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Fluorescent Lights Magically Activates iMac?
bats asks: "In my computer room at home, I have several machines -- and a fluorescent desk lamp. Among my various boxen is an iMac DV (slot loading) circa 1999. Its configured to go into power saving mode, but respond to wake-on-lan packets. The weird thing is this: If I flip on the fluorescent desk lamp, the sleeping iMac will suddenly wake up! This happens with 100% consistency. The desk lamp is plugged into a power strip and into the wall. The iMac is plugged into a UPS and then into the wall. The network switch for the room is near the desk lamp (1-2 feet) but the iMac is some distance away (8-10 feet). My question is: WTF?! How the heck does the iMac know when the light comes on? It seems like it must be some power spike in the AC or noise on the network interface. However, the power strip and the UPS should block an AC spike and the chance of electrical noise in the cat-5 looking like a wake-on-lan packet seem more than miniscule. So again I ask you, dear AskSlashdot reader, WTF?! I await conspiracy theories, pseudo-science, wild rantings, and hopefully, the right answer."
Perhaps you can setup/run some kind of program that will tell you what exactly is bringing it out of power-save mode... I'm not familiar with any, but I'm sure one is out there... and if one isn't - I'm sure it can be written! : )
If you find out its a WOL... make sure your neighbor isn't peeking through the window just to screw with ya!
Well, since this is a somewhat useful behavior, I believe I am correct when I say that this rules out hidden M$ software completely.
My guess would be cat-5 noise. I've had problems with my computer turning on erratically whenever I plugged/unplugged a port, or jiggled a loose connection. For whatever reason, the noise on the network woke it up. I finally just turned off WOL, since I wasn't really using it for anything... just playing.
Try putting more distance between the hub/switch and the light, and see if it still causes it to happen. I wouldn't imagine the light could cause much interference over more than a few feet or so. You might also try hooking up another machine, and monitoring all the electrical activity on the network. Myabe something will poke up.
Experiments must be reproducible; they should all fail in the same way.
one way to go about figuring it out, i would think, would be to remove the mac from the lan, turn on the lamp... does it wake up? if it does you can rule out WOL. If it doesn't, then it seems to be something on the network. Is the hub/switch plugged into the same surge protector as well as being perhaps too close? just step through the problem.
--Ks9
it turns that some of my body thetans had gotten trapped at the electrical outlet, and any kind of a disruption to the old AC current would cause them to send out signals that would wake my laptop. I couldn't figure out what was going on, so I called my counselor at the Church of Scientology. He sent over some of their scientists, and they turned my place upside down with a special device, like an e-meter, that detects escaped body thetans. I'd recommend you give them a call. It'll only cost you about US $15,000.
Just pop in Celine Dion's "copycally-challenged" CD before you turn off the iMac.
Probably it's receiving some nonsence data when you switch on the lamp. Also, UPS might be trying to tell you something via it's COM port connection or whatever. Network interference via switch is also possible. Plug out one by one and check.
:( ) though they was not 'Wake up on ring' option in BIOS. Turned out that 'Wake up on LAN' also works as 'Wake up on ring'.
My PC turned on after any phone ring (very disturbing while installing some new hardware
BTW does you mac have external modem? Probably your modem tells RING each time you turn on the lamp. Easy to check with any terminal program.
My cordless-phone (900Mhz) base is about 2 feet above my DSL bridge and hub. Any time there is activity on the ethernet/DSL and I'm on the phone, I can hear it as noise. On certain channels, the noise is more prevailant. Which means either the channel's frequency or one of its harmonics is near the frequency of the ethernet/DSL or one of its harmonics and the power is significant enough to be picked up by the phone. I would guess that a lot of power is needed to first "start" the flourecent lamp. The big "spike" causes enough EMI that your ethernet cable "picks up". The ethernet cable is then acting like an antennea. The wake-on-lan must just detect ANY activity on the ethernet, not a valid packet. Anyway, that's my guess.
come with a compact flash reader? Oh...
unfinished: (adj.)
Here's a fun one: If it has an Airport card installed then maybe it's waking on wireless LAN, getting a random ping from the desk lamp. But since you are already using CAT5 we can rule that one out, right?
=^..^= all your rodent are belong to us
My guess is that one of the periodic cell checkin transmissions induced enough of a current in the on/off circuit that the metronome decided to switch on. Spooky!
--
> The wake-on-lan must just detect ANY activity on the ethernet, not a valid packet.
IBM has a White Paper, Wake up to Wake-on-Lan which describes the specific format of a Wake-Up packet (6 bytes of F (XX'FF') followed by a 48-bit target address repeated at least 8 times). Even if the target address was a broadcast address, I don't see how this could be reliably generated by the starting of a fluorescent lamp. Plus, your average LAN has a whole bunch of traffic going on all the time anyway.
I have an iMac DV (graphite), and I DON'T have it plugged into a network, and it's NOT configured for Wake-on-Lan, nor is it configured to wake on phone rings, and I don't have any infrared devices that I know about, and I have an optical mouse, so it won't wake if the mouse gets moved, and it still wakes up when I vaccum my living room or turn on my slide projector.
if you have a mouse anywhere near the light and then some light could be getting into the mouse makeing it think it has moved.
Try the experiment with the mouse covered up with a rug and switching the light on.
I had an experiance where at certain times of the day the mouse cursor would go a bit funny. took a while to work out it was when the sun peeped throught the window at just the right angle...
Since I installed Windows XP Pro and a UPS, every time I turn on or off my fluorescent desk lamp, windows goes "doo doop" as if I've pulling in or unplugged a USB device. Usually one of the USB devices then reinstalls as if the whole bus has been reset. freaky
This space available.
As kid I used to have a C64. After some years its power supply was slowly dying and it became more and more instable: electric equippement like a vacuum switched on nearby caused it to crash or made it reset. But the /really/ funny thing is that flushing the toilet next to my room caused a reset---and that nearly 100% repeatable.
:-(. IIRC the toilet has gone by now as well.
It was one of those old style toilets whith a big water tank high above the seat and if you pulled the trigger a huge amount of water caused a "whoosh" that would have made Al Bundy happy...
I think I worked around the problem by stabilizing the reset line with a condensor or so. Then the power supply finally died, so I played with 6V batteries to power my C64 and one day accidently killed it somehow
I have no clear idea that the physics behind that was: Was it the same effect that made rising/falling raindrops cause thunders? Or did the quick movement of a large mass of (soemwhat) electric conductive material disturbed the electric field?
BTW: Switching on the light+fan in the toilet had no effect on the C64.
Is your UPS connected to the network
so that it can inform the machines
when there is a change of status of
power line? Maybe when the light is
turned on, the power surge makes UPS
send a packet to your network? Just
guessing.
Fluorescent lights cause horrible interference when placed within ~5ft of cat5. Flipping the switch on the light is probably overloading the NIC and waking it up.
This sig intentionally left blank.
The answer to your dillema is pretty straightforward: when you turn the light on, your *optical* mouse is noticing a change in the pattern on the desk, and interpreting this as the mouse being moved to wake the Mac.
The way to test this hypothisis 100%? Unplug the optical mouse, let the bugger go to sleep, and turn on the light.
Easy, neh?
P.S. It does that in a few of my setups (I work in the dark, with a Kensington Flylight over the keyboard usually) -- but the Apple optical mouse seems much more succeptible than my Logitech cordless optical. Chances are this is because the Apple mouse is mostly transparent.
I've got a 15" LCD Studio Display on my machine at work. The walkie-talkies that the maintenance and security staff use will activate the power button on it, turning the entire computer off if someone is walking by and their radio receives a broadcast.
Ever get the feeling you're being _bathed_ in RF?
--saint
Exactly true. Shielded Cat-5 is more expensive. It is more difficult to find a supplier. And, in this case, shielding would almost certainly not help. The noise is definitely not coming from some electromagnetic connection with one wire inside one of the twisted pairs.
The problem is probably a ground loop; probably the noise is being conducted along the ground wires. More directly grounding the components to each other may help.
Also, it seems to me that Wake-on-LAN is a technology that is usually not implemented well. I've seen cases where it was a selling point, but caused problems.
One thing that helps stop Cat-5 noise is grounding the unused four wires. There are 8 wires in Cat-5, and only four are normally used. (It is possible to buy adapters that allow one Cat-5 to carry Ethernet for two computers, but that is not normally done.) There is electrical capacitance between one Cat-5 pair and the others. When you ground the unused two pairs, you are grounding most of the common-mode noise that would otherwise be experienced on the two pairs that are used. In a low-noise environment like the one mentioned, grounding the unused wires would be the equivalent of having shielded Cat-5. This is something you can try without cost if the Ethernet signal travels through an accessible wall or other connector.
However, as I said, the problem sounds to me like noise conducted along the ground wires, a "ground loop".
Different room, OK, but same circuit? Play with breakers in the basement -- my guess would be that your fridge is on the same AC line, and when it kicks in there's a voltage flucuation while it gets the pump started.
This next song is very sad. Please clap along. -- Robin Zander
This is a new iMac, right?
Okay, look in your office, and put your hand on the lamp. Is your hand resting on the thing with a rounded base, a stalk, and a flourescent emitter at the end? That's your computer. Don't worry, a lot of people make that mistake.
Kevin Fox
The Cubes had a similar problem to this, for some reason the power switch circuitry was susceptible to RF noise generated by flourecent lights and other noisy electrical devices. Other G3 iMacs have also demonstrated their weirdness. It isn't static on the electrical wiring itself but RF noise being generated by the RF generated by the flourecent light. Call up Apple and ask them in there is a tech article about the power switch RF interference problem. It's a probablem that cropped up in a couple of different Mac models though not necessarily all of those models.
I'm a loner Dottie, a Rebel.
Energy saving fluorescent tubes emit light alon the infrared spectrum. I see this all the time at work - the infrared interferes with the remotes for some of our products. Try an incadescent lamp of the same power consumtion specs, or disable your IR port.
.sig wanted: Must be concise, funny, and display my cleverness.
I think I worked around the problem by stabilizing the reset line with a condensor or so. Then the power supply finally died, so I played with 6V batteries to power my C64 and one day accidently killed it somehow :-(. IIRC the toilet has gone by now as well.
You'd have had to use more than 6V batteries to get your C64 to boot; the power supply provided both DC and AC voltage (5VDC and 11VAC IIRC) -- I had built a power supply from a small transformer and some small gel-cell batteries since I had no decent 78xx regulators on me.
Yes, but how is the noise signal getting into the computer? Generally, there is some problem with the ground. The noise from outside wags the entire computer around because of the bad ground.
If there is a bad ground, the noise on the ground side can overwhelm the common-mode capability of the differential pair.
They put out a lot of RF garbage. IIRC there was an early mainframe that was put out of action by a florescent fixture. Keyboard or mouse most likely gets a signal that gooses the computer.
Was that a Proview or EMC brand monitor by chance? If so I might know why they worked after being unplugged.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
If you still had the thing, I'd say touch up the power supply PCB connections with a soldering pencil, or better, replace the 7805 3 pin voltage regulator at the same time.
Used to work at a company producing C-64 software way back when, I had to fix some of those beasties... the C-64 really wasn't intended to run 18+/7.
Tech Public Policy stuff
Someone wrote the following e-mail message to me. I decided to remove his name and company, but post the messages, so that everyone could benefit.
______________________
G.T. wrote:
Just read your slahsdot posting on CAT5 cables. I am at the moment constructing an ethernet to fiber converter for long haul applications.
I have been looking at various application notes from different ethernet chip companies, and I have noticed that some (but not all) designers does just what you writes: they connect the unused ethernet pairs via a resistor to ground, and after reading your post I finally understood why
Soooo, where did you learn this? I have read (or browsed trough) the IEEE ethernet standards, and have not seen this anywhere. I believe that there are other tricks like this that I really should know. Do you know of any good resources for ethernet from a hardware point of view ?
Best regards
G.T.
____________________________________
G.,
I am happy to help. The attached information is very difficult to find on the internet. That's why I carefully saved it to PDF files. If you need more information, let me know.
My information about the likely causes of problems with noise comes from having been an electronics circuit design engineer. You would not use a resistor to ground the unused Ethernet pairs, that would defeat the purpose a little bit. You would ground them directly. You can ground two wires, one from each pair, at one end and the other two at the other end. You should not ground any wire at both ends, because there may be a voltage difference between the two grounds.
My experience with 100 BaseT Ethernet is that it is generally problem-free. That's what led me to suspect a problem with grounding. Something is overcoming the common mode noise rejection of the Ethernet receiver, I guessed. That is most likely to be a loose ground. For example, maybe the computer in the Slashdot example is not grounded at all. It could be that the outlet to which it is plugged has a bad ground connector. I would suspect something simple like that.
Often with ground problems, people have symptoms which cause them to look in the wrong place. Before I was a design engineer, I was a repair technician. I repaired aircraft automatic flight control systems. One day an aircraft came in with 4 very serious malfunctions. Partly lucky and partly smart, I said, hey, wait a minute. I don't believe 4 malfunctions happened in one flight. I began to look for one thing that could cause all 4 malfunctions. The only thing they had in common was the ground. I told the crew chief to look for a bad ground. They found that someone installing some equipment had not remembered to re-attach the ground to the entire bay of equipment.
Again, it seems reasonable to repeat that Ethernet and 100 BaseT are very well-designed, robust technologies. Anyone who has problems should suspect something simple. Shielding of the Cat-5 and grounding of the unused pairs is only necessary when the noise is extreme, such as when doing arc welding 1 foot away.
Regards,
Michael Jennings
It would appear that the ATX power supply predates the ATX power supply switch by about a year, depending on manufacturer.
A lot of those first-gen ATX power supplies had severe reliability problems as well (I've seen batches with %20+ failure rates after six months), so they're increasingly rare.
Fluorescent Lights Magically Activates iMac
Fluorescent lights cause RF [interference], I would suspect that is raising a rail in you network cable.
We use large numbers of ADSL modems pushed towards there upper bandwidth limits to serve a digital TV project. As you can expect some of our hardware enginners have become real experts in the field of RFI and crosstalk. We had a particular set of problems that could not be tracked down, crosstalk was supected and test gear indicated RF interference on the lines.
However further tests revealled crosstalk was not the cause, the RFI spikes occured in exchanges that had not even been xDSL upgraded and somebody noticed when the engineers entered the exchanges, the situation deteriorated and QoS problems got worse. The network management systems reported thoughput and packets dropped. This was before the networking had been touched the, after much head scratching the problem was discovered as the Fluorescent lights, they had to ve removed from every one of our exchanges because of the RFI problems they cause.
Generally, most UPS's today don't do anything to condition the line. While you have AC power that falls within "normal" ranges, you're literally getting line power just as if you were plugged into the wall. The UPS isn't doing anything to filter noise here. Now, if the voltage were to drop or rise outside of the normal range, the UPS should generally kick in and get you onto battery, but I don't think that would be happening here (you'd notice).
Similarly, power strips generally do nothing to protect you from anything except too much current. Voltage can drop way below or rise way above normal and the power strip would keep supplying this power. If your power strip doubles as a surge suppressor, you might get some protection from voltage spikes in addition to too much current, but don't confuse this with a real line conditioner, which would remove noise from the power as well and guarantee you a clean power source.
Yeah, i guess that is kinda funny, i guess you are taking rug as a peice of floor carpet or something?
I guess rug has slightly different meanings in different parts of the world. (over here we often just use it to mean a cover. eg: blanket or even a jumper / shirt eg: dont forget to rug up! meaning don't forget to put a jumper on its cold outside!)