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'Peltier Junction'
1997\04\19@223138 by deicide

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This is off topic....but since the people on this list know a lot I
figured i might get an answer faster than searching a lot for one....
I wanted to know where to get a Peltier Junction.....and some info on
Laser cooling.....But i'd really like to but a peltier junction....
I saw one that was one inch square for like 17 dollars...but that seemed
expensive so i didn't buy one...and now i can't find any...

John

1997\04\20@140316 by Mike Ghormley

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John wrote:

>I wanted to know where to get a Peltier Junction.....

I found what I consider a good bargain on Peltier junctions, although
your experience with a $17 version might not make this look so good to
you.  As you might know, in order for PJ's to work well you will at least
need a heat sink on one side.  There is a company called HSC (Halted
Specialties Company) which advertises in Nuts & Volts magazine (April
`97, page 3) which has a combo PJ/heat sink/12V fan for ~$25 (HSC#
16106).  It was originally intended as a cooler for non-metallic Pentium
Chips.  I have one and it works like a charm.  A drop of water will boil
on one side and freeze on the other.

They can be reached at:
       http://www.halted.com
or at:
       1-800-442-5833

Best regards,

Mike

When the way of the Tao is forgotten, kindness and ethics must be taught.
Men must learn to pretend to be wise and good.  --  Lao Tzu

1997\04\20@143156 by Lee Jones

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>> I wanted to know where to get a Peltier Junction.....

> good bargain on Peltier junctions [...] company called HSC (Halted
> Specialties Company) http://www.halted.com or at 1-800-442-5833

I've had good dealing with them in the past.

> combo PJ/heat sink/12V fan for ~$25 (HSC# 16106).  It was originally
> intended as a cooler for non-metallic Pentium Chips.  A drop of water
> will boil on one side and freeze on the other.

I think Mike is exagerating. :-)

As I recall, you get about 20-25 deg C temperature difference from
one side of a Peltier junction device to the other side.  You can
stack them (multiple stages) for more.  Transferring the heat energy
is not free -- there's a not inconsequential current consumption.

                                               Lee Jones

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1997\04\20@152639 by Kalle Pihlajasaari

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Hi Lee,

Apologies for the of topic nature.  One can always use a PIC or Stamp
to control the PJ cooler system.  Thermal mass being what it is there
is not much of a rush if you do not have to do very accurate temperature
control.  Simple setpoint controller can easyli be implemented.

You  would monitor for over temperature and current to prevent damage
to the PJ cooler modules.

> > combo PJ/heat sink/12V fan for ~$25 (HSC# 16106).  It was originally
> > intended as a cooler for non-metallic Pentium Chips.  A drop of water
> > will boil on one side and freeze on the other.
>
> I think Mike is exagerating. :-)

I think not.

> As I recall, you get about 20-25 deg C temperature difference from
> one side of a Peltier junction device to the other side.  You can
> stack them (multiple stages) for more.  Transferring the heat energy
> is not free -- there's a not inconsequential current consumption.

The temp difference can be over 150 degC.  The problems are when the
hot side gets hotter than the solder that is used in the assembly and
the whole unit destructs.  I would be cautios about using them for
heating as the efficiency is only about 25% you don't gain much over
just using a heating element and you risk toasting the PJ device.

For cooling you have to dissapate 4 times as much heat as what you
are actually pumping.  It also means that the cold side heats up
pretty fast after you turn of the pump as the heat from the hot side
now can 'run back' with the pumping current off.

I have done a design analysis on a PJ water cooler that almost worked
well except that the efficiency is so poor and a large temp gradient
does not help any.  The water cooler actually uses a 60 mm x 60 mm
PJ cooler device and a LARGE 120 mm x 120 mm x 30 mm finned heatsink
with a large fan (I have a box of these for sale, see my SirPlus page)
and there still was not quite enough to get all the waste heat out.
With two fans the water coolers work a treat and make a 60mm dia by 6mm
thick ICE brick that after it reaches a predetermined thickness
is allowed to melt free (current switched off) and floats to the
top of the cooling space, the cooler turns on and starts to make
another ice brick.

So in heating mode

  Ambient    PJ     Box
  20W    +   80W =  100W

and in cooling mode

  Ambient    PJ     Box
  100W   =   80W +  20W

You are correct about the current consumption obviously and the potential
for stacking the devices but you usually only stack them 2 or 3 high so
with just 25 degC you could only get a temp difference of 75DegC and much
more is atainable as long as one keeps in the device limits.
{
Just had a look at the RS components (UK) catalog at some specs.  They have
got quite a range now 15 in total with a stacked module, a ring module
and a fan cooled module.  Smallest is 0.32W of pump largest is 120W which
is what was used in the water cooler.  Max temp is listed as a conservative
85 degC but 110 degC for the Fan cooled unit.  Max temp differential is
65 .. 70 degC for the single stage units and 83 degC for the stacked units.
}
You have to build a pyramid with more cooler required to cool the cold one
with a minimum recommended ratio of 2:1 but better at 4:1 unless you only
use a small fraction of the coldest coolers capacity.  Expensive.

  -50 degC
                    XXXXX
    0 degC       ===========
                 XXXXX XXXXX
   50 degC =======================
           XXXXX XXXXX XXXXX XXXXX
  100 degC =======================
           |||||||||||||||||||||||
  BIG fan

Cheers
--
Kalle Pihlajasaari   .....kalleKILLspamspam@spam@ip.co.za   http://www.ip.co.za/ip
Interface Products   P O Box 15775, DOORNFONTEIN, 2028, South Africa
+ 27 (11) 402-7750   Fax: 402-7751    http://www.ip.co.za/people/kalle

DonTronics, Silicon Studio and Wirz Electronics uP Product Dealer

1997\04\20@161837 by Lee Jones

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Hi Kalle,

>>> combo PJ/heat sink/12V fan for ~$25 (HSC# 16106).  It was originally
>>> intended as a cooler for non-metallic Pentium Chips.  A drop of water
>>> will boil on one side and freeze on the other.

>> As I recall, you get about 20-25 deg C temperature difference

> The temp difference can be over 150 degC.  The problems are when the
> hot side gets hotter than the solder that is used in the assembly and
> the whole unit destructs.

> Just had a look at the RS components (UK) catalog at some specs.
> Max temp differential is 65 .. 70 degC for the single stage units

Thanks, I stand corrected.  Unstated in my comments, but I assumed
that for $25 the device in question was a single stage unit.


{Quote hidden}

Remember it's temperature difference.  So for any given final
target temperature (say -50 deg C), if you start with a lower
temperature you need fewer stages.

An alternate scheme is to cool the "hottest" side stage with
something better than ambient air.  For example, pump chilled
fluid (alcohol or anti-freeze) through passages in the heat
sink.  Modifying Kalle's example above:

  -50 degC
                    XXXXX
    0 degC       =========== <-- heat sink
                 OOOOOOOOOOO <-- passages for chilled fluid
                 =========== <-- heat sink

In astronomy (cooling CCD cameras), I've heard of a small 12V
pump in a bucket of ice water.  Portable and environmentally
friendly -- at the end of the observing run, you can water the
plants around your site.

This scheme has much lower power consumption for an increase
in "mess" (cooling fluid, ice, hoses, etc).
                                               Lee Jones

1997\04\20@162630 by John Doe

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How cold can peltier junctions actually get...???

and has anyone ever seen anything on laser cooling...besides those
expensive systems.....like info on how they work?

1997\04\20@164917 by Christopher Zguris

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At 12:22 PM 4/20/97 -0700, John Doe wrote:
>How cold can peltier junctions actually get...???
>

If memory serves, one of best practical applications I've heard for PJs is
on nuclear submarines for heating & cooling. Don't know the exact app - but
I've read PJs are used because they are compact and reliable. Obviously,
providing lots of power for a large PJ is not much of an issue on a nuclear sub.

Chris

   ======================================================================
                 Christopher Zguris  -  czgurisspamKILLspaminterport.net

                               HSTA, HRCA, AMA

               "I know that you believe you understand what you
               think I said, but I'm not sure you realize that
                     what you heard is not what I meant."
                               - Richard Nixon

   ======================================================================

1997\04\21@034927 by Keith Dowsett

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At 19:17 19/04/97 -0700, you wrote:
>This is off topic....but since the people on this list know a lot I
>figured i might get an answer faster than searching a lot for one....
>I wanted to know where to get a Peltier Junction.....and some info on
>Laser cooling....

You might like to try a few computer suppliers, for a while they were used
for cooling CPUs.

.But i'd really like to but a peltier junction....
>I saw one that was one inch square for like 17 dollars...but that seemed
>expensive so i didn't buy one.

That seems pretty cheap to me.  Over here you can get a decent range of them
from RS components but they're pretty expensive, a 30mm square will pump 28
watts for 40 GBP (about $60!!)

Hope this helps,

Keith.
==========================================================
Keith Dowsett         "Variables won't; constants aren't."

E-mail: .....kdowsettKILLspamspam.....rpms.ac.uk
  WWW: http://kd.rpms.ac.uk/index.htm

1997\04\22@120106 by Martin McCormick

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       There was a  good article in "QST" a year or so ago about Peltier
Junctions being used in the reverse mode of what they are usually used for.
Someone had taken a P.J. which was intended for use as the active part of
a mobile refrigerator and had run a small amateur radio transmitter from the
difference in temperature between a bucket of ice water and another of hot
water.  It works until the temperatures equalize.

       I don't remember the numbers, but I think the transmitter may have
been one Watt or less.  There are the usual energy transfer inefficiencies,
but one might be able to scrape together enough power to run a PIC-based
control system off of the waste heat of an engine on a boat or something
like that in which something is always going to be hot like the engine and
something else will always be cold like the water.

       I would think one would want a _GOOD_ brown out protective circuit
and probably a switching regulator to make the power supply as stable as it
can be in such a variable world.  One would want it either up and running
or off and not sort of trying to run which is what you would get when the
temperatures were equalizing after the engine stopped or when it was just
starting.

Martin McCormick

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