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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
This is the sstc i have been working on for awhile, and finally finished the lashup a few days ago. The results are fairly decent, and with only 80vac input so far, i am expecting some fine results. The driver is all build on a 2 1/2" by 1 1/2" board from radioshack. It is one of the most convenient PCB's i have used. The white outline is what the copper underneath looks like. The halfbridge board and capacitors where from Sam/Anon01/TeslaWasHere/disorder/Chaosanddisorder (just so everyone knows) , which BTW works great.
The mosfets are some STP25nm50n 500v 22a TO-220 mosfets, and the freewheeling diodes are two completely different fast diodes, rated for about 5 amps. I thought it would be a problem, but it hasn't been at all yet.
So far i have only used 80vac in, and i have not tuned or messed with coupling. Also, i am planning on experimenting with CT's. The secondary isn't any good really, and i still need to make a topload and tune accordingly. And of course, i need to put it all into a case :P. I will likely just put the driver and halfbridge into a case and whenever i want to use it, i plug it up to the wall and the primary. Not as good as one thing that hold the driver and primary and stuff in one base, but this way i can use different primarys and secondaries. I am also planning on a fullbridge at some point. Next sstc will likely be a PLL with audio mod . But that is much later, after i get a scope.
After that video, i put interrupter frequency down to minimum and duty cycle to minimum, and put a large topload on and got about 10 inch sparks with 80v in, but mosfets died shortly after because i did not tune so it probably pulled too much current.
Registered Member #1157
Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307
Arcstarter wrote ...
Hurry and get your minibrute running!
Bah, with the new baby here, I barely have time to wind a secondary for Steve Ward Mini. I need someone to work on it and get it up and running, because If I set the O-Scope up in the kitchen one more time, my wife is going to strangle me with my Probes.
Either that or I wait a few more months so that I can spend more than an hour in the workshop without both of them screaming at me.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
You want to work on it Matt?
I can see right through your sarcasm.
That sucks though, but i know the feeling. I have no room to myself, which is somewhat like not being able to do your stuff :P. I cannot do my stuff sometimes, because "it makes the TV explode violently" and "it blew your father's face off when he tried to get a shirt from the closet". Like that is such a big deal that i cannot do my stuff?
Registered Member #1911
Joined: Mon Jan 05 2009, 06:30PM
Location: Salem, Oregon, USA
Posts: 165
Arcstarter wrote ...
You want to work on it Matt?
I can see right through your sarcasm.
That sucks though, but i know the feeling. I have no room to myself, which is somewhat like not being able to do your stuff :P. I cannot do my stuff sometimes, because "it makes the TV explode violently" and "it blew your father's face off when he tried to get a shirt from the closet". Like that is such a big deal that i cannot do my stuff?
You need a 30-amp RFI filter, my friend. That way, even a non-ballasted MOT won't kill your filter, and the T.V. won't "Blow Up". I know, tried making filter chokes for my coil and they were too close to eachother. They set up interacting magnetic fields and, while they did dampen the RF to the point that my smoke alarm was no longer going off, they also made it so that my dad's 'new' big-screen T.V. in our living room did some crazy sh!t. There were lines going across the screen and, luckily, my brother was watching the T.V. I'm not sure how abusive it was to the poor thing, but I know it couldn't have been good! But, then again, if it fires, I can get the flyback out of it! =) There's always a positive!
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
PlasmaLover wrote ...
Arcstarter wrote ...
You want to work on it Matt?
I can see right through your sarcasm.
That sucks though, but i know the feeling. I have no room to myself, which is somewhat like not being able to do your stuff :P. I cannot do my stuff sometimes, because "it makes the TV explode violently" and "it blew your father's face off when he tried to get a shirt from the closet". Like that is such a big deal that i cannot do my stuff?
You need a 30-amp RFI filter, my friend. That way, even a non-ballasted MOT won't kill your filter, and the T.V. won't "Blow Up". I know, tried making filter chokes for my coil and they were too close to eachother. They set up interacting magnetic fields and, while they did dampen the RF to the point that my smoke alarm was no longer going off, they also made it so that my dad's 'new' big-screen T.V. in our living room did some crazy sh!t. There were lines going across the screen and, luckily, my brother was watching the T.V. I'm not sure how abusive it was to the poor thing, but I know it couldn't have been good! But, then again, if it fires, I can get the flyback out of it! =) There's always a positive!
Lol, i was being sarcastic. I have never burned anything out with my electronics.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Some minor changes have been made to the coil. I put a smooth topload, which is a small-ish pan. Even without a breakout point and nothing grounded near, it will still break out.
The next thing i did was make a new primary. It is just a smaller form length with about 20 less turns. The last one was for my VTTC's, which have never really been built. It was too tall and had too many turns. the wire was too high, so i got arcs to part of the unused primary windings occasionally.
Then, i put some back-to-back zeners on the gates of the mosfets. the zeners each consist of two 6.1 volt zeners in series, courtesy of Tom. I also put some game resistors to suppress ringing on the gates which could cause higher dissipation from switching losses. This could also cause nasty waveforms, which could reduce performance.
The biggest improvement was the new mosfets, that where also courtesy of Tom. they are 48 amp (iirc) super TO-247. They had to be clamped to a heatsink of course, so i made a clamp for them. I found a fan that suited the large heatsink i used well. It had some pieces of plastic on the cowling that would keep it from moving back and forth, and a clip that kept it from falling when the heatsink was tilted.
As you can see, i put it together in a hurry, so it is uneven and cruddy looking. The piece of metal that clamps it is an aluminum block that i had sitting around. It also helps, as it takes heat from the front of the device. I soldered wires onto them for attaching to the bridge circuit. I used so called Bell wire for the source and drain, as the wire is two conductor, which will keep the wires together to reduce stray inductance. The gate wire is just....... wire . After the soldering onto the leads, i put some heatshrink on the leads to keep from shorting to the heatsink. That was all the heatshrink i had around here .
The mosfets, if that where not painfully obvious. The mosfets again (wow, really being captain obvious, aren't i?) The doubled up capacitors on the half bridge heat many times more than the mosfets do. Even the secondary wound with 28AWG wire heats literally a few times more than the mosfets do, after running for 10 minutes straight, uninterrupted with 80vac in and CW. I can run near indefinitely without mosfets getting too hot, at least if i had a better fan (this one you cannot even feel).
I used one sil pad on one of the mosfets, which is much too small. This is a big no no, as i do not want the mosfets to heat up at different temperatures, as once they get hot, resistance increase, as does dissipation. And someone stepped on my thermal compound, so i did not use any of that, as i am out and have no money for more
Sparks pics anyone?
All at 80vac input, fullwave rectified and CW uninterrupted. Before using good topload. Sparks where about 5 inches in that picture, they are currently up to 6 inches at 80vac input CW.
Also, the interrupter will not work. I have changed the 555, changed the diodes on interrupter, checked pots, changed timing cap, checked the timing resistor (actually a wire, for different frequency), checked the traces, changed ucc's (running low ), checked wires, checked the regulator, but i am not positive that the 555 is getting power as i don't even have a DMM (don't worry, i checked input voltage before it died). So, i am officially puzzled about it. Sometimes the interrupter will suddenly work for a second or two, and go back to CW. Ideas?
Slightly off topic: Me after becoming puzzled about the interrupter:
Me after seeing the heatsink work like a charm:
My face after posting last sentence: (twas a mixture)
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My new SStc.
. But that is much later, after i get a scope.
), checked wires, checked the regulator, but i am not positive that the 555 is getting power as i don't even have a DMM (don't worry, i checked input voltage before it died). So, i am officially puzzled about it. Sometimes the interrupter will suddenly work for a second or two, and go back to CW. Ideas?
(twas a mixture)