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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

PISCO Atmospheric Dispersion Compensator

Will High

Harvard University

December 2006

an adc for pisco
An ADC for PISCO
  • ADC placeholder in blue below
  • After shutter (green below)
  • Before collimator
  • Mounted on PISCO’s optical bench
an adc for pisco3
An ADC for PISCO

r

i

D3

g

z

D1

D2

ADC placeholder

an adc for pisco4
An ADC for PISCO

r

i

D3

g

z

D1

D2

ADC placeholder

2 prisms
2 Prisms

18 mm apart

130 mm diam

18 mm thick

stainless steel housings
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

stepper driven non slip timing belts
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
stepper driven non slip timing belts9
Stepper-Driven Non-slip Timing Belts

180˚ groove

(zero-pointing)

Teeth + 360˚ groove

(timing belt)

2 microswitches to mark zeropoint
2 Microswitches to Mark Zeropoint

180˚ groove

(zero-pointing)

Teeth + 360˚ groove

(timing belt)

purely rectangular profile
Purely Rectangular Profile

Beam toward you

Beam away from you

zero pointing
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
rollers
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
timing belts
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
steppers
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

wiring
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

summary
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)