An elevator manufacturer asked Alpha Omega to produce a microprocessor based controller for their hydraulic elevators. The circuit board had to be two-layer to reduce costs, it had to fit into a limited space, and they wanted prototype boards in a month.


The customer supplied a schematic for the switching circuits they wanted to use and we designed the control circuit around it. We used the Motorola 6809 8-bit micro controller that was popular in the early 1980s. Fitting the hundreds of components onto the relatively small board was a bit of a challenge, especially so because of the large through-hole components. Several \ early programmable logic devices were used to reduce the parts count and increase the functional density of the board.

To make matters more interesting, this project occurred before computerized circuit layout programs existed, so it was produced on Alpha Omega's proprietary "PreCAD" computer un-aided drafting system. The layout was initially sketched with colored dry-erase markers on a white board scribed with parallel lines representing a 1/10 inch grid. This layout was then transcribed to a drafting board where the original artwork was produced with tape on clear plastic sheets as was common at the time. Because of the short schedule the board layout was sketched starting at one end of the board and working to the other before the full schematic was finished, and the artwork taping started before the complete layout was finished. The entire design effort from the start of the electrical schematic to the finished circuit board artwork took two weeks (long days and nights).


The customer received the prototype boards on schedule and used the board design in their products for many years.

Elevator Control Software