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Spedy

Mon Oct 29 2007, 12:32AM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

Before I go and save up for parts for a SSTC, I want a couple of questions answered.

How do you implement a feedback antenna?

1) Are there full-wave rectifier "chips" available or will I have to wire together 4 diodes myself? which way would be more budget-friendly?

2) What are good sources for heat sinks? my local radio-shack only carries little tiny ones.... Or would it be simple enough to make my own?

3) What is the average cost for a small-ish SSTC? I'm thinking of using Steve's Micro SSTC circuit.

Thanks

...

Mon Oct 29 2007, 02:08AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

1. yes you can buy fullwave rectifiers, and the cost isn't really all that different than using discrete diodes. It would be called a 'bridge diode'
2. Ebay. You can also scavenge them out of old amps/etc, or use a nice big plate of aluminum or copper (don't use steel/brass, their thermal conductivity is crap) would work fine.
3. Depends on how much you are willing to scavenge, how long of a spark you need, and how cautious you are when you are running it. If you went to digikey and ordered all of the parts you need, it could break $100 easily. If you scavenge wire for the secondary, heatsinks, diodes, etc, sample the fets, and UCCs you could build one for free.

cheers!

Bauerb2

Mon Oct 29 2007, 02:13AM

Registered Member #973 Joined: Tue Aug 28 2007, 07:32PM
Location: Pittsburgh, PA
Posts: 66

Hello Spedy.

I have been where you are and i think i have some answers.

1) For a fullwave rectifier, i'd use 4 separate diodes rated appropriately (easier to find in junk electronics), but thats my opinion. they shouldn't cost much at all; both a fullwave rect. chip or 4 separate diodes shouldn't cost more than $3 all together.

2) I bought a big box of used computer heatsinks for $5 on eBay. I am currently using two pentium 3 heatsinks that came in the box for a full bridge of FETs. Iv'e checked radioshack as well but they dont have nice big ones, so i would check eBay or any other electronic store you can find.

3) I spent a grand total of maybe $70 for my whole SSTC. My design is almost like Steve's SSTC, but with a few more parts. All the parts i've bought include: Logic chips, op amps/comparators, 12 IRFP460 FETs, UF diodes, schottkys, gate drivers, pack of resistors, 32 AWG wire for secondary, and a 10 amp variac. The rest of the parts i got for free from either my basement (my dad is an electrician, so it helps...), or from old electronic parts (used TVs VCRs printers PSUs etc..)

It all depends on how much you want to spend. you can build it very cheap (almost free) if you know where to look for parts, or you can build a brand new shiny coil with brand new parts. Whatever floats your boat. I end up in the middle. i wanted it to perform well, so i bought parts, but i scavanged from old electronic junk people threw away in my neighborhood. By the way, i've bought all my parts from

Good luck!

-Andrew

Spedy

Mon Oct 29 2007, 03:15AM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

Thanks. I'll probably end up buying most of it, but I should be able to scavenge a bunch. My dad is a pack rat, we must have like 5 monitors and other assorted electronic bits in our 4-car garage. I can get Al or Cu sheet easy at Orchard Supply Hardware if they still have it, so I guess I'm set for heatsinks, all I will need is something to cut it with.

I should be able to get wire for the secondary easy. Is that thin wire from old microwaves good? If so, I'll be able to get some from a microwave from FreeCycle. If not, Magnet wire isn't that hard to get.

What do you recommend for the primary wire?

What is a good for a coil form? I have almost every size of PVC pipe up to 2" diameter available to me, and up to I forget diameter ABS pipe. I can also get various sizes of Acrylic pipe probably cheaper than PVC would be, but I'm concerned about machine-ability

Maybe it's because I forgot to number it, but I haven't had an answer on how to implement antenna feedback. :P
Is it just a bit of wire next to the secondary connected to the circuit?

I'm not too worried about a case, I have a really nice enclosure from an old CD burner.

Bauerb2, that site has EVERYTHING in it. Thank you for pointing it out for me.

Geeze.. $70 is a lot. Hopefully I will be able to scavenge a bunch, if not I can wait for 11 weeks....I wish my 6.50/week allowance was larger...

Edit: In this schematic, what can replace D1 and D2? I can;t seem to find 1N60's. Also, R3 says "10R" next to it. What does this mean?

Zum Beispiel

Mon Oct 29 2007, 10:10AM

Registered Member #514 Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295

The magnet wire from a microwave fan is fine for a small SSTC. In fact, this is what I used for my first coil (Steve's MicroSSTC). I scavenged almost all the parts exept for the UCC chip which cost about 2â‚¬. Overal cost of the coil was less than 20â‚¬.

About the antenna. You just plug it in to the gate drive chips input and experiment with the distance from resonator. And remember the clamping diodes, or you might burn the drive chip. Regular signal diodes seem to work fine.

R3 is 10ohm resistor

Spedy

Mon Oct 29 2007, 03:18PM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

Thanks. Although I can't seem to find any "ucc" chip in the schematic. Is that the triangular-looking IC? If it is I'm ok.
Otherwise, I'm clueless...

...

Mon Oct 29 2007, 04:01PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Yes, the 'ucc' is the triangle shaped thing. Usually when we are reffering to a ucc37321 when we say 'ucc'

Bauerb2

Mon Oct 29 2007, 08:19PM

Registered Member #973 Joined: Tue Aug 28 2007, 07:32PM
Location: Pittsburgh, PA
Posts: 66

My sstc primary is 4" diameter. 7" hieght. with 32 awg wire makes around 1000 turns. AS for primary wire i'd use somehing with a diamter of 1/8" or more, depending on the power input. make sure the secondary pipe material is not black (black contains carbon = conductivity = bad).

i spent 70 all together because i had nothing really to build with. i couldn't just find mosfet gate drivers in a vcr, its impossible. a variac is not neccessary to have, but it helps a great deal with testing (start at low, then ramp it up), but if you cant find a cheap one, its not the end of the world.

richie burnett's site has helped out a lot, includes A LOT of info that'll help.

good luck on building, hope it works.

-Andrew

Zum Beispiel

Mon Oct 29 2007, 08:46PM

Registered Member #514 Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295

Bauerb2 wrote ...

make sure the secondary pipe material is not black (black contains carbon = conductivity = bad

If the coil form is plastic, it has carbon in it. End of story. I've used black polypropylene on lots of HV things and have never had problems. Only type of (black) plastic that I've found to be eletrically conductive was anti-static, and that is actually meant to be conductive!

Of course, you are going to spend a while winding that resonator, so no need to take any chances. Just saying, that saying that all black plastic is conductive is wrong.

Tom540

Mon Oct 29 2007, 08:58PM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617

Yes I was going to mention the same thing. I always use black ABS pipes on my secondaries and never had a problem.

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