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'[EE] Using pilot Flame Thermopiles as PIC Power So'
2005\11\23@140407 by Brooke Clarke

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face
Hi:

I got a Honeywell Q313 series "750 millivolt Powerpile Generator" and
have measured it's output when in one finger of a gas stove flame.
It puts out about half a volt at 100 ma with a 5 Ohm load (50 mw) and
probably would produce more power with a lower resistance load.
See: http://www.pacificsites.com/~brooke/batt.shtml#Heat

Is there a circuit that would transform this into say 3.3 volts at 10 ma
that would be suitable to power a PIC?

Have Fun,

Brooke Clarke, N6GCE

--
w/Java http://www.PRC68.com
w/o Java www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com

2005\11\23@144410 by olin piclist

face picon face
Brooke Clarke wrote:
> I got a Honeywell Q313 series "750 millivolt Powerpile Generator" and
> have measured it's output when in one finger of a gas stove flame.
> It puts out about half a volt at 100 ma with a 5 Ohm load (50 mw) and
> probably would produce more power with a lower resistance load.
> See: http://www.pacificsites.com/~brooke/batt.shtml#Heat

Your figures for open circuit and 5 ohm load indicate the pile has about 3
ohms resistance.

> Is there a circuit that would transform this into say 3.3 volts at 10
> ma that would be suitable to power a PIC?

Not without some serious magic.  3.3V x 10mA = 330mW.  That's nearly 7 times
what you measured with a 5 ohm load.  Where exactly do you expect this power
to come from?


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\11\23@151134 by Russell McMahon

face
flavicon
face
> I got a Honeywell Q313 series "750 millivolt Powerpile Generator"
> and have measured it's output when in one finger of a gas stove
> flame.

> It puts out about half a volt at 100 ma with a 5 Ohm load (50 mw)
> and probably would produce more power with a lower resistance load.
> See: http://www.pacificsites.com/~brooke/batt.shtml#Heat
>
> Is there a circuit that would transform this into say 3.3 volts at
> 10 ma that would be suitable to power a PIC?

Yes. But if you are trying to use the heat rather than trying to use
the specific device you may be better off using a Peltier 'cooling'
module. These produce substantially more voltage (due to having more
thermopiles in series)(and possibly the pile you have uses lower
voltage but more robust thermopiles).

Using the present module will be a challenge due to the low voltage.
Not hard, but easy to be inefficient. Several boost converter
topologies will work. A simple flyback converter would be an easy
start. Inductor in the drain of a FET. Pulse FET on and then off and
coil "rings" to a higher voltage. Coil resistance needs to be lowish.
FET needs to be low Rdson, or if a bipolar transistor is used it needs
good low saturation voltage. Care needed with all tracks etc to
minimise losses. The circuit will almost certainly need to be operated
from a higher voltage supply - probably from the output that it
supplies. Starting a circuit using silicon components on 0.5 volts is
approximately impossible. However, on no load the pile probably makes
at least the claimed 750 mV and may make more. Even that is
challenging and using an external higher voltage for starting makes
the job much easier.

A self oscillating converter with a couple of transistors could
probably be implemented but an IC based one would be easier. You could
use one of the single-cell converter ICs but a package of CMOS
inverters would probably do as well.


       RM

2005\11\23@151214 by Wouter van Ooijen

face picon face
> Not without some serious magic.  3.3V x 10mA = 330mW.

I am a muggles so I don't know about magic, but I do have a pocket
calculator :)

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\23@151635 by Dwayne Reid
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At 12:44 PM 11/23/2005, Olin Lathrop wrote:
>Brooke Clarke wrote:
> > I got a Honeywell Q313 series "750 millivolt Powerpile Generator" and
> > have measured it's output when in one finger of a gas stove flame.
> > It puts out about half a volt at 100 ma with a 5 Ohm load (50 mw) and
> > probably would produce more power with a lower resistance load.
> > See: http://www.pacificsites.com/~brooke/batt.shtml#Heat
>
>Your figures for open circuit and 5 ohm load indicate the pile has about 3
>ohms resistance.
>
> > Is there a circuit that would transform this into say 3.3 volts at 10
> > ma that would be suitable to power a PIC?
>
>Not without some serious magic.  3.3V x 10mA = 330mW.  That's nearly 7 times
>what you measured with a 5 ohm load.  Where exactly do you expect this power
>to come from?

I'm probably being obtuse today, but 3.3V @ 10mA sure looks like 33mW to me.

You might consider putting a pair of those thermopiles in series and
then using one of the Maxim single-cell switchers to convert the
resulting voltage to your desired level.  Might just work . . .

dwayne

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2005\11\23@151754 by olin piclist

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Olin Lathrop wrote:
> Not without some serious magic.  3.3V x 10mA = 330mW.

Oops.  Looks like I slipped a decimal point.  3.3V x 10mA = 33mW, which is
at least possible to get from 50mW.  While it is theoretically possible,
it's going to be difficult converting from such a low voltage.  If you can
somehow bootstrap, maybe with the use of a battery, to the 3.3V or 5V then
you have enough to run a switcher to sustain the higher voltage.  Getting
there from only 500mV will be tough.

Two of these in series would do it.  That would allow a simple analog
circuit to make 5V at low current and medium efficiency, which then allows
more complex circuit to run that makes the final output voltage much more
efficiently from the 500mV in.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\11\23@152337 by Richard Prosser

picon face
Open circuit voltage - 812mV, Source impedance 3 ohms = matched load.
So maximum power out is 0.812*0.812/(3+3) = 110mW, 1/2 of which is
available in the load.
So you have a 400mV source that will give you 55mW.
Unfortunately 400mV is not enough to turn a silicon transistor on but
you might be able to sustain an oscillation once you got it going.
There are circuits aroound that boost a (dead) 1.5V cell to drive an
LED.
(eg <http://www.nifty-stuff.com/LED-boost-circuit-joule-thief.php>)

But I doubt you could do much useful with it.
RP


On 24/11/05, Olin Lathrop <.....olin_piclistKILLspamspam@spam@embedinc.com> wrote:
{Quote hidden}

> -

2005\11\23@161203 by Spehro Pefhany

picon face
At 11:04 AM 11/23/2005 -0800, you wrote:
>Hi:
>
>I got a Honeywell Q313 series "750 millivolt Powerpile Generator" and have
>measured it's output when in one finger of a gas stove flame.
>It puts out about half a volt at 100 ma with a 5 Ohm load (50 mw) and
>probably would produce more power with a lower resistance load.
>See: http://www.pacificsites.com/~brooke/batt.shtml#Heat
>
>Is there a circuit that would transform this into say 3.3 volts at 10 ma
>that would be suitable to power a PIC?

Although it's not a complete solution, you may find this IEEE paper of
interest:
http://power.ece.uiuc.edu/chapman/papers/LVpaper.pdf

Startup is the difficult issue with such low voltage circuits, after the
circuit is started it can bootstrap enough voltage to run. Note the novel
unijunction transistor method used in the paper, and also the mechanical
switch idea.

Although it's not as elegant, you could consider using button cells
(perhaps you need a real-time clock anyway) for the startup and then
run off of the thermopile when power is available.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\11\23@185448 by Bob Blick

face picon face
Hi Brooke,

You might try a variation on this:

http://bobblick.com/3cell/

I forget exactly what voltage it starts with, but you should be able to
play with resistors here or there and get it to start.

Moving Q2's emitter to the input voltage is probably required too.

Cheers,

Bob


On 23 Nov 2005 at 11:04, Brooke Clarke wrote:
>
> I got a Honeywell Q313 series "750 millivolt Powerpile Generator" and
> have measured it's output when in one finger of a gas stove flame.
> It puts out about half a volt at 100 ma with a 5 Ohm load (50 mw) and
> probably would produce more power with a lower resistance load.
> See: www.pacificsites.com/~brooke/batt.shtml#Heat
>
> Is there a circuit that would transform this into say 3.3 volts at 10 ma
> that would be suitable to power a PIC?

2005\11\23@194425 by Mark Jordan

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face
On 24 Nov 2005 at 9:23, Richard Prosser wrote:

> Open circuit voltage - 812mV, Source impedance 3 ohms = matched load.
> So maximum power out is 0.812*0.812/(3+3) = 110mW, 1/2 of which is
> available in the load.
> So you have a 400mV source that will give you 55mW.
> Unfortunately 400mV is not enough to turn a silicon transistor on but
> you might be able to sustain an oscillation once you got it going.
> There are circuits aroound that boost a (dead) 1.5V cell to drive an
> LED.
> (eg <http://www.nifty-stuff.com/LED-boost-circuit-joule-thief.php>)
>
> But I doubt you could do much useful with it.
> RP
>

       Maybe you could try a germanium transistor like those old AC187
running a "joule-thief" circuit.

       Mark Jordan


2005\11\24@150901 by Peter

picon face

On Wed, 23 Nov 2005, Bob Blick wrote:

> Hi Brooke,
>
> You might try a variation on this:
>
> http://bobblick.com/3cell/
>
> I forget exactly what voltage it starts with, but you should be able to
> play with resistors here or there and get it to start.
>
> Moving Q2's emitter to the input voltage is probably required too.

Would a JFET based hf oscillator work to produce an initial bias ? A
JFET may have gain at zero Vg. There are also 'programmable base'
mosfets afaik. Could one of these be used ? e.g.:

http://www.aldinc.com/ald_epadfaq.htm

can produce parts programmed for Vg=0.2V.

Last, a vibrator <g> circuit could be used to convert the bootstrap
voltage, using a depletion mode mosfet to turn it off once the main
voltage is present.

Peter

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