I was minding my own business... Getting ready for bed...

Several nights ago, after getting tired from many hours of research and browsing, I decided to head off to bed, but thought I would check my email, before shutting down.

Immediately upon clicking my email shortcut, the computer shut down instantly, then there was the sound of a massive short circuit, with a simultaneous flash of orange against the wall, a small puff of smoke, and the smell of burnt electrical components.

Over the years, I have had a couple power supplies just die, while working on the computer, but I have never experienced a power supply failure like this one. It was truly a unique experience :)

Considering the severity of the short circuit, I thought it might be possible for the power supply wiring to catch on fire, so of course I removed surrounding documents and unplugged the supply. Quietly I thought to myself, well there goes my main computer.

So for the last couple of days, I have been reorganizing my computing strategy, and scrambling to retrieve my unbacked files, as well as get a computer back online for browsing. To my amazement, the hard drive survived the fatal blow to the PC :)

As you can clearly see, I am back online, but now I have to set up a different computer for all my older files. :(

Anyhow, that's my story for the week :)


Novel Solutions - http://www.novelsolutionsonline.com/ - Machinery Design • - • Product Development
"Necessity is the mother of invention." - Author unknown.

Comments

  • 14 Comments sorted by Date Added Votes
  • Gosh, that's a shocking tale, Bruce !

    Seems like you didn't suffer any injury, and your house is still standing. That's the good news in your story.

    I do wonder why you've had multiple fails though. Is your Neutral (if that's what you call the partner to the Live cable), making a good non-intermittent connection to your house?
  • idbruceidbruce Posts: 5,515
    edited May 6 Vote Up0Vote Down
    VonSzarvas
    I do wonder why you've had multiple fails though. Is your Neutral (if that's what you call the partner to the Live cable), making a good non-intermittent connection to your house?

    The past power supply failures have occurred at various locations, however I do believe I either have a bad connection with either a neutral or an ungrounded conductor. In fact, several years ago, I had the electric utility company come out, to unplug the meter and inspect their portion of the supply lines. While they inspected their portion, I cleaned and checked all connections from the bottom side of the meter to the main breaker, as well as the neutral running from the meter to the SEP (Main Breaker Panel). While I was at it, I additionally tightened all the house side neutral wires terminating in the SEP, as well as tightening all the branch circuit wires terminating at circuit breakers. Everything looked good on my end and they said everything looked good on their end, however I still suspected a bad connection on their end and asked them to put a voltage monitor on the meter, which they did for approximately 2 weeks. After 2 weeks, they reported that nothing is wrong with their lines, but I suspect they are wrong, because a problem still exists, which affects more than one circuit. So in conclusion, I still suspect a loose neutral on their end, because the affected circuits do not share a neutral within the house.

    EDIT: Another reason that I highly suspect the utility company lines, is because heavy winds will cut power to the house for a brief second or two.


    Novel Solutions - http://www.novelsolutionsonline.com/ - Machinery Design • - • Product Development
    "Necessity is the mother of invention." - Author unknown.

  • Heavy winds-

    Just what I was thinking. I don't think it's uncommon for the connections at the top of the pole to become intermittent from winds. Usually from over-tightened or weather-weary screw terminals failing or breaking the cable.

    I've noticed the utility companies here tend to try saving money by using low cost/quality termination blocks and neglecting to replace very old ones when running new cables or inspecting problems. It invariably leads to the customer having costly problems (which I suppose does represent a fools success in moving some cost from the network to the customer). Remarkably though, it also means the utility firm having to make several costly trips to look at a hard-to-find problem created by cheap part!

    If you've got a good Earth which you can control, then you're not living in a totally lethal situation, but I can imagine with a floating Neutral you'd be having over-voltage issues which could be the cause of your exploding gear. If you don't have over-voltage protection at your main circuit breakers, that should be something to consider. Keeping a log of when that trips might help with the diagnosis.

    I'd have thought there must be 24hr loggers you can plug into an outlet to monitor your supply quality... If not- that must be a project with application!

  • kwinnkwinn Posts: 7,495
    VonSzarvas wrote: »
    .........

    I'd have thought there must be 24hr loggers you can plug into an outlet to monitor your supply quality... If not- that must be a project with application!

    Same thought I had part way through reading idbruce's post. I have seen more than one data logger project between the OBEX and the forum so there is a pretty good starting point. Add circuitry and software to monitor the incoming voltage, current, phase shifts, and high voltage spikes and you can collect data to asess the quality of the incoming power.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • You know, your shorted power supply could have been a bug.
    A literal bug, like a spider or beetle.
  • Here is a related thread, which I started nearly six years ago and it contains some ideas to tracking voltage: forums.parallax.com/discussion/134090/i-need-a-mains-voltage-tracking-circuit


    Novel Solutions - http://www.novelsolutionsonline.com/ - Machinery Design • - • Product Development
    "Necessity is the mother of invention." - Author unknown.

  • CounterRotatingPropsCounterRotatingProps Posts: 1,130
    edited May 6 Vote Up0Vote Down
    idbruce, I feel your rebuild pain :-/ Though I don't have any better suggestions for fixing the line problems, perhaps I can at least boost your mood with a story. I too have had many devices crash hard or suffer demise. Aside from the traditional hard-drive failure, we've had floods, lightning strikes, surges, spikes - (yes plural for all those) - and the occasional cat nibbling on a cord (she was ok :) ).

    But the best and weirdest horror story happened 30 years ago while taking a C programming class. To qualify for a job I wanted, completing the class with a good grade was essential. It was stressful. For taking exams, the teacher encouraged us to log in at school or remotely. Considering "remote" in those days was via a 1200 Baud modem, it was unusual and progressive for the time. The popular use of the term "On Line" was still a decade away.

    I had found a used modem and a VT100 terminal, the contraption took up my whole desk. But wow, I could code and do the exams from home.

    During the final - which had to be completed in one sitting - I had two or three questions to go and only a few minutes to spare. I was going to make it, but was so stressed out, I was actually sweating.

    While typing in my answer to the *last* question, the terminal literally exploded, with a large puff of smelly smoke: something blew out of the top through the vent slots, plastering a big gob of black goo on the ceiling over head. Screen went blank, modem line dropped ... oops ... the end of my future programming career ...

    I took it apart, of course. And, like most visual inspections, the problem was immediately evident: a large tantalium cap in the power supply had blow its top - the goo on the ceiling was its innards. I unsoldered the cap and the next day went to the Prof's office: "I have a story better than 'my dog ate my exam'," I said. And, "I hope you'll let me complete the exam even though I missed the deadline." I handed him the cap, telling him what happened. I think he believed me (or found the story so bizarre that I got extra credit for "creativity"). He let me retake it - and I passed with a good score ...

    Moral of the Story: never underestimate a Gremlin's power of stress detection.

    - H
    schro.png
  • Dave HeinDave Hein Posts: 5,233
    edited May 6 Vote Up0Vote Down
    idbruce wrote: »
    The past power supply failures have occurred at various locations, however I do believe I either have a bad connection with either a neutral or an ungrounded conductor. In fact, several years ago, I had the electric utility company come out, to unplug the meter and inspect their portion of the supply lines. While they inspected their portion, I cleaned and checked all connections from the bottom side of the meter to the main breaker, as well as the neutral running from the meter to the SEP (Main Breaker Panel). While I was at it, I additionally tightened all the house side neutral wires terminating in the SEP, as well as tightening all the branch circuit wires terminating at circuit breakers. Everything looked good on my end and they said everything looked good on their end, however I still suspected a bad connection on their end and asked them to put a voltage monitor on the meter, which they did for approximately 2 weeks. After 2 weeks, they reported that nothing is wrong with their lines, but I suspect they are wrong, because a problem still exists, which affects more than one circuit. So in conclusion, I still suspect a loose neutral on their end, because the affected circuits do not share a neutral within the house.

    EDIT: Another reason that I highly suspect the utility company lines, is because heavy winds will cut power to the house for a brief second or two.
    Bruce, I had a problem with a floating neutral at my house for over a year. It was so bad that we would see the lights get brighter and dimmer. I checked the wiring in my house, and the neutral always had zero volts on it relative to ground. The problem was intermittent, and usually occurred when it was raining and/or there were high winds. I called the electric company about this many times, but by the time they would come out the problem was gone, and they never saw it themselves.

    I finally resorted to building a line monitor using a Propeller board with and ADC on it. I ran the power through a transformer to get it down to a lower voltage that I then fed into the ADC. The Propeller would monitor the voltage and send out a time-stamped message to my computer over a serial line whenever it changed by more than a volt. The computer captured the messages into a file, and I imported the file into Excel for plotting.

    I was able to verify that the voltage between the two split phases was always at 240, but the voltage on either single phase would vary significantly. At one point I measured a low voltage of 70VAC, and a high of 170VAC! I reported the problem to the power company one more time, and when they came out I showed them the plots of the line voltages I measure and the rig that I used to measure it. That finally convinced them that there was a real problem, and they replaced the wiring that came from the power transformer. I haven't had a problem with the voltage since then.

  • whicker wrote: »
    You know, your shorted power supply could have been a bug.
    A literal bug, like a spider or beetle.

    I had a problem like that once. My keyboard developed a buzz when I pressed the left shift key. The buzzing lasted as long as the key was held down. While I was looking at the keyboard and trying to think of what might be wrong a small insect climbed out from between the keys a flew away! No more buzz.
    Infantryman's Axiom; Always cheat, always win.
  • idbruceidbruce Posts: 5,515
    edited May 6 Vote Up0Vote Down
    @CounterRotatingProps

    I believe your story is much better than mine :)


    @Dave Hein

    Yours is also a good story. I should really set aside some time to locate this problem. However I do not believe my problem is a floating neutral, otherwise I am certain that I would have some major appliance issues :) 240V at the TV BAM!!! 240V at the stove BAM!!! Refridgerator BAM!!!! BAM!!! BAM!!!

    I have had several discussions on floating neutrals, most of them resulting in BAM!!!! BAM!!! BAM!!! :)


    @Alexander (Sandy) Hapgood
    While I was looking at the keyboard and trying to think of what might be wrong a small insect climbed out from between the keys a flew away! No more buzz.

    You would buzz to, if someone was pressing on your head with a SHIFT key :)

    EDIT: There is nothing wrong with sharing a neutral between two branch circuits, to save a little money, providing that all splices make a good and solid connection.... BUT share a neutral between two branch circuits, with a bad splice and BAM!!!


    Novel Solutions - http://www.novelsolutionsonline.com/ - Machinery Design • - • Product Development
    "Necessity is the mother of invention." - Author unknown.

  • Slightly off topic but it's incredible how brown/black-outs can still cause damage to equipment in factories, supposedly equipped with sophisticated power conditioning. The single best thing we did with our PC-based CNC controls was to provide them with a dedicated UPS.
    PropBASIC ROCKS!
  • You would buzz too, if someone was pressing on your head with a SHIFT key :)
    <chuckle> <ouch> <buzz>
    EDIT: There is nothing wrong with sharing a neutral between two branch circuits, to save a little money, providing that all splices make a good and solid connection....
    yes, code in most places permits that. I've wired entire buildings using that technique; saves cable and seems to leave enough room to pull a few more circuits through the conduit. As you say, if a connector fails, it gets interesting ...

    Any luck figuring out what's going on there ?
    Mickster wrote: »
    it's incredible how brown/black-outs can still cause damage to equipment in factories, supposedly equipped with sophisticated power conditioning. The single best thing we did with our PC-based CNC controls was to provide them with a dedicated UPS.

    That works great - until a power out and you discover that the circuit firing the "Protected" or "Battery Good" LED in the supposedly sophisticated UPS has failed and you've been unprotected for who knows how long AND the battery is dead. :-( (Have had it happen at least 5 times %-/ )

    schro.png
  • kwinnkwinn Posts: 7,495
    idbruce wrote: »
    @CounterRotatingProps

    I believe your story is much better than mine :)


    @Dave Hein

    Yours is also a good story. I should really set aside some time to locate this problem. However I do not believe my problem is a floating neutral, otherwise I am certain that I would have some major appliance issues :) 240V at the TV BAM!!! 240V at the stove BAM!!! Refridgerator BAM!!!! BAM!!! BAM!!!

    I have had several discussions on floating neutrals, most of them resulting in BAM!!!! BAM!!! BAM!!! :)


    @Alexander (Sandy) Hapgood
    While I was looking at the keyboard and trying to think of what might be wrong a small insect climbed out from between the keys a flew away! No more buzz.

    You would buzz to, if someone was pressing on your head with a SHIFT key :)

    EDIT: There is nothing wrong with sharing a neutral between two branch circuits, to save a little money, providing that all splices make a good and solid connection.... BUT share a neutral between two branch circuits, with a bad splice and BAM!!!

    Sharing a neutral between 2 branches is fine as long as they are on different phases. If they are on the same phase the neutral current is the sum of the two branch currents, and that can be bad. For the 120/240V panels that means adjacent breakers.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • @CounterRotatingProps
    Any luck figuring out what's going on there ?

    Not really, I have been much too busy with other stuff. My mother's care has picked back up again, so that is keeping me pretty busy, as well as working on my projects when I can.

    @kwinn
    Sharing a neutral between 2 branches is fine as long as they are on different phases. If they are on the same phase the neutral current is the sum of the two branch currents, and that can be bad. For the 120/240V panels that means adjacent breakers.

    Yes, when sharing neutrals, they must be on different phases, and yes, if they are on the same phase, the neutral is handling the load for both circuits, which can lead to overheating, insulation degradation, etc...
    For the 120/240V panels that means adjacent breakers.

    In theory, that is not necessarily true, because in the past, you could share neutrals, just as long as they were on different phases. However, I do believe that you are correct again. If I am not mistaken, I think recent changes to the NEC require shared loads to be adjacent, with a common trip, but I could be wrong, because I have not studied the NEC for quite some time, and that is just what an electrical contractor told me the new NEC stated.


    Novel Solutions - http://www.novelsolutionsonline.com/ - Machinery Design • - • Product Development
    "Necessity is the mother of invention." - Author unknown.

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