Transcript Document
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 D2 D1 An ADC for PISCO r i D3 g z D2 D1 Our ADC from the Ground Up 2 Prisms 18 mm apart 130 mm diam 18 mm thick Stainless Steel Housings Gear teeth + 360˚ groove for timing belt Another 180˚ groove for zeropointing with microswitches Lip: precision machined chamfer with semi-circular cross section 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 Belts 180˚ groove (zero-pointing) Teeth + 360˚ groove (timing belt) 2 Microswitches to Mark Zero-point 2 Microswitches to Mark Zeropoint 180˚ groove (zero-pointing) Teeth + 360˚ groove (timing belt) 3 V-groove Track Rollers per Prism 3 V-groove Track Rollers per Prism Aluminum Case Aluminum Case Purely Rectangular Profile Beam toward you Beam away from you Zero-pointing McMaster-Carr Long Roller Lever SnapActing 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 McMaster-Carr AdjustableHeight Perma-Lube V-GrooveGuided 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 McMaster-Carr DoubleSided 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 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: – – – Stock Driver 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 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 onboard PISCO driver rack (water cooled) Drivers controlled downstairs 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)