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
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 2 Microswitches to Mark ZeropointZeropoint
Teeth + 360˚ Teeth + 360˚ groovegroove
(timing belt)(timing belt)
180˚ groove180˚ groove
(zero-pointing)(zero-pointing)
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)