THE MAGAZINE FOR COMPUTER APPLICATIONS
Circuit Cellar Online offers articles illustrating creative solutions
and unique applications through complete projects, practical
tutorials, and useful design techniques.

SCHEDULING REVISITED

by George Martin

Start ý Experience Required? ý An Example ý Requirements ý Estimating ý User Interface ý Breaking it Down ý Sources and PDF

AN EXAMPLE

Suppose youýre designing and building a glue dispenser for placing glue dots for surface-mounted printed circuit boards. Marketing has asked for an estimate of how much and how long. The equivalent of, "the sky is falling, the sky is falling!"

Letýs assume that itýs PC-based and has a custom (ISA) plug-in card for driving and sensing. The work will fall into three areas: software, electrical, and mechanical. You donýt have in-house mechanical, so youýre going to have to go outside for that.

The best specification you could get was "make it as low-cost as possible but fast and accurate." Youýll have to start with some assumptions. The PC can run any operating system you want, and the board sizes are reasonable, say 12ý ý 12ý. The positioning accuracy is ý 0.005ý over the entire work area, and the glue dispensing components are a readily available system from an existing manufacturer.

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