Many years ago, I got a call from a client saying its computer had crashed. It followed with the fact that it had been doing that for about a week, but only at the end of the day and always, so far, while it was not being used.
This turned out to be a blessing, as each time it came back without apparent data loss or corruption. I went over the computer with a fine-tooth comb, and all I could discover from the event logs was that it rebooted a few minutes earlier each day. I returned a little before the time it had crashed the night before and started my vigil, monitoring with all my senses.
Nothing happened at the time it had the previous night. A minute or two later, my mind wandered from the bright screen, and I momentarily gazed out the window at the approaching twilight. A billboard lit up across the street, breaking my reverie, and I glanced back to my now dark screen.
With winter approaching, the billboard's photoelectric sensor was turning on the lights a little earlier each night. The culprit was at hand. After a power line analyzer confirmed the source, I contacted the billboard company to make it aware of the problem.
For some time, I had been trying to convince this customer of the value of having its workstations on UPSes. Now, with compelling evidence and a bill for debugging time, it took the plunge and put UPSes on all its appropriate computer and networking equipment. The demon was throttled.
This entry was submitted by Dave Ussell and edited by Jennifer Campbell.
Dave Ussell is a graduate of San Diego State University with a degree in physics. He has worked most of his professional career seeking out problems he has no experience with whatsoever, such as repairing electron microscopes or C-141s. He spent 15 years working at Children's Hospital and Health Center in San Diego supporting evoked potential research. He later founded and is now the principal of ASCII 27, a company that does everything from designing widgets for disabled persons, medical instrumentation, and the fishing industry to computer forensics.
Tell us your experience in solving a knotty engineering problem. Send to Jennifer Campbell for Sherlock Ohms.
This is indeed a rare one. I have heard of people having problems with power, but it is generally with the power company. To have another user cause this type of problem is interesting.
Years ago (decades) there were routine brown outs. This is when the voltage is lowered intentionally. This caused a lot of computer equipment to malfunction. Things are better now.
From what I have heard, we still have scheduled brownouts but they are carried out less obtrusively than in the past. I would imagine there was some type of drop in voltage or dip as Ann mentioned - it would be interesting to know the exact cause. While UPS's would solve the power loss problem during equipment operation - maybe the root cause could be addressed...good job making the connection between the computer's power loss and that billboard!
I used to do computer controllered conveyor systems and my partner and I would work through the night and never have a problem. But everyday around 10 am, the computer would crash. We reasoned it was due to brownouts and finally were persuasive enough to get a UPS added and the problem went away.
I had another site that kept crashing and the plant managers swore up and down that they were using less power than they ever had and pointed to their terminals attached to their mainframe that power couldn't be the problem. I pointed out their mainframe was on the other side of a massive UPS and those were only terminals. Did they have any PCs in the plant? They said only on the worker punchclock and that the vendor had placed a line monitor on it. So I wasn't the only one suspecting power problems. The next morning on the cab ride to the plant I asked the cabbie if he knew anything about the area, He said yes, he remembered when the plant was the only building in this huge industrial park we were driving through. One UPS later, the problem was solved.
I'd come back to visit my home town and my aunt would handcuff me to her machine to fix it. I determined the power in her small town flickered enough to scramble her hard drive controller, but leave her CPU running just fine. One UPS later, I could come and just visit instead of spending my entire visit fixing her computer.
I know, right? I mean, I understand if it might cause a power surge to an electrical supply, but why would that crash a computer? Wouldn't the battery take over if the power went out? Just goes to show, I suppose, how fragile computers can be...
I worked in power line analyzing/conditioning and UPS decades ago: it's a field ripe for Sherlock Ohms stories. Thanks for this one, although I agree with 3drob--what exactly was the computer's failure mode? In this situation, a dip of some kind may be more likely to occur after the billboard comes on than a spike or surge, unless a grid adjustment then causes a spike or surge.
We have these wonderful strip-malls here in Maine that have one single power feed, they're usually on a fairly rural road and the 5 or so tenants which vary from high energy metal processing to insurance agencies to supermarkets, all in the same building. Firing-up a high energy plasma cutter and air compressor, a couple of refrigeration compressors and an annealing oven all at the same time tends to put more noise on the AC lines than any sane designer ever imagined. Now take your critical items like PC's in insurance and law offices, cash registers in supermarkets, wi-fi sites in book stores, and try to convince all of them they need UPS at THEIR cost. Our power distribution grid in some of these areas is still using #10 copper insulated with tar installed in the 1920's. It's asking an awful lot of a 21st century power-supply make by the lowest bidder to deal with that kind of noise.
A good quality UPS does a lot more than solve a power loss problem during operation--that's an aspect of their power conditioning function. It also, and most important, provides clean, conditioned backup uninterruptible power (UP) when the regular AC goes down. When I worked in the field, the main machines were great, big honking things for hospitals and the IT departments of major corporations. Now we've also got very low-end systems, as bob from maine describes (although those excessive conditions aren't normal where I live). These products are over-priced, not very capable, and not very useful. They're also extremely user-unfriendly, at least to purchase correctly, unless you happen to be an electrical and/or UPS specialist. After 25 years, I have yet to buy one for my home office.
When I first got into industrial systems I worked at a company that made a lot of production line test equipment. Our chief engineer demanded that every machine that utilized logic more complex than relays had to have a Sola Constant Voltage Transformer. Of course, it did add to the machine cost, but those machines never suffered from power problems, other than total feed collapse. The CVTs were not that efficient, they still run too hot to touch, even today, but preventing both spikes and dips from getting into the sensitive circuits has avoided a wole big lot of headaches and grief. So possibly just using a CVT could be beneficial.
But I did work at one company where my UPS would sound it's warning every day a bit after three. It would happen on many of the ups systems on many of the computers. WE never did find the cause, but the systems paid for themselves in less than a year, in lost time avoided. So sometimes the workaround is cheaper thanbnan actual solution. "Long live the UPS"
If it can cause a temporary brown out, how much current must those electronic billboards draw? Don't we have better ways to waste nonsustainable resources?
At least they turn it off during the day, but still they seem a total waste. I have even seen them cause traffic accidents.
I know of one occasion where there was a computer on a UPS in an apartment where the electrical plug was on the same circuit breaker as part of the kitchen. An appliance in the kitchen caught fire which triggred the circuit breaker. The UPS alarm was triggered well before the smoke detector went off.
The author didn't say that it was an electronic billboard. An electronic billboard would be illuminated all day (maybe shut down late at night when nobody will see it?). This was a good old fashioned billboard with lights so that it could be seen at night.
I am curious why the billboard lights coming on caused the computer to reboot. The author seems to know or suspect but didn't say.
The reason the computers rebooted is that when you first turn on anything with a large capacity or has low resistance until it heats up, temporarily there is such a drop in voltage that it is equivalent to a power cycle.
Billboard lighting across the street should not be causing a voltage dip on the computer power circuit in the office sufficient to reboot the computer. Sounds like a utility issue. If it was a 200HP motor...
We thought we were being careful and clever.. integrated UPS into wiring of our offices.. no box , common maintenance location for mulitple small UPS boxes.
The only indication of UPS was involved.. orange colored outlets indicating the power was supplied by UPS. Standard outlets had regular while/beige color.
Problem: the cleaning lady coming through in the evening didn't know the significance of the orange outlets.. yup, she put a high current draw device (vaccum cleaner) on the limited current UPS outlet.. causing the current limiting on the UPS to kick in .. and shutting down the workstation running simulations overnight.
What did I learn?... - communications to everyone is important (and is hard to maintain), and UPS is just one aspect of clean power.
Be careful. I have a very bad attitude about the unfortunately named Uninterruptable Power Supply. I've seen more failures in those things than in the "dirty" building power.
A proper UPS has a full time inverter running off of batteries with a completely independent charger. Not all UPS gear is like that. Some have standby inverters, some have synchronous inverters, and some are just plain bizarre.
If you expect the UPS to "clean up" your power, you'd better get a full time inverter and make certain that the circuit that you use doesn't go far and that ALL outlets are VERY clearly marked so that some cleaning crew doesn't plug in to them.
Dirty power is usually best fixed at the source: the building ground system. Make sure the neutrals are properly bonded in the correct places. If you don't know what I'm talking about, hire a master electrician and have them explain it to you.
This fix sounds to me like using a small bandage for a sucking chest wound of a problem.
The thing you have to remember is that a billboard will be using lamps more like in a theater than what you would be used to inside a building. They could have a large ballast to fill or many filiments to heat up. Remember a filiment has very little resistance until it gets hot. Electric motors use statges or capatitors to limit starting drop, but lamps may not. I agree the utility is probably cutting corners, but that is a constant problem and pretty much a fact of life.
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