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This is a question Desperate Times

Stranded in a hotel in an African war zone with no internet access for two weeks, I was forced to resort to desperate measures. Possessing only my passport and the clothes I stood up in; and the warning "You can catch it shaking hands with a vicar out there" ringing in my ears, I had to draw my own porn in order to preserve my sanity.

Alas, it all came out looking like Coronation Street's Audrey Roberts, but, as they say, any port in a storm.

What have you done in times of great desperation?

(, Thu 15 Nov 2007, 10:10)
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Scientific improvisation at its best (worst?)
I was reminded of this by the earlier post regarding checking the polarity of a power supply.

Working as I do in academic research, I get to play with lots of nice toys. The kit is usually bought from research grants, but in the last few years my funding situation has been, shall we say, less than generous. This has meant that while my salary has been paid and we've had a bit of cash for consumables and travel, the equipment capex budget has been essentially zero. I'm sure this will be a familiar tale to anyone involved in science these days.

So when I urgently needed a high voltage power supply, I was stuck, as they're quite expensive and we didn't have one. OK, brain in gear - I'm desperate here. What do I need to make one?

Source of ac signal - yup, we've got a function generator.
Amplifier - no, but I ordered up a couple of power FETs (big transistors) from RS for a few quid, rummaged around the lab for the other components, and built my own.
DC supply for amplifier - OK, we've got power supplies in the lab.
Step-up transformer - scrounged old Fiat ignition coil from a workmate who does a bit of car work on the side.
HT cable - got from car accessory shop for minimal sum.

So half an hour's work and I had myself a high voltage AC supply. This thing was great. Dr Frankenstein would have been spluffing his pants just watching it in operation. It even glowed a nice shade of purple in the dark. I was especially pleased with the fact that it broke so many rules and regulations:

1 - I had no high voltage warning signs. I used to just yell to people who came in the lab to keep clear.
2 - Large quantities of ozone were generated, for which I had no extraction rigged up.
3 - I had no current limiting. Normally high voltage supplies are required to have current limiting resistors built in to prevent too much current being drawn in the case of a short to earth, mainly through the human body. I didn't bother, so this thing was totally lethal.
4 - No shielding of high tension wires. I had bare wires hanging out the end connected to my experiment. I measured the voltage at 80,000V!
5 - As for electromagnetic radiation emissions, let's just say it wouldn't have been awarded a CE mark. Didn't hear of Radio Tay going off air, but it must have been a close thing!

It also emitted a pleasing high pitched whine (it resonated at 8-9kHz) and crackled and sparked a bit from time to time.

If get the chance, I'll look it out when I get in to work tomorrow and try to get a picture of the purple glow!

EDIT: Pictures now included. Check replies.
(, Sun 18 Nov 2007, 13:18, 17 replies)
sounds like our lab - scottish supervisor=not much cash spending, so if anything breaks, we spend hours trying to fix it with autoclave tape, and if we need a new kist for anything, we improvise. luckily not with electricity, being a molecular bio lab, but some interesting radiactivity/cat 3 pathogens/liquid nitrogen stories...
it's probably why scientists aren't allowed out into the real world too often...
(, Sun 18 Nov 2007, 14:54, closed)
It really suck to be without funding
The funding dried up on my research assistantship. I have to teach four labs now (and get paid much less) and there is no equipment budget. This has resulted in much MacGuyvering of the robot. Rubberbands and duct tape are put to good use.
(, Sun 18 Nov 2007, 15:24, closed)
If only
You had managed to take radio Tay off the air.
(, Sun 18 Nov 2007, 15:38, closed)
you sir
are a legend! Photos please
(, Sun 18 Nov 2007, 15:40, closed)
That was me!
Great story. And add me to the list of people who would like to see pictures.

also: *click*
(, Sun 18 Nov 2007, 21:54, closed)
This reminds me of the vehicle maintainence facility down here... nice big sign on the door to the shop "If it can't be fixed think...what would McGuyver do?"

yup first time...im lame.
(, Sun 18 Nov 2007, 22:55, closed)
I clicked...
...and thus you have now entered a legally binding contract to provide said photographic delights.
(, Mon 19 Nov 2007, 9:56, closed)
I NEED to see those pics!
(, Mon 19 Nov 2007, 10:01, closed)
Sounds like the technician was in the minerals lab at uni - she repaired an electrostatic separator with pipe cleaner & duct tape. Thankfully we had a rubber mat to stand on - though the thickness wasn't really sufficient for 50000 volts...
(, Mon 19 Nov 2007, 10:33, closed)
OK, I've rummaged in the lab this morning
and I've found the kit, which appears to be all there. I'll fire it up later when a) I can use the power supply, as I'm using it on another bit of kit for the next couple of hours, and b) my boss is away for lunch.

Watch this space...
(, Mon 19 Nov 2007, 11:06, closed)
Are you
Dr Emmett Brown?


Marty McFly
(, Mon 19 Nov 2007, 11:10, closed)
That sounds fun...
..like me ol' Chemsitry lecturer who happily tested the conc. collection (concerntrated acids etc) in front of us student who would all promptly half-choke to death.

Would love to see a piccy of this going :)
(, Mon 19 Nov 2007, 11:31, closed)
Here it is
Unfortunately the air's a bit humid today as it's pissing with rain outside, so I couldn't get the whole HT side to glow. I did however manage to form a corona discharge through the cable insulation to the coil casing:

and also managed to light a small fluorescent lamp which was sitting next to the HT cable, just from the electric field. You can also see a glow from a corona discharge between the HT cable and an earthed wire deliberately left beside it. The amplifier heatsink can just be seen to the right, among the wiring.

Sorry it's not a bit more spectacular, but it's a bit damp today and I had to put the lights out in the lab to take the pics.

And here's some video footage. Click here to watch the sparks when the high tension end comes close to an earthed wire.
(, Mon 19 Nov 2007, 13:12, closed)
genius. I doff my cap to you sir.
(, Mon 19 Nov 2007, 14:18, closed)
I'm impressed
Very Heath Robinson - but cool all the same
(, Mon 19 Nov 2007, 14:26, closed)
Very impressive!
I just hope it doesn't give you leukemia when you run it, or make your unborn children into CHUD or something...
(, Mon 19 Nov 2007, 14:41, closed)
Nah, it's not on long enough for any serious health effects from the EM radiation. Mainly because it gets quite hot! I try not to breathe the ozone though.

As for kids, I don't intend fathering offspring anyway, although perhaps an earthed copper codpiece might be an idea to protect the nads from radiation!
(, Mon 19 Nov 2007, 15:29, closed)

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