EMI filter?
Firnagzen, Sun Apr 29 2007, 05:35AMI was looking through the HvWiki earlier, and came across something at the bottom of the Solid state tesla coil page. It says that the secondary side grounding can be achieved through a EMI filter to the mains grounding.
Thing is, I've never heard of an EMI filter, and searching "EMI filter" on google just gives me a lot of websites and companies selling the things. Could someone elucidate me on this subject, or direct me to a site which would be helpful?
Thanks.
Ps. What kind of ratings would be needed for a EMI filter for a tesla, anyway?
Re: EMI filter?
..., Sun Apr 29 2007, 05:44AM
We usually rip them out of old junk, or buy them (since they are dirt cheap). I like the ones out of computer power supplies, as they provide a nice looking power connector for the project, and give you filtering
They are just a few caps/inductors, I don't think their values are too critical.
..., Sun Apr 29 2007, 05:44AM
We usually rip them out of old junk, or buy them (since they are dirt cheap). I like the ones out of computer power supplies, as they provide a nice looking power connector for the project, and give you filtering
They are just a few caps/inductors, I don't think their values are too critical.
Re: EMI filter?
Firnagzen, Sun Apr 29 2007, 05:53AM
Um, but what does the filter do? And can I use one for a tesla coil? Would special ratings be required?
Thanks.
Ps. Hmm, I've got an unused computer power supply knocking around. How to identify the filter section?
Firnagzen, Sun Apr 29 2007, 05:53AM
Um, but what does the filter do? And can I use one for a tesla coil? Would special ratings be required?
Thanks.
Ps. Hmm, I've got an unused computer power supply knocking around. How to identify the filter section?
Re: EMI filter?
Ken M., Sun Apr 29 2007, 06:16AM
From what I've gathered is, they are used to prevent feedback from the coil to the ac lines that might harm sensitive electronics, the ones from PC PSU's are right where the 3 prong plug is at.
Ken M., Sun Apr 29 2007, 06:16AM
From what I've gathered is, they are used to prevent feedback from the coil to the ac lines that might harm sensitive electronics, the ones from PC PSU's are right where the 3 prong plug is at.
Re: EMI filter?
Firnagzen, Sun Apr 29 2007, 06:39AM
Hm.
I've just had a look at that PSU, and what I've found is this: On the 3 prong plug, I found what (appears to be) a resistor connected across the two prongs and a 2.4uF 250V capacitor.
I'm somewhat doubtful that any of these is/are an EMI filter, and I've had a look at the circuit board, too. There's nothing which looks like an EMI filter. (I had a look at a site selling the things for some pictures. They all seem to be some weirdly shaped enclosed modules, right?)
So it seems like I'll have to buy one, any tips as to how to pick an EMI filter for grounding the secondary? (ratings, etc?)
Thanks.
Firnagzen, Sun Apr 29 2007, 06:39AM
Hm.
I've just had a look at that PSU, and what I've found is this: On the 3 prong plug, I found what (appears to be) a resistor connected across the two prongs and a 2.4uF 250V capacitor.
I'm somewhat doubtful that any of these is/are an EMI filter, and I've had a look at the circuit board, too. There's nothing which looks like an EMI filter. (I had a look at a site selling the things for some pictures. They all seem to be some weirdly shaped enclosed modules, right?)
So it seems like I'll have to buy one, any tips as to how to pick an EMI filter for grounding the secondary? (ratings, etc?)
Thanks.
Re: EMI filter?
cjk2, Sun Apr 29 2007, 06:14PM
What you have above is actually just the first stage of an EMI filter. A typical filter used in a SMPS will be a CLCL circuit or a CLC circuit. What you have above is the first C in a CLCL circuit. If you look at the board that was in that PSU case, you will find at least 1 more inductor(2 windings on a powered iron core) and a high grade capacitor.
Heres what a CLC circuit typically looks like.
cjk2, Sun Apr 29 2007, 06:14PM
What you have above is actually just the first stage of an EMI filter. A typical filter used in a SMPS will be a CLCL circuit or a CLC circuit. What you have above is the first C in a CLCL circuit. If you look at the board that was in that PSU case, you will find at least 1 more inductor(2 windings on a powered iron core) and a high grade capacitor.
Heres what a CLC circuit typically looks like.
Re: EMI filter?
Firnagzen, Mon Apr 30 2007, 09:55AM
Dang. And I clipped the wires to get the picture. Looks like I'll find another one. Thanks for the help, though!
On a slightly different note, how do I apply one to a tesla coil, anyway? As I understand it, the filter goes between the coil secondary's ground wire, and straight to mains ground. But that's two wires accounted for. There are five in the above schematic!
By the way... kpF? Kilo pico farads?
Firnagzen, Mon Apr 30 2007, 09:55AM
Dang. And I clipped the wires to get the picture. Looks like I'll find another one. Thanks for the help, though!
On a slightly different note, how do I apply one to a tesla coil, anyway? As I understand it, the filter goes between the coil secondary's ground wire, and straight to mains ground. But that's two wires accounted for. There are five in the above schematic!
By the way... kpF? Kilo pico farads?
Re: EMI filter?
uzzors2k, Mon Apr 30 2007, 02:07PM
The other 4 wires are AC input and output. Line/Neutral in and Line/Neutral out. kpF <= roflol, yeah I think he means 3nF.
uzzors2k, Mon Apr 30 2007, 02:07PM
The other 4 wires are AC input and output. Line/Neutral in and Line/Neutral out. kpF <= roflol, yeah I think he means 3nF.
Re: EMI filter?
Dr. Shark, Mon Apr 30 2007, 02:42PM
That would leave him with the secondary ground directly connected to mains ground and the filter not connected at all. Seriously, I also don't get how this would be connected but I _guess_ the secondary would not be connected to ground at all but to the power rails via the two 3nF capacitors. This way any interference would have to go through the choke.
Dr. Shark, Mon Apr 30 2007, 02:42PM
That would leave him with the secondary ground directly connected to mains ground and the filter not connected at all. Seriously, I also don't get how this would be connected but I _guess_ the secondary would not be connected to ground at all but to the power rails via the two 3nF capacitors. This way any interference would have to go through the choke.
Re: EMI filter?
IamSmooth, Mon Apr 30 2007, 06:15PM
I connected one for my coil. The EMI filters have amp ratings so make sure it can handle the current you plan to draw through your transformer.
I have my transformer ground connected to a rod in the ground. The input of the EMI is connected to the hot/neutral and ground. The output of the EMI is connected to the input to the transformer.
IamSmooth, Mon Apr 30 2007, 06:15PM
I connected one for my coil. The EMI filters have amp ratings so make sure it can handle the current you plan to draw through your transformer.
I have my transformer ground connected to a rod in the ground. The input of the EMI is connected to the hot/neutral and ground. The output of the EMI is connected to the input to the transformer.
Re: EMI filter?
CT2, Mon Apr 30 2007, 07:31PM
To connect it, it goes like this: There are three connections in and three connections out. There will be two for the 110VAC in (neutral and live) and then one for ground. On the other side there will be two for 110VAC out (live and neutral) and a ground connection. It just goes in series with the power to your coil.
CT2, Mon Apr 30 2007, 07:31PM
To connect it, it goes like this: There are three connections in and three connections out. There will be two for the 110VAC in (neutral and live) and then one for ground. On the other side there will be two for 110VAC out (live and neutral) and a ground connection. It just goes in series with the power to your coil.
Re: EMI filter?
Firnagzen, Tue May 01 2007, 04:11AM
But, direct quote from HVWiki http://wiki.4hv.org/index.php/Solid_State_Tesla_Coil (All the way to the bottom.) :
My understanding from this is that there is some way of using the EMI filter and the mains ground to totally eliminate the need for an RF ground at all. Is my understanding right, or does the wiki need a fix? And if my understanding is right, how?
Firnagzen, Tue May 01 2007, 04:11AM
But, direct quote from HVWiki http://wiki.4hv.org/index.php/Solid_State_Tesla_Coil (All the way to the bottom.) :
RF ground
...is directed just like any other tesla coil. Directly to mother earth or through an EMI filter to the power line's ground.
My understanding from this is that there is some way of using the EMI filter and the mains ground to totally eliminate the need for an RF ground at all. Is my understanding right, or does the wiki need a fix? And if my understanding is right, how?
Re: EMI filter?
CT2, Tue May 01 2007, 04:31AM
The EMI filter's ground is just the same ground as your house ground. This is because you hook up the ground to the green wire (ground) of your house wiring. The filter is suposed to stop interference from getting through it and into/out of what ever you have it hooked up to. You can hook a tesla coils secondary RF ground to your house's ground, or through a filter to the houses ground, doesn't matter because I'm pretty sure the filter only filters the line voltage and not the ground wire. But some people recommend against hooking up your tesla coils RF ground to your house' ground, I personally havent had any problems with doing that but my coils are small...
CT2, Tue May 01 2007, 04:31AM
The EMI filter's ground is just the same ground as your house ground. This is because you hook up the ground to the green wire (ground) of your house wiring. The filter is suposed to stop interference from getting through it and into/out of what ever you have it hooked up to. You can hook a tesla coils secondary RF ground to your house's ground, or through a filter to the houses ground, doesn't matter because I'm pretty sure the filter only filters the line voltage and not the ground wire. But some people recommend against hooking up your tesla coils RF ground to your house' ground, I personally havent had any problems with doing that but my coils are small...
Re: EMI filter?
ragnar, Tue May 01 2007, 05:03AM
Grounding the secondary to mains ground can be dangerous for a number of reasons:
If the ground isn't as low-impedance as it should be (reactive or just resistive), then devices connected to ground can float to high voltages.
Mains ground wires aren't made for carrying high-frequency RF currents. They'll get hot, and you can set the insulation on fire deep inside your walls. Maybe you can get away with it for small coils... but there's no guarantee. That's why I use a copper sheet as a floating counterpoise.
ragnar, Tue May 01 2007, 05:03AM
Grounding the secondary to mains ground can be dangerous for a number of reasons:
If the ground isn't as low-impedance as it should be (reactive or just resistive), then devices connected to ground can float to high voltages.
Mains ground wires aren't made for carrying high-frequency RF currents. They'll get hot, and you can set the insulation on fire deep inside your walls. Maybe you can get away with it for small coils... but there's no guarantee. That's why I use a copper sheet as a floating counterpoise.
Re: EMI filter?
..., Tue May 01 2007, 05:19AM
I should also point out that in that schematic of a line filter the grounds are drawn a little funny, all of the grounds must be connected together (not floating between a few caps) or you run a rick of a 'hot' chassis.
..., Tue May 01 2007, 05:19AM
I should also point out that in that schematic of a line filter the grounds are drawn a little funny, all of the grounds must be connected together (not floating between a few caps) or you run a rick of a 'hot' chassis.
Re: EMI filter?
Firnagzen, Tue May 01 2007, 05:37AM
Dang, and I was hoping that using a EMI filter would solve all the problems associated with grounding a tesla coil to a mains ground. Oh, well...
One last thing, though, what's a floating counterpoise? (Blackplasma mentioned this in his post.)
Firnagzen, Tue May 01 2007, 05:37AM
Dang, and I was hoping that using a EMI filter would solve all the problems associated with grounding a tesla coil to a mains ground. Oh, well...
One last thing, though, what's a floating counterpoise? (Blackplasma mentioned this in his post.)
Re: EMI filter?
..., Tue May 01 2007, 01:36PM
A counterpoise is just a large sheet of metal (preferably copper/aluminum) that you use as the ground. Because there is only an AC current, and it is at a very high frequency, the counterpoise acts like a capacitor in series with ground, and likewise the coil thinks it is grounded :)
..., Tue May 01 2007, 01:36PM
A counterpoise is just a large sheet of metal (preferably copper/aluminum) that you use as the ground. Because there is only an AC current, and it is at a very high frequency, the counterpoise acts like a capacitor in series with ground, and likewise the coil thinks it is grounded :)
Re: EMI filter?
Firnagzen, Wed May 02 2007, 09:54AM
Oh, I see. But I live in a high rise flat (Well, third floor, but you get the idea.), will a counterpoise still work? It'd be relative to the third floor, well, floor!
Firnagzen, Wed May 02 2007, 09:54AM
Oh, I see. But I live in a high rise flat (Well, third floor, but you get the idea.), will a counterpoise still work? It'd be relative to the third floor, well, floor!
Re: EMI filter?
uzzors2k, Wed May 02 2007, 10:15AM
Yepp. The counterpoise acts as a ground, so you don't need a real earth ground. It doesn't matter where you are.
uzzors2k, Wed May 02 2007, 10:15AM
Yepp. The counterpoise acts as a ground, so you don't need a real earth ground. It doesn't matter where you are.
Re: EMI filter?
Dr. Shark, Wed May 02 2007, 12:26PM
Whoa, this is getting confusing! The original question was about grounding the SECONDARY coil, the later post all address the PRIMARY side of the Tesla coil.
The filter from the first schematic is not "funny" but rather common practice with Class II devices like laptop PSUs which have two-prong plugs and no physical ground connection. They derive their ground through the so-called Y-capacitors from the AC mains. The point of this practice is exactly what we are trying to achieve here: Keeping noise out of the mains ground.
I don't know if connecting a Tesla Coil there would be a major safety hazard, so I'd like to hear a qualified comment on this.
Dr. Shark, Wed May 02 2007, 12:26PM
Whoa, this is getting confusing! The original question was about grounding the SECONDARY coil, the later post all address the PRIMARY side of the Tesla coil.
The filter from the first schematic is not "funny" but rather common practice with Class II devices like laptop PSUs which have two-prong plugs and no physical ground connection. They derive their ground through the so-called Y-capacitors from the AC mains. The point of this practice is exactly what we are trying to achieve here: Keeping noise out of the mains ground.
I don't know if connecting a Tesla Coil there would be a major safety hazard, so I'd like to hear a qualified comment on this.
Re: EMI filter?
Steve Conner, Wed May 02 2007, 01:13PM
Sorry, no qualified comments for liability reasons
Having said that, I have operated my DRSSTC in my third floor apartment without any trouble so far, by just connecting the secondary base to mains ground. I didn't use any kind of EMI filter, although it is good practice to use one. This picture was taken with it sitting on the table in the living room... Of course YMMV and I don't guarantee that what worked safely for me will work for you.
PS: All an EMI filter will really do, is distribute the RF from the Tesla coil evenly onto the live, neutral and earth wires, instead of sending it all down the earth wire. That may be good, as it would reduce the risk of flashovers between earth and the other wires, if they all have the same voltage. I tried to avoid putting RF through my mains wiring altogether, by connecting the secondary base to the ground right at the service entrance to my house.
Steve Conner, Wed May 02 2007, 01:13PM
Sorry, no qualified comments for liability reasons
Having said that, I have operated my DRSSTC in my third floor apartment without any trouble so far, by just connecting the secondary base to mains ground. I didn't use any kind of EMI filter, although it is good practice to use one. This picture was taken with it sitting on the table in the living room... Of course YMMV and I don't guarantee that what worked safely for me will work for you.
PS: All an EMI filter will really do, is distribute the RF from the Tesla coil evenly onto the live, neutral and earth wires, instead of sending it all down the earth wire. That may be good, as it would reduce the risk of flashovers between earth and the other wires, if they all have the same voltage. I tried to avoid putting RF through my mains wiring altogether, by connecting the secondary base to the ground right at the service entrance to my house.
Re: EMI filter?
Firnagzen, Wed May 02 2007, 01:28PM
I think I understand the concept of an EMIO filter much better now, thanks for all your help! But I think I'm just going to use a counterpoise, it seems easier!
I wonder if the HVwiki page should have a link to this thread?
Firnagzen, Wed May 02 2007, 01:28PM
I think I understand the concept of an EMIO filter much better now, thanks for all your help! But I think I'm just going to use a counterpoise, it seems easier!
I wonder if the HVwiki page should have a link to this thread?
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