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Old 03-27-2009, 02:48 PM   #681 (permalink)
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Roger, do you guys have a water jet cnc as well that can do very large sheets? I read this technique that some guys used to create molds for HPV shell. They took foam sheets of something like 4'x8'x1" and had the cnc cut out profile templates every one inch of their mold design. They then glued the sheets together and sanded down the edges to make a smooth shell.

I'll find a link for it for you so you can better understand what I am talking about. I want to get a ball park price on how expensive this process would be. (I think the guys that did it said it only cost around $15 a sheet to do, and they maybe 25 sheets....)

http://ecomodder.com/forum/showthrea...ring-1175.html

I've seen another one done like that, but the team had the mold cut with a CNC. Is your company able to do something like that? I am in upstate NY, which is why I am curious.

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Old 03-27-2009, 03:00 PM   #682 (permalink)
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Paul, if that routine is using 15%, i don't think it can handle state-space. Too much matrix multiplication and you'd want good resolution (better than 8-bit). Next time don't sissy out on the processor, k?
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Old 03-27-2009, 03:34 PM   #683 (permalink)
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Ben, we don't have a water jet, just the PlasmaCAM. With a router attached this machine could certainly do this type of cutting. In fact, it could do profile cuts every 0.25" so you wouldn't even have to do much sanding. The table size is 4' x 4' to do anything bigger you would have to split it into sections.

So it is possible, just would take a while to do. Where are you located? Contact me directly off line at rheuckeroth@hvc.rr.com I don't want to hijack Paul's thread.
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Old 03-27-2009, 08:10 PM   #684 (permalink)
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To reduce noise at low switching frequencies, could the clock be modulated to spread the spectrum and avoid concentrating power at any one particular frequency?
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Old 03-27-2009, 10:04 PM   #685 (permalink)
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Quote:
Originally Posted by NiHaoMike View Post
To reduce noise at low switching frequencies, could the clock be modulated to spread the spectrum and avoid concentrating power at any one particular frequency?
I'd have to guess that this would be pretty taxing on the system.

As an alternative, how about a driver (speaker) that sends out the offending frequency, but offset by 1/2 the wavelength? That's the basic concept behind noise canceling technology, and possibly easy to implement in this scenario.


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Old 03-28-2009, 12:02 AM   #686 (permalink)
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I am fairly certain that the Zilla controller uses spread spectrum modulation to produce its characteristic white noise whoosh sound when starting out. Otmar said that this was engineered into the controller because he didn't like that Curtis squeel.
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Old 03-28-2009, 01:59 AM   #687 (permalink)
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Quote:
Originally Posted by wjdennis View Post
...the squeal from a Curtis controller (or the growl from a Zilla),
So THAT'S where we first heard that "futuristic cougar sound."
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Old 03-28-2009, 10:49 AM   #688 (permalink)
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I really hate when my login times out when I'm writing a post.

So I guess this is going to be the short version.

1: Congratulations to Paul.
2: Alternative power electronics mounting setup: The Power Wheel

Symmetrical Layout Enhances Power Controller

No etching! Just drilling and bolting.

3: Single freewheeling diode module (1200V, 450A, $40):

MEO450-12DA IXYS 1200V 450A Fast Recovery Epitaxial Diode Module at The Electrostore.com - Electronic Surplus Parts & Equipment

4: Paul referred to a couple of lower cost MOSFETs and diodes. Can you please post part # and distributors please?

5. Do caps have to be colocated with the MOSFETs? The Power Wheel only has B- and M-. Could the caps be on a separate board or located at the battery pack? Or does the power wheel need 3 disks (M-, B+, B-)

Thanks for any answers and thanks for the inspiration to DIY.

ga2500ev
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Old 03-28-2009, 11:50 AM   #689 (permalink)
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Originally Posted by ga2500ev View Post
I really hate when my login times out when I'm writing a post.
Boy, I'm with you on that one. I don't know how many times I've worked over the 20-or-whatever-it-is minutes on a post, only to have to use the back arrow, cut the text, sign back in, and paste it in a new reply.

Hey, Paul! While you're working on all of this programming, could you do some sort of code that would sneak in and change our time-out times to something more like 30 or 40 minutes? I would be so happy, I'd adopt another mosfet!
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Old 03-28-2009, 01:13 PM   #690 (permalink)
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The power wheel looks great! I read about it a while back, but I never tried it. As for the freewheel diode, the reverse recovery time is 20x longer than the ones I'm using, and I think that might be a problem causing voltage spikes. Mine take 22ns, but that monster diode takes 450 ns. Someone should try it. New they are $80, and I don't know how many there are for $40. It seems like a good idea to try it! Also, you need to de-rate modules to about 1/3 for their continuous rating, according to Lee Hart. But maybe that's OK still? You don't use that much current under normal driving.

I would be a little concerned about a connection between brass bolts, mosfet leads, and an aluminum disk. They used aluminum in wiring in the 70's, and down the road it lead to fires because of corrosion with the different metals, and because of the aluminum creeping I think. Maybe a copper disk if you wanted to be super careful.

I didn't see where he has his freewheel diodes, or what type. I guess you could think about where they have to be, and just put them there.

the paths of the capacitors, mosfets, and diodes must all be kept as short as possible. Otmar calls it the holy trinity.

Overall, it looks awesome!
His mosfets have almost 3 times the heat loss of mine. His RdsOn is 23 mOhms, and mine is 8. He didn't have a problem with heat loss, so maybe it doesn't matter.

I really like the idea of the layout! Maybe I'll try it. I'm just concerned about the long-term connection with the mosfet leads to the aluminum.

His aluminum disk is electrically hot, so you'd have to be careful about that.

Thank you for bringing that idea up! The guy made it work! It must be good!

Intrigued: Those days are behind me. hehehe. Oops, I'm just kidding, I mean. I have never excrypted whole dictionaries and compared the results to unshadowed password files in Unix. Never!

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