Sciencetech FWG-6 motorized filter wheel has six filter positions. Each filter position accepts 1” diameter round or square filters. The belt driven model, which only accepts round filters, can handle filters up to 5mm thick whereas the axial driven model, which accepts both round and square filters, can only handle filters up to 2.5mm thick. The filter wheel is a compact pancake design with an exposed stepper motor mounted on the backside of the housing protruding outwards. This stepper motor can be computer controlled via an optional Sciencetech MD-100 stepper motor controller module, which connects the motorized filter wheel to the RS-232 serial port (or optional USB port) of a PC computer. The MD-100 is an external unit that provides power and communications to the motorized filter wheel for filter position selection. The MD-100 also interfaces with a PC host computer via RS-232 serial commands. A Windows based Active-X component Sci-FilterWheel library allows programmers to incorporate high level filter wheel logic controls into their own software application or could be used as a stand-alone software. This active-X software is available free of charge. Sciencetech’s Sci-Spec and Sci-LDA monochromator and detector software applications (which are sold separately) can also control the motorized filter-wheel via the optional MD-100 controller. Please note individual filters are sold separately.

Purchasing Filter-Wheel without MD-100 Controller
The FWG-6 Motorized filter-wheel is designed to be controlled with Sciencetech's MD-100 Stepper motor controller. If a customer wishes to purchase the FWG-6 Filter-wheel without the MD-100 stepper motor controller, the customer must provide their own stepper motor controller to control it.

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.

Light Tight Housing and Flat Surface Mounting
The aluminum housing is light tight and with the stepper motor mounted on one side of the filter-wheel, the opposite side remains completely flat without obstruction for mounting purposes.

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 sofware supports reading this home position switch. A third party stepper motor driver may not.

Two Models Available
Sciencetech Standard FWG-6-S Filterwheel is axial driven, meaning the filter-wheel is connected directly to the drive shaft of the motor. This makes its position precise as the stepper motor can be micro stepped for 2000 discrete positions. The Sciencetech Special FWG-6-Rus is belt driven and was made for a robust application with thick filters and shutter. This FWG-6-Rus is custom made and not always in inventory.

Axial Driven Filter-Wheel

• different internal filter-wheel holder design for square and round filters
• accommodates up to 2.5mm thick filters.
• for round filters, 1/8" lip at bottom prevents filters from falling through and a top retainer ring sandwiches the filter in place. Hence 1/8" edge of the filter is blocked and not used.
• for square filters, the lip holds the 4 corners of the filter in position. A round retainer ring, which only holds the 4 corners of the filter is used to sandwich the filters in place. Hence the corners of the filter is blocked and cannot be used.
• Housing internal cavity depth is 9mm. A thicker internal filter-wheel holder can be custom made to hold 5mm thick filters without redesigning the outside housing. Please inquire if this is required

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 to 2000 steps for greater precision. At the standard 200 steps per revolution, the precision is 1.8 degrees, while at 2000 steps, the precision is 0.18 degrees. Please note that only the axial driven model can use the mechanical precision of the 2000 steps, as the belt driven model is limited by its backlash.

Supports 1" or 25mm diameter filters
The 1" diameter slots of the filter-wheel can also hold 25mm diameter filters since 25mm is slightly smaller than 1" (25.4mm). The filters are held in place by a top retaining ring which presses down onto the edge of the filter and works whether they are 1" diameter or 25mm diameter. Due to the retaining ring, the clear aperture is reduced to 23mm diameter.

Technical Specifications
Filter Sizes: 1" diameter up to 2.5mm thick. (Filters sold separately)
Retaining rings included for all slot positions
Axial Driven Model Stepper Motor: VEXTA 12VDC, 1A, 5.7 Ohms, with rotational precision of 0.18° (based on 2000 micro-steps per revolution of the stepper motor)
Electronics Controller: Sciencetech MD-100 Stepper motor controller module microprocessor based, two 8 bit stepper motor controller ICs
Communication: RS232 handling standard ASCII commands, serial cable
USB interface option available
Adjacent filter switch time: less than 400ms
Clear Aperture: 23mm
Software: Sci-FilterWheel Windows based Active-X component (ASCII commands)
Home Position: IR end switch for home position verification