Merging modern software development with electrons and metal
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A Big 2015 Thank You

For all my few readers – and a special thank you for all the insightful comments I received this past year.

Happy New Year!

January 1, 2016   No Comments

Sensitive Circuit Breakers

A couple years back we had to add a UL489 circuit breaker to one of our machines.  I ended up choosing the Weidmuller 9926 series because it was DIN rail mount, compact (only 26mm wide for double pole), affordable, and readily available.  The 9926 worked fine in the original machine, which had a fixed panel for the electrical components.

Then another customer required a UL489 circuit breaker in our smaller machine, where the electrical equipment is mounted in a slide-out drawer.  I made the easy decision, and specified the 9926 series again.   When the first new machine was assembled, the technician noticed that if he hit the side of the electrical drawer, the circuit breaker would trip.

So we did some more testing and verified a bit of mechanical shock would cause the 9926 to trip to the OFF position.  However, when the electrical drawer was retracted, it was hard to get the circuit breaker to trip, so we didn’t change the circuit breaker.  But I still wasn’t comfortable with the possibility of shock-induced trips, so I looked at other circuit breakers.

I choose because the ABL Sursum UL series from Altech because the price was within reason, I was able to get a sample to test, and they were impervious to shock.  The Altech L series were better than the Weidmuller 9926, but I could still get them to trip via hitting them.  Then I had the challenge of finding space, because the DIN Rail was full, and the ABL UL series was 10mm wider than the 9926, which I solved by finding a narrower power supply.

On my last trip to Excess Solutions, they had a large selection of DIN rail circuit breakers; I couldn’t resist testing them to see how shock sensitive they were; all the ones I tested passed, including models from ABB, Eaton, and Merlin Gerin.

As a side note, I enjoy seeing the where the circuit breakers were made.  Here, the 9926 takes the prize, because it is made in Lesotho, a country inside of South Africa, by CBi (Circuit Breakers Incorporated).  The Eaton model was made in Spain.  I believe (but am not 100% sure) the Altech L series in made in India.  The ABL Sursum and ABB breakers were made in Germany.CC

Final note: the 9926 series has several pluses, including compact size and competitive price, and we haven’t heard of any problems with them in our machines in the field, but they aren’t a good choice for high vibration environments or other places where they might receive mechanical shock.



November 15, 2015   No Comments

Blog Schedule

First off, my apologies for not posting at all for a couple months.  I have been very busy with a combination of work (new project with a tight schedule), family activities, taxes, and such.

I will not make any specific promises, but my life has calmed down a bit, and I will do my best to get more posts out – I have way too many partially written posts.

May 31, 2015   3 Comments

Common Equipment Failures

Most of the time, industrial equipment is rock solid.  However over the years, I’ve noticed a tendency for certain products to have characteristic failures or problems.  Examples:

  • MEI PCI/DSP Motion Controllers and blown I/O.  The PCI/DSP is pretty expensive motion controller, and as befits its price, has opto-isolated I/O, but the general purpose I/O is not protected against over current, so anything over say 20 mA will kill the opto-isolator.  The result: blown I/O and, if you’re lucky, a $500 repair bill.  We learned pretty quickly to make sure we always had appropriate current limiting resistors.
  • AMC DX15 and DX60 CANOpen servo drives have the blinking red light.  The drive powers up, the red light starts blinking, and the drive stays mute: it will not communicate over the CAN bus (and there’s no alternate port to try).  I’ve done some troubleshooting, but haven’t made any progress.  Of all the DX15/DX60 drives I’ve bought from eBay, probably about 50% had this problem (yes, an unfair sample, since the good ones are less likely to get on to eBay.  AMC is a good company, but this record indicates that the DX has a design weakness).
  • Parker ACR9040 Motion Controllers seen to have an easily blown 24V power supply, based on eBay: I’ve seen a few advertised as “won’t power up”, and I bought one that was in “unknown condition” that won’t power up (its physical condition is fine).  I’ve spent a little time troubleshooting, but haven’t found the problem yet.  On the plus side, I’ve enjoyed taking it apart and looking at Parker’s design decisions.
  • I’ve also had bad luck with Elmo servo drives off eBay, with only 1 of 3 working.
  • I have a number of old servo drives with broken halls or broken encoders.  My guess is too much heat for the halls, and too much mechanical shock for the encoders (one even had broken glass).

Now it’s time for some screw-up stories that were totally operator error:

  • One day many years ago, as I came in the back door, I was greeted by blue fireball about 1 foot in diameter.  A tech was live troubleshooting a variable speed conveyor motor, and accidentally shorted out the motor driver, causing the fireball and the top of a driver chip to vaporize.
  • More recently, I was going to measure the current supplied by an AMC PS300 unregulated linear power supply, but had my probes setup wrong, so I shorted across the power supply.  Result: a welder!  The meter and power supply survived, but my meter probe tip melted.
  • I had a weird problem with a FP-Sigma PLC output partially failing.  The PLC’s light was coming on, but the relay driven by that output wasn’t.  The problem was that Common at the relay coil was about 2V different from the PLC’s Common, and over time that destroyed the PLC’s output.  On the other hand, I’ve shorted Panasonic PLC’s (easily if you accidentally swap the input and output cables) and they’ve always survived.


October 22, 2014   2 Comments

Busy Time

I apologize that blogging has been pretty light lately (and I really need to get my Robot series going again), but I’ve been having to spend a lot of time on various things that can’t wait.  I’ll still try to get some posts up in August, but be patient.

August 5, 2014   No Comments