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200KV PLUS voltage multiplier

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LAN_403

Sparks

Sat Aug 08 2009, 09:49AM

Registered Member #2263 Joined: Mon Aug 03 2009, 04:57PM
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Posts: 20

Lutz, thanks, I have a little way to go with this. The introduction if rings is going to change the frame a bit but I have that figured out. Resistor network is really only what is holding me back at this point. I like the Idea of adding resistors through the VM. When you say they are added between the capacitors do you mean in parallel to the diodes (zigzag up the tower) or two vertical chains up both sides of the tower?

Harry, I guess I could wind the resistors on plastic rod, they would look good too, calculating the length of wire and the thickness would be an impossibility for me though LOL If you hadn't already guessed I am fairly new to electronics

Proud Mary

Sat Aug 08 2009, 10:59AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Sparks wrote ...

Harry, I guess I could wind the resistors on plastic rod, they would look good too, calculating the length of wire and the thickness would be an impossibility for me though LOL If you hadn't already guessed I am fairly new to electronics

How to wind non-inductive resistors made simple.

Take any old piece of wire a foot long and fold it exactly in half, so that you now have a length doubled back on itself like a woman's hair grip six inches long.

Now take a pencil and mark exactly half way along its length. This is the point where you start winding, Now take the closed, folded end of your wire and press it to that point with your thumb nail to hold it in place.

Now take one of the free ends and wind it to the left. Then do the same with the other free end but winding it to the right. When you have wound all the wire onto the pencil hold it in place with a few pieces of tape and have a look at your handiwork.

You'll see that the winding changes direction - or 'sense' - when you reach the point where the wire is folded back on itself at the centre of the pencil.

What is all this about? Effectively, you have two coils - inductors - which are equal and opposite in every way, so the magnetic field of one cancels out the magnetic field of the other. This is why this technique is called 'non-inductive winding'.

If you simply wound all your resistance wire onto a plastic rod in the same direction it would be both a resistance and an inductance - what we might call 'a lossy inductor' because of the resistance - which is absolutely not what you want at all in this kind of circuit.

Sparks

Mon Aug 10 2009, 02:36PM

Registered Member #2263 Joined: Mon Aug 03 2009, 04:57PM
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Posts: 20

I think you could still use a plastic rod but you would have to wind two layers, one over the other so that the magnetic fields produced by each layer cancel out.

I was looking at this

circuit design to see how to attach the resistors, they are put in series with the diodes. Its a real shame I didn't know this earlier because I would have put them at the ends of the diodes before potting them in wax. That way I would have had my diode/resistor all in one.

Is there another way I could attach the resistors because this is going to mess up my design

MinorityCarrier

Mon Aug 10 2009, 04:56PM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

Carefully read what Harry wrote about winding non-inductive resistors.

Herr Zapp

Mon Aug 10 2009, 05:50PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Sparks -

I think you may have misinterpreted Harry's example of winding a non-inductive resistor. It's very simple - a single length of resistance wire, wound end-to-end on a cylindrical form, 1/2 the wire length wound right-hand twist, the second half of the wire wound left-hand twist (imagine RH and LH threaded rods or springs, placed end-to-end). The use of a pencil as a winding form was only so you could easily visualize the winding technique. After you understand the winding technique, you would design and wind a "real" resistor using resistance wire of the correct resistivity and length, wound on a plastic, phenolic, ceramic or glass form, with appropriate end contacts for terminating the resistance wire, and coated with an appropriate encapsulant to secure and insulate the wire, etc.

Regards,
Herr Zapp

Sparks

Tue Aug 11 2009, 01:08PM

Registered Member #2263 Joined: Mon Aug 03 2009, 04:57PM
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Posts: 20

OK sorry had visualised it differently, that's why a picture is worth a thousand words

Looking at the two images attached the one on the left shows the resistors in series with the diodes, whilst this would have been structurally easy when making the diodes it is now not so easy as it will result in poor structure (mechanically speaking)

I wanted to know if it would be OK to attach the diodes as in the image on the right?

Proud Mary

Tue Aug 11 2009, 01:10PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Herr Zapp wrote ...

Sparks -

I think you may have misinterpreted Harry's example of winding a non-inductive resistor. It's very simple - a single length of resistance wire, wound end-to-end on a cylindrical form, 1/2 the wire length wound right-hand twist, the second half of the wire wound left-hand twist (imagine RH and LH threaded rods or springs, placed end-to-end). The use of a pencil as a winding form was only so you could easily visualize the winding technique. After you understand the winding technique, you would design and wind a "real" resistor using resistance wire of the correct resistivity and length, wound on a plastic, phenolic, ceramic or glass form, with appropriate end contacts for terminating the resistance wire, and coated with an appropriate encapsulant to secure and insulate the wire, etc.

Regards,
Herr Zapp

Thank you, Herr Zapp: I hadn't realized that I'd been so vague!

Proud Mary

Tue Aug 11 2009, 01:22PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Sparks wrote ...

I think you could still use a plastic rod but you would have to wind two layers, one over the other so that the magnetic fields produced by each layer cancel out.

I'm not sure this is such a good idea, Sparks - large PDs are involved, and you'd have to put a lot of work into the insulation. Also, symmetry is a key feature of the NIR, and this is much easier for the amateur to achieve in the winding-from-the-centre technique, which, in any case is the method almost universally employed by manufacturers
of high quality parts. (NIRs are not cheap, which is why I have suggested making them yourself!)

And in amateur use, I really do think better results will be obtained by winding on dielectric cards - say the size of playing cards - of mica, or PTFE, for preference, but any good polymer where funds are an issue.

Don't take my word for it. Wind the resistors to different morphologies - the coil on the rod, or the flat card, and see which has the least inductance. Making a resistor into the shape of a solenoid is not a way of making life easy!

Sparks

Tue Aug 18 2009, 04:32PM

Registered Member #2263 Joined: Mon Aug 03 2009, 04:57PM
Location:
Posts: 20

In the rather bad quality sketch I have attached there is an alternative method of adding resistors to the vm tower. on the right I have showed the same method but retained the threaded support bar which connects the capacitors together. Will this work or is it necessary to remove the support bar and replace with a non conducting threaded bar?

CT2

Tue Aug 18 2009, 05:07PM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

If the "support bar" is threaded rod that conducts then no that won't work. What you've done is basically short out your resistors, current takes the path of least resistance, what looks more appealing then? A near 0 ohm piece of rod or hundreds of thousands of ohms of the resistor?

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