PISCO Atmospheric PISCO Atmospheric Dispersion Dispersion

CompensatorCompensator

Will HighWill High

Harvard UniversityHarvard University

December 2006December 2006

An ADC for PISCOAn ADC for PISCO

ADC placeholder in blue belowADC placeholder in blue below After shutter (green below)After shutter (green below) Before collimatorBefore collimator Mounted on PISCO’s optical benchMounted on PISCO’s optical bench

An ADC for PISCOAn ADC for PISCO

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An ADC for PISCOAn ADC for PISCO

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Our ADC from the Our ADC from the Ground UpGround Up

2 Prisms2 Prisms

18 mm apart18 mm apart

130 mm diam130 mm diam

18 mm thick18 mm thick

Stainless Steel HousingsStainless Steel Housings

Gear teeth + Gear teeth + 360˚ groove for 360˚ groove for timing belttiming belt

Another 180Another 180˚ ˚ groove for zero-groove for zero-pointing with pointing with microswitchesmicroswitches

Lip: precision Lip: precision machined machined chamfer with chamfer with semi-circular semi-circular cross sectioncross section

Stepper-Driven Non-slip Timing Stepper-Driven Non-slip Timing BeltsBelts

McMaster:McMaster:Non-slip, double Non-slip, double sided timing belts sided timing belts (teeth + groove)(teeth + groove)

2 specialty 2 specialty pulleyspulleys

Oriental Motor Oriental Motor stepperssteppers

Custom axles and Custom axles and stepper mounting stepper mounting flangesflanges

Stepper-Driven Non-slip Timing Stepper-Driven Non-slip Timing BeltsBelts

Teeth + 360˚ Teeth + 360˚ groovegroove

(timing belt)(timing belt)

180˚ groove180˚ groove

(zero-pointing)(zero-pointing)

2 Microswitches to Mark Zero-2 Microswitches to Mark Zero-pointpoint

2 Microswitches to Mark 2 Microswitches to Mark ZeropointZeropoint

Teeth + 360˚ Teeth + 360˚ groovegroove

(timing belt)(timing belt)

180˚ groove180˚ groove

(zero-pointing)(zero-pointing)

3 V-groove Track Rollers per 3 V-groove Track Rollers per PrismPrism

3 V-groove Track Rollers per 3 V-groove Track Rollers per PrismPrism

Aluminum CaseAluminum Case

Aluminum CaseAluminum Case

Purely Rectangular ProfilePurely Rectangular Profile

Beam toward youBeam toward you Beam away from youBeam away from you

Zero-pointingZero-pointing McMaster-Carr Long Roller Lever McMaster-Carr Long Roller Lever

Snap-Acting SwitchesSnap-Acting Switches 2 x $8.502 x $8.50 0.95" x 1.94" x 0.69“0.95" x 1.94" x 0.69“ Max ratings:Max ratings:

– 15 Amps15 Amps– 250 Volts AC/DC (Screw terminals)250 Volts AC/DC (Screw terminals)– 186 Watts186 Watts

3 terminals (SPDT)3 terminals (SPDT) ““Rising edge” means zero, “falling Rising edge” means zero, “falling

edge” can mean anti-zero if edge” can mean anti-zero if machined preciselymachined precisely

RollersRollers McMaster-Carr Adjustable-McMaster-Carr Adjustable-

Height Perma-Lube V-Height Perma-Lube V-Groove-Guided Track Groove-Guided Track RollersRollers

6 x $62.936 x $62.93 1/32" adjustable height 1/32" adjustable height

playplay Ball bearingsBall bearings Permanently lubricated Permanently lubricated

and sealed = maintenance and sealed = maintenance freefree

9090˚ groove˚ groove Smallest available:Smallest available:

– About 1 2/3” longAbout 1 2/3” long– 1 ½” roller diameter1 ½” roller diameter

Timing BeltsTiming Belts McMaster-Carr McMaster-Carr

Double-Sided Flexi-Double-Sided Flexi-Timing Belts and Timing Belts and PulleysPulleys

2 x $29.66 (belts) + 2 2 x $29.66 (belts) + 2 x $23.56 (pulleys)x $23.56 (pulleys)

Single stranded (one Single stranded (one groove)groove)

0.20" wide0.20" wide 24” outer 24” outer

circumfrence beltscircumfrence belts 1 ½” diam pulleys1 ½” diam pulleys Anodized aluminum Anodized aluminum

pulleyspulleys

SteppersSteppers Oriental Motor 5-Phase Oriental Motor 5-Phase

Microsteppers (CRK513PAP)Microsteppers (CRK513PAP) 2 x $367, in stock2 x $367, in stock 0.720.72˚ Basic Step˚ Basic Step 24 Volts, ~1/4 Amp24 Volts, ~1/4 Amp < 80< 80˚ C operating temperature... ˚ C operating temperature...

BUT:BUT:– We don’t need high speeds nor We don’t need high speeds nor

long run timeslong run times– Can turn off current if we install Can turn off current if we install

friction devices on prism housingfriction devices on prism housing– ““High torque motor current is High torque motor current is

reduced to suppress heat reduced to suppress heat generation. Eg, to avoid generation. Eg, to avoid temperature rise in precision temperature rise in precision machinery.” I think this means a machinery.” I think this means a lower current gives the same lower current gives the same torque as the standard modeltorque as the standard model

We make the flangesWe make the flanges Want to use the same focus Want to use the same focus

stepper driversstepper drivers 5 pins per stepper5 pins per stepper

Stock Stock DriverDriver

WiringWiring Goal: single cableGoal: single cable WiresWires

3 x 2 microswitches3 x 2 microswitches+ 5 x 2 steppers+ 5 x 2 steppers= 16 wires= 16 wires

Run wires along inside Run wires along inside case surfaces to single case surfaces to single D connectorD connector

ADC cable runs to on-ADC cable runs to on-board PISCO driver board PISCO driver rack (water cooled)rack (water cooled)

Drivers controlled Drivers controlled downstairsdownstairs

Single D ConnectorSingle D Connector

SummarySummary About 18 lbsAbout 18 lbs 4 ½” deep x 11” wide x 10” tall4 ½” deep x 11” wide x 10” tall GoalsGoals

– Single cable from ADC to driver rackSingle cable from ADC to driver rack– Use focus stepper driver instead of stockUse focus stepper driver instead of stock– Minimize stepper heat dissipation by switching off current and Minimize stepper heat dissipation by switching off current and

using simple friction devicesusing simple friction devices Heat dissipation by ADC negligibleHeat dissipation by ADC negligible

– Assumed by driversAssumed by drivers– Driver rack water cooledDriver rack water cooled

To doTo do– Mounting holesMounting holes– Internal wire guidesInternal wire guides– Microswitch mountsMicroswitch mounts– Alignment (tolerances)Alignment (tolerances)