[Lab] Open Question: Dumbest Thing You've Done While Making

Jason Cobill jason.cobill at gmail.com
Mon Jun 24 16:53:04 EDT 2013

That's amazing! I had no idea the uO solar car generated that much current!
What kind of motor was all that power being used to drive? I was under the
impression it was a tiny motor running at high RPM and geared down for

Zot's a pretty cool nickname, though. ;)

   -Jason Cobill

On Mon, Jun 24, 2013 at 4:49 PM, Richard Guy Briggs <rgb at tricolour.net>wrote:

> On Mon, Jun 24, 2013 at 04:00:51PM -0400, Jason Cobill wrote:
> >    Experiments gone wrong? Tools gone out of control? What's the dumbest
> > thing you should have caught before you nearly set your house on fire?
> What
> > did you learn from it?
> >
> >    Me first: I plugged in a table saw without checking the switch first -
> > it was on. And it was covered in 2x4s and sheetwood scraps, which it
> > proceeded to launch across the garage and nearly take out a window.
> >    It _should_ have been off, but I _should_ have checked. So now I
> check.
> > Every. Time.
> Oh, this one's easy.  ;-)    I have two related to electricity.
> 1)  When I was about 10 I had a power transformer that I had taken out of a
> wood-cabinet vacuum tube TV set.  I had learned to solder when I was about
> 8.
> I knew which side was the primary and I wanted to test the secondaries.  I
> knew
> they would be high.  I had a cheap analog multimeter from Radio Scrap with
> a
> 750V rating.  I carefully attached and shielded the primary wires to a
> standard two-prong plug.  I was sitting on my bed (so no danger of
> grounding out, plus it was an isolated secondary).  I pinched one
> secondary wire with the meter test lead, then grabbed the second test
> lead and went to pinch it with the other secondary...  (It was about 350V.)
>         I haven't done that ever again!  Now I used insulated leads.
> 2)  In my last year of Electrical/Computer Engingeering at U of Ottawa,
> I was working on the U of Ottawa solar rayce car RALOS-II, wiring up the
> main power backplane of the car (I was the Electrical Systems
> Co-ordinator) working on some low-voltage wires on one card that
> happenned to be facing a high-voltage, high-current card connected to 7
> car batteries in series (90VDC, 1000A?). As I pulled my hands away from
> my work something sparked.  Naturally I pulled back, jamming my family
> gold ring into the high-voltage card.  Once the sparks stopped, two of
> my fingers were black.  After a quick throw of the main power switch for
> the car to avoid any further incident, one of my teammates packed me off
> to the hospital to clean things up.  On the way to the hospital, I was
> babbling with all the wire cross-sectional diameters, materials and
> resistances per metre still fresh in my mind, calculating that must have
> been a 100kW arc welding burn.
>         I was lucky.  I still have all my fingers, but one has an
> interesting ring-shaped scar (that was 20 years ago this month) and the
> bloodstone with the family crest in the ring cracked.  I thought of
> getting it repaired, then decided to leave it as a reminder.  I was very
> lucky it didn't instead hit the iron ring on the adjacent finger that I
> had earned not 2 months prior.  Gold is a much better conductor, so it
> didn't heat up much compared with the other parts involved.  The two
> one-inch spade terminals on the card along with 1/2" PC board traces
> vanished.  I had to check a second identical card to find out what was
> there.  I earned the nicname "Zot" for that one...
>         I now remove my rings when working with high voltage/current.
> I still love electricity!  :D
> >    -Jason Cobill
>         slainte mhath, RGB
> --
> Richard Guy Briggs               --  ~\    -- ~\            <
> hpv.tricolour.net>
> <www.TriColour.net>                --  \___   o \@       @       Ride yer
> bike!
> Ottawa, ON, CANADA                  --  Lo_>__M__\\/\%__\\/\%
> Vote! -- <greenparty.ca
> >_____GTVS6#790__(*)__(*)________(*)(*)_________________
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