on the silkscreen) the stepper motor is full-stepped. When this jumper is to the right (towards the HALF lettering on the silkscreen) the stepper motor is half-stepped. Half-stepping doubles the resolution per step and approximately halves the revolutions per minute for each speed setting.