Dear Dennis...
analogZONE's Dennis Feucht answers your design queries in his new Circuit Design Clinic!
July 2006
Dear Dennis... analogZONE's Dennis Feucht answers your design queries in his new Circuit Design Clinic! July 2006 |
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analogZONE presents a new, interactive analog design service to readers! Send us your design questions (with relevant data; schematics in JPEG or GIF, please) for some free engineering advice from analogZONE's circuit consultant, Dennis Feucht, on how you might solve a design problem or improve circuit performance. Submissions may be edited for clarity or brevity, and submitters and their email addresses will remain anonymous (unless otherwise indicated). Please send your questions to Dennis here.
Mixed-Technology Laser System
Problem:
Two digital engineering partners were consulting for a company designing a medical laser. It contained three microcontrollers, each a commercial product on a single board. One controller ran the main functions and commanded the other two. One of the others ran the user interface and the third controlled the laser system. The RS-485 interfaces between the slave controllers and the main one were via serial ports on a motherboard. At power-on, they were seeing unreliable start-up activity. Sometimes the user interface would be unresponsive. The software engineers could not find any clues to the malfunction in their programming. The hardware design partners would repeatedly test each of the controller boards and they performed flawlessly. By swapping in different controller units, the behavior would change, but the unreliability of the start-up did not go away.
Solution:
The fact that power-on behavior was not repeatable was the key clue…