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Registered Member #46251
Joined: Sat May 10 2014, 12:55PM
Location:
Posts: 16
Hello everybody,
I've just built a microbrute, it seems to be working.
I want to add a fixed strike target to it but I'm not sure how. Unfortunately there's no way I can go outside and stick a metal spike in the ground. Simply not possible in a 5th floor flat. I gather that using mains ground is bad.
Does my strike target need grounding? Can I connect it to the base of the secondary?
Can I just use a large metal object? I read about people using metal trays but where do the electrons go to?
Thanks for any help...
PS: I live in a 230V country so the whole thing is powered through a 230->110V isolation transformer (iron).
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
You should have a strike ring just outside the primary for safety, and that should be grounded and connected to base of the secondary too. I connect the base of the secondary to the earth wire from the mains supply too. I prefer to not have strikes going to these grounded objects as the EMF interference creates havoc with other electronics in the house. Letting it arc to a large un-grounded metal object works fine and current draw is less.
Registered Member #46251
Joined: Sat May 10 2014, 12:55PM
Location:
Posts: 16
Steve Conner wrote ...
fungus wrote ...
This is the bit that confuses me. Where do the electrons go if the strike target is ungrounded ?
Well, where are the electrons going when the Tesla coil produces an air streamer that doesn't connect with anything? Same answer
(thinks about it... )
OK, I tried jumping across to a piece of wire held in a vice on a wooden bench. I managed to set the bench on fire - a spark was going from the vice down through the bench to a screw in the metal table leg.
Next ... I connected the end of the strike wire to the PCB (where the base of the secondary connects). It seems to work...but it feels very very wrong to be sending 200,000V sparks into a PCB populated to 5V, 74-series logic chips.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
fungus wrote ...
Next ... I connected the end of the strike wire to the PCB (where the base of the secondary connects). It seems to work...but it feels very very wrong to be sending 200,000V sparks into a PCB populated to 5V, 74-series logic chips.
It is very wrong.
Grounding a Tesla coil means completing the circuit for the RF current. The base of the secondary is only a valid return point for current at the resonant frequency of the coil. It is no good for grounding the high frequency spikes created by ground arcs. To do that, you want to connect the strike target to a large metal object that has lots of capacitance to its surroundings.
If I were running a coil in an apartment I would connect all the grounds together, connect them to mains ground, and to an area of metal as large as possible underneath the coil, forming a kind of partial Faraday cage. I would also use an EMI filter so that noise gets injected into all three of the mains conductors equally.
Registered Member #46251
Joined: Sat May 10 2014, 12:55PM
Location:
Posts: 16
Steve Conner wrote ...
fungus wrote ...
Next ... I connected the end of the strike wire to the PCB (where the base of the secondary connects). It seems to work...but it feels very very wrong to be sending 200,000V sparks into a PCB populated to 5V, 74-series logic chips.
It is very wrong.
Lucky I only did a quick test....
Steve Conner wrote ...
Grounding a Tesla coil means completing the circuit for the RF current. The base of the secondary is only a valid return point for current at the resonant frequency of the coil. It is no good for grounding the high frequency spikes created by ground arcs.
The Microbrute documentation has the base of the secondary connected to mains ground. Is that a correct thing to do?
Steve Conner wrote ...
To do that, you want to connect the strike target to a large metal object that has lots of capacitance to its surroundings.
I've read about people using metal tea-trays for this...
Steve Conner wrote ...
If I were running a coil in an apartment I would connect all the grounds together, connect them to mains ground, and to an area of metal as large as possible underneath the coil, forming a kind of partial Faraday cage. I would also use an EMI filter so that noise gets injected into all three of the mains conductors equally.
...I've also seen a lot of dire warnings to not use mains ground for anything (maybe that's just for really big TCs though). I don't want to blow up any TV sets or give anybody a 200,000V tickle in the shower.
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Strike target grounding
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