DDK Engineering


Dennis Davis, Franz Kuhlmann, Gunnmeet Dhillon

Presents: ELDACS

The Electroluminescent Devices Automated Characterization System

Objective

The current method used for characterization of electroluminescent (EL) devices can take up to eight hours to complete. Furthermore, the lab assistant performing the characterization can make mistakes that will lead to erroneous measurements and conclusions. Due to the time constraint involved, the number of measurements that can be taken is severely limited.

Abstract

The Electronic Device Laboratory of The University of Texas at El Paso, under the supervision of Dr. Gregory Lush, sponsored the Electroluminescent Devices Automated Characterization System (ELDACS). Based on the main issue of time, an automated process for characterization was implemented; one that allows the researcher to free up valuable time while also giving more reliable and numerous measurements. ELDACS conducts the necessary measurements to automatically characterize an EL sample (8 EL devices) once initiated and then store that data for a lab assistant to view later. Test runs of the systems have resulted in a total running time of approximately two hours and ten minutes, which is a drastic reduction from the six hours it would take for a lab assistant.

Method of Completion

Using a combination of software developed in the LabVIEW programming environment, interfaces with hardware using data-acquisition (DAQ) and general purpose interface bus (GPIB) cards, and mechanical motors and electrical circuits, a well-integrated system will be developed that can operate independently of outside input after initial setup. The software will control the flow of the process, the interfaces will link the software with the hardware, and the hardware will perform the required tasks. Each section will be designed and developed by a competent and experienced electrical engineering student. Each student will also be responsible for the integration of their assigned section into the overall scheme. This division of work will ensure the project will be completed within the prescribed time frame of August 26, 2001 to May 3, 2002.

This block diagram shows the interconnection of the components, the signal flow and the control flow. Different colors indicate the different responsibilities.

Issues

ELDACS was incorporated into the previously existing characterization system. This situation allowed for a reduced cost of supplies but also came with a drawback. As most of the equipment was already purchased, this meant that ELDACS had to be built specifically for those instruments.

Schematics

This is the stepper motor circuit used to control and drive the stepper motors in the X and Z directions

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This is the high voltage switching circuit which relays the signal to the engaged EL device

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This is the override circuit which enables the user to run a test on the El devices without the aid of a computer

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This is the control circuit, which provides all the logic fuctions needed in the hardware

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Results

This is the enclosure that houses all the circuits which provide the connection between the old and new characterization systems. The topmost circuit contains the hardware interface that allows the user to manually select devices if the system is in manual mode or to override the automated run if something is wrong

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This is the XYZ table that holds the sample along with the motors that align each device with the spectrometer. The enclosure around the table allows the process to run while the lights in the room are on

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This plot shows the correlation between the old intensity measurements (denoted by Minolta) and the new measurements (Slit 0.25-1.5). The conversion factor between the old measurements and those found using a slit opening of 0.25mm is 10,350. This will allow for the comparison of older data with that of the new system.

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Acknowledgments

DDK Engineering would like to thank the following people and organizations:

Dr. G. Lush for sponsoring the project

Ralph Loya for technical support

Carlos Hererra from allowing the use of the machine shop

Dave Brown for supplying special probe tips

Maxim Integrated Products for donating parts

Isocom Incorporated for donating parts

L.S. Starrett Co. for donating parts

Mr. Rubio, Mr. Woo, and Thomas Krause

Our family and friends