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Inductive loads failure due to small resistance in connector 
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1N4001 - Signed up
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Joined: Tue Jun 10, 2008 5:17 pm
Posts: 1607
This article is about a 12V driven stepper that was failing internal to the stepper via over voltage arc and burning. Most people would have considered it to be a MFG problem, however Ed points out how and why it was a design problem. Article is titled "Stepper Failure" by Ed Nisley in Circuit cellar #191 pg 50. Found at this link.

Sorry not a free article. However, here's the spoiler alert.

The problem was that the chosen connector after some wear and tear would exhibit a resistance around .1 to .01 ohms. This slight resistance would create a tank circuit that would allow voltage potential to exceed the insulations ratings, causing the stepper to go up in flames. The design did have OV protection on the drive board, however, the connector wouldn't allow the current to shunt to ground, instead it would shunt at the stepper. The problems were intermittent, and were hard to replicate at the bench.

All the more reason why those DB37 connectors are junk, they will be laden with troubles. You might get it working today with those connectors, but after a little use, they will go to junk.

Sun Apr 17, 2011 2:46 pm
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