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Mystery - Electronics expert needed.

Matty1973

Critical Thinker
M
Joined
Mar 27, 2005
Messages
253
Can anyone explain this - I don't know what is happening.

http://www.youtube.com/watch?v=mgVxSu8XBqw

I have just uploaded a video on youtube showing a little experiment I was doing. I made a circuit using lots of metal objects and put a high voltage (personal safety device - 50,000V?) through the circuit and where there are gaps between the objects little arcs form. However the strange thing is I noticed the TV remote controls which are not that near the circuit suddenly start blinking when the voltage stops. Why is this?

The remotes are undamaged and still work fine.

I don't know if it was related but also the smoke alarm went off for a couple of seconds and that must be over 5 meters away from the circuit. That did freak me out so I stopped doing it after that in case it was dangerous. Do you think it is dangerous?
 
Your smoke detector is going off because it detects ionisation of the air. Its designers meant this to be ionisation caused by fire, but it will also detect ions produced from electrical discharges. I was once in charge of a 100kV HV lab. The fire detectors we used had to be of the rate of rise of temperature type, for this very reason. The ions themselves are not dangerous, but I would ventilate the room to remove ozone, and be very careful with the high voltages you are producing.

As for your remote controls blinking, my best guess is that the discharges are inductively coupling their circuitry, which discharges through the LED circuit. It's probably not doing them much good.
 
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Since the LED comes on quite a bit after the pulse, the remote controls are getting some sort of pulsed EMF that very likely causes a "reset" to the unit. Probably like removing and reinstalling the battery would do. I can't imagine the LED's lighting if the battery is removed, but worth a try. As for the smoke detector, I would be surprised if it is actually detecting ions, but not impossible. I would think that it is just RF (radio frequency energy) overloading of the circuitry that detects ionization, sort of like noise that you would get in an AM radio.

We had a severe problem with static electricity in a lab with 30 or so flat panel monitors that would all reset (because of lost horizontal sync) every time anyone would get zapped by sliding across the rug. I think all this is similar.
 
You are right about the light flashing when the batteries are replaced and also that it doesn't happen if there are no batteries in the device at all.

Is this kind of EMF dangerous to people or computers? It's quite a fun effect to demonstrate but I don't want to do anything too risky.
 
Sounds like, as others said, you are inducing a voltage in the circuitry due to the electric field you are creating with this set up. There is probably some capacitor attached to the LED that gets charged as you zap the metal pieces and as it discharges, the LED's light up. As for damage to equipment such as TV's or computers, it could happen. Damage to people is probably not going to happen. I wouldn't let anyone too close as they could get a nasty shock from the personal safety device if they were to touch it, but injury from any EMF that may be induced is unlikely outside of somebody with say a pacemaker (don't know a whole lot about them but there may be some weird interaction).
 
Matty1973 said:
You are right about the light flashing when the batteries are replaced and also that it doesn't happen if there are no batteries in the device at all.
Is this kind of EMF dangerous to people or computers? It's quite a fun effect to demonstrate but I don't want to do anything too risky.
Click to expand...

It is probably not a problem for people, unless you touch it. If you smell ozone, it is probably time to quit playing. The high voltage RF energy can damage some electrical equipment, depending on how robust it is. Lots of stories about various sparking equipment that damaged all kinds of stuff in my experience. It will also play havoc with people trying to listen to the radio.

van_dutch said:
...There is probably some capacitor attached to the LED that gets charged as you zap the metal pieces and as it discharges, the LED's light up. ....
Click to expand...

Not likely, since it does not happen with the battery removed, as he states. It is just a reset, as the LED lights momentarily when the battery is installed also.
ETA: The "reset" is caused by the RF spikes getting into the logic and confusing it with too many inputs at the same time, so the device gives up and resets, as if it has lost power and regained battery power.
 
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That's good enough odds to stop me doing it. I'll stick to showing people the video from now on!
 
Because of the delay we can know with almost certainty that a watch-dog is rebooting the microprocessor in the remotes, or probably more likly, that it has a brown out circuit. What happens is that the chip measures its own voltage and can reset it self when there is a problem. That sort of voltage could easily cause currents making the chip think it has to brown out.
 
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