This simple piece of equipment is based on a PIC16C84 microcontroller, and uses an AD9850 DDS to generate the sinewave output.
The CPU and optical circuitry was mounted on vero-board attached to the back of the LCD. This is held in place with double-sided foam tape. Surface mount resistors and capacitors were fitted to the copper side of the board, leaving only the semiconductors to be mounted on the top side.
The step and lock switches are conventional through-hole push button switches that have been mounted to vero board using a surface mount technique. The board was then glued to the back of the enclosure. This allows the switch shaft to protrude slightly through the front panel. By coating the front panel in a clear plastic, these switches then function as membrane switches – pressing lightly on the panel activates the switch.
Article by Steven J. Merrifield at http://users.on.net/~merrifield/
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