Planning my first DRSSTC / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Planning my first DRSSTC

previous 1 2 3 next

Move Thread

LAN_403

skawesome

Tue Jun 01 2010, 01:26PM

Registered Member #2861 Joined: Sun May 16 2010, 08:34PM
Location: Bavaria
Posts: 10

sry for double post, but i dont know how to upload an image in an edited post.

1275398770 2861 FT89335 Dimmer Schematics

Goodchild

Tue Jun 01 2010, 03:00PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Steve McConner wrote ...

Goodchild wrote ...

Sorry but you can't use a SCR like circuit with a doubler, you need to input AC to the doubler in order for it to double the voltage.

Yeah you can! Just replace the two diodes in the doubler with SCRs. It worked for me.

Or you can use diodes in the doubler and insert a triac in series with the AC input, it amounts to the same thing.

I've built two SSTCs with the DC bus voltage controlled by SCRs in this way.

Cheap lamp dimmers won't work, because the rectifier load is so non-linear. A professional dimmer rated for reactive loads might work, but I built my own phase angle controllers with hard firing.

Ya you can do that, I was talking about feeding DC into a doubler, guess what I said was a little confusing.

skawesome

Sun Aug 22 2010, 10:27PM

Registered Member #2861 Joined: Sun May 16 2010, 08:34PM
Location: Bavaria
Posts: 10

Hi,

I'm almost finished with my DRSSTC. Pictures are in the attachment. :)

But I have a problem with Steve Ward's DRSSTC Driver (1.3b). Excactly the part between IC1A and IC1B. Here is the diagram.
I'm not sure about he circuit consisting of R2, C3 and D7, but I think that it adds some delay to the interrupter signal to reset the flipflop. C3 gets charged across R2 until the voltage reaches the threshhold voltage of the IC1B. Then IC1B's output changes to low and resets the flipflop IC3A. In theory. In praxis the voltage across C3 never reaches the threshhold voltage of about 3V.
So i calculated how long it takes to charge C3 to 3V and got about 400Âµs as result. Isnt this much too long on-time for a DRSSTC?
I hope you can help me.

Regards,
skawesome

ScotchTapeLord

Sun Aug 22 2010, 10:50PM

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

Your coil looks very nice, but may be a bit overcoupled, as the primary envelopes a good portion of the secondary. You should probably raise the secondary up a bit to prevent flashover.

skawesome

Mon Aug 23 2010, 12:39PM

Registered Member #2861 Joined: Sun May 16 2010, 08:34PM
Location: Bavaria
Posts: 10

Thanks ScotchTapeLord!
Thats excactly what I'm going to do. The secoundary is adjustable in height.

But for my problem: I decreased C3 to 5nF. Calculated the threshhold voltage at IC1B is reached after 90Âµs. So I tested it with 100Âµs on-time and it works. With "works" I mean, that IC1B has some low-outputs with the frequency of the interrupter signal. But now the output of IC3A looks like the inverted interrupter signal. So I would have a duty cycle of about 90% for a DRSSTC. :-/
Any opinions on that?

Regards,
skawesome

HV Enthusiast

Mon Aug 23 2010, 10:52PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Coil looks great. The upper strike rail should also be discontinuous - can't tell from the photos if it is or not. And probably make the upper strike rail a bit wider in diameter. Don't want to get too close the secondary (esp. that high up) and have arcing from secondary to strike rail. That would kill the secondary in a hurry.

And i agree. Its probably overcoupled. Just as a comparison, my miniBrute coil's bottom of the secondary is even with the top turn of the primary.

Just compare coupling of already proven DRSSTCs, and use the MANDL CALC program to come up with a similar geometry. This will provide a good starting point.

Martin King

Mon Aug 23 2010, 11:02PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

EastVoltResearch wrote ...

The upper strike rail should also be discontinuous - can't tell from the photos if it is or not.

Upper left hand side of the photos you can see the break. Nice to see that he's gone for red led's rather than the blue that everyone seems to use these days

Martin.

skawesome

Mon Aug 23 2010, 11:14PM

Registered Member #2861 Joined: Sun May 16 2010, 08:34PM
Location: Bavaria
Posts: 10

Thanks EastVoltResearch. :)
Yes, the strike rail is discountinous. You can see it on the left of the photos. I hope the diameter is big enough, otherwise I would have to make a new primary attachment. :/

With this configuration the coupling is about 18%. If I set the coil 5cm higher, the coupling will be 13%. That should work, I think. These values were calculated with JavaTC, but I will also try MANDL CALC.

Edit:
Google found no tesla coil calculator named MANDL CALC. Where do I find it?

HV Enthusiast

Tue Aug 24 2010, 11:34AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Not sure what you mean by 15 or 18% coupling. Usually its given as a k factor.

MANDK is a very powerful program for calculating coupling based on different types of the most common geometries. Its command line only, but works fantastic.

See attached.

]mandk.zip[/file]

skawesome

Tue Aug 24 2010, 02:05PM

Registered Member #2861 Joined: Sun May 16 2010, 08:34PM
Location: Bavaria
Posts: 10

18% -> 0.18 ?
I have seen k in both ways: xx% and 0.xx. Is xx% not usual here?

Uhm.. I think the .zip is about ATTiny stuff as far as I identify.
I found MANDK anyway, but it doesn't run on my computer, because my OS is a 64-bit version.

Edit:
Updates! The board works and I connected the driver to the IGBT. Made two pictures of the gate signal (unfortunately with my mobile phone). Please give some comments on that because I don't know how I should estimate the signal.
[Pictures are in the next post, cause I can't upload them in an edited post.]

previous 1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob