Need a couple of chunky peltier coolers, one around 120 W another
above 60 W. Recommended are 12709 and 12710, plenty of suppliers on
Amazon/eBay but they all seem to be Far East based.

CPC etc have such devices but at £15 to £20 each, where as the Far
Eastern ones are less than a fiver delivered. Can anyone recommend
(or not) a Far Eastern supplier?

The lad wants to build a cloud chamber as a Christmas present for
himself. Old ATX PSU for the peltiers, hefty CPU heatsink, sealable
clear bowl, sponge soaked in isopropanol and Americium-241 from old
smoke detector as a source. Peltiers are a bit more convenient than
dry ice, though might not work quite as well.

--
Cheers
Dave.

In article o.uk,
Dave Liquorice wrote:
Need a couple of chunky peltier coolers, one around 120 W another
above 60 W. Recommended are 12709 and 12710, plenty of suppliers on
Amazon/eBay but they all seem to be Far East based.

CPC etc have such devices but at £15 to £20 each, where as the Far
Eastern ones are less than a fiver delivered. Can anyone recommend
(or not) a Far Eastern supplier?

Oddly enough been looking at them myself, but I'd just go with the
Farnell offerings as I'm too lazy to spent time looking at the imports...

The lad wants to build a cloud chamber as a Christmas present for
himself. Old ATX PSU for the peltiers, hefty CPU heatsink, sealable
clear bowl, sponge soaked in isopropanol and Americium-241 from old
smoke detector as a source. Peltiers are a bit more convenient than
dry ice, though might not work quite as well.

Saw something on the box recently about this - A BBC article on weighing
a cloud - apparently there are ultrasonic devices you can buy in garden
centres that make water vapour out of cold water - designed for garden
water features, etc.

Google for garden fog maker - eg

http://www.amazon.co.uk/Generic-Colo.../dp/B00EQ231WW

Gordon

On 17/12/2014 23:24, Dave Liquorice wrote:
Need a couple of chunky peltier coolers, one around 120 W another
above 60 W. Recommended are 12709 and 12710, plenty of suppliers on
Amazon/eBay but they all seem to be Far East based.

CPC etc have such devices but at £15 to £20 each, where as the Far
Eastern ones are less than a fiver delivered. Can anyone recommend
(or not) a Far Eastern supplier?

The lad wants to build a cloud chamber as a Christmas present for
himself. Old ATX PSU for the peltiers, hefty CPU heatsink, sealable
clear bowl, sponge soaked in isopropanol and Americium-241 from old
smoke detector as a source. Peltiers are a bit more convenient than
dry ice, though might not work quite as well.

Chances are you are only going to use it a few times so I'd suggest
buying in a block of dry cold after you have built the contraption. I
used methylated spirits in mine way back. You need really good black
velvet and a powerful compact light source.

It is actually quite hard to maintain large temperature differences on
Peltiers and you will probably need the hot side heat sink fan cooled
with forced air ventilation (or possibly even water cooled). Otherwise
you will end up with the cold side -80C below the hot side which will
end up about 50C or maybe even warmer.

I have long suspected although never actually tried it that you can
almost get to cloud chamber conditions in the gap above a cup of freshly
made coffee in a cold room.

The old design in Scientific American by C. L. Stong is pretty robust
and relatively easy to get working. Beware of frostbite!

http://www.amazon.co.uk/Scientific-A...ur+scien tist

Book out of print CD version also available but no idea what it is like.
(BEWARE that US edition includes some vivisection experiments that have
been illegal in the UK for several decades)

I have a friend who built half the atom smasher - the Van de Graph.

--
Regards,
Martin Brown

Martin Brown wrote:

You need really good black velvet

Vantablack would be the modern choice ;-)

On Thu, 18 Dec 2014 09:12:04 +0000, Martin Brown wrote:

Chances are you are only going to use it a few times so I'd suggest
buying in a block of dry cold after you have built the contraption.

This is probably true but *IF* it works it should just work provided
there is enough propanol in the chamber. It could be left running...

You need really good black velvet and a powerful compact light source.

The blacking I've yet to really consider, depends on what chamber we
can get. Powerful light sources are easy these days with 5 W LED
tourches...

It is actually quite hard to maintain large temperature differences on
Peltiers and you will probably need the hot side heat sink fan cooled
with forced air ventilation (or possibly even water cooled).

Air cooled, f'ing great CPU cooler, 120 mm fan, supposed to be able
to handle 180 W. Heat pipes transfer the heat from the CPU contact
area into the heatsink fins. Hum, they'll actually be upside down, so
might no work as well as they might. ie the condensed heatpipe
"stuff" won't be running back to the hot bit, hum....

you will end up with the cold side -80C below the hot side which will
end up about 50C or maybe even warmer.

We shall see... Needs to get down to around -25 C, so provided the
heat sink doesn't get much above 40 C it should work.

The old design in Scientific American by C. L. Stong is pretty robust
and relatively easy to get working. Beware of frostbite!

Is that based on dry ice? I sort of looked at using dry ice but the
places I could find only wanted to sell rather large quantities, 10
kg or more.

--
Cheers
Dave.

On Thu, 18 Dec 2014 09:11:31 +0000 (UTC), Gordon Henderson wrote:

Google for garden fog maker - eg

Different sort of cloud. B-)

This is to show ionising radiation from a source (the Americium-241)
or just the background "cosmic rays".

--
Cheers
Dave.

On Thursday, 18 December 2014 09:12:14 UTC, Martin Brown wrote:
On 17/12/2014 23:24, Dave Liquorice wrote:
Need a couple of chunky peltier coolers, one around 120 W another
above 60 W. Recommended are 12709 and 12710, plenty of suppliers on
Amazon/eBay but they all seem to be Far East based.

CPC etc have such devices but at £15 to £20 each, where as the Far
Eastern ones are less than a fiver delivered. Can anyone recommend
(or not) a Far Eastern supplier?

The lad wants to build a cloud chamber as a Christmas present for
himself. Old ATX PSU for the peltiers, hefty CPU heatsink, sealable
clear bowl, sponge soaked in isopropanol and Americium-241 from old
smoke detector as a source. Peltiers are a bit more convenient than
dry ice, though might not work quite as well.

Chances are you are only going to use it a few times so I'd suggest
buying in a block of dry cold after you have built the contraption. I
used methylated spirits in mine way back. You need really good black
velvet and a powerful compact light source.

It is actually quite hard to maintain large temperature differences on
Peltiers and you will probably need the hot side heat sink fan cooled
with forced air ventilation (or possibly even water cooled). Otherwise
you will end up with the cold side -80C below the hot side which will
end up about 50C or maybe even warmer.

I have long suspected although never actually tried it that you can
almost get to cloud chamber conditions in the gap above a cup of freshly
made coffee in a cold room.

The old design in Scientific American by C. L. Stong is pretty robust
and relatively easy to get working. Beware of frostbite!

http://www.amazon.co.uk/Scientific-A...ur+scien tist

Book out of print CD version also available but no idea what it is like.
(BEWARE that US edition includes some vivisection experiments that have
been illegal in the UK for several decades)

I have a friend who built half the atom smasher - the Van de Graph.


FWIW I have the 'Amateur Scientist' CD-ROM, bought a few years ago. IIRC it is
a bit annoying in that it wants to run an application which you then use to
navigate to the year, issue etc. that you are interested in. I think the scans
are in TIFF or similar form as well. A little background project is going to be
to try and extract all of the 'meat' of the CD and create a series of PDFs,
which is really what I wanted in the first place...

Jon N

In article o.uk,
"Dave Liquorice" writes:
Need a couple of chunky peltier coolers, one around 120 W another
above 60 W. Recommended are 12709 and 12710, plenty of suppliers on
Amazon/eBay but they all seem to be Far East based.

I bought a couple of the 40mm square ones from a radio fair many
years ago - not sure such things happen much anymore.

One possible source might be the small pelier fridges, which might
appear in the sales after (or even just before) Christmas.
(I was buying them to fix two such fridges 30 years ago.)

Note they come in sealed and not-sealed types. If you will be
running one side below the dew point, you need sealed ones, or
they will have a short life due to internal moisture and corrosion.
(That's what had killed the ones in the fridges, although I
managed to fix one of the peltiers afterwards by bypassing the
first junction.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 18/12/2014 10:19, Dave Liquorice wrote:
On Thu, 18 Dec 2014 09:11:31 +0000 (UTC), Gordon Henderson wrote:

Google for garden fog maker - eg

Different sort of cloud. B-)

This is to show ionising radiation from a source (the Americium-241)
or just the background "cosmic rays".


The last cloud chamber I saw worked at room temp without cooling other
than that produced by reducing the pressure with a hand operated pump
(bike pump with washers reversed type).

On 18/12/2014 10:16, Dave Liquorice wrote:
On Thu, 18 Dec 2014 09:12:04 +0000, Martin Brown wrote:


The old design in Scientific American by C. L. Stong is pretty robust
and relatively easy to get working. Beware of frostbite!

Is that based on dry ice? I sort of looked at using dry ice but the
places I could find only wanted to sell rather large quantities, 10
kg or more.

Sounds about right. 10kg block of dry ice will keep nicely for a week or
so inside one of the thick polystyrene boxes with a bit of additional
polystyrene around it (you don't want a gas tight seal). It will keep
for a few days in the bag it is usually supplied in.

Cutting it up is very noisy (wear ear defenders noisy). Beware of cold
metal that has been used to cut it up or crush it.

You might be able to cadge some for a nominal sum from your local
university physics department if you explained what you want it for (as
opposed to dodgy Jekyll&Hyde/Pangalactic gargleblaster drink additive).

It is annual Xmas lecture season and we were out supporting the RSC last
night in Newcastle. Saw two new variants of old tricks by Nick Barker of
Warwick University. One was elephants toothpaste with realistic pigment
based stripes in it and the other was a large cloud made by dropping
bulk crushed dry ice into a large conical flask 1/3 full of boiling
water (stand well clear of the back draft).

--
Regards,
Martin Brown

On Thu, 18 Dec 2014 13:48:33 +0000, Dennis@home wrote:

This is to show ionising radiation from a source (the
Americium-241)
or just the background "cosmic rays".

The last cloud chamber I saw worked at room temp without cooling other
than that produced by reducing the pressure with a hand operated pump
(bike pump with washers reversed type).

I've certainly seen ones in museums etc that are just there working
and didn't appear to have any cooling (ie not covered in frost)...

Maybe this is technology for technologies sake?

--
Cheers
Dave.

On Thu, 18 Dec 2014 11:18:07 +0000 (UTC), Andrew Gabriel wrote:

I bought a couple of the 40mm square ones from a radio fair many
years ago - not sure such things happen much anymore.

They do but I doubt they have quite the range of "useful bits" that
they did in the late 70's early 80's.

One possible source might be the small pelier fridges, which might
appear in the sales after (or even just before) Christmas.
(I was buying them to fix two such fridges 30 years ago.)

It would have to be a very cheap (not powerful enough?) fridge to
cost less than CPC et al, and VERY cheap to beat the Far East. Also
as I'm stacking them I need two different power ratings.

Note they come in sealed and not-sealed types. If you will be
running one side below the dew point, you need sealed ones, or
they will have a short life due to internal moisture and corrosion.

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?

--
Cheers
Dave.

On Thu, 18 Dec 2014 14:16:35 +0000, Martin Brown wrote:

Is that based on dry ice? I sort of looked at using dry ice but
the
places I could find only wanted to sell rather large quantities,
10
kg or more.

Sounds about right. 10kg block of dry ice will keep nicely for a week or
so inside one of the thick polystyrene boxes with a bit of additional
polystyrene around it ...

That long. Longevity in storeage wasn't really mentioned but making
2+2=5 I got the impression it sublimed fairly quickly as almost every
where effectively made to order.

... (you don't want a gas tight seal).

I wonder why that is? B-)

You might be able to cadge some for a nominal sum from your local
university physics department if you explained what you want it for (as
opposed to dodgy Jekyll&Hyde/Pangalactic gargleblaster drink additive).

I don't know anyone in the local University Physics Departments.

It is annual Xmas lecture season and we were out supporting the RSC last
night in Newcastle.

Unless ...

--
Cheers
Dave.

In article o.uk,
"Dave Liquorice" writes:
On Thu, 18 Dec 2014 11:18:07 +0000 (UTC), Andrew Gabriel wrote:

I bought a couple of the 40mm square ones from a radio fair many
years ago - not sure such things happen much anymore.

They do but I doubt they have quite the range of "useful bits" that
they did in the late 70's early 80's.

One possible source might be the small pelier fridges, which might
appear in the sales after (or even just before) Christmas.
(I was buying them to fix two such fridges 30 years ago.)

It would have to be a very cheap (not powerful enough?) fridge to
cost less than CPC et al, and VERY cheap to beat the Far East. Also
as I'm stacking them I need two different power ratings.

Note they come in sealed and not-sealed types. If you will be
running one side below the dew point, you need sealed ones, or
they will have a short life due to internal moisture and corrosion.

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.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 18/12/2014 23:39, Andrew Gabriel wrote:
In article o.uk,
"Dave Liquorice" writes:
On Thu, 18 Dec 2014 11:18:07 +0000 (UTC), Andrew Gabriel wrote:

[snip]

Note they come in sealed and not-sealed types. If you will be
running one side below the dew point, you need sealed ones, or
they will have a short life due to internal moisture and corrosion.

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.

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

BTW if your two stage cooler has two different sized devices you will
need to interpose a thin ~2mm aluminium plate between them. This trick
is common in Peltier cooled cameras where a large device pumps the
output of a smaller device attached to the back of the small CCD.

Not quite so relevant for a cloud chamber since you are trying to make a
fairly large region very cold.

--
Regards,
Martin Brown

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.

On Fri, 19 Dec 2014 23:44:42 +0000 (GMT), Dave Liquorice wrote:

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.

TK Marx may have come up trumps with a "Secret de Gourmet Boite de
Conservation Hermetique 0.4l" £2.99. Google/TK Marx site (nasty
horrible javascript only thing) seems remarkably reluctant to produce
an image or anything that looks similar. It's clear, round, flat
bottomed(*) with a lid that seals with a lever action.

(*) Apart from some slightly raised markings for recyling (7 SAN,
styrene acrylonitrile) and food safe logos etc. They won't last long
under the influence of fine sand paper and block...

--
Cheers
Dave.

On 19/12/2014 23:44, Dave Liquorice wrote:
On Fri, 19 Dec 2014 08:15:24 +0000, Martin Brown wrote:

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

Non acid cure silicone ...

Probably a better choice.

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.

Epoxy can be made a little bit rubbery if you deliberately alter the
proportions to I think be resin rich. It isn't as strong then but it
does have a bit of give. Exeriment on scrap first.

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.

The Japanese store Muji have some low profile water clear acrylic boxes
that would probably be ideal for this. ISTR Mine was a glass petri dish.

http://www.muji.co.uk/

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...

I wouldn't worry about clearing it. The chances are you won't have a
source strong enough to cause too many tracks. They appear and rain out
over a period of 5-10s thick ones for alpha and thin ones for beta.

--
Regards,
Martin Brown