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PISCO Atmospheric Dispersion Compensator

PISCO Atmospheric Dispersion Compensator. Will High Harvard University December 2006. An ADC for PISCO. ADC placeholder in blue below After shutter (green below) Before collimator Mounted on PISCO’s optical bench. An ADC for PISCO. r. i. D3. g. z. D1. D2. ADC placeholder.

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PISCO Atmospheric Dispersion Compensator

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  1. PISCO Atmospheric Dispersion Compensator Will High Harvard University December 2006

  2. An ADC for PISCO • ADC placeholder in blue below • After shutter (green below) • Before collimator • Mounted on PISCO’s optical bench

  3. An ADC for PISCO r i D3 g z D1 D2 ADC placeholder

  4. An ADC for PISCO r i D3 g z D1 D2 ADC placeholder

  5. Our ADC from the Ground Up

  6. 2 Prisms 18 mm apart 130 mm diam 18 mm thick

  7. Stainless Steel Housings Gear teeth + 360˚ groove for timing belt Another 180˚ groove for zero-pointing with microswitches Lip: precision machined chamfer with semi-circular cross section

  8. Stepper-Driven Non-slip Timing Belts • McMaster: • Non-slip, double sided timing belts (teeth + groove) • 2 specialty pulleys • Oriental Motor steppers • Custom axles and stepper mounting flanges

  9. Stepper-Driven Non-slip Timing Belts 180˚ groove (zero-pointing) Teeth + 360˚ groove (timing belt)

  10. 2 Microswitches to Mark Zero-point

  11. 2 Microswitches to Mark Zeropoint 180˚ groove (zero-pointing) Teeth + 360˚ groove (timing belt)

  12. 3 V-groove Track Rollers per Prism

  13. 3 V-groove Track Rollers per Prism

  14. Aluminum Case

  15. Aluminum Case

  16. Purely Rectangular Profile Beam toward you Beam away from you

  17. Zero-pointing • McMaster-Carr Long Roller Lever Snap-Acting Switches • 2 x $8.50 • 0.95" x 1.94" x 0.69“ • Max ratings: • 15 Amps • 250 Volts AC/DC (Screw terminals) • 186 Watts • 3 terminals (SPDT) • “Rising edge” means zero, “falling edge” can mean anti-zero if machined precisely

  18. Rollers • McMaster-Carr Adjustable-Height Perma-Lube V-Groove-Guided Track Rollers • 6 x $62.93 • 1/32" adjustable height play • Ball bearings • Permanently lubricated and sealed = maintenance free • 90˚ groove • Smallest available: • About 1 2/3” long • 1 ½” roller diameter

  19. Timing Belts • McMaster-Carr Double-Sided Flexi-Timing Belts and Pulleys • 2 x $29.66 (belts) + 2 x $23.56 (pulleys) • Single stranded (one groove) • 0.20" wide • 24” outer circumfrence belts • 1 ½” diam pulleys • Anodized aluminum pulleys

  20. Steppers • Oriental Motor 5-Phase Microsteppers (CRK513PAP) • 2 x $367, in stock • 0.72˚ Basic Step • 24 Volts, ~1/4 Amp • < 80˚ C operating temperature... BUT: • We don’t need high speeds nor long run times • Can turn off current if we install friction devices on prism housing • “High torque motor current is reduced to suppress heat generation. Eg, to avoid temperature rise in precision machinery.” I think this means a lower current gives the same torque as the standard model • We make the flanges • Want to use the same focus stepper drivers • 5 pins per stepper Stock Driver

  21. Wiring • Goal: single cable • Wires 3 x 2 microswitches + 5 x 2 steppers = 16 wires • Run wires along inside case surfaces to single D connector • ADC cable runs to on-board PISCO driver rack (water cooled) • Drivers controlled downstairs Single D Connector

  22. Summary • About 18 lbs • 4 ½” deep x 11” wide x 10” tall • Goals • Single cable from ADC to driver rack • Use focus stepper driver instead of stock • Minimize stepper heat dissipation by switching off current and using simple friction devices • Heat dissipation by ADC negligible • Assumed by drivers • Driver rack water cooled • To do • Mounting holes • Internal wire guides • Microswitch mounts • Alignment (tolerances)

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