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Marko's DRSSTC v1.1

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Marko

Fri Jan 12 2007, 01:41AM

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

Hi everyone over here

I've done some work on a new DRSSTC these holydays. It's practically a whole new coil, secondary and control electronics are only from previous mockup.

I hammered a piece of brass in shape for driver board holder.
THe wide part will also act as an heatsink for bridge rectifier and as single ground point.

This is another piece of brass. It will be a spine for new H-bridge.

My heatsinks of choice. Cheap Spire CPU heatsinks, with threads engraved in their backs.

This is how I etched the board for H bridge. I found some old nail varnish my mom threw away. It was quick drying and soft when dry so it was perfect for engraving. I used sticky tape only for larger parts.

With my primitive etching techniques I couldn't get statisfactionary clearance between copper, so I forced the etching for 2 hours hoping acid will eat through 'edges'. But I ended with lots of small holes in board... luckily just cosmetic.
Board is double sided, and planes are used separately for DC supply to nullify parasitic inductances. I also tinned them, and put large blobs of cheap high-lead solder in places where I needed physical strength and smaller resistance.

Bridge outputs are used with both sides of the clad in paralell.

Some 30N60's soldered on. Resistors, diodes, TVS and stuff are from other side.

Brass is hammered and everything is bolted together making one pretty robust construction.

Front side populated. I'l use flat cables to connect gate drive and CT's to the board since they are pretty practical and low inductance.
I hoarded the board with decoupling caps. I put two sets of CT's on board in case I need them.

I made this casing in meanwhile. Board and bridge are shown in final arrangement. Secondary is shown in behind. I now need a nice primary form for 6mm copper pipe.

And yeah, bridge needs a proper high current capacitor... I even left exact space for vishay 76*146mm standard cap, but highest voltage I could get here was 100V 21000uF...

I'l also (ofcourse) add a nice acrylic dashboard, and then wire all things up.

I have to wait for toroid to dry it's polyester and most things will be done..

This is how I drilled holes for connectors... I taped a piece of perfboard ona desired place and followed the holes... But, it went very wrong first two tries, until I figured to use large piece of board with lots of tape to hold it in place.

update 13.01.07

toroid

For my top toroid connection, I used a small brass plate wich I can solder the wire to, and it seemed great.

I started thinking about doing the same to the bottom, but then I remembered those red-hot induction heater nuts!
Since this is going to be basically in middle of my primary, I made some cuts in it as shown on pics. I'm going to use weakly magnetic stainless steel screw for it.

I don't know how good idea is it, I can only hope coupling and RMS current will be low enough. Any toughts on it anyone?

23.1. ...

Some more construction pics. My tripod has died recently beyond fixing. Pics are much uglier now :(

I put two 1000uF 400V caps in paralell as bridge flters.
It's not much, 150 joules, but will be somewhere near lower limit of 20 bang energies.
They also don't look like they are rated forextreme pulse discharges.
I hope to get a real cap at once.

I use my old inty for this coil... it's the only thing that always worked perfectly no matter of anything!

The bent plexi dashboard has a michrophone connector for inty, plus two scope BNC's for tuning. (primary current and drive signal).

I have enough pipe for the primary... just need a good supports for it.

Hot wire plexi bender and cuter. (cutter is just a piece of wire suspended between two wooden sticks, works beautifully!)

These were pretty ugly after cutting, but then I managed to screw them together (through pre-drilled holes) and polish until perfection. I needed to use 3mm plexi as anyting thicker is tedious to bend.

Then I glued them together to get 2mm displacement. There are 5 of these 'displacements' so I needed to have holes like 10mm spread.

Pipe screwed in. It's nice to finally have a proper primary.
Second pic is mains connector and a fuse.

[Edit: Please don't mess with the formatting of the board]

11.2: so here is the coil, and ghetto MMC. Toroid is somewhere at limit of looking silly.. I hope it will do it's work at least. Just need to screw everything in place and fire it up!

13.3.07: First light, sort of. Ceramic caps are terribly undeperforming considering the power level, so back to the drawing board about them.

3.6.07. new CDE942C20P15K MMC:

New updates!

Zero current switching looks perfect.
The primary current on pic is 100A div, 120us. It grows, attempts to heterodyne 3 times and freewheels out after turned off.
Some small 20cm arcs from toroid for now.

teravolt

Fri Jan 12 2007, 04:34AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Firkragg I like your work can't wate to see the final product

ragnar

Fri Jan 12 2007, 04:48AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Marko, I love the heavy-duty brasswork and some very well designed copper plane. Can't wait to see it in action! =)

Part Scavenger

Fri Jan 12 2007, 03:17PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

That thing is beautiful! Great work!

Daniel Uhrenholt

Fri Jan 12 2007, 10:18PM

Registered Member #125 Joined: Fri Feb 10 2006, 01:52PM
Location: Aalborg, Denmark
Posts: 155

Nice Work!

I like the CPU heatsinks, time for me to go dumpster diving again

Good luck with it.

Cheers, Daniel

Marko

Sat Jan 13 2007, 12:22AM

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

Thanks guys

I have the toroid finished, and I'l post pics of it tommorow here.. One more pic now.

Now, I have to find some 3mm acrylic...

And yeah, have to get my signal generator fixed, so I can test the new toroid and finally probe that beastie fulbridge.

Steve Ward

Sat Jan 13 2007, 01:58AM

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

Nice clean work indeed.

One thing i haven't figured out is, where are your electrolytic storage caps for the H-bridge?

Marko

Sat Jan 13 2007, 10:26AM

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

where are your electrolytic storage caps for the H-bridge?

I don't have any screw terminal caps of that voltage, although I left space for 76*146mm vishay cap. (holes on left side of board).
I have some 100V 21000uF caps but I would have to stack 4 of these to make them work.

I used 1000uF 400V solder therminal caps before, and I can bolt two there if really needed, although I don't believe anymore they are rated for that high peak currents.

PS: update: toroid...

And, how do you guys generally fix your secondary base? while having a neat ground connection and easily movable secondary?

Steve Conner

Sat Jan 13 2007, 08:59PM

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

This is how I fixed my secondary base. Conductive metals like copper and brass really don't induction heat much.

Marko

Sat Jan 13 2007, 09:28PM

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

Thanks a bunch Steve... I hope this brass plate will be good enough.

Next week I'm going for some 3mm acrylyc, finally a test for my new hot-wire bender.

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