Filter Labeling

The filter holders should be labeled in accordance with the naming scheme used by the PTF Science Team in order to properly identify the filters. The suggestion is to apply some type of permanent label such as a stamped tin plate riveted to filter holder frame, or a simple engraving directly into the frame. The filters should be identified by both ID and NAME as:

1 g
2 R
3 z
11 Haon
12 Haoff


Filter Assembly

Brief Description: The filter changer assembly is a mechanism which provides for motorized selection of one of two filters. One filter will always be in the field. The mechanism provides access for occasional manual exchange of the two filters which can be carried within the assembly. Motion will proceed under commands received by motor controller via TCP socket.

Items/Tasks remaining until completion:

X 07/28 Re-write limit switch algorithm DH
  08/01 Drill & tap hole for motor cable shield drain wire lug KB
X 08/01 Receive from shop 2nd Base Plate Filter Carriage Assembly KB
X 08/01 Receive from shop 2nd Filter Frame KB
X 08/01 Procure fasteners for nut drive assembly KB
  08/01 RE-Design and RE-fabricate limit switch arm retainers (or simply purchase). Current ones not adequate. KB
  08/01 Lubricate shafts to reduce shaking/vibration/squeaking (suitable lubricant for proximity to filters?) Roger comments...consider thin film of vacuum grease, which has very low volatility and thus will not evaporate. Interaction with air? This will look downward and will thus be relatively immune to dust accumulation. KB,RS
X 08/05 Assemble filter mechanism drive assembly and frame holders (for limit switch software test) KB
X 08/05 Check new limit switch algorithm in assembled mechanism DH
  08/08 Modify housing for cable clearance KB
  08/08 Receive from shop Cover Door Assembly KB
  08/08 Procure Cover Door Hinge KB
  08/08 Add hinged cover on the open side to stop particles/grease falling from mechanism from landing on primary KB
  08/15 Fix limit switch #2 -- sometimes sticks such that it doesn't fully close (this may have been due to faulty limit switch arm retainer) KB
  08/15 Investigate (solve?) stiction (heavy stiction seen in 08/04 test) KB
  08/15 Repair cable braid on D-shell end which connects to filter mechanism DH
  08/15 Final mechanical assembly KB,DH
  08/18 Re-check software after final assembly (may need to be checked after limit switches in their final place) DH
  09/05 Assemble motor controller and power supply into enclosure (need to select a suitable enclosure, probably from campus electronics store) DH
  09/05 Fabricate and fasten name plates or engrave filter labels (see above) into frames KB

Motion Control

  • IMS MicroDrive MForce controller
    • numerous typos in IMS manual
    • when looking at RS422 port, pin 1 is at upper right. See my attached drawing for pinout description.
    • added 0.01 uF capacitors to IO lines for limit switches, otherwise noise from stepper controller could sometimes trigger limits
  • 51200 steps/rev
  • 1 rot of lead screw = 0.057 inch linear travel (according to KB)
  • Perle IOLAN SDS4 Terminal Server
    • terminal server serial ports are 10 pin RJ-45 but most cables are 8 pin -- use middle 8 pins so subtract 1 from pinout description in Perle manual

Control Algorithm

REVISED ALGORITHM 7/28/08 To make up for the lack of hard limits, I've implemented a timeout and distance measuring function. Essentially, the controller will first locate and measure the distance of a filter exchange upon power up (measure in motor steps). It will then move between the soft limit switches and note the distance traveled as a check. If a limit isn't reached within an expected time (about 15 seconds to travel from one end to the other) then the motion will stop. An updated flowchart is attached (page 1 and page2). External software will monitor the reported traveled distances in order to monitor troubles.
Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf Filter_Flowchart_p1r2.pdf r1 manage 101.4 K 2008-08-04 - 18:47 DavidHale Filter changer flowchart page 1 of 2 (homing) Rev.2
PDFpdf Filter_Flowchart_p2r2.pdf r1 manage 68.1 K 2008-08-04 - 18:49 DavidHale Filter changer flowchart page 2 of 2 (move command) Rev.2
Unknown file formateasm Filter_mechanism_assy_MOSAIC.easm r1 manage 2002.9 K 2008-07-18 - 05:42 DavidHale eDwg of filter assembly only
PDFpdf MFI_Micro_manual.pdf r1 manage 4376.1 K 2008-07-18 - 05:39 DavidHale IMS Motion Controller Manual
PDFpdf P48Mosaic_Filter_Changer_Flowchart_p1.pdf r1 manage 61.9 K 2008-07-25 - 20:19 DavidHale Filter changer flowchart page 1 of 2 (homing)
PDFpdf P48Mosaic_Filter_Changer_Flowchart_p2.pdf r1 manage 71.7 K 2008-07-25 - 20:23 DavidHale Filter changer flowchart page 2 of 2 (move command)
PDFpdf filter_changer_pinout.pdf r1 manage 14.2 K 2008-07-18 - 05:06 DavidHale wiring / pinout description for filter changer assembly
Unknown file formatmxt testloop.mxt r1 manage 0.7 K 2008-07-18 - 05:25 DavidHale motor controller test program to driver filter back & forth every 3 sec
Edit | Attach | Watch | Print version | History: r13 < r12 < r11 < r10 < r9 | Backlinks | Raw View | Raw edit | More topic actions
Topic revision: r13 - 2008-08-18 - DavidHale
This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2008-2020 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback