HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Comment
Jon Titus
User Rank
Blogger
Re: Part IV: Fundamentals of Digital Debugging
Jon Titus   1/19/2012 3:19:31 PM
NO RATINGS
Q: Re: power problems with logic circuits. I designed a CMOS (not MCU) circuit for a starlight camera control function, and while it worked perfectly on the bench, it didn't work when hooked up the the camera system. It took a memory storage scope to discover that the pan/tilt function, which was 120 VAC switched by electromechanical relays, was generating extreme voltage spikes that showed up in the logic as spurious signals. Fixing the problem required capacitor filters across every 120 V relay contact.


So if it works in the lab, but not the actual environment, start looking beyond the MCU.

 

A:  Yup.  But in the lab you might have found the problem if you simulated the tilt/pan loads and ran 110V to them.  Switching loads with relays almost always causes problems, either from RFI caused by the contact closure or by back EMF caused when the relay coil field "collapses."  To reduce contact switching, look for a solid-state relay with zero-crossing switching.  That arrangement will limit inrush current as the 110V AC line voltage is at zero when the SSR switches.




Partner Zone
Latest Analysis
Thanksgiving is a time for family. A time for togetherness. A time for… tech?
The promise of the Internet of Things (IoT) is that devices, gadgets, and appliances we use every day will be able to communicate with one another. This potential is not limited to household items or smartphones, but also things we find in our yard and garden, as evidenced by a recent challenge from the element14 design community.
Researchers have developed a new flexible fabric that integrates both movement and sensors, introducing new potential for technology-embedded clothing and soft robots.
Made by Monkeys highlights products that somehow slipped by the QC cops.
If you didn't realize that PowerPoint presentations are inherently hilarious, you have to see Don McMillan take one apart. McMillan -- aka the Technically Funny Comic -- worked for 10 years as an engineer before he switched to stand-up comedy.
More:Blogs|News
Design News Webinar Series
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
11/6/2014 11:00 a.m. California / 2:00 p.m. New York
10/7/2014 8:00 a.m. California / 11:00 a.m. New York
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Dec 1 - 5, An Introduction to Embedded Software Architecture and Design
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Last Archived Class
Sponsored by Littelfuse
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service