Colleen Lau

Colleen was born and raised in Honolulu, O‘ahu. She graduated from Roosevelt High School in 2015 and will be a sophomore in the fall attending the University of Hawaii at Manoa. Colleen is pursuing a BS degree in Electrical Engineering and intends to obtain a master’s degree in Electrical Engineering. After graduation she hopes to either go into the app-making business or go into nanotechnology to explore water purification devices. When Colleen has free time she enjoys hiking with friends, spending time with family, and trying exotic ice creams

Home Island: Honolulu, O‘ahu
High School: Roosevelt High School
Institute when accepted: University of Hawaii at Manoa

Archiving Current Drawn from the Gemini Cassegrain Rotator and Wrap Motor System
Project Site: Gemini Observatory
Mentor: Neal Masuda, Chris Yamasaki

The Gemini Observatory has a Cassegrain Rotator and Wrap system consisting of six individual pulsed width modulated amplifiers used to drive six three-phased motors that positions the Cassegrain Rotator and Wrap system located under the telescope’s mirror cell. This system allows the instruments under the telescope to be rotated to a precise angle needed for planned observations. During conditions of extremely cold temperatures in the telescope’s dome (especially in the winter months) the rotator and wrap system exhibits signs and symptoms of unresponsiveness observable from the lack of movement. These intermittent occurrences in rotator and wrap motor positioning could be attributed to varying levels of excessive bind-up in the rotator and wrap system, causing the motors to draw in an excessive amount of current. The objective was to measure and archive the currents being drawn by a single motor’s three phases to prove that the design concept would be viable. In order to measure the current drawn from the motor, we have installed a current transducer to monitor each of the motor’s individual phase currents. The transducer sends a corresponding output current signal with a proportional magnitude between 4-20 milliamps to the Programmable Logic Controller (PLC). The PLC then processes the data and makes the current measurements available to the Gemini Engineering Archive system (GEA) which will allow the data to be stored for reviewing at a later date and time. Comparisons of the current measurements from a hand held digital clamp meter to the current measurements produced and stored by the transducer in the GEA system have confirmed and proven that the current transducers provide accurate readings of the currents being drawn by each of the six motors. With the current transducers installed, GEA will be able to accurately archive the phase currents being drawn by each of the six motors. Engineers and technicians will then be able to utilize the data to interpret which motors are exhibiting unusual current demand discrepancies in the rotator and wrap system and to track anomalies in the system if they should occur.