Don’t Trust Connectors, Solder, or Wires (EE Tip #138)

Engineer Robert Lacoste is one of our go-to resources for engineering tips and tricks. When we asked him for a few bits of general engineering advice, he responded with a list of more than 20 invaluable electrical engineering-related insights. One our team’s favorite “Lacoste tips” is this: don’t trust connectors, solder, or wires. Read on to learn more.

One of my colleagues used to say that 90% of design problems are linked either to power supplies or to connector-related issues. It’s often the case. Never trust a wire or a connector. If you don’t understand what’s going on, use your ohmmeter to check if the connections are as planned. (Do this even if you are sure they are.) A connector might have a broken pin, a wire might have an internal cut, a solder joint might be dry and not conductive, or you might simply have a faulty wiring scheme. (See the nearby photo.)

Using the wrong pinout for a connector is a common error, especially on RS-232 ports where it’s approximately 50% probable that you’ll have the wrong RX/TX mapping. Swapping the rows of a connector (as you see here) is also quite common.

Using the wrong pinout for a connector is a common error, especially on RS-232 ports where it’s approximately 50% probable that you’ll have the wrong RX/TX mapping. Swapping the rows of a connector (as you see here) is also quite common.

Another common error is to spend time on a nonworking prototype only to discover after a few hours that the prototype was working like a charm but the test cable was faulty. This should not be a surprise: test cables are used and stressed daily, so they’re bound to be damaged over time. This can be even more problematic with RF cables, which might seem perfect when checked with an ohmmeter but have degraded RF performance. As a general rule, if you find that a test cable shows signs of fatigue (e.g., it exhibits intermittent problems), just toss it out and buy a new one!—Robert Lacoste, CC25, 2013

 

Leave a Reply

Your email address will not be published. Required fields are marked *

CAPTCHA Image

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>