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Ryan

Wed Nov 17 2010, 04:39AM

Registered Member #1606 Joined: Fri Jul 25 2008, 02:40PM
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Posts: 71

Hi everyone,

I'm testing out my first coil and it doesn't seem to be working. The board was built by somebody else, and has been tested before (it worked). Whats wrong with mine? I have 12v dc running into the board as an input, 2 wires running from my board to my primary and the 2 wires from the secondary are running to stationary electrodes with a 1/2" gap (just off to the right of the frame). There is no toroid in this setup. The board is powered as the LED lights up, and I can hear a high pitch sound change when I turn the interuptor knobs. Is 12v not enough input? Is my primary too big/ far away from the secondary to transfer energy properly? The secondary is approx 10"x 4". 32g wire.

Ryan

ScotchTapeLord

Wed Nov 17 2010, 04:52AM

Registered Member #1875 Joined: Sun Dec 21 2008, 06:36PM
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Posts: 635

The bottom of your coil has to be grounded.

Your board doesn't seem to have anything to adjust the frequency, but I don't see any particularly obvious feedback system.
If that is a primary tank capacitor, then does that make this DRSSTC?

Do you have any specifications at all? What topology is this? What is the primary tuned to? What is your secondary Fres?

Ryan

Wed Nov 17 2010, 04:58AM

Registered Member #1606 Joined: Fri Jul 25 2008, 02:40PM
Location:
Posts: 71

The topology is in the picture.

Based on Tesla Map, the coil is tuned to 331khz. There is an interuptor at the bottom of the board with a pulse and width dial. The primary is 1/4" copper pipe.
]noob.pdf[/file]

Nicko

Wed Nov 17 2010, 06:26AM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

Ryan wrote ...

The topology is in the picture.

Based on Tesla Map, the coil is tuned to 331khz. There is an interuptor at the bottom of the board with a pulse and width dial. The primary is 1/4" copper pipe.

Looking at the schematic, the HT is generated from rectified mains - looking at your setup, you only have 12VDC going into the board - no mains so no HT, so you are powering the logic but not the half bridge, so no sparks. It uses secondary feedback but I can't see if the CT is on the PCB. Also you are using the most feeble wires to connect the primary to the board - if your HT was working, I suspect those little wires would melt - they will be trying to carry 10s of amps... You'll see the logic LED light & hear the GDT buzz because of the 12V supply, but there seems to be nothing for the half-bridge to switch. Also, there is no primary current limiter in the schematic.

There should be a transformer on that board and the board should take US mains directly onto it - how good is your electronics? Can you read a schematic like the one you posted?

Cheers

Ryan

Wed Nov 17 2010, 02:13PM

Registered Member #1606 Joined: Fri Jul 25 2008, 02:40PM
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Posts: 71

How do I ground the coil, and to where? Does one lead from the secondary have to connect to a lead from the primary like an automotive coil? There is an "Earth" connection on the board with no tab soldered to it, can I connect the secondary lead there? I only want to use this coil with a spark gap, no toroid.

Thanks, Ryan

Ryan

Wed Nov 17 2010, 02:31PM

Registered Member #1606 Joined: Fri Jul 25 2008, 02:40PM
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Posts: 71

Hmm ok I'll switch out my primary leads, I didn't know that the primary would draw that many amps. As for the schematic, I come from an automotive back ground and while I can read a detailed schematic, that one is beyond my scope of understanding, hence why somebody else built the board on my behalf. The transformer for household ac voltage was left off because this board will only be ran from 12v or 24v dc. Where I have the 12v hooked in too, I assume that is a diode and I'm basically bypassing that with my connections? aka ac current would be otherwise be behind that diode if I had a transformer? The current limiter issue, I really don't know.

ScotchTapeLord

Wed Nov 17 2010, 04:47PM

Registered Member #1875 Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635

The 12V is for the control circuit and the power circuit needs the mains line. You can use your 12V to directly to the electronics past the diodes like you are, but you'll need the mains AC on J3 and J4. Also, for secondary feedback, you'll need to run the secondary's wire through the transformer labeled "CT" in the schematic. It must be one of those CTs on the board. You can figure out which one it is by seeing how many connections it makes with the board/how many separate windings it has. The CT will (probably) only have two connections to the board and one set of windings. The issue here is that the secondary base wire will probably arc to other things on the board with this configuration, so you'll need to attach some HV insulated wire to your secondary's wire to run through the CT and over the board. The loose end of that wire (the end not connected to the secondary) must then be grounded to, well, the ground. For a lower power coil, many people use the nearest mains outlet ground, but clamping to a copper drainpipe or sticking a rod into dirt are probably better ideas safety-wise.

Tesla coils aren't typically meant for triggering tiny spark gaps. In fact, a continuous ground strike (which is what you're trying to do, since one of the electrodes in your setup has to be directly connected to the ground) changes the frequency of the coil and that will bring down the feedback frequency. This could potentially lower the frequency so much that the primary will demand so much current that it could destroy your circuit.

If you really want this type of spark then I recommend not using secondary feedback.

Coronafix

Wed Nov 17 2010, 08:51PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

That looks like only the driver section of what you need.
There should be a half bridge attached to that driver then the half bridge actually attached to the mains and the primary coil.
You should do a lot more research before you attempt to power this thing up. You'll need a variable transformer and an oscope to test it too.

Nicko

Wed Nov 17 2010, 09:54PM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

I just realised that this is an old Tom Blitch design (I think he was banned from 4HV after a slanging match).

You really need to learn a bit more of the basics - where did you get this stuff from?

Cheers

Ryan

Wed Nov 17 2010, 10:03PM

Registered Member #1606 Joined: Fri Jul 25 2008, 02:40PM
Location:
Posts: 71

Nicko, it is infact a Tom Blitch design. He built the board and sold it to me. I told him what I wanted to do with it (run 12-24v input dc) and he said that would work for me... but.. apparently it wont.. I really don't know a whole lot about the board or operation of these coils hence why I purchased the board and wanted to make the rest myself. If the board is missing a bunch of pieces then I'm really outa luck.. I paid 100 bucks for it..

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