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."

Comments

Find the reason...

[Bladesnitz]

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!

Does it have IR port?

[marat]

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.

My PC turned on after any phone ring (very disturbing while installing some new hardware :( ) 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'.

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.

Airport?

[theCat]

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?

Mobiles phones

[cowbutt]

I woke up early one morning to the sound of my electronic metronome going tick-tick-tick-tock quite loudly. My first thought was that I'd somehow managed to leave it on before going to bed and sleeping right through it. When I checked, I found that my old Nokia 6150 was charging right next to it and the aerial was pointing right at it.

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!

--

USB Desk Lamp

[Jafafa Hots]

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

Even more weird: Flushing toilet can caouse reset

[T-Punkt]

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.

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 :-(. IIRC the toilet has gone by now as well.

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.

Your UPS is sending a heads up ...

[kousik]

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.

Lamp + Ethernet

[FreeMath]

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.

Re:Cat-5 noise

[Tuzanor]

There is such a thing as shielded Twisted Pair (Cat5). Though people rarely impliment it properly. They forget (actually, they probably don't know) that you have to ground the shield in order to properly shield the inside wires.

Studio displays.

[saintlupus]

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