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View Full Version : Way off topic: why does a Jacob's ladder trigger smoke alarms?


Skippii
2004-10-10, 01:57 AM
I'm building a JL to give my halloween pumpkin cool antennae.
I'm making arcs at 50,000 volts which will start a jump over a 2.5 inch gap.
I've designed my own drvier circuit (this thing operates off DC rather than using a neon sign transformer) so I can adjust the frequency. If the arcs are over 2 cm, and the frequency is above about 30 hz, the smoke alarm a few rooms away will go off, in time with the arcs. It starts and stops immediately with the first and last arcs, so it's not like it's picing up any smoke or ozone or ions or anything. If I decrease the spark gap to less than 2 cm, it won't go, or if I drop the frequency below 30hz, it won't go, but other than that, it's a very annoying noise with which to deal while working on this stuff.
It's running off the wall current and draws about 3 or 4 amps. The smoke detector is also wall-powered, so it could be picking up disturbance down the line, although they are on different breakers.
It might also be picking up the eletromagnetic pulses, which would expain why the spark length makes a difference. But I don't know anything about how smoke detectors work, but I don't see why magnetic pulses should trigger it.
Any other ideas?

Catboy
2004-10-10, 02:27 AM
Do you have any battery powered smoke alarms??? If you don't go to Walmart or Home Depot or something and pick one up. Check to see if that those are set off by the JL. I personally think it is beeping because the JL is draining power, or causing a short to the smoke detector, so the smoke detector beeps because it thinks its low on power and needs fixin', as most smoke detectors do. A battery powered smoke detector is a good thing to have because if you ever have and electrical fire then the wall powered one could short and die, and so could you, they run on a 9v battery and only needs replacing once every 3 months or so. Hope I helped.

asupercoolguy
2004-10-10, 06:07 AM
AhAA, fellow HV enthusiasts!

50 KV, huh? NICE!

One thing I can tell you is that we have a wired smoke detector. And whenver the power goes out it starts to chirp - so it seems to be affected by the quality of power being given to it.
My guess on the cause of the chirp would be interference down the line, but I'm not reallly sure. -- I don't THINK different breakers are isolated from each other.
One thing you might try if the smoke detector has to stay, is to isolate the whole circuit from the line with a 1:1 transformer - That should reduce any noise being produced by it.



If that smoke alarm is as old as ours is, it's probably not much good anyway.... So if Catboy's suggestion works, just replace that dang old thing and make yourself SAFER.



--Disclaimer: I'm no expert, so just be careful. You sound like you know what you're doing if you've gotten this far without roasting flesh..... haha ;)

daino149
2004-10-10, 07:11 AM
Personally, I think that the amount of power the JL is drawing is causing the voltage to drop enough that the alarm doesn't like it but not enough to trigger the breaker. Another thing to check is if the JL causes interferences in other devices like the TV or radio. For the most part these are just WAGS.

In any case, I would like to see some pics of the JL, it sounds wicked cool.

Daniel

Tim
2004-10-10, 07:32 AM
Originally posted by daino149
Personally, I think that the amount of power the JL is drawing is causing the voltage to drop enough that the alarm doesn't like it but not enough to trigger the breaker. Another thing to check is if the JL causes interferences in other devices like the TV or radio. I was just going to type the same thing, scrolled down and saw you breat me.

The tv in my house is effected by the washing machine that is on a diffent breaker and is a good distance away. Both the tv and washer are relitively new. Every time the washer switchs in to one cycle (I'm not sure which one) a small line of fuzz momentarilly apears on the top of the screen.

I think its just a safe guard thing built into the detector like battery powerd ones chirp for a new battery like Daniel said.