# Oscillator running on home made thermocouple

Started by September 30, 2012
Oscillator running on home made thermocouple:

I did some transformer winding and some soldering.
The thermocouple is made with simple resistance wire (conrad 543-074-12)
100 Ohm / meter, soldered against normal coper transformer wire.
this makes a type 'T' thermocouple,
although my calculation show it should then give 18.342767 mV,
not sure it made good thermal contact.
The idea is to light a LED, or drive a power MOSFET chopping
the low voltage (that has a very low impedance).
output is now 1 Vpp, either need a lower voltage LED or more turns.
Frequency is around 7 to 10 kHz.

The idea is from
http://www.dicks-website.eu/fetosc/enindex.htm

On Sep 30, 6:46=A0am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
> Oscillator running on home made thermocouple: > =A0http://www.youtube.com/watch?v=3Dyu0IXX6OXtY&feature=3Dyoutu.be > > I did some transformer winding and some soldering. > The thermocouple is made with simple resistance wire (conrad 543-074-12) > 100 Ohm / meter, soldered against normal coper transformer wire. > this makes a type 'T' thermocouple, > although my calculation show it should then give 18.342767 mV, > not sure it made good thermal contact. > The idea is to light a LED, or drive a power MOSFET chopping > the low voltage (that has a very low impedance). > output is now 1 Vpp, either need a lower voltage LED or more turns. > Frequency is around 7 to 10 kHz. > > The idea is from > =A0http://www.dicks-website.eu/fetosc/enindex.htm
If the frequency changes as a function of voltage, I think you just made an interesting wireless thermometer. Remember the cricket chirping thermometer? Somewhere there's a calibration curve for number of chirps versus temperature. May have appeared April 1 in EDN, or such.
On Sun, 30 Sep 2012 08:01:12 -0700 (PDT), the renowned Robert Macy
<robert.a.macy@gmail.com> wrote:

>On Sep 30, 6:46&#2013266080;am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote: >> Oscillator running on home made thermocouple: >> &#2013266080;http://www.youtube.com/watch?v=yu0IXX6OXtY&feature=youtu.be >> >> I did some transformer winding and some soldering. >> The thermocouple is made with simple resistance wire (conrad 543-074-12) >> 100 Ohm / meter, soldered against normal coper transformer wire. >> this makes a type 'T' thermocouple, >> although my calculation show it should then give 18.342767 mV, >> not sure it made good thermal contact. >> The idea is to light a LED, or drive a power MOSFET chopping >> the low voltage (that has a very low impedance). >> output is now 1 Vpp, either need a lower voltage LED or more turns. >> Frequency is around 7 to 10 kHz. >> >> The idea is from >> &#2013266080;http://www.dicks-website.eu/fetosc/enindex.htm > >If the frequency changes as a function of voltage, I think you just >made an interesting wireless thermometer. > >Remember the cricket chirping thermometer? Somewhere there's a >calibration curve for number of chirps versus temperature. May have >appeared April 1 in EDN, or such.
There was a Scientific American Amateur scientist column on making a small transistorized battery-powered RF probe that would change frequency with temperature. It allowed the person to map the temperature profile through the GI tract of his dog as well as acting as a beacon to retrieve the probe from a corner of the back yard. Of course a thermocouple will not produce any usable voltage in such an essentially isothermal situation. 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
On 9/30/2012 9:46 AM, Jan Panteltje wrote:
> Oscillator running on home made thermocouple: > http://www.youtube.com/watch?v=yu0IXX6OXtY&feature=youtu.be > > I did some transformer winding and some soldering. > The thermocouple is made with simple resistance wire (conrad 543-074-12) > 100 Ohm / meter, soldered against normal coper transformer wire. > this makes a type 'T' thermocouple, > although my calculation show it should then give 18.342767 mV, > not sure it made good thermal contact. > The idea is to light a LED, or drive a power MOSFET chopping > the low voltage (that has a very low impedance). > output is now 1 Vpp, either need a lower voltage LED or more turns. > Frequency is around 7 to 10 kHz. > > The idea is from > http://www.dicks-website.eu/fetosc/enindex.htm
Low voltage oscillators are rather interesting. For some real power use a thermoelectric cooler module backwards as a thermocouple. Years ago Russians made a thermoelectric powered radio for the boonies that ran off the heat from a kerosene lantern.
On a sunny day (Sun, 30 Sep 2012 08:01:12 -0700 (PDT)) it happened Robert Macy
<robert.a.macy@gmail.com> wrote in

>On Sep 30, 6:46&#2013266080;am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote: >> Oscillator running on home made thermocouple: >> &#2013266080;http://www.youtube.com/watch?v=yu0IXX6OXtY&feature=youtu.be >> >> I did some transformer winding and some soldering. >> The thermocouple is made with simple resistance wire (conrad 543-074-12) >> 100 Ohm / meter, soldered against normal coper transformer wire. >> this makes a type 'T' thermocouple, >> although my calculation show it should then give 18.342767 mV, >> not sure it made good thermal contact. >> The idea is to light a LED, or drive a power MOSFET chopping >> the low voltage (that has a very low impedance). >> output is now 1 Vpp, either need a lower voltage LED or more turns. >> Frequency is around 7 to 10 kHz. >> >> The idea is from >> &#2013266080;http://www.dicks-website.eu/fetosc/enindex.htm > >If the frequency changes as a function of voltage, I think you just >made an interesting wireless thermometer. > >Remember the cricket chirping thermometer? Somewhere there's a >calibration curve for number of chirps versus temperature. May have >appeared April 1 in EDN, or such.
Fortunately the frequency does not depend on the voltage, just on the capacitance of the load.
On 30 Sep., 17:29, "bjac...@teranews.com" <bjac...@iwaynet.net> wrote:
> On 9/30/2012 9:46 AM, Jan Panteltje wrote: > > > > > > > > > > > Oscillator running on home made thermocouple: > > =A0http://www.youtube.com/watch?v=3Dyu0IXX6OXtY&feature=3Dyoutu.be > > > I did some transformer winding and some soldering. > > The thermocouple is made with simple resistance wire (conrad 543-074-12=
)
> > 100 Ohm / meter, soldered against normal coper transformer wire. > > this makes a type 'T' thermocouple, > > although my calculation show it should then give 18.342767 mV, > > not sure it made good thermal contact. > > The idea is to light a LED, or drive a power MOSFET chopping > > the low voltage (that has a very low impedance). > > output is now 1 Vpp, either need a lower voltage LED or more turns. > > Frequency is around 7 to 10 kHz. > > > The idea is from > > =A0http://www.dicks-website.eu/fetosc/enindex.htm > > Low voltage oscillators are rather interesting. > > For some real power use a thermoelectric cooler module backwards as a > thermocouple. Years ago Russians made a thermoelectric powered radio for > the boonies that ran off the heat from a kerosene lantern.
the deep pace probes are powered by something like that, heat comes from the decay of a plutonium pellet The russians have a number of lighthouses and navigation beacons power by Stronium decay -Lasse
On a sunny day (Sun, 30 Sep 2012 11:24:25 -0400) it happened Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote in
<5rog6855i70nbb86nm1i7hcd9qfu12dv3r@4ax.com>:

>There was a Scientific American Amateur scientist column on making a >small transistorized battery-powered RF probe that would change >frequency with temperature. It allowed the person to map the >temperature profile through the GI tract of his dog as well as acting >as a beacon to retrieve the probe from a corner of the back yard. > >Of course a thermocouple will not produce any usable voltage in such >an essentially isothermal situation. > > >Best regards, >Spehro Pefhany
I actually found the reason for the voltage difference, it is simply the voltage drop in the thermocouple resistance wire due to current. Also this thermocouple I am using has resistance wire taken from an old wirewound resistor. I measure about 1.5 Ohm or so (for 10 cm) so 18 or 15 Ohm / meter. Now you can calculate the current for the 10 BF254, it is quite a bit.
Jan Panteltje wrote:

> On a sunny day (Sun, 30 Sep 2012 11:24:25 -0400) it happened Spehro Pefhany > <speffSNIP@interlogDOTyou.knowwhat> wrote in > <5rog6855i70nbb86nm1i7hcd9qfu12dv3r@4ax.com>: > > >>There was a Scientific American Amateur scientist column on making a >>small transistorized battery-powered RF probe that would change >>frequency with temperature. It allowed the person to map the >>temperature profile through the GI tract of his dog as well as acting >>as a beacon to retrieve the probe from a corner of the back yard. >> >>Of course a thermocouple will not produce any usable voltage in such >>an essentially isothermal situation. >> >> >>Best regards, >>Spehro Pefhany > > > I actually found the reason for the voltage difference, > it is simply the voltage drop in the thermocouple resistance wire due to current. > Also this thermocouple I am using has resistance wire taken from an old wirewound resistor. > I measure about 1.5 Ohm or so (for 10 cm) so 18 or 15 Ohm / meter. > Now you can calculate the current for the 10 BF254, it is quite a bit. >
I'll try the thermocouple idea. I have a roll of thermocouple twin lead so that's no problem here, simply twist the ends and use the gas soldering tool with silver bronze solder. Jamie
On Sun, 30 Sep 2012 15:40:48 GMT, the renowned Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

>On a sunny day (Sun, 30 Sep 2012 11:24:25 -0400) it happened Spehro Pefhany ><speffSNIP@interlogDOTyou.knowwhat> wrote in ><5rog6855i70nbb86nm1i7hcd9qfu12dv3r@4ax.com>: > >>There was a Scientific American Amateur scientist column on making a >>small transistorized battery-powered RF probe that would change >>frequency with temperature. It allowed the person to map the >>temperature profile through the GI tract of his dog as well as acting >>as a beacon to retrieve the probe from a corner of the back yard. >> >>Of course a thermocouple will not produce any usable voltage in such >>an essentially isothermal situation. >> >> >>Best regards, >>Spehro Pefhany > >I actually found the reason for the voltage difference, >it is simply the voltage drop in the thermocouple resistance wire due to current. >Also this thermocouple I am using has resistance wire taken from an old wirewound resistor. >I measure about 1.5 Ohm or so (for 10 cm) so 18 or 15 Ohm / meter. >Now you can calculate the current for the 10 BF254, it is quite a bit. >
There's a thermodynamic thing going on here- the less heat you have flowing down the thermocouple wires, the less power is available for your circuit. Thicker wires will tend to suck more heat from your source and thus reduce the available temperature difference. Make them really long to reduce the heat flow, and you get more resistance again. No free lunch. 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
On a sunny day (Sun, 30 Sep 2012 12:05:36 -0400) it happened Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote in