Sciencetech's FWF-4 is a motorized filter wheel unit. The wheel can hold up to four 3.05" diameter filters in a light tight enclosed housing. The thin housing design allows full use of the filters' aperture area with no f/# restrictions. An internal micro-stepping motor is used, permitting precise positioning at each filter position with high reproducibility. An optional external motor drive controller (Sciencetech MD-100 Universal Motor Drive Controller) provides power and communications to the filter wheel's stepper motor for filter position selection. The filter wheel's internal stepper motor is connected to the optional motor drive controller via a DB-9 cable, which in turn is connected to a host computer via RS-232 serial interface. A Windows based Active-X software module is provide to control the filter position via software commands. This Active-X Software module can be used as a stand-alone software application or have its features incorporated into a larger custom software application for system wide control. The filters can be up to 7.5mm thick. The filter wheel is belt driven through a high precision 1.8° stepping motor with a 1:2 de-multiplication gear ratio for high torque.
 
Notes:
Filters sold separately.
External Motor Drive Controller with Active-X Software Control is optional.
Filter Inserts Required to hold 3", 3.3" or smaller diameter filters


Mounting Provisions  
There are no mounting screw holes.
 
Customer Supplied Motor Driver
If the customer wish to supply their own stepper motor controller instead of using Sciencetech's MD100 stepper motor controller, they would need one that is compatible to the 2 Phase VEXTER Model PK264-018 by Oriental Motors uses inside the filter-wheel.
 
Bi-Directional Rotation
When used with Sciencetech MD-100 Stepper Motor Controller and Sciencetech Sci-FilterWheel Active-X software, the filter-wheel can change slot positions bi-directionally. For example, if the filter-wheel is on Slot Position 3, the Sci-Filterwheel software would instruct the filter-wheel to move forward to Slot Position 4 or move backwards to Slot Position 2. It would not say, move from Slot Position 3 to Slot Position 2 by going forward around the entire slot positions. However, there is still one small software flaw that needs to get fixed. Since Sci-Filterwheel software is used universally for all Sciencetech filter-wheels from the 4 slot model to the 8 slot model, it cannot apply this intelligent logic at the cross over point from the last slot to the first slot. For example, in a 4 slot filter-wheel, it would still go back 3 positions from Slot Position 4 to Slot Position 1 rather than going forward one position.
 
Homing Switch
The Filter-wheel has a built-in IR optical switch for home position detection. Please note that there is only one home position on the entire wheel that corresponds to the first slot. It does not have multiple home positions corresponding to each filter slot position. Please note that the Sciencetech MD-100 Stepper Motor Controller and Sci-FilterWheel Active X software supports reading this home position switch. A third party stepper motor driver may not.

Rotation Precision
The stepper motor that powers the filter-wheel is energized at all times and hence does not loose its rotational position. The stepper motor also has 200 counts per revolution and can be micro-stepped for greater precision, but the overall precision is limited by the backlash of the belt drive to the final wheel. However, this backlash is insignificant in comparison to the limited slot positions available.
 
Technical Specifications
Filter Sizes: 3" or 3.05" diameter with inserts, up to 7.5mm thick (sold separately) Stepper Motor: 2 phase, DC 1Amp, 5.7Ohm manufactured by Oriental Motors (Vexta Model PK264-01A) Clear aperture: 3.1" diameter Communication: RS232 handling standard ASCII commands, serial cable (if optional controller is purchased) Overall Dimension: ~ 13” x 10.5” x 2.6” (thickness is 1.2" except in the area of the motor where is 2.6")