Strike target grounding
fungus, Sat Jun 14 2014, 07:32AMHello 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).
Re: Strike target grounding
Dr. Dark Current, Sat Jun 14 2014, 10:25AM
Connect it to the base of the secondary coil, anyway that's the best thing you can do in all situations.
Dr. Dark Current, Sat Jun 14 2014, 10:25AM
Connect it to the base of the secondary coil, anyway that's the best thing you can do in all situations.
Re: Strike target grounding
Graham Armitage, Mon Jun 16 2014, 12:24PM
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.
Graham Armitage, Mon Jun 16 2014, 12:24PM
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.
Re: Strike target grounding
fungus, Tue Jun 17 2014, 07:03AM
This is the bit that confuses me. Where do the electrons go if the strike target is ungrounded ?
fungus, Tue Jun 17 2014, 07:03AM
Bushman wrote ...
Letting it arc to a large un-grounded metal object works fine and current draw is less.
Letting it arc to a large un-grounded metal object works fine and current draw is less.
This is the bit that confuses me. Where do the electrons go if the strike target is ungrounded ?
Re: Strike target grounding
fungus, Tue Jun 17 2014, 07:08AM
OK, I will try this too.
fungus, Tue Jun 17 2014, 07:08AM
Dr. Dark Current wrote ...
Connect it to the base of the secondary coil, anyway that's the best thing you can do in all situations.
Connect it to the base of the secondary coil, anyway that's the best thing you can do in all situations.
OK, I will try this too.
Re: Strike target grounding
Steve Conner, Tue Jun 17 2014, 10:01AM
Well, where are the electrons going when the Tesla coil produces an air streamer that doesn't connect with anything? Same answer
Steve Conner, Tue Jun 17 2014, 10:01AM
fungus wrote ...
This is the bit that confuses me. Where do the electrons go if the strike target is ungrounded ?
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
Re: Strike target grounding
fungus, Thu Jun 19 2014, 11:28AM
(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.
fungus, Thu Jun 19 2014, 11:28AM
Steve Conner wrote ...
Well, where are the electrons going when the Tesla coil produces an air streamer that doesn't connect with anything? Same answer
fungus wrote ...
This is the bit that confuses me. Where do the electrons go if the strike target is ungrounded ?
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.
Re: Strike target grounding
fungus, Thu Jun 19 2014, 12:10PM
PS: The masking tape holding the primary will be replaced as soon as I tune it.
fungus, Thu Jun 19 2014, 12:10PM
PS: The masking tape holding the primary will be replaced as soon as I tune it.
Re: Strike target grounding
Steve Conner, Thu Jun 19 2014, 12:27PM
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.
Steve Conner, Thu Jun 19 2014, 12:27PM
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.
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.
Re: Strike target grounding
fungus, Thu Jun 19 2014, 02:00PM
Lucky I only did a quick test....
The Microbrute documentation has the base of the secondary connected to mains ground. Is that a correct thing to do?
I've read about people using metal tea-trays for this...
...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.
It's all a bit confusing.
fungus, Thu Jun 19 2014, 02:00PM
Steve Conner wrote ...
It is very wrong.
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.
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.
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.
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.
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.
It's all a bit confusing.
Re: Strike target grounding
fungus, Thu Jun 19 2014, 03:58PM
Assuming I connect everything to mains ground (ie. base of secondary, base of strike target, tea tray): Does the tea-tray act as a sort of capacitor to smooth out the spikes going into the mains wires?
Would it be better for the neighbors if I connect the strike target to one end of the tea tray and the other end to mains ground? (ie. the tray is between the target and the mains wires).
fungus, Thu Jun 19 2014, 03:58PM
fungus wrote ...
I've read about people using metal tea-trays for this...
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.
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...
Assuming I connect everything to mains ground (ie. base of secondary, base of strike target, tea tray): Does the tea-tray act as a sort of capacitor to smooth out the spikes going into the mains wires?
Would it be better for the neighbors if I connect the strike target to one end of the tea tray and the other end to mains ground? (ie. the tray is between the target and the mains wires).
Re: Strike target grounding
fungus, Thu Jun 19 2014, 07:52PM
I just noticed that one of my monitors flickers on/off when I give it a blast.
That monitor flickers when you plug other stuff in as well. It's pretty sensitive.
fungus, Thu Jun 19 2014, 07:52PM
I just noticed that one of my monitors flickers on/off when I give it a blast.
That monitor flickers when you plug other stuff in as well. It's pretty sensitive.
Re: Strike target grounding
Steve Conner, Fri Jun 20 2014, 10:06AM
Yes that's exactly it, though something bigger than a tea tray would be preferable. :/
I don't think the exact order of the connections makes much of a difference. Most of the noise from a Tesla coil is in the 10s of MHz, where the tea tray is small compared to a wavelength.
Recently there has been talk of an inductively loaded breakout point. Basically putting a tiny Tesla coil on top of your main coil. The inductance acts as a buffer between the topload capacitance and any arcs to ground, which significantly reduces the amount of HF noise generated. It is still experimental but seems to give good results.
Steve Conner, Fri Jun 20 2014, 10:06AM
fungus wrote ...
Assuming I connect everything to mains ground (ie. base of secondary, base of strike target, tea tray): Does the tea-tray act as a sort of capacitor to smooth out the spikes going into the mains wires?
Would it be better for the neighbors if I connect the strike target to one end of the tea tray and the other end to mains ground? (ie. the tray is between the target and the mains wires).
Assuming I connect everything to mains ground (ie. base of secondary, base of strike target, tea tray): Does the tea-tray act as a sort of capacitor to smooth out the spikes going into the mains wires?
Would it be better for the neighbors if I connect the strike target to one end of the tea tray and the other end to mains ground? (ie. the tray is between the target and the mains wires).
Yes that's exactly it, though something bigger than a tea tray would be preferable. :/
I don't think the exact order of the connections makes much of a difference. Most of the noise from a Tesla coil is in the 10s of MHz, where the tea tray is small compared to a wavelength.
Recently there has been talk of an inductively loaded breakout point. Basically putting a tiny Tesla coil on top of your main coil. The inductance acts as a buffer between the topload capacitance and any arcs to ground, which significantly reduces the amount of HF noise generated. It is still experimental but seems to give good results.
Re: Strike target grounding
fungus, Sun Jun 22 2014, 11:14AM
One wave of light would be 30m at that frequency. Electricity is a bit slower...but yeah, a 30m tea tray would be difficult to find/install.
So what counts? The total mass of metal? Capacitance is usually about surface area. I don't have a lot of space ... I guess I could stack a couple of tea trays on top of each other if it helps.
Is there a thread on this subject?
How about a coil of wire between the strike target and the tea tray to take the edge off the pulses? (Or between the tea tray and mains ground?) I've got some magnet wire left, I could wind some around a piece of pipe.
I know it's a lot of questions but I don't really have a feel for this stuff and no way of measuring anything.
fungus, Sun Jun 22 2014, 11:14AM
Steve Conner wrote ...
Yes that's exactly it, though something bigger than a tea tray would be preferable. :/
I don't think the exact order of the connections makes much of a difference. Most of the noise from a Tesla coil is in the 10s of MHz, where the tea tray is small compared to a wavelength.
Yes that's exactly it, though something bigger than a tea tray would be preferable. :/
I don't think the exact order of the connections makes much of a difference. Most of the noise from a Tesla coil is in the 10s of MHz, where the tea tray is small compared to a wavelength.
One wave of light would be 30m at that frequency. Electricity is a bit slower...but yeah, a 30m tea tray would be difficult to find/install.
So what counts? The total mass of metal? Capacitance is usually about surface area. I don't have a lot of space ... I guess I could stack a couple of tea trays on top of each other if it helps.
Steve Conner wrote ...
Recently there has been talk of an inductively loaded breakout point. Basically putting a tiny Tesla coil on top of your main coil. The inductance acts as a buffer between the topload capacitance and any arcs to ground,
Recently there has been talk of an inductively loaded breakout point. Basically putting a tiny Tesla coil on top of your main coil. The inductance acts as a buffer between the topload capacitance and any arcs to ground,
Is there a thread on this subject?
How about a coil of wire between the strike target and the tea tray to take the edge off the pulses? (Or between the tea tray and mains ground?) I've got some magnet wire left, I could wind some around a piece of pipe.
I know it's a lot of questions but I don't really have a feel for this stuff and no way of measuring anything.
Re: Strike target grounding
fungus, Sun Jun 22 2014, 08:41PM
Or would it need a ferrite...?
fungus, Sun Jun 22 2014, 08:41PM
fungus wrote ...
How about a coil of wire between the strike target and the tea tray to take the edge off the pulses? (Or between the tea tray and mains ground?) I've got some magnet wire left, I could wind some around a piece of pipe.
How about a coil of wire between the strike target and the tea tray to take the edge off the pulses? (Or between the tea tray and mains ground?) I've got some magnet wire left, I could wind some around a piece of pipe.
Or would it need a ferrite...?
Re: Strike target grounding
fungus, Mon Jun 23 2014, 02:30PM
Anybody have any ideas? Right now it's freaking out everything in the room when it runs.
My mouse locks up, the monitor flickers, the Arduino has to be unplugged and plugged in again. Not good.
I've tried attacking a large metal tray to the wire. I've put lots of ferrite on the wire from target to GND, they might have helped a bit...but not much.
Without the ground connection target the sparks are leaping off all over the place after they hit the target. I already set my table on fire.
fungus, Mon Jun 23 2014, 02:30PM
Anybody have any ideas? Right now it's freaking out everything in the room when it runs.
My mouse locks up, the monitor flickers, the Arduino has to be unplugged and plugged in again. Not good.
I've tried attacking a large metal tray to the wire. I've put lots of ferrite on the wire from target to GND, they might have helped a bit...but not much.
Without the ground connection target the sparks are leaping off all over the place after they hit the target. I already set my table on fire.
Re: Strike target grounding
Steve Conner, Mon Jun 23 2014, 03:32PM
This is more or less what I'd expect from running a DRSSTC on a table in an apartment.
Steve Conner, Mon Jun 23 2014, 03:32PM
fungus wrote ...
My mouse locks up, the monitor flickers, the Arduino has to be unplugged and plugged in again. Not good... I already set my table on fire.
My mouse locks up, the monitor flickers, the Arduino has to be unplugged and plugged in again. Not good... I already set my table on fire.
This is more or less what I'd expect from running a DRSSTC on a table in an apartment.
Re: Strike target grounding
fungus, Mon Jun 23 2014, 04:06PM
I'm not even making big sparks yet. It's on minimal power and a 1" gap.
fungus, Mon Jun 23 2014, 04:06PM
Steve Conner wrote ...
This is more or less what I'd expect from running a DRSSTC on a table in an apartment.
This is more or less what I'd expect from running a DRSSTC on a table in an apartment.
I'm not even making big sparks yet. It's on minimal power and a 1" gap.
Re: Strike target grounding
Steve Conner, Mon Jun 23 2014, 06:50PM
The best thing you can do is lose the strike target and just make streamers to air. A 1" gap is actually worse than a larger one, as a shorter gap generates more high frequency EMI.
Steve Conner, Mon Jun 23 2014, 06:50PM
The best thing you can do is lose the strike target and just make streamers to air. A 1" gap is actually worse than a larger one, as a shorter gap generates more high frequency EMI.
Re: Strike target grounding
fungus, Mon Jun 23 2014, 07:38PM
I think you may be right.
I just gave it a blast at full power with no strike target and nearly jumped out of my skin. The streamers were scarily long, I didn't even tune the primary yet...
I admit I cowered.
But ... nothing in the room flickered or glitched.
That definitely seems to be the way to go.
Thanks for the help!
fungus, Mon Jun 23 2014, 07:38PM
Steve Conner wrote ...
The best thing you can do is lose the strike target and just make streamers to air.
The best thing you can do is lose the strike target and just make streamers to air.
I think you may be right.
I just gave it a blast at full power with no strike target and nearly jumped out of my skin. The streamers were scarily long, I didn't even tune the primary yet...
I admit I cowered.
But ... nothing in the room flickered or glitched.
That definitely seems to be the way to go.Thanks for the help!
Re: Strike target grounding
fungus, Mon Jun 23 2014, 08:14PM
A week trying to figure out how to set up a strike target, and... you don't need one!
I feel like such a clod sometimes.
Let this thread stand as a warning...
(Now I just need to get the Arduino control working (basically done), incorporate the smaller sparkers, and ... get to work programming my musical masterpiece!)
fungus, Mon Jun 23 2014, 08:14PM
A week trying to figure out how to set up a strike target, and... you don't need one!
I feel like such a clod sometimes.
Let this thread stand as a warning...
(Now I just need to get the Arduino control working (basically done), incorporate the smaller sparkers, and ... get to work programming my musical masterpiece!)
Re: Strike target grounding
Graham Armitage, Mon Jun 23 2014, 09:18PM
I built the MiniBrute a couple of years ago and had the same problems you are experiencing. I had everything grounded to the mains ground wire - base of secondary, strike ring and a strike object. Whenever it hit the strike object the USB on the laptop would be hosed, TV's go berserk. Just way to much EMF noise. Following advise from others here I now try and prevent the arcs from striking any grounded object. Strikes to the basement concrete floor are fine, and the strike ring is just for added protection. I keep the breakout long enough and pointed up so it never wants to hit the strike ring. The concrete is more of an indirect ground.
For demo's I have a small torroid on plastic stick as a strike target. The streamers hit that and it looks good, but EMF is not an issue and current draw is no where near that of a true ground strike. I can run a laptop 10ft from the coil (throwing 34" streamers) without any problems. One ground strike though and I have to reboot the machine.
I had to play around with the setup in my environment and see what works. I didn't want to depend on RF grounds or anything I may not have at a school or somewhere I was doing a demo.
Graham Armitage, Mon Jun 23 2014, 09:18PM
I built the MiniBrute a couple of years ago and had the same problems you are experiencing. I had everything grounded to the mains ground wire - base of secondary, strike ring and a strike object. Whenever it hit the strike object the USB on the laptop would be hosed, TV's go berserk. Just way to much EMF noise. Following advise from others here I now try and prevent the arcs from striking any grounded object. Strikes to the basement concrete floor are fine, and the strike ring is just for added protection. I keep the breakout long enough and pointed up so it never wants to hit the strike ring. The concrete is more of an indirect ground.
For demo's I have a small torroid on plastic stick as a strike target. The streamers hit that and it looks good, but EMF is not an issue and current draw is no where near that of a true ground strike. I can run a laptop 10ft from the coil (throwing 34" streamers) without any problems. One ground strike though and I have to reboot the machine.
I had to play around with the setup in my environment and see what works. I didn't want to depend on RF grounds or anything I may not have at a school or somewhere I was doing a demo.
Re: Strike target grounding
Sigurthr, Tue Jun 24 2014, 04:03AM
FWIW I have had excellent luck protecting household devices by using Class-Y capacitors between all three conductors. I use 300V 100nF Class-Y2 caps (but I'm on 120V mains - don't use these for 240v!) between Live and Neutral, and between Live and Earth, and Neutral and Earth. I've one set of caps set up near the TC, and another set at the outlet where the home electronics are plugged in. I've been able to run my 3kW CW SSTC (280KHz) in the house without frying anything as a result. I do have a dedicated ground rod and grounding cable, but the cable is more than 6 meters long, so everything is tied into mains ground as well.
Sigurthr, Tue Jun 24 2014, 04:03AM
FWIW I have had excellent luck protecting household devices by using Class-Y capacitors between all three conductors. I use 300V 100nF Class-Y2 caps (but I'm on 120V mains - don't use these for 240v!) between Live and Neutral, and between Live and Earth, and Neutral and Earth. I've one set of caps set up near the TC, and another set at the outlet where the home electronics are plugged in. I've been able to run my 3kW CW SSTC (280KHz) in the house without frying anything as a result. I do have a dedicated ground rod and grounding cable, but the cable is more than 6 meters long, so everything is tied into mains ground as well.
Re: Strike target grounding
fungus, Tue Jun 24 2014, 07:06AM
I'm not sure how much of it is due to the wires and how much is RF.
At one point I had the secondary and strike target completely disconnected from any ground and I still had problems.
fungus, Tue Jun 24 2014, 07:06AM
Sigurthr wrote ...
FWIW I have had excellent luck protecting household devices by using Class-Y capacitors between all three conductors.
FWIW I have had excellent luck protecting household devices by using Class-Y capacitors between all three conductors.
I'm not sure how much of it is due to the wires and how much is RF.
At one point I had the secondary and strike target completely disconnected from any ground and I still had problems.
Re: Strike target grounding
Hydron, Tue Jun 24 2014, 11:22AM
Has anyone here actually looked at what makes it onto the mains from TC usage? Probably varies a bit depending on the mains grounding scheme used, but shouldn't be hard to chuck a scope across the mains to check (obviously this should be done with care). Unfortunately my coil is in pieces right now, otherwise i'd have a look.
What I can say about my DRSSTC is that I haven't had any issues with other devices in the house using just a standard line filter and a short ground stake (it has mains earth, ground stake, secondary base and strike rail all bonded to the large heatsink the bridge is mounted on). Here in New Zealand we have an earth stake per house, with earth and neutral also bonded at the switchboard, which should help keep the noise between earth and phase/neutral reasonable.
Hydron, Tue Jun 24 2014, 11:22AM
Has anyone here actually looked at what makes it onto the mains from TC usage? Probably varies a bit depending on the mains grounding scheme used, but shouldn't be hard to chuck a scope across the mains to check (obviously this should be done with care). Unfortunately my coil is in pieces right now, otherwise i'd have a look.
What I can say about my DRSSTC is that I haven't had any issues with other devices in the house using just a standard line filter and a short ground stake (it has mains earth, ground stake, secondary base and strike rail all bonded to the large heatsink the bridge is mounted on). Here in New Zealand we have an earth stake per house, with earth and neutral also bonded at the switchboard, which should help keep the noise between earth and phase/neutral reasonable.
Re: Strike target grounding
fungus, Tue Jun 24 2014, 11:47AM
I've just been tuning the primary a bit, here's some pics:
They're stills from this video:
For scale, the toroid is 15cm (6 inches) across. That makes the streamers 12 inches or so.
I don't know exactly how many volts that is.... but this room is NOT big enough for the both of us.
fungus, Tue Jun 24 2014, 11:47AM
I've just been tuning the primary a bit, here's some pics:
They're stills from this video:
For scale, the toroid is 15cm (6 inches) across. That makes the streamers 12 inches or so.
I don't know exactly how many volts that is.... but this room is NOT big enough for the both of us.
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