Parametric Automated Filter Wheel Changer
by jpearce, published
This Arduino-controlled open-source automated filter-wheel changer is set up to move to 8 different filter positions. Normally these devices are used in scientific experiments that need good optics. Commercial versions cost over $2,500 and you can make this yourself for less than $50. So if you make just one -- you more than justify the purchase of your own open source 3-D printer!
This component is part of the Open-source optics project, whose goal is to radically reduce the cost of scientific optical hardware: by the Michigan Tech's Open Sustainability Technology Research Group.
For similar see the Open-Source Lab How to Build Your Own Hardware and Reduce Research Costs
This project was featured in an article and podcase in Science. Pearce, Joshua M. 2012. Building Research Equipment with Free, Open-Source Hardware. Science 337 (6100): 1303-1304.
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This filter wheel is designed for 50.8mmx50.8mm standard filters, but the OpenSCAD code will be included for you to refine for your needs.
Full instructions here
Bill of Materials:
Non Printed Parts* 28 M3x10 Screws 8 M3x22 Screws 1 M3x10 Set Screw (Grub Screw) 33 M3 Nuts 1 Nema 17 Motor 1 Arduino Uno 1 Motor Shield from Adafruit 1 Optical Switch Printed Parts 7 Filterwheel Segments (pie slice segements) 1 Filter Wheel Final Segment (This one is different from the rest) 1 Motor Hub 1 Motor Mount 8 Filter Brackets 1 Optical Switch Flag
*Please note that we are working on different designs for the case of the filter wheel and will post separately. The BOM is for a wheel and a completely printed case.
With your favorite RepRap variant print preferably in black ABS or PLA in order to cut down on reflected light.
Start off by Printing the Motor hub in ABS or PLA. We used a 35% infill with 2 perimeters and 2 solid layers.
Then print off 7 Filter wheel Segments. We suggest printing these out in PLA to prevent warping. Warped prints are not useable. After each print, drill out all the holes. An 1/8Ã¢â¬Â drill bit works fine if you don't have a 3mm bit.
Attach the Segments to the Motor Hub by first placing a M3x22 screw through the Motor hub bottom piece, the segment, then the top piece, attach a nut to the screw. Do not tighten all the way, this can make aligning the segments more difficult. Once a segment is placed next to it, rotate them so that the tab in one aligns with the slot in the other place and place an M3x10 screw through the hole, and tighten with nut. To get them to fit, some shaving down of the edges might be necessary with a file or sandpaper.
When it comes to the final Segment, print it out. (It does have a longer bridge then the rest, so you might want to use a fan to cool it. We also slowed the print speed of bridges in Slic3r from 60 mm/s to 30mm/s. It did a much nicer bridge.) When it is finished drill out the holes, just as before. Then take the piece, next to the final one, with the slot in it, and cut out the small portion of the print at the edge of the bridge. Slide the final segment in, it should fit perfectly, if not, shave down the edges until it does.
- The Optical Switch Flag can be inserted into the slot on any of the segments. The Slot is on the back end of the segments. The flag is used to block the Optical switch, so any segment with the flag in it will be the first one.
The OpenSCAD file is included for those that want to alter the filter wheel for their own experiments. With it you can change the size of the filter, shape, number of filter holder pie slices, etc.
Electronics: Full details here http://www.appropedia.org/Parametric_automated_filter_wheel_changer
This project was developed by the Michigan Tech Open Sustainability Technology research group http://www.mse.mtu.edu/MOST
Thanks to Nick for the OpenSCAD code and Rodrigo for the Arduino code and electronics.
This component is part of the Open-source Optics Library: Zhang C, Anzalone NC, Faria RP, Pearce JM (2013) Open-Source 3D-Printable Optics Equipment. PLoS ONE 8(3): e59840.
This is part of a larger project to reduce the cost of scientific equipment using open-source hardware. Read more here