[Techtalk] Re: Electrical hacking

Conor Daly conor.daly at oceanfree.net
Sun Apr 13 19:18:39 EST 2003

On Sun, Apr 13, 2003 at 01:55:46PM +0100 or so it is rumoured hereabouts, 
Maria Blackmore thought:
> On Sun, 13 Apr 2003, Conor Daly wrote:
> > Things you just don't touch:
> > 
> > o High voltage stuff inside your sick monitor (see [0]).
> Not actually that bad, since it's quite low current, there are a number of

But doesn't it take only a few milliamps to kill?
> > o The wiring in gadgets in your bathroom (see [0] also).
> Once again, perfectly safe, so long as you know what they do[2], why they
> do it[0] and how to avoid making them not do it[3]

Given the above, it's perfectly safe.  It _is_ vital though to understand
the interaction between electricity and water and how really really
important that little rubber seal that just tore was...
> > Things I have successfully fixed:
> I've never let the fact that I've never done something from stopping me
> doing something.  I think this is a very important thing that other people
> should do, too.  Take the knowledge you have and extrapolate it, reuse it
> as appropriate, and use it to find what you don't know.

Agreed.  I enjoy reverse engineering tape decks, VCRs etc.  The above is
one of the main things holding poeple back in all sorts of fields.  Once
you overcome the fear of being unable to do something, there's pretty much
nothing to stop you.
> It's important to challenge yourself, it's how you learn.

> > Of course, the other thing to remember is the cost efficiency.  How much
> > is your time worth?  Will you spend more time fiddling around than you
> > would spend in cash on the ready made device.
> Ah, yes, the bane of the throw-away society :(

That's something that really bothers me.  I bought a new car exactly once
and that was through work with some major discount included.  My current
car is 11 years old and I plan to keep it for another 15 or more.  I had
to tear myself away from an old oscilloscope (dunno if it was working) in
the skip recently 'cos I _knew_ that it would sit in the attic forever
more "just in case".  
> Maria
> Who does this for fun, and profit[4] :)
> [2] It's an isolating transformer, to isolate the socket from you in an
> electrical sense, it makes the power coming out of the socket on
> the two pins relative to each other instead of to ground, this means that
> it's safe to connect one pin from the socket to ground through yourself,
> and not get hurt.  Of course you'll still get a jolt if you connect
> yourself between the two pins, but this is covered by the Being Bloody
> Stupid Act. :)

Ah so _that_ how they work!  I've seen these and understood the notion of
them isolating the user from the mains supply but I was never clear on
exactly _how_ they do it.  The transformers you see on building sites and
used by trades people work similarly:  They have a transformer with a
centre tap (which AFAIK is connected to ground) and 55VAC available off
either end of the transformer.  This supplies 110VAC to the tool but
nowhere is there more than 55V above ground so shock hazard is very low.

> [4] I've worked as a sparky in a theatre, as local crew, assistant, and
> occasional sound engineer in various venues, and as an engineer in a TV
> station

Did/do you see much sexism in those fields?  You're in the UK yes?  Here
in Ireland, there seems to be much less of a barrier to women than I've
heard cited on these lists though the various motor workshops I've worked
in/visited did tend to have the ubiquitous girlie pinup calender hanging
up somewhere...

Conor Daly <conor.daly at oceanfree.net>

Domestic Sysadmin :-)
  6:36pm  up 24 days, 12 min,  0 users,  load average: 0.03, 0.06, 0.02
  6:35pm  up 24 days, 11 min,  1 user,  load average: 0.00, 0.04, 0.05

More information about the Techtalk mailing list