Weird, I posted this in LJ, and not in MT -- this was definitely meant as an MT post! Ah well, you get a duplicate. Whee!
No spark for me. I'm trundling through the bring-up instructions, interspersed by crimp connectors, hole drilling, tapping, soldering, and various other cleanups (everything works fine! No, that's not true, see below) and then I see "power up the advanced modulator." Crap. I forgot about that. Oh well, time to solder that board together! Should be a breeze, but it means I won't get through the rest today... so no sparks for me.
During my tests, for the display board, I heard a "crick, crick, crick" sound... like... heat expansion! Crap! Click off and feel around, my 15-volt regulator is TOASTY. And putting out about 2 volts. That means... dead short. Somewhere.
Maybe I did something stupid with the jumper cable, like connected 15-volts to ground. I futz around with that some, and no, even though the topology of IDC ribbon cables hurts my brain, it's all good.
Test the power board, and it's powerful. No problems there.
Test the display board and yup, 15-volts is shorted to ground! But where? Out comes the jeweler's loupe, for a detailed inspection. While I don't approve of many of the things Daniel did with this layout (e.g. soldering directly to power planes SUCKS and is avoidable; needs larger dead spaces around pads in the middle of power planes; weird connector placement, etc etc), it's all good under magnification.
So, resistors. Nope, they are resisting. Diodes? Diode-rific! The IC? Pull it! Nope. The capacitors. Well, I can't really test those, they read as shorts anyway, since they bridge 15v and ground (being there to give the system that old stiff upper lip, what what).
Fortunately, there are only two caps, a 10uF and a 0.1uF, so I pull them and whaddya know! No short. It was the 10uF cap that was the problem, dead short through the device. Bastards.
I find another 0.1 and drop it in, and I'm clean out of 10s so I get one an order of magnitude smaller (whatever, it will be fine) and put it in. All is good, and the display works now, with no burning sensations coming from the power supply.
The next sphincter moment is when I calibrate the current feedback display, which is a bar-chart showing 0 to 1,000 Amps in 100A increments. 1,000 Amps is represented by 12 volts at a particular place in the system, so I bring out my variable power supply and wire it up to that sensor point.
Twiddle twiddle, peg! The supply pegs at 1A (it's limit) at just about a volt. I can get it it twitch up to maybe two volts before it clamps. Hmmmm.
I get out the HEFTY power supply, see what 10 amps does heheheheheh (yes, I realize I'm not thinking clearly here, it was my afternoon brain slump, clearly). What it _does_ it get fiendishly hot, I can tell by the smell. Oh look, here's a 1.6 ohm, 3-watt resistor! Taking 12 volts across it, that what, 7 amps or so, around 90 watts of dissipation? Yeah, that's not good -- and to make it even MORE embarassing, I read about some OTHER guy frying his resistor in the forums. Derrrr.
So I attach the signal generator and get NEARLY 8 volts peak to peak out of it when loaded, zapping pulses into the sensor. This works pretty darned good and I get it rough-tuned with that.
To fine tune, I dial the monster power up to 12 volts (again) and just TAP the sensor with it; 90 watts in short bursts is fine. Tuned up and happy, now I can indicate 1,000 amps of fancy tesla goodness during operation. Yayy! Overcurrent is set to about a third of that for startup, but we can change this in time.
In other news, I remembered that I don't _do_ finances on Sunday, but on Monday -- since Mondays already suck, I just throw more suck into it and I don't really notice. I still have to do taxes next weekend, either that, or get hit by a truck or something. People keep going, "Oh, I just hand it off to the accountant..." well yeah, but doing the actual tax stuff isn't my hassle (I love Turbo Tax, even if I do enter the data manually and not via Quickbooks)... no, it's the polishing and buffing (or, perhaps. nine months of data entry) on the biz account that is looming like dark clouds on my horizon.
Ah well. Maybe THIS year I'll keep that account up to date. I haven't been SO FAR but hey, the year is young.
Ugh.
Being a responsible adult really runs against my grain. I should go out and be an artist in the woods or something.
And I would too! Except then I couldn't afford parts. Tesla coils can be spendy.
Posted by Edwin at March 31, 2008 07:48 AM