Homebrew PCBs

Wow.

Interesting story, though it doesn't seem very relevant.

I guess that's the sort of thing we can look forward to
as a result of emphasizing self-esteem over achievement
in our public schools. If we manage to dumb down
everyone to the lowest common denominator then no one
will ever do anything dangerous because they won't know
how. And we wouldn't need groups like this one.

Here's something that will make your hair stand on end:
My exposure box design is the eventual result of a YouTube
video I saw where a guy used Hg vapor lamps with the
glass envelop broken off because apparently *any* such
bulb will produce the necessary radiation if the borosilicate
envelope is removed. I was trying to make the thing as cheap
as possible, so I tried it. Turned out the exposure time was
longer than I wanted and then I found an Hg bulb made for
"safe" UV and so used that. $10 for the bulb and $40 for
the ballast, some MDF and cheap drawer slides and voila!
A spiffy exposure box with reasonably fast exposure times.
Does it leak? Sure, some, but not much. I squint when I
slide the drawer out. The problem with Hg lamps is that
they require a minute to "warm up" and you can't turn them
on again right away if you turn them off, so interlock switches
are not practical. I thought about some elaborate mechanical
interlocks, but decided not to make "perfect" the enemy of
"good enough." The advantage of the Hg lamp is it is nearly
a point UV source. I haven't been able to do 8/8 yet but I
have done 12mil traces with spaces probably less than 8.
My biggest problem now is making high-enough quality masks.
--
Phil M.

----- Original Message ----- 
From: "Mitch Davis" <mjd@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, July 07, 2013 9:54 AM
Subject: Re: [Homebrew_PCBs] Re: For a DIY exposure box ... is collimated 
light an issue?


> On Mon, Jul 8, 2013 at 4:19 AM, brane2 <brankob@...> wrote:
>> Dne 07. 07. 2013 15:37, pis(e epa_iii:
>>>
>>> consider the idea that this device may not always be in your possession 
>>> or control.
>>
>> Chill out a little FFS...
>
> Some people live in very litigious societies.  However well meaning
> you are, some asshole will always be looking for a reason to sue you,
> and scumbag lawyers are altogether too happy to oblige.  Safety
> mechanisms are a way to be seen to take the safety issue seriously,
> which can be a legal defence.
>
> Also, such a box may end up in the hands of minors, or people who just
> don't realise the danger.  Here's an example of how 4 people
> (including a 6 year-old child) died, as a result of not knowing of the
> dangers of the pretty glowing blue stuff they'd found:
>
>  http://en.wikipedia.org/wiki/Goi%C3%A2nia_accident
>
> Would be a shame if some young boy or girl lost their eyesight just
> for want of a safety switch...
>
> Mitch.
>
>