Small DRSSTC / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

Small DRSSTC

1 2 next

Move Thread

LAN_403

williamn

Fri Feb 10 2006, 06:10AM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

After viewing Reaching's mini coil, I now have the itch to build a smallish DRSSTC. The idea of being able to run it in the house without too much setup time or worry apeals to me. I am going to use a halfbridge of 40N60A4 IGBTs and 3000uf/200V worth of lytics. The hole shebang will fit on a 4"x5" PCB(bridge and all). No variac, the last interuptor I made(for my BigDRSSTC testcoil) worked very well with very fine adjustability, I will use something similar for this one too. Secondary specs are 3.5" x 8" wound with 34AWG. A unloaded Fres of approx 350Khz. I hope to make it a weekend thing. I have everything I need laying around. I shall call him Mini Me.

EDIT: 17/2/06 MiniMe is just about finished. I just have to make a few connections and it should be up and running. I will tune it up and take some pictures tonight.

EDIT: 20/2/06 Here is a video clip of the coil running. This was one of the earlier runs. (first full power run with no primary to secondary racing arcs.

Bennem

Sun Feb 12 2006, 05:23PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

Hi William, i too built a small DRSSTC with a full bridge of HGT1N40N60A4D igbts.....my secondary dia is 2.9 inch by 8.9 inch tall,32AWG wire, fres with torroid is about 300khz,with overcurrent/primary current feedback,it works great! giving 24 inch spark. good luck with your mini me!

williamn

Sun Feb 19 2006, 07:27PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

Here is my small DRSSTC build and ready to go. It works great and I have run it for quite long run times. I am using the 30N60A4 as I found a bunch of them while cleaning. I will post a link to a video today. I am trying to find a nice spun toroid for it, the one in the pic is dreadful.

Bennem

Sun Feb 19 2006, 08:11PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

It looks great William!
Did you use Primary current feedback?
What are your coil parameters?
Once again, nice looking coil!
look forward to seeing it in action!

williamn

Sun Feb 19 2006, 09:38PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

I use primary current feedback, anlong with OCD. I used Steve Ward"s #3 circuit, the only thing I changed was the OCD circuit(uses a different comparator) and the RC timing components on the flipflop. The halfbridge of 30N60s has two 1500uf 250V lytics and two ultrafast high current diodes to form a doubler. The MMC consists of 3 parallel strings of two serriesed 47nf 1500V LCR PE caps. So its 70nf 3KV. Everything is on one 4.5"x 4" PCB. I am really happy with the PCB layout, it could run a mutch larger coil. I built up the bridge traces with a ton of solder, then using MEK scrubbed off all of that nasty flux residue. The whole mess is stuffed inside an old stand I built sometime ago. I use a dual 555 timer setup(pwm) interuptor (no burst mode). I can adjust from 5usec to 200usec on time (in 10 turns) so I dont use a variac, which is my favorite part! Here is a 20ish inch strike picture. This coil is really durable, I have run it most of the weekend!
1140402722 55 FT0 Drsstc 20inch

[Edit: Fixed oversized picture]

JimG

Mon Feb 20 2006, 02:41AM

Registered Member #52 Joined: Thu Feb 09 2006, 04:22AM
Location: Austin TX
Posts: 57

What are the dimensions on your secondary and top load?

williamn

Thu Feb 23 2006, 03:46AM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

Secondary is 9" total length. It is elevated by a spacer 1.5". Torroid is 3.25"x9". Total hieght of the whole setup is just under 19". I have been fooling around with more primary capacitance. I think I nailed the coupling as I no longer get racing sparks or primary to secondary arcs at full power. I added another string of capacitors to bring total C up to 106nf. Length has improved a few more inches and now all the coil wants to do is strike the controls underneath. I have had too many strikes to the BNC jack already, so I am going to add the hardware cloth shielding method as Steve Ward has done with his coils. I also noticed the OCD comparator is quite sensitive to noise. I had to load down the CT with more resistance. I ordered one of those 12"x3" spun toroids from (shutter) infounlimited. I really like this coil.

Steve Ward

Thu Feb 23 2006, 07:32AM

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

Cool little coil. Looks like there are a lot of DRSSTCs out there now! I cant wait till i can work on TCs again

.

Oh, and the OCD should be pretty noise immune if you followed 2 details of the design. First, mount the main burden resistor right on the PCB. Second, you should have about 100 ohms after the full-wave rectifier, which will give the comparator input an impedance of 100 ohms now (instead of many MEG ohms as it would typically be). Also, adding some .1uF ceramics right at the pins of the comparator inputs really helps out. Before adding the 100R across the input, my comparator would trigger from the smallest amount of noise. The circuit as ive shown now is quite reliable on all of my coils (i only see it light up during ground strikes, as it should).

Dr. Drone

Tue Mar 14 2006, 06:17AM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

GimpyJoe

Tue Mar 14 2006, 02:45PM

Registered Member #316 Joined: Mon Mar 13 2006, 01:30PM
Location: Marietta, GA
Posts: 212

wow! That's a nice coil! Does the efficiency suffer with the smaller coil? What's your input power to get 35" arcs?

1 2 next

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