On Fri, 19 Dec 2014 08:15:24 +0000, Martin Brown wrote:

Yes, I've picked up on that, the Far East ones tend not to
mention
sealed or not, though pictures show solid edges not open. Could
one
get away with DIY sealing with a bead of silicone sealant?

I don't know if the acetic acid might damage the junctions
or PCB tracks. It would be a question of finding a sealant
which doesn't harm these during curing or after set.

I think acetic acid would be decidedly bad for them or at least for the
metallic interconnects.

Non acid cure silicone ...

Epoxy glue or acrylic car body filler should be OK provided you never
want to take it apart again.

There is going to be considerable thermal cycling, hopefully not far
short of 50 C (-25 to +20). I think something with a bit of "give" is
in order.

BTW if your two stage cooler has two different sized devices you will
need to interpose a thin ~2mm aluminium plate between them.

I think they are both 40 mm square so will just be "stuck" together
with a thinlayer of thermal compound.

Finding a suitable chamber is looking to be the hard bit. All the
plastic food storeage containers I've looked at so far are milky not
clear. There is a glass biscuit jar in Tesco for £2 that has flatish
sides but is quite large and glass is relatively poor conductor of
heat, so getting the inside cold enough might be tricky.

Oh and the low pressure devices seem to be a repeatable single shot
sort of thing. That is you have a sealed chamber cotaining your
saturated vapour then rapidly reduce the pressure this lowers the
temp and super saturates the inside enabling the tracks become
visible. For a while? Presumably it soon warms back up and you have
to repeat the pressure drop?
On the DIY version I found there is also a "clearing" 150 V DC charge
involved. The Peltier thing I've looked at uses a poly cup or
balloon. I might try as many series connected PP3's as I can find...

--
Cheers
Dave.