thermocouple to a battery

[Bughuggger]

How do I make a thermocouple the same voltage as a battery to charge it. I want
to do it with a copper wire, an iron wire, a magnifying glass, a small chamber,
and the sun. To a 12 volt battery.

Thanks,

Dave (Bughuggger@aol.com)

 

[CBarn24050]

you can't, thermocouples produce millivolts.

 

[Gareth]

Bughuggger wrote:

How do I make a thermocouple the same voltage as a battery to charge it. I want
to do it with a copper wire, an iron wire, a magnifying glass, a small chamber,
and the sun. To a 12 volt battery.

Thanks,

Dave (Bughuggger@aol.com)

I don't think iron and copper are a good choice of metals for a
thermocouple.

Type J thermocouples use iron and constantan[1] and give an output of
21.8mV with a junction temperature difference of 400 degrees C

Type T thermocouples use copper and constantan[1] and give an output of
20.9mV with a junction temperature difference of 400 degrees C

I think that if you used iron and copper you would only get the
difference in voltage of the two above

21.8 - 20.9 = 0.9 mV with 400 degrees C temperature difference.

You can get a higher voltage by connecting lots of thermocouples in
series, but notice that if you connect lots of copper and constantan
wires together you will end up with half the joins the wrong way round -
these will produce the opposite voltage so you need to keep these
junctions cold and the others hot.
for example connect as below and keep the junctions marked + hot, and
the junctions marked - cold you will get three times the voltage you
would get with a single thermocouple.

copper+constantan-copper+constantan-copper+constantan

Unfortunately you would need about 500 hot junctions to get 12V with a
temperature difference of 400 degrees C.

You can get DC-DC converters which will step up voltages, but I you will
still need to get about a volt before you can operate one of these. I
don't think your idea is practical.

There are a couple of other things which may interest you though:

A) Solar Cells - these convert light to electricity directly and are
often used to power small, low power portable things (e.g. calculators)
or when electricity is required away from mains electricity.

B) Peltier Effect Devices - these are very similar to an array of
thermocouples and use electricity to move heat (Peltier Effect), but
they can be used in reverse to generate electricity from a temperature
difference (Seebeck Effect).

Notes:

1 Constantan is an alloy of copper and nickel.

--
-----------------------------------------------------------------------
To reply to me directly:

Replace privacy.net with: totalise DOT co DOT uk and replace me with
gareth.harris

 

[Reg Edwards]

How do I make a thermocouple the same voltage as a battery to charge it.

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

You need many hundreds of thermocouples all in series. And it will take hell
of a long time to recharge the battery.

 

[Spehro Pefhany]

On 21 Mar 2004 13:52:23 GMT, the renowned bughuggger@aol.com
(Bughuggger) wrote:

How do I make a thermocouple the same voltage as a battery to charge it. I want
to do it with a copper wire, an iron wire, a magnifying glass, a small chamber,
and the sun. To a 12 volt battery.

Suppose you can get the thermocouple to 200°C and your ambient is
30°C. You will get 9.24mV for each junction. You need about 13.8V to
charge a 12V battery, so you'll need about 1500 junctions in series.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Spehro Pefhany]

On Sun, 21 Mar 2004 15:53:12 +0000 (UTC), the renowned "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

How do I make a thermocouple the same voltage as a battery to charge it.

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

You need many hundreds of thermocouples all in series. And it will take hell
of a long time to recharge the battery.

If the magifying glass is, say, 36" in diameter, it might not.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[John Woodgate]

I read in sci.electronics.design that Bughuggger <bughuggger@aol.com>
wrote (in <20040321085223.20632.00001918@mb-m28.aol.com&gt about
'thermocouple to a battery', on Sun, 21 Mar 2004:

How do I make a thermocouple the same voltage as a battery to charge it. I want
to do it with a copper wire, an iron wire, a magnifying glass, a small chamber,
and the sun. To a 12 volt battery.

Copper/iron gives you roughly 40 uV per kelvin. How hot can you get the

hot junctions and how cool can you keep the cold ones? If you could get
250 K temperature difference (water-cooling the cold junction), you get
10 mV from one junction. So you need about 150 of them, minimum, because
the battery needs MORE than 12 V to charge it and there will be some
voltage drop in the thermocouple wires themselves.

Make the iron wires thicker: iron conducts both heat and electricity
less well, so you can pitch for equal losses by making the iron wires
about 2.6 times the diameter of the copper wires.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Spehro Pefhany]

On Sun, 21 Mar 2004 16:36:29 +0000, the renowned John Woodgate
<jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that Bughuggger <bughuggger@aol.com
wrote (in <20040321085223.20632.00001918@mb-m28.aol.com&gt about
'thermocouple to a battery', on Sun, 21 Mar 2004:

How do I make a thermocouple the same voltage as a battery to charge it. I want
to do it with a copper wire, an iron wire, a magnifying glass, a small chamber,
and the sun. To a 12 volt battery.

Copper/iron gives you roughly 40 uV per kelvin.

Are you sure about that? I see the number I gave earlier is wrong (it
was for iron/constantan which is about 50uV/K). But Iron and Copper
are both the + leads, so I think the difference is much less, more
like 10uV/°C.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[John Woodgate]

I read in sci.electronics.design that Gareth <me@privacy.net> wrote (in
<c3k9na$298a9l$1@ID-211380.news.uni-berlin.de&gt about 'thermocouple to a
battery', on Sun, 21 Mar 2004:

I don't think iron and copper are a good choice of metals for a
thermocouple.

Fairly often used in the past, but not for measurement; the V/T is
rather non-linear.

Type J thermocouples use iron and constantan[1] and give an output of
21.8mV with a junction temperature difference of 400 degrees C

Type T thermocouples use copper and constantan[1] and give an output of
20.9mV with a junction temperature difference of 400 degrees C

I think that if you used iron and copper you would only get the
difference in voltage of the two above

21.8 - 20.9 = 0.9 mV with 400 degrees C temperature difference.

Thermocouples don't work quite like electrochemical potentials.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[John Woodgate]

I read in sci.electronics.design that Reg Edwards
<g4fgq.regp@ZZZbtinternet.com> wrote (in <c3kdp8$92t$1@titan.btinternet.
com&gt about 'thermocouple to a battery', on Sun, 21 Mar 2004:

How do I make a thermocouple the same voltage as a battery to charge it.

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

You need many hundreds of thermocouples all in series.

Yes.

And it will take hell
of a long time to recharge the battery.

Not necessarily. Thermocouples are basically low-impedance devices.

Getting current is less of a problem than getting voltage.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <ejir501s430edn09cpabn368n5onmr57rb@4ax.com&gt
about 'thermocouple to a battery', on Sun, 21 Mar 2004:

Are you sure about that? I see the number I gave earlier is wrong (it
was for iron/constantan which is about 50uV/K). But Iron and Copper are
both the + leads, so I think the difference is much less, more like
10uV/°C.

I had 40 uV from an old book that I no longer have. I can't confirm it
from any of my present books, but I don't have any figures for a big
enough temperature difference to make the project practicable.

Silicon/germanium is a very good combination; 750 uV/K at 0/100 C.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Fred Bartoli]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> a écrit dans le message
news: 3fIoxFFpgcXAFwFq@jmwa.demon.co.uk...

I read in sci.electronics.design that Reg Edwards
g4fgq.regp@ZZZbtinternet.com> wrote (in <c3kdp8$92t$1@titan.btinternet.
com&gt about 'thermocouple to a battery', on Sun, 21 Mar 2004:
How do I make a thermocouple the same voltage as a battery to charge
it.

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

You need many hundreds of thermocouples all in series.

Yes.
And it will take hell
of a long time to recharge the battery.

Not necessarily. Thermocouples are basically low-impedance devices.
Getting current is less of a problem than getting voltage.
--

Yep. So put a few in series, use a step up transformer and set a punched
rotating disc between the TCs and the lens...
More seriously, use the 12V battery to supply the driver for a mosfets
switcher that'll drive a step up transformer.
@40uV/K and 250K difference it's 10mV/TC.
Say we want 100mV. That's 10 TCs. So far, not to difficult.

Say we want 100mA/12V output. At 100mV input that's a 120:1 ratio, i.e. 12A
primary current.
A pair of 2mOhm IRF6609 SMT mosfets will easily do the job and give .002x144
= 300mW of joule losses for 1.2W output, *neglecting* the transformer
losses. Not bad.
Of course at a 120:1 ratio the transformer will be impractical but splitting
the supply in 2 or 3 stages may render this not as unrealistic as it may
seem at first sight with a not to ridiculous efficiency.

Oops, why a transformer ?
We'll be better with a boost, but I'm too lazy to do the maths.

Still is the pb of cooling the cold junction.


BTW I visited the Ampere Museum near Lyon a few years ago and I remember a
nice coal fed thermoelectric generator that provided a comfortable amount of
(DC) power. I can't remeber the figures but for those days it was quite
impressive.


Thanks,
Fred.

 

[Glenn Ashmore]

I don't think you can do it. The Russians used to make a thermocouple
powered radio for use in remote places. It was a sleeve with about
2,000 iron and something (not copper) junctions that fit over the
chimney of a kerosene lamp. Produced about 9V. It only worked in
Siberia in the winter.

Bughuggger wrote:

How do I make a thermocouple the same voltage as a battery to charge it. I want
to do it with a copper wire, an iron wire, a magnifying glass, a small chamber,
and the sun. To a 12 volt battery.

Thanks,

Dave (Bughuggger@aol.com)

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

 

[TBFisher]

"Bughuggger" <bughuggger@aol.com> wrote in message
news:20040321085223.20632.00001918@mb-m28.aol.com...

How do I make a thermocouple the same voltage as a battery to charge it. I
want
to do it with a copper wire, an iron wire, a magnifying glass, a small
chamber,
and the sun. To a 12 volt battery.

http://www.hi-z.com/

 

[TBFisher]

Speaking of thermopiles and power generation, is it possible to buy a
plutonium powered thermopile for generating electricity in remote
areas, or is this sort of thing limited only to the government?

http://www.globalte.com/intro.htm

 

[Bob Stephens]

On Sun, 21 Mar 2004 14:14:16 -0500, BFoelsch wrote:

Don't know if they are still available, but through at least the 1980's
there were made large thermopiles for "Millivolt" gas valves on domestic gas
furnaces. These things were pretty good sized and put out 750 mV, enough to
run the appropriate gas valve directly. You could buy special "Millivolt"
thermostats, complete with night setback and all that. Ran on the furnace
pilot light. These were very common, and often used on old gravity and wall
furnaces, so you could have a remote mounted thermostat even though the
furnace itself used no line power.

If the OP is serious, that might be a place to start.

They're still available in Southern California. Check out your local
plumbing and heating supply or Mom and Pop hardware store.

Bob

 

[Bob Stephens]

On Sun, 21 Mar 2004 18:39:16 -0500, Glenn Ashmore wrote:

don't think you can do it. The Russians used to make a thermocouple
powered radio for use in remote places. It was a sleeve with about
2,000 iron and something (not copper) junctions that fit over the
chimney of a kerosene lamp. Produced about 9V. It only worked in
Siberia in the winter.

Iron Constantan is one of the standard ones - "J - Type" I think.

Bob

 

[Bughuggger]

Bughuggger wrote:
How do I make a thermocouple the same voltage as a battery to charge it. I
want
to do it with a copper wire, an iron wire, a magnifying glass, a small
chamber,
and the sun. To a 12 volt battery.

Thanks,

Dave (Bughuggger@aol.com)

Gareth Harris replies:

I don't think iron and copper are a good choice of metals for a
thermocouple.

Type J thermocouples use iron and constantan[1] and give an output of
21.8mV with a junction temperature difference of 400 degrees C

Type T thermocouples use copper and constantan[1] and give an output of
20.9mV with a junction temperature difference of 400 degrees C

I think that if you used iron and copper you would only get the
difference in voltage of the two above

21.8 - 20.9 = 0.9 mV with 400 degrees C temperature difference.

You can get a higher voltage by connecting lots of thermocouples in
series, but notice that if you connect lots of copper and constantan
wires together you will end up with half the joins the wrong way round -
these will produce the opposite voltage so you need to keep these
junctions cold and the others hot.
for example connect as below and keep the junctions marked + hot, and
the junctions marked - cold you will get three times the voltage you
would get with a single thermocouple.

copper+constantan-copper+constantan-copper+constantan

Unfortunately you would need about 500 hot junctions to get 12V with a
temperature difference of 400 degrees C.

You can get DC-DC converters which will step up voltages, but I you will
still need to get about a volt before you can operate one of these. I
don't think your idea is practical.

There are a couple of other things which may interest you though:

A) Solar Cells - these convert light to electricity directly and are
often used to power small, low power portable things (e.g. calculators)
or when electricity is required away from mains electricity.

B) Peltier Effect Devices - these are very similar to an array of
thermocouples and use electricity to move heat (Peltier Effect), but
they can be used in reverse to generate electricity from a temperature
difference (Seebeck Effect).

Notes:

1 Constantan is an alloy of copper and nickel.

Thanks for your thoughtful reply. Perhaps a series of capacitors would not
waste too much energy between my thermocouple and battery, or perhaps when I
look at the solar cell, I notice that with a small input it creates a large
voltage though small current. I think the thermocouple creates a large current
but small voltage. Tell me if I'm mistaken. Causally speaking, what is the
difference between the solar cell and the thermocouple with equivalent energy
input? Also, look up thermocouple in the encyclopedia. In World Book there's a
bunsen under a thermoelectric tea kettle powering what looks about like a 3
volt fan. Certainly I could power a 1.5 volt battery then with a magnifying
glass, and put eight in series. Right? So if electricity is a stream, all I
wanted was to collect it in a big enough lake before discharging it all at once
for a pulse charge of the battery. This seems reasonable to me.

Thanks,

Dave (Bughuggger@aol.com)

 

[Bughuggger]

Okay smartasses, I'll change my question. How do you convert amps to volts,
even if you don't care if it takes a year to charge your battery.

Dave (Bughuggger@aol.com)

 

[Bughuggger]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> a écrit dans le message
news: 3fIoxFFpgcXAFwFq@jmwa.demon.co.uk...
I read in sci.electronics.design that Reg Edwards
g4fgq.regp@ZZZbtinternet.com> wrote (in <c3kdp8$92t$1@titan.btinternet.
com&gt about 'thermocouple to a battery', on Sun, 21 Mar 2004:
How do I make a thermocouple the same voltage as a battery to charge
it.

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

You need many hundreds of thermocouples all in series.

Yes.
And it will take hell
of a long time to recharge the battery.

Not necessarily. Thermocouples are basically low-impedance devices.
Getting current is less of a problem than getting voltage.
--

Yep. So put a few in series, use a step up transformer and set a punched
rotating disc between the TCs and the lens...
More seriously, use the 12V battery to supply the driver for a mosfets
switcher that'll drive a step up transformer.
@40uV/K and 250K difference it's 10mV/TC.
Say we want 100mV. That's 10 TCs. So far, not to difficult.

Say we want 100mA/12V output. At 100mV input that's a 120:1 ratio, i.e. 12A
primary current.
A pair of 2mOhm IRF6609 SMT mosfets will easily do the job and give .002x144
= 300mW of joule losses for 1.2W output, *neglecting* the transformer
losses. Not bad.
Of course at a 120:1 ratio the transformer will be impractical but splitting
the supply in 2 or 3 stages may render this not as unrealistic as it may
seem at first sight with a not to ridiculous efficiency.

Oops, why a transformer ?
We'll be better with a boost, but I'm too lazy to do the maths.

Still is the pb of cooling the cold junction.


BTW I visited the Ampere Museum near Lyon a few years ago and I remember a
nice coal fed thermoelectric generator that provided a comfortable amount of
(DC) power. I can't remeber the figures but for those days it was quite
impressive.


Thanks,
Fred.

THis is what I'm looking for. The spiritual intermission of the cognitive
giants. What is it in nature that gives me a large shock from my lamp even
though the actual currents towards it may have been extremmely small. Could
somebody write down this circuit for me? Seems to be only the large resistance
from the air that does the trick. So how much air do I need between my
thermocouple and a 1.5 volt battery?

Dave (Bughuggger@aol.com)