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Jrz126

Fri Sept 01 2006, 07:01PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

I started soldering the cap bank yesterday, its going surprisingly well considering I'm attaching 120 caps onto a 6"x9" pcb. Hopefully I dont regret not hi-pot testing the bare pcb...

My girlfriend and I were heading out to get something to eat and we drove past this huge microwave sitting at someone's curb. I went back later and picked it up. I'm not sure of the wattage, but it has a huge transformer in it. Is there anything special that I have to do to use it for my OLTC? or even a link to how the transformer operates would be helpful. I dont quite understand how it works.

Steve Conner

Sun Sept 10 2006, 11:32PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Hi guys

I found some high resolution pictures of the cap bank on my old OLTC2 coil:

Marko

Mon Sept 11 2006, 12:32PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I always liked steve's pics..

And flat-cable for low L gate drive idea, hmmmmm

My girlfriend and I were heading out to get something to eat and we drove past this huge microwave sitting at someone's curb. I went back later and picked it up. I'm not sure of the wattage, but it has a huge transformer in it. Is there anything special that I have to do to use it for my OLTC? or even a link to how the transformer operates would be helpful. I dont quite understand how it works.

You have lots about mot's in aarchives adn around web.

Problem is that voltage is going to be somewhat too high for your use.

I would stay with 900V multiplier and resonant charger for now..

Jrz126

Fri Oct 06 2006, 01:42PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

Havent really had much time to work on it lately. Senior year is really kicking my butt at the moment.

I've got Steve's circuit all soldered up and I'm currently testing it.

I'm going to redesign a 2-turn primary using some copper flashing. I was able to pick up a roll of 10" x 20 ft. How high should I make it? I was thinking of going with 5" or 2.5". I'm going to use some of that weatherstip foam stuff (.5" thick, adheasive on the one side) to insulate and support the foil. Anything else that I need to consider in my design?

Also, I figure I'm going to have a Fres of 22-27khz once I get my toploads on there. (A 4"x24" to proect the top and then a 4"x36" for the streamers). Is there a problem with a very low Fres?

Hopefully I can finally get this thing running before it starts to snow...

Steve Ward

Fri Oct 06 2006, 04:25PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

For the primary i would probably go with 5" wide strip, just to keep the resistance down. The primary current is likely to bunch near the top of the ribbon due to higher coupling with the secondary, but all of the strip width will still contribute something beneficial. Also, beware that inductance calculations for using really wide flat conductors is somewhat tricky. Anyway, the inductance is smaller than that of a coil made with a dimensionless strip width. I picture the coil to really be composed of infinitely many coils, stacked upon each other. Since each coil has a coupling of slightly less than 1 with respect to the others, the inductance goes down (parallel inductors). Anyway, you are gonna have to fine tune the machine anyway, so just take a best guess at the primary size, and tune it by adding/subtracting tank caps.

There shouldnt be any problems/anomalies with the low operating frequency. Luckily, its not audible for humans.

Jrz126

Wed Oct 18 2006, 05:28PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

Well now that the week from hell (mid-terms, career fairs, etc) is over, I might have some time to work on it this weekend.

How much distance should I put between my primary and secondary? I was thinking about using an inch or 2. (the secondary is 12 3/8" in diameter).

Do I need to have the ends of secondary air tight? I have a couple of MDF disks attached to the ends, but I didnt put any sort of sealer over them.

Is there an alternative to the black drain pipe stuff for the topload construction? I'm having some trouble getting a 4" diameter piece into a 24" circle.

some pretty basic questions, but I figure it would be better to ask and get it right the first time.

Steve Ward

Wed Oct 18 2006, 06:53PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

I sealed my sonotube coil just to keep moisture out, but maybe make sure its dry before doing this so you dont seal too much moisture in. It probably doesnt matter too much though.

Im not sure on what spacing the primary should be, i would probably guess about 3" or so.

About the black drain pipe, it shouldnt be too hard to form. Make sure you have the right kind! They make rigid black drain pipe, and then the flexible stuff. I have regularly made 16" diameter toroids from the 4" stuff, so 24" should be relatively easy to form.

Jrz126

Fri Nov 03 2006, 01:18AM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

Finally got around to posting some pics of the cap bank...
here
closeup autofocus > my camera

The coil is starting to take shape as well...
coil

edit:
I was going to add more info last night, but a vhdl assignment was kicking my butt.
Anyhoo...
For my small toroid, how "tight" does it have to be to the top turns of the secondary to protect the top turns?
Is there a better method for attaching the aluminum foil to the toroid? My hot glue gun isnt quite up to the task, so I was wondering if there might be a spray-on adheasive that would be suitable?
Finally, what method do you use to hold the drain pipe in a circular shape? I'm having alittle trouble shaping the smaller toroid.

For The cap bank, I think I went alittle overboard on the spacings...hopefully they wont generate too much heat

I've come up with a possible design for the primary, so I think I might duck out of work early to go work on it.

Jrz126

Mon Nov 06 2006, 05:58PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

I finished the primary...
wood form
Inner tap 1
inner tap 2
I'm going to attach another piece of copper to this and have it run to the cap bank. I'm planning on just using a block of wood and some screws to hold it together.

the finished primary

???? I dont know how I convinced the girlfriend to do that...

The smaller secondary
The string was just temporary. I ran some drywall screws in through the pipe to secure it.
taped up
I'm currently attaching the foil. Hopefully I will have the foil finished up pretty soon. I was showing this to my professor the other day and he mentioned that I can borrow a frequency generator from school for tuning.

Would these be suitable for pulse transformer use? I'm going to try to order some sample inductors from them for a high power LED driver. Maybe get a couple of these while im at it.

Hopefully I will be making sparks soon

Steve Conner

Tue Nov 07 2006, 10:44AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The Coilcraft SD250-1 ought to do. It's not really that critical: I also got it to work with a common mode suppressor choke from a SMPS. The insulation between windings just needs to be good. And you probably want to dremel away that bit of the groundplane to get some more safety clearance

(if you haven't already)

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