Projects / Laboratory and scientific instruments
Controller and drive electronics for a vacuum cell inside an electron microscope: motor control, current-feedback closure and tight mechanical integration.
The customer needed a vacuum cell for an electron microscope. The sample could not simply be placed into the chamber because vacuum conditions made part of the material evaporate quickly. The cell had to enter the microscope closed, wait for vacuum mode, then open so measurements could be made in time.
The mechanics and electronics of the cell were designed. Power and control used the microscope connector for external equipment, and the cell received a drive and controller for controlled opening and closing in a very constrained space.
Project materials
Engineering context
The device had to work inside an existing electron microscope and respect the instrument constraints.
The sample had to remain closed until the chamber reached vacuum mode.
The drive had to close the cell tightly enough without rough mechanical overload.
Motor-current feedback was needed to determine closure and stop the drive.
Available space, connectors and permitted power were part of the engineering problem.
Work done
Vacuum-cell mechanical design.
Universal drive-control board.
Control of DC motors up to 20 V and 5 A with peak modes up to 30 A.
Drive shutdown by motor-current feedback.
Integration with microscope external-equipment connection.
Testing of cell movement and closure behavior.
Details
The project started from a physical limitation of the experiment, not from an abstract control board. The material had to be studied in a microscope, but the vacuum mode itself damaged the storage conditions of the sample. The device therefore had to protect the sample until the right moment, not merely move a shutter.
In this type of task, mechanics cannot be designed separately and then simply given a motor. The design has to account for cell travel, closing force, available space, microscope connectors, available power and the operator workflow during the experiment.
The controller is designed for DC motors, limit switches and position sensors, although position sensors were not needed in this implementation. Current feedback helps stop the drive when the cell closes tightly, instead of relying only on movement time.
Contact
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