Life, The Universe, and Everything

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Here, you can discuss anything (well, anything legal and not offensive) you want to. Use this for gassing about any half-baked theories, general getting to know one another, and other things that as someone once said, should be forgotten after awhile. This sub forum is set to auto-remove threads that haven't been posted on for a couple weeks, emptied like the office trash can. Almost anything goes here, the idea being to keep the other forums and threads more on topic but in a maximally friendly way. If anything actually worthwhile should wind up here, let me know and I will make it immune from being removed.

Re: Life, The Universe, and Everything

Postby Bob Reite » Sat Feb 24, 2018 12:01 am

This must be the year for roof issues. I woke up Monday AM to the sound of drip drip drip from one corner of the living room and the attic storage area. I had buckets in the attic from before, so no drywall damage, and the living room corner where the sound comes from, you can't see anything.

I pretty much know where the issues are with the roof here. The chimney flashing and a place where the addition meets the original house. Yep, the patch tar from 3 years ago shrunk and left gaps. Lucky that Wednesday was a sunny record breaking 71 degrees. Used a 1/2 gal of patch on everything. Got a test Thursday with more rain. Looks like it's fixed. No more dripping sounds.

My fusor has also taken a back seat to "RL work that pays the bills", as well as the roof repair.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Re: Life, The Universe, and Everything

Postby Doug Coulter » Sat Feb 24, 2018 9:40 am

Wonder if that super cold snap had some effect on all this? Anyway, life happens while you had other plans, as usual. I'm about to get back in to the fusor here, at least for another bag of data's worth, but then the new solar panels and batteries will come and I'll have to be back on that, along with replacing some of the upper part of the roof before putting new panels over it (the best time for that). And for what that's worth, a nearly $10k sudden expense isn't doing my budget any good and if I had the option, I'd be looking for paying work myself. Just that there doesn't seem to be any of that around here that I could do. And no one seems to want a telecommuting engineer for the kind of things I have domain expertise in (I will NOT develop web pages), so...scrimp time.

I guess we'll all get through it, but gheez, the universe doesn't give away some secrets lightly - seems we have to earn it.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Life, The Universe, and Everything

Postby Doug Coulter » Sat Feb 24, 2018 4:15 pm

Snuck in a few minutes of fusor test time and got some interesting results. Not great, just interesting. When I get more, I'll make another thread under Nuclear.
Interesting that moving the setup across the yard seems to have increased the amount of power when there's no gas load....

At any rate, it seems that one doesn't want the max coupling capacitor, or more directly, doesn't want too much time/energy at the positive part of the cycle - it seems to drive the ions into the tank walls, and in fact it makes it harder to stay lit - I had to press the DC ion source into action here. This setup used 3 750pf in parallel, the previous test just one of them. I'm guessing that was closer to correct, and I may be fiddling with doorknob caps in series and parallel to get close, given that I can't just make the waveform I want and amplify it at this point - it's going to have to be created at the point of use by dodges like this (let's hope we don't wind up needing anything too elaborate or pulse forming by saturable reactors).

With more voltage, the neutrons that are produced come out _after_ the negative peak. So frequence has to go up with voltage, not a surprise at all.

This was far enough off that I didn't see any multiple ion bursts going by either faraday probe, but when I did get neutrons, I got more than last time, fat bursts. More on the audible counter too.

I'm having trouble probig the HV correctly. My old B&K type TV probes are way off on the AC content - read too high (while DC reads low due to the scope being 1 meg vs 10). I'm fairly sure that just adding a load capacity won't fix this - as just waving my hand a foot away changes the apparent divide ratio more than 2::1. But if you try to shield that thing, you add more capacity to ground than you'd want, and it'll arc - you need the spacing from the HV end for that reason. I need to get a solution to this so I can feed this info into the rest of the data aq and have some confidence in it.

I may revert to the last setup to get a more direct relative measurement at least for one run, just so I know where I stand.

But it did work "at all" and in fact better than last time. I'm going to need to compute the actual input power to the fusor, as a lot seems to be going into warming up things outside of it - even at 100-200w dc input to the H bridge.
DS0002.png
big scope

Scope trace, nothing calibrated here. Trace one (yellow) is the neutron detector. The sine wave looking magenta trace is a capacitive pickup near the HV feedthrough. Blue is the "near" faraday probe, green is the "far" one on the opposite side of the tank. I couldn't get a clear reading on transit time between them, it's faster than the risetimes. The sudden step in the drive waveform appears to be real, but since it seems to be lit off continuously I'm not sure I have a good explanation for the discontinuity.

Since the trigger is on the neutron detector - and I set that to only trigger on a fat burst, I used another scope to track the waveform and frequency as well as i could:
DS0013.png
Don't think this is showing DC/AC ratio correctly
DS0013.png (5.17 KiB) Viewed 143849 times


I'll have to make a few tweaks and try more...as always.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Life, The Universe, and Everything

Postby Bob Reite » Sun Feb 25, 2018 7:08 pm

Trouble with the multiplier resistors in those old TV HV probes is that they have an unknown reactance, which was not an issue for measuring the DC second anode voltage on a TV set, but is a problem to measure AC. If you just need to measure the AC component, consider a capacitor/resistor divider and allow for 6 db per octave response when interpreting the results. There are compensated HV probes for scopes out there good to 150 MHz, but I haven't see one that can take more than 18KV or so.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Re: Life, The Universe, and Everything

Postby Doug Coulter » Mon Feb 26, 2018 2:01 pm

Yeah, and the resistance is super high. The issue here is that there's a lot of AC capacitive coupling into the divider itself. So, you can't just hang a variable cap across the output like a scope probe to get a flat attenuator. And in this case I do want/need DC->HF response, flat. The only way I can see to get this is to somehow shield the probe, but the shield would have to go up so close to the top that there would be arcing issues at ~ 50kv. Like I said, just waving your hand back and forth 2 feet away changes the readings ~ 2::1 (DC average stays the same, but...).

I'm trying to figure out where the "diode" of the fusor electrons starts drawing real current when going positive, and what the peak negative excursion is. The current arrangement gives me neither.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Life, The Universe, and Everything

Postby Doug Coulter » Thu Mar 01, 2018 5:35 pm

I think I just want to go sit somewhere till this is over...Doug, the 9.8 fingered now.
20180301-1843-life-1.jpg
Fan blade won.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Life, The Universe, and Everything

Postby Bob Reite » Thu Mar 01, 2018 9:42 pm

This year is not off to a good start for you. Maybe I should send you a bunch of "rotating parts" warning stickers to put on/in your equipment.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Bob Reite
 
Posts: 142
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Re: Life, The Universe, and Everything

Postby Doug Coulter » Thu Mar 01, 2018 10:19 pm

Well, I met a cute surgeon....the expensive way.
I *will* overcome, but gheesh.
Maybe I can at least get some follow up data. I think I see a trend like I predicted, and it'd be real nice to have a few more points to see if I was on the right page or not, it's kind of make or break time for that sheaf of hypotheses. It would be nice to know after all this work and investment.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Life, The Universe, and Everything

Postby Doug Coulter » Mon Mar 12, 2018 11:11 am

Gee, I don't want to come off as a whiney old man, but gheesh. I did get all the stuff to replace my roof...and am now glad I took a break from that and wasn't in the middle of the work when the fun weather hit.
https://youtu.be/vZl0b-kvtpE


I needed to take a step back on the fusor to get to some replication on recirculation - the power supply used for this wasn't going to live a lot longer and in fact refused to oscillate for me yesterday.
Not that big a deal as the new driver is more or less able to fo the same stuff - and more, relatively loafing. Which just about got me back to where the recirc video was made.
In case I forgot to link that here: https://www.youtube.com/watch?v=fQYqOsk5QRo


For whatever reason, the "better" (full loop of ferrite ) transformer that measured so much better on my bench absolutely stank in use. I tried a larger gap in the cores, but only a minor improvment. So for now I'm back to the original 1" sq by 4" long slug, but with the new "exciter" driving it. I got pretty close to seeing the same stuff with this as before, using one 750 pf coupling cap to the fusor grid, but had to stop for the day for other reasons more soon. I read -6k DC on the grid due to the fusor rectification, and saw these kind of waveforms. Note on the 2ch scope - this is NOT calibrated for this frequency so might be a little misleading (and even so, with a one meg scope vs a 10 meg multimeter...isn't going to be right) - if it is right, it's luck. I'm going to make a little rectifier/filter so I can use that B&K probe on DC where it IS right.
So, the 2ch scope here is showing the HV probe and one of the outputs of the full H bridge (nasty!). Maybe that leakage inductance is what makes this all work, though - this is definitely not at one of the transformer resonances. At those, the stepup ratio is vastly bigger, but it's like driving a short circuit. Seems less efficient there...
SmallScope.PNG
The drive and output (output DC coupled at fusor grid)
SmallScope.PNG (9.11 KiB) Viewed 143681 times


The big scope shows an almost double humped faraday trace (ch2) here - and the late bump does move more into alignment with higher volts OR lower frequency. But it appears I need a better vernier on this - it's touchy as heck. I decided if I'm going to do that, I'll add the second power supply on input to get up to twice the drive volts.
BigScope.PNG
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Life, The Universe, and Everything

Postby Doug Coulter » Tue Mar 13, 2018 3:18 pm

So, I ran this harder the other day and got some neutrons - more than usual per volt, if not per watt (it's pretty obviously off-tune). I had to press a replacement power suppy into service to do it, as one had died earlier - I'm using 2 30v, 10A supplies in series (and yes, with reverse protection diodes and so on). Seems these guys, available from a couple vendors on amazon (but with identical guts, down to the PCB house and company name on the board) use a pretty close to the edge switching fet that really can't take some kinds of EMI...looking it up it's "not recommended" for design. I got some hopefully better ones on the way from Digikey and we'll see if that fixes these - I now have $160+ worth of blown supplies that have ~ 10 minutes total life...I'd like to improve that ratio.
I also ordered a honking linear supply from Marlin Jones - 60v/10a, which is probably better all around, but of course, won't be as efficient at the wall socket. It's likely more repairable.

The "China Special": https://www.amazon.com/Eventek-KPS3010D ... wer+supply
These have actually gone up in price over the past few months. If you believe the reviews, they're good for what others are using them for (electroplating). It appears they are just picky about some kinds of noise. Inside they look a lot like a simplified desktop computer supply main board, with a nice separate front panel board for the knobs and meters. Could be remoted with 10k digital rheostats (2 wire).

The MPJA one: http://www.mpja.com/0-60V-10A-Variable- ... o/29960+PS
I have the half size version of an older model of this on one of the tinker benches. Works pretty well, the pots are a bit noisy - if you're going to run close to a limit, it's a good idea to preset things.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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