Error Analysis: Protect Against Reverse Polarity
May 05, 2020
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Members of Elektor’s global community of pro engineers, technical students, academics, and makers know the importance of learning from their engineering mistakes. Edward Ringel is a Maine, USA-based physician and electronics hobbyist recently told us how to “defend against error” and to protect against reverse polarity with a “$0.50 component and 30 seconds of soldering.” Read on to learn more.
The Reverse Polarity Problem
"I have toasted more components more times than I care to remember while prototyping because a momentary lapse in vigilance led to reversing the leads of my power supply. This is not as much of an issue when creating a final build, but while experimenting it is easy to get distracted or excited or just make a dumb mistake. I am then greeted by the unpleasant odor of frying plastic and silicon. Particularly in complex projects, or projects using expensive components, I now put a Schottky diode in series with the positive side of the supply. Schottky diodes have a small voltage drop and often permit Vpos to remain within operating specifications of the components without modification of the power supply. If the component or board is more finicky, power supply voltage can be increased by 0.2 V (although rarely necessary.) Schottkys come in many power ratings and are cheap. Some might argue that I am substituting components for being observant or being careful. To an extent, this is true. However, most rigorous analyses of human error conclude that error cannot be reduced to zero, and that creating backstops and safety nets to catch and defend against error are as important as error reduction itself. So, if a $0.50 component and 30 seconds of soldering (lead-free, I promise!) can protect my Teensy 3.6, as it did just a couple of weeks ago, I'm all for it.” — Edward Ringel
Subscribe to the diode tag on the Elektor website for future updates.
Want to tell the Elektor community about your electronics-relate errors and learnings? Whether you are a pro engineer, a student, or hobbyist, we want to hear from you. Fill out our "Error Analysis" form and tell us about your experience.
The Reverse Polarity Problem
"I have toasted more components more times than I care to remember while prototyping because a momentary lapse in vigilance led to reversing the leads of my power supply. This is not as much of an issue when creating a final build, but while experimenting it is easy to get distracted or excited or just make a dumb mistake. I am then greeted by the unpleasant odor of frying plastic and silicon. Particularly in complex projects, or projects using expensive components, I now put a Schottky diode in series with the positive side of the supply. Schottky diodes have a small voltage drop and often permit Vpos to remain within operating specifications of the components without modification of the power supply. If the component or board is more finicky, power supply voltage can be increased by 0.2 V (although rarely necessary.) Schottkys come in many power ratings and are cheap. Some might argue that I am substituting components for being observant or being careful. To an extent, this is true. However, most rigorous analyses of human error conclude that error cannot be reduced to zero, and that creating backstops and safety nets to catch and defend against error are as important as error reduction itself. So, if a $0.50 component and 30 seconds of soldering (lead-free, I promise!) can protect my Teensy 3.6, as it did just a couple of weeks ago, I'm all for it.” — Edward Ringel
More on Reverse Polarity and Schottky Diodes
Want to learn more about reverse polarity, diodes, and Schottky diodes? Check out these resources:- M. Ossmann, "No Varicap? Try a Schottky Diode," Elektor 2/2009.
- G. Klein, "Converter IC with Integrated Schottky Diode," Elektor 7/2005.
- G. Klein, "Polarity Protection," Elektor 7-8/1999.
- K. Lorenz, "Polarity Reverser," Elektor 12/1998.
Subscribe to the diode tag on the Elektor website for future updates.
Want to tell the Elektor community about your electronics-relate errors and learnings? Whether you are a pro engineer, a student, or hobbyist, we want to hear from you. Fill out our "Error Analysis" form and tell us about your experience.
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