[comp.sys.ibm.pc.misc] Peltier effect device

peng@chaource.cs.wisc.edu (PENG) (12/15/90)

I hope this has not been asked before.  On the December issue of Byte (p.132),
there is a short article on an interesting cooling device, which can be
mounted on a CPU and is able to cool the chip down to 0 degree centigrade.
This device, according to Byte, is a Peltier effect device, which is
"a thermoelectric cooling system based on the principle that passing a current
between two physically connected, dissimilar materials produces cooling on one
side and heat on the other."  I am not quite sure if I know what this
sentense is talking about.  Can someone knowledgeable elaborate this a little
bit?

-peng

BTW, in case you are interested, this device is used to push the 486 to 50Mhz.
I am not sure what the 486 is originally rated?  (33Mhz?)
-- 
+--------
|C. J. Peng @ University of Wisconsin - Madison                 
|ARPA:  peng@cs.wisc.edu                                         
|UUCP:  ...!{ihnp4,hplabs,seismo,topaz,etc.}!uwvax!chaource!peng  

grege@gold.gvg.tek.com (Greg Ebert) (12/15/90)

In article <1990Dec14.213730.10078@spool.cs.wisc.edu> peng@chaource.cs.wisc.edu (PENG) writes:
>I hope this has not been asked before.  On the December issue of Byte (p.132),
>there is a short article on an interesting cooling device, which can be
>mounted on a CPU and is able to cool the chip down to 0 degree centigrade.
>This device, according to Byte, is a Peltier effect device, which is
>"a thermoelectric cooling system based on the principle that passing a current
>between two physically connected, dissimilar materials produces cooling on one
>side and heat on the other."  I am not quite sure if I know what this
>sentense is talking about.  Can someone knowledgeable elaborate this a little
>bit?
>
>-peng
>
>BTW, in case you are interested, this device is used to push the 486 to 50Mhz.
>I am not sure what the 486 is originally rated?  (33Mhz?)
>-- 

The device is manufactured by Velox Computer Technology, and sells for ~$150
in quantities. See the Article in EDN (Dec 6. , 1990).

The Peltier Effect is significant in an Antimony/Bismuth junction. The process
is reversible: you can measure an emf when the junction is heated (its a few
millivolts), or if a potential is applied across the junction, electrons
will absorb (thermal) energy while traversing the junction. I know zilch about
solid-state physics, but I think it's the result of differing work-functions
of the 2 materials; ie, there is an 'energy gap' at the junction, and the
electrons with sufficient thermal energy can cross the gap and get whisked
away because of the externally applied emf. As one thermally active electron
leaves town, another follows behind which results in a net flux of electrons
with higher thermal energy away from the junction, hence cooling is
observed.

Add a bunch of these together and you can soak-up a few watts of heat.

BUT, before all of you go charging out to by one of these electric ice cubes
and a crystal, be aware that the logic surrounding to CPU probably wont
be able to run at 50Mhz (well, actually 100Mhz).

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josephc@nntp-server.caltech.edu (Joseph I. Chiu) (12/15/90)

grege@gold.gvg.tek.com (Greg Ebert) writes:

>>I hope this has not been asked before.  On the December issue of Byte (p.132),
>>there is a short article on an interesting cooling device, which can be
>>mounted on a CPU and is able to cool the chip down to 0 degree centigrade.
>>This device, according to Byte, is a Peltier effect device, which is
>>"a thermoelectric cooling system based on the principle that passing a current
>>between two physically connected, dissimilar materials produces cooling on one
>>side and heat on the other."  I am not quite sure if I know what this
>>sentense is talking about.  Can someone knowledgeable elaborate this a little

>The Peltier Effect is significant in an Antimony/Bismuth junction. The process
>is reversible: you can measure an emf when the junction is heated (its a few
>millivolts), or if a potential is applied across the junction, electrons
>will absorb (thermal) energy while traversing the junction. I know zilch about
>solid-state physics, but I think it's the result of differing work-functions
>of the 2 materials; ie, there is an 'energy gap' at the junction, and the
>electrons with sufficient thermal energy can cross the gap and get whisked
>away because of the externally applied emf. As one thermally active electron
>leaves town, another follows behind which results in a net flux of electrons
>with higher thermal energy away from the junction, hence cooling is
>observed.

>Add a bunch of these together and you can soak-up a few watts of heat.

In other words, it is (in big oversimplification) a refrigerator.  What it does
is it absorbs heat in one plate, and transfers the energy to the other plate,
releasing it in the form of heat again.   You can sort of think of it as shoving
the heat from one side of the device to the other.

Speaking of refrigerators, I have heard the there is a peltier-effect fridge
that can hold a six-pack.  Anyone know if this is true, and if so, what
the availability is?  ( I read this in a magazine somewhere... )

-Joseph

--
josephc@coil.caltech.edu               ...Just another lost soul in the universe

-- 
--
josephc@coil.caltech.edu               ...Just another lost soul in the universe

derek@sun4dts.dts.ine.philips.nl (derek) (12/17/90)

josephc@nntp-server.caltech.edu (Joseph I. Chiu) writes:

>grege@gold.gvg.tek.com (Greg Ebert) writes:

>>>I hope this has not been asked before.  On the December issue of Byte (p.132),

[lots of stuff deleted for brevity]

>Speaking of refrigerators, I have heard the there is a peltier-effect fridge
>that can hold a six-pack.  Anyone know if this is true, and if so, what
>the availability is?  ( I read this in a magazine somewhere... )

About 10 years (!) ago I bought a very good fridge for camping based on the 
Peltier effect. It worked off the car battery. I doubt if this model is still
available, though. It would not just hold a six-pack more like a crate of wine!
(It was made in France). 

However, these days I think you can get 3-way fridges - car/line/gas. Check
out your best local camping shops, or post to rec.? what is there as camping
section?

My fridge was 'reversible' so in the summer you could keep stuff cold, and
in the winter, (or for barbeques) could keep stuff hot. Great!

>-Joseph

>--
>josephc@coil.caltech.edu               ...Just another lost soul in the universe

P.s. your sig is coming up twice.

Best Regards, Derek Carr
DEREK@DTS.INE.PHILIPS.NL           Philips I&E TQV-5 Eindhoven, The Netherlands 
Standard Disclaimers apply.

mir@opera.chorus.fr (Adam Mirowski) (12/17/90)

In article <1990Dec14.213730.10078@spool.cs.wisc.edu>, peng@chaource.cs.wisc.edu (PENG) writes:
%% I hope this has not been asked before.  On the December issue of Byte (p.132),
%% there is a short article on an interesting cooling device, which can be
%% mounted on a CPU and is able to cool the chip down to 0 degree centigrade.
%% This device, according to Byte, is a Peltier effect device, which is
%% "a thermoelectric cooling system based on the principle that passing a current
%% between two physically connected, dissimilar materials produces cooling on one
%% side and heat on the other."  I am not quite sure if I know what this
%% sentense is talking about.  Can someone knowledgeable elaborate this a little
%% bit?

That is one of the less known of the 4 thermoelectrical effects.
I remember having done some exercises on it on the second year. As
far as I remember, the Joule/Peltier ratio wasn't very impressive.
The materials must be semi-conductors.

French popular science magazine "Science et Vie" proposed its readers
to construct an experimental cooler based on Peltier principle early
in the eighties. The machine was able to produce ice cubes (< 0C), but
had to include a ventilator (good as a camping cooler).

-- 
Adam Mirowski,  mir@chorus.fr (FRANCE),  tel. +33 (1) 30-64-82-00 or 74
Chorus systemes, 6, av.Gustave Eiffel, 78182 Saint-Quentin-en-Yvelines CEDEX

jvincent@bnr.ca (John Vincent) (12/18/90)

In article <1990Dec14.213730.10078@spool.cs.wisc.edu> peng@chaource.cs.wisc.edu (PENG) writes:
>I hope this has not been asked before.  On the December issue of Byte (p.132),
>there is a short article on an interesting cooling device, which can be
>mounted on a CPU and is able to cool the chip down to 0 degree centigrade.
>This device, according to Byte, is a Peltier effect device, which is
>"a thermoelectric cooling system based on the principle that passing a current
>between two physically connected, dissimilar materials produces cooling on one
>side and heat on the other."  I am not quite sure if I know what this
>sentense is talking about.  Can someone knowledgeable elaborate this a little
>bit?
>

The devices mentioned are fairly common in the opto-electronics world and are
usually used to cool laser diodes used in opto transmission systems.  They 
are, in the most simple terms, a reverse thermocouple.  These things come in a
bunch of sizes. The biggest I have seen is about two inches square. They can
freeze water, although they suck a lot of power.
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cramer@optilink.UUCP (Clayton Cramer) (12/22/90)

In article <1990Dec14.213730.10078@spool.cs.wisc.edu>, peng@chaource.cs.wisc.edu (PENG) writes:
> I hope this has not been asked before.  On the December issue of Byte (p.132),
> there is a short article on an interesting cooling device, which can be
> mounted on a CPU and is able to cool the chip down to 0 degree centigrade.
> This device, according to Byte, is a Peltier effect device, which is
> "a thermoelectric cooling system based on the principle that passing a current
> between two physically connected, dissimilar materials produces cooling on one
> side and heat on the other."  I am not quite sure if I know what this
> sentense is talking about.  Can someone knowledgeable elaborate this a little
> bit?
> 
> -peng

A Peltier effect device is essentially a thermocouple run backwards.
(A thermocouple involves heating two dissimilar metals, and getting
electron flow -- and therefore electricity -- from one metal to the
other.  Such devices are used in places where simplicity and reliability
are more important than efficiency -- say a spacecraft).

I can visualize the process by which heat causes electron flow from
one metal to another (since different metals have different electro-
negativities) -- for some reason, I can't picture how electron
flow causes cold.
-- 
Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer
Self-defense is the most basic of human rights.  Lacking the right to defend
yourself today can make it very hard to exercise any other rights tomorrow.
You must be kidding!  No company would hold opinions like mine!

valdes@bgsuvax.UUCP (oscar Valdes) (12/22/90)

In article <5070@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes:
>I can visualize the process by which heat causes electron flow from
>one metal to another (since different metals have different electro-
>negativities) -- for some reason, I can't picture how electron
>flow causes cold.


	See if the following helps.  The electrons, as they flow, carry
heat away from the junction.   In the thermocouple, heating increases the
electron flow.  In the Peltier device, the voltage produces the electron flow
that carry the heat from one metal to the other.  Thus, one metal gets hotter
and the other gets colder.


*******************************************************************************

	Sooner or later reality bites you in the ass

*******************************************************************************

whit@milton.u.washington.edu (John Whitmore) (12/22/90)

In article <5070@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes:
>
>A Peltier effect device is essentially a thermocouple run backwards.
>
>I can visualize the process by which heat causes electron flow from
>one metal to another (since different metals have different electro-
>negativities) -- for some reason, I can't picture how electron
>flow causes cold.

	You're SO close!  Stand back and look at what you just said.
Heat causes electron flow from one metal (carrier-rich) to another 
(carrier-poor), by diffusion from high carrier concentration to low
carrier concentration.  This diffusion, since it spontaneously
creates a charge separation, requires energy.  The heat
that CAUSES this electron flow is used up thereby.
	Entropy still increases, because the charge carriers
are spread out more evenly (diluted, as it were.)  Osmosis
is a VERY similar phenomenon.
	It is the difference in charge carrier densities at
the two disparate temperatures that drives the complete circuit
as a thermocouple, by the way.  The back-EMF caused by the charge
transfer would otherwise equilibrate at a relatively low voltage,
and only if mechanical work (lifting one material off the other)
is done on the charge would any significant energy be noticed.
That is the principle of rubbing materials together to generate
a static charge (and the original 'electricity' phenomenon.)
	
	All this is actually very close to common elementary
electric experimentation that we all did in our youth.
	It is common nowadays to show the charge separation in
the absence of rubbing, by the way (to clarify the fact that
friction has nothing to do with it).  The usual technique is to
pull a piece of sticky tape off of another (identical) strip
of tape.  The sticky-side has different charge density from
the slick side, so the two strips, once separated, have opposite
charges.
	
	John Whitmore

userDHAL@mts.ucs.UAlberta.CA (David Halliwell) (12/25/90)

In article <5070@optilink.UUCP>, cramer@optilink.UUCP (Clayton Cramer) writes:
>In article <1990Dec14.213730.10078@spool.cs.wisc.edu>, peng@chaource.cs.wisc.edu (PENG) writes:
>> I hope this has not been asked before.  On the December issue of Byte (p.132),
>> there is a short article on an interesting cooling device, which can be
>> mounted on a CPU and is able to cool the chip down to 0 degree centigrade.
>> This device, according to Byte, is a Peltier effect device, which is
>> "a thermoelectric cooling system based on the principle that passing a current
>> between two physically connected, dissimilar materials produces cooling on one
>> side and heat on the other."  I am not quite sure if I know what this
>
>A Peltier effect device is essentially a thermocouple run backwards.
>(A thermocouple involves heating two dissimilar metals, and getting
.                         ^^^^^^^^
.                       not quite!!!!
 
>electron flow -- and therefore electricity -- from one metal to the
>other.  Such devices are used in places where simplicity and reliability
>are more important than efficiency -- say a spacecraft).
>
>I can visualize the process by which heat causes electron flow from
>one metal to another (since different metals have different electro-
>negativities) -- for some reason, I can't picture how electron
>flow causes cold.
>--
 
.   A thermocouple circuit does involve two dissimilar metals, but the
current flow is generated because the junctions are at different
temperatures. However, current flow is not the governing electrical
characteristic - voltage is. For each unit of temperature difference,
the thermocouple will output a certain voltage, in a nearly linear
fashion (at least over a small temperature range). For example, a copper-
constantan thermocouple puts out about 40 microvolts per Celcius degree
difference. Thermocouples are often used for temperature measurement, but
because they just give a difference there must be an independent method
of measuring the absolute temperature at one junction. The thermocouple
then gives a voltage indicating the temperature at the second junction.
The reference junction can be placed in something of known temperature -
e.g an ice/water mixture - or measured using a thermistor, platinum RTD,
etc.
 
.   Given this basic understanding of a thermocouple, a Peltier module
basically reverses the process. By imposing a voltage in a thermocouple
circuit, we can force a temperature difference between the two junctions.
This in itself will not create cooling, but if we cool the warm junction
we will still have the cold junction at the same offset below it. The heat
added to the system through the electrical power consumption must also be
removed from the warm side, but the cold side should be cooler than it
would be if we didn't have a Peltier module and just tried to cool the
component directly.
 
.    Years ago I worked in a lab where Peltier modules were used for
freezing tests on soil samples. We used a water-cooled warm side, which
kept the warm junction around room temperature. It was easy to get
sub-freezing temperatures from the system. The module was controlled by
a rather large mass of electronics, to get the stability needed for the
tests. It made a rather impressive demo during show-and-tell at the
open houses, to have a block of ice sitting on a module at room temperature
showing no signs of thawing...
 
 
Dave Halliwell
 
P.S. Merry Christmas to all. Or Season's Greetings, etc. Choose one.

valdes@bgsuvax.UUCP (oscar Valdes) (12/28/90)

In article <2036@mts.ucs.UAlberta.CA> userDHAL@mts.ucs.UAlberta.CA (David Halliwell) writes:
>.   A thermocouple circuit does involve two dissimilar metals, but the
>current flow is generated because the junctions are at different
>temperatures. However, current flow is not the governing electrical


	Check again.  You don't need two junctions to make a thermocouple.

Heating a single junction will produce a voltage that depends on the

temperature of the junction.



*******************************************************************************

	Sooner or later reality bites you in the ass

*******************************************************************************

pierson@ggone.enet.dec.com (Dave Pierson) (12/29/90)

In article <6792@bgsuvax.UUCP>, valdes@bgsuvax.UUCP (oscar Valdes) writes,
in part:

>	Check again.  You don't need two junctions to make a thermocouple.
>Heating a single junction will produce a voltage that depends on the
>temperature of the junction.
	There are always two junctions.  One may be the juction of the
	TC leads with the measuring instrument terminals.  TC rigs always
	measure the difference between the two junction temperatures.  To get
	an "absolute" reading, the temperature of one junction is measured
	by independent means.  In "lab" TCs, this is typically an RTD type
	detector, mounted on a comon thermal mass with the screw terminals.
	The terminal block temp is then "added" either analog fashionm, or
	digitally.  TCs are non linear over large delta t's, but reasonably
	linear over small ones.

	TCs are perfectly happy as either voltage or current output devices.
	Current (8)>>) practice treats them as voltage sources, due to the
	availability of good, hiZ amps.  In the past, the were commonly used
	with microammeters.  (Hi precision work used manually or automatically
	balanced bridges, which is voltage source mode.)

	(attempted graphics, Cu/Con couple...)
                 _______Cu_____________o_(Cu)____>Amp hi
		/                      |
	       /measuring junction     |<-Ref temp
	       \                       |	
		\______Con_____________o__(Cu)___>Amp Lo
				       ^-the "other" junction
	
	(As i write this, i sit next to a logger with 16 TCs on it...)

thanks
dave pierson			|the facts, as accurately as i can manage,
Digital Equipment Corporation	|the opinions, my own.
600 Nickerson Rd
Marlboro, Mass
01752				pierson@cimnet.enet.dec.com

"He has read everything, and, to his credit, written nothing."  A J Raffles

valdes@bgsuvax.UUCP (oscar Valdes) (12/30/90)

In article <18522@shlump.nac.dec.com> pierson@ggone.enet.dec.com (Dave Pierson) writes:
>	There are always two junctions.  One may be the juction of the
>	TC leads with the measuring instrument terminals.  TC rigs always
>	measure the difference between the two junction temperatures.  To get
>	(attempted graphics, Cu/Con couple...)
>                 _______Cu_____________o_(Cu)____>Amp hi
>		/                      |
>	       /measuring junction     |<-Ref temp
>	       \                       |	
>		\______Con_____________o__(Cu)___>Amp Lo
>				       ^-the "other" junction
>	




	In other words, what you are saying is that if there is no

measuring instrument there is no voltage generated due to the 

dissimilarity of the two metals.

	I wonder how the metals "know" there is a measuring instrument

present.



******************************************************************************

	Sooner or later reality bites you in the ass

******************************************************************************

mitchell (Bill Mitchell) (12/30/90)

In article <6793@bgsuvax.UUCP> valdes@bgsuvax.UUCP (oscar Valdes) writes:
>
>	I wonder how the metals "know" there is a measuring instrument
>present.
>

If a tree falls in the desert where there is no one to hear it, does it
make a sound?

What is the sound of one hand clapping, anyway?

-- 
mitchell@mdi.com (Bill Mitchell)