Electrical hacking (was Re: [Techtalk] [OT] charging USB device without a PC)

[Maria Blackmore]

On Sun, 13 Apr 2003, Conor Daly wrote:

> On Sat, Apr 12, 2003 at 11:15:30PM -0400 or so it is rumoured hereabouts, 
> Brenda Bell thought:
> > I'm impressed.  But then again, I'm a electrical wimp (would have probably
> > bought a powered USB hub :)

blimey, that's boring.
hmm, you know that didn't even cross my mind as a solution :)

> It's not that hard.  It _is_ important to know what you _can_ safely[0] or
> usefully[1] mess with and what you _just don't touch_.  

ah yes, quoting footnote [1] it's important to know what you can fix
without making it worse :)

> 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
things that you can do to mitigate it's effects, especially when you're in
a hurry.  They usually involve something that insulates, and standing a
low way away, and then observing the rather pretty spark and strong smell
of ozone that comes after 27 kV finds it's way to earth. :)

> 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]

> o The silk screened flexible printed circuit in your ergonomic keyboard

heh :)

> o The extremly fine printed circuits on your mobo (see [1]).

Ah yes, now these are the toughy, you need a temperature controlled iron
to stop you from putting in so much heat that they melt or lift up, and
when removing solder it's vitally important to use braid instead of a
solder sucker, lest your solder sucker sucks the whole track off the
board.

> Things I have successfully fixed:

Cool :)

I won't list things here, because I just to get paid to do this kind of
stuff, but I will say that at the moment I'm in the middle of a project to
fix up a 20 kVA UPS at work :)

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.

It's important to challenge yourself, it's how you learn.

> Things I have fixed after I broke them in the first place:
> 
> o The wiring in the wall of the house after I drove a screw right through
>   it thus shorting out the whole house.

I've got this little widget that tells me when there's a mains cable
nearby, would you like to borrow it :)

> o The aforementioned printed circuit in the keyboard which I regularly
>   need to patch with conductive paint (Good tip actually, The "silver"
>   paint for repairing windscreen demisters sold in automotive shops is
>   just the thing for silk screened printed circuits).

It's actually a colloid of real silver that's coated with stuff and held
in a suspension in something that evapourates when you paint it.  The
silver is left behind on whatever you painted it on, it's very useful for
repairing fine tracks.  You can protect it by spraying with a layer of
clear laquer.

> 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 :(

> Incidentally, there's an in-car USB charger available for $15 (google
> for usb treo charger) if you do have a need for PC-less USB
> charging...

cool

> Conor (who does this stuff for fun)

Maria

Who does this for fun, and profit[4] :)


[0] Without killing yourself or your family.
[1] Likely to be successful.
[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. :)
[3] Common Sense, which is sadly rather uncommon, it would seem, and also
relies in this case in the knowledge of [2].  The trick is to not connect
anything on the bathroom side of the transformer with or to anything on
the mains side of the transformer
[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, and started off fixing things for my parents as a way of getting
more pocket money.  How many teenagers do you know who got more pocket
money for cleaning the VCR? :)