Electric stove ignition causing an EMP?

[mattlima]

Hi everyone,

I'm a musician and I'm having a very strange electrical issue with my home studio setup. I'm hoping someone here might have some advice for where I could investigate this further or who I could ask for more information. In a nutshell, my monitor speakers (JBL LSR4326P) are exhibiting a strange behavior where they half-power cycle or 'reboot' (as if they were turned off and on instantaneously). I was also having an issue with my mac pro tower not waking from sleep correctly and restarting instead. The apple store ended up replacing the power supply and the problem has become much less frequent but has not gone away. I suspected the problems were related and later noticed the monitor reboots coinciding with kitchen appliances like the fridge turning on and off. After some testing I've established that I can reliably cause the speakers to power cycle by lighting a burner on my stove (an electric ignition system I believe uses a sparking capacitor circuit but I'm way out of my depth there.)

OK, now for the really weird part. So far it looks like some sort of garden variety grounding or other electrical issue at home, right? So I disconnect ALL of my equipment (computer, speakers, etc) and reconnect it so everything is on my uninterruptible power supply. I then disconnect the UPS from the mains. Just to be clear: no part of the electrical system that constitutes my studio is connected to the electrical system in any way. The system is totally separated from the house electrical system and running on the UPS battery. I try the stove and STILL get the power cycling in the speakers. With no electrical connection between my computer/speakers/sound card/etc and the stove, how is this possible? Could the capacitor in the stove (which was just replaced, incidentally, because it wasn't lighting correctly, although this problem pre-dates that replacement) be creating a tiny EMP that's being picked up by the many cables in the studio? I realize that may sound stupid to a trained engineer, but I'm way out of my depth here and grasping at straws. Help!

 

[neyzenyelda]

I agree with you.
I guess stove generates electromagnetic waves and cables catch the waves.
I had a similar problem with my home studio. my old computer monitor was generating EM waves and the microphone cable was acting as if it was an antenna and making noise. the solution was turning off the monitor while recording.
the other problem was the house electical system was old and causing noise in a similar way. the solution was using an UPS.
your solution is simple: use UPS for studio equipments and turn off everything other than studio equipments while recording.
I am a musician and home studio recording is one of my fields of interest.
edit: I am a physicist.
I think an electrical engineer without having any home studio experience may not be as proefficient as you and me on this subject!
the key point is being a musician with home studio experience! :)

 

[mattlima]

There is also the question of whether this is bad for the equipment. I wouldn't light my stove while recording but I do need to cook to eat from time to time. I wonder if I could shield the capacitor behind the stove?

 

[AlephZero]

I think it is very unlikely the problem is caused by electromagnetic radiation (radio waves, or EMP). it is much more likely to be coming through the power supply somehow.

Do you still have a ground connection for your studio gear when it is powered by the UPS? (I expect you should have one, for safety reasons). That could be where the electrical noise is getting in.

The best way to fix this is to suppress it at the source. You should be able to get a "transient suppressor" to stop your fridge, cooker, etc putting the noise into the mains wiring when they switch.

 

[mattlima]

Hey thanks for the reply. The weird thing is, there's absolutely no connection whatsoever between my equipment and the house electrical when it is on the UPS - no ground, no nothing, it's not connected to anything and nothing it is connected to is plugged into the mains either. It also seems crazy to me that there would be an EMP but the fact is, lighting the stove causes my speakers to cycle even when there is no way for an electric current to be conducted, which means it must be induction. I will definitely look into transient suppression, and I will also have the ground checked.

 

[Mike_In_Plano]

Hertz and Marconi did their early radio experiments by creating arcs at one point which would induce an arc at another. JC Bose was using electrical arcs to produce microwaves in the 5cm wavelength around the turn of the century.

So, can an electrical arc transmit to something in your house? You betcha!

Many of us grew up with TTL and 4000 series logic, and can't quite comprehend how such low energy events could make a difference on a remote piece of equipment. However, the transistors in those old parts had features of about 10 microns. Now, the 200nm features are common and 45nm parts are standard for many devices.

Such tiny transistors require very tiny energies to switch. Furthermore, they are extremely fast parts, so electrical transients need not have a great deal of energy as long as they achieve a fairly high power for a very short time.

 

[Bassalisk]

http://www.youtube.com/watch?v=F44MeeHKBb0#t=02m55s

This might help. EMP can definitely come from sparks.

 

[mattlima]

Thanks again for the replies, everyone. It's starting to make sense now. I guess my only option would be to try and insulate the equipment in the other room or the entire room, somehow, neither of which seem particularly feasible (imagining covering the walls with aluminum foil or something). I just hope it's not killing my equipment.

 

[AlephZero]

Check if you still get the problem with all inputs unplugged from your active speakers. If the problem does go away, you should be able to track down which cable(s) it is coming from, and your problem might be a faulty cable, or a badly designed shielding/earthing setup.

 

[cmb]

It may be difficult to prove your igniter is a source, but maybe easier to discount it - do you have a MW/LW/FM portable radio? Just put it next to your kit (presumably a few meters from the oven), and tune into a station on each band in turn, and run the igniter. If you don't get much of a click (suggesting it is comparable with the teeny strength of the radio station signal) then I'd say you can mostly discount direct EM interference.

 

[mattlima]

I will give that a shot but I'll need to wait until I can get someone into help me since I can't be in both rooms at once. Thanks for the advice, I'll write back with results.