convert 150 - 300mV into 5Vdc

[Winfield Hill]

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]

Here's a URL for a converter that takes an input of .3VDC and converts
it to 5VDC. It uses FETs to get around the .6V problem with silicon
BJTs. http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf

Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

In the article he touts the importance of MOSFETs in performing the
work of converting as little as 150mV of source voltage into a nice
5V supply, but in truth this is a simple task given say 8 to 10V to
run the MOSFETs. Damaschke created a 8.5V source for the job, and
that circuit is the real innovation. The tough task of working with
as little as 300mV at startup is provided by a nifty JFET blocking
oscillator, which creates sufficient voltage to start running the 5V
converter. Once the +5V output voltage is well on its way, a MAX630
(RC4193) step-up converter takes over, providing 8.5V for the FETs
If high load conditions on the 5V output drag the input thermopile
down to as low as 150mV, the full converter continues to work.

Damaschke says his blocking oscillator is similar to those used in
pacemakers, which are credited to Wilson Greatbatch's 1958 invention,
http://www.engology.com/eng5greatbatch.htm In Greatbatch's own words,
http://www.winstonbrill.com/bril001/html/article_index/articles/151-200/article190_body.html

Let's examine Damaschke's JFET circuit. At startup the depletion-mode
JFET is on and current starts flowing in the transformer, charging the
1nF cap with a negative voltage. When the current rises sufficiently
to saturate the transformer core, the secondary voltages collapse, and
the JFET gate is forced negative, ending the cycle. A 1M resistor
discharges the 1nF cap, setting the cycle period to about 1200Hz.

| 1:45:65
| +in ,------,
| O--|----, | ,-----|>|----+---- +8.5V
| | # # # |
| | # # # |+
| | # # # ---
| | | | | 1.0nF --- 470uF
| | |-' '-|-+--||--, |
| '->|-, | | | |
| | | '-/\/\-+ |
| J105 | | 1.0M | |
| O-------+---+--------+---+---- gnd

Sadly, Damaschke doesn't have much to say about the critical aspects
of this circuit, e.g. transformer properties or JFET requirements.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Fred Bartoli]

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]

Here's a URL for a converter that takes an input of .3VDC and converts
it to 5VDC. It uses FETs to get around the .6V problem with silicon
BJTs. http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf

Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

In the article he touts the importance of MOSFETs in performing the
work of converting as little as 150mV of source voltage into a nice
5V supply, but in truth this is a simple task given say 8 to 10V to
run the MOSFETs. Damaschke created a 8.5V source for the job, and
that circuit is the real innovation. The tough task of working with
as little as 300mV at startup is provided by a nifty JFET blocking
oscillator, which creates sufficient voltage to start running the 5V
converter. Once the +5V output voltage is well on its way, a MAX630
(RC4193) step-up converter takes over, providing 8.5V for the FETs
If high load conditions on the 5V output drag the input thermopile
down to as low as 150mV, the full converter continues to work.

This can probably be simplified by eliminating the MAX630 stage and getting
the "high voltage" supply from the T3 gate connection.
Plus the choice of an 1N4001 for D2 can be improved (small schottky), or
simply deleted.

For the transformer, probably nothing critical. Just make sure that the
transformer saturates before the lowest IDSS value of T1.


Thanks,
Fred.

 

[Winfield Hill]

Fred Bartoli wrote...

Winfield Hill wrote...

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]

Here's a URL for a converter that takes an input of .3VDC and converts
it to 5VDC. It uses FETs to get around the .6V problem with silicon
BJTs. http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf

Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

[ snip Win's post ]

This can probably be simplified by eliminating the MAX630 stage and
getting the "high voltage" supply from the T3 gate connection.

Good call.

Plus the choice of an 1N4001 for D2 can be improved (small schottky),
or simply deleted.

Delete. Damaschke appears to ignore the MOSFET's intrinsic diode.

For the transformer, probably nothing critical. Just make sure that
the transformer saturates before the lowest IDSS value of T1.

Lots of turns.

How low can the starting voltage be? Damaschke implies 300mV.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Watson A.Name \Watt Sun - the Dark Remover\]

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]
Here's a URL for a converter that takes an input of .3VDC and converts
it to 5VDC. It uses FETs to get around the .6V problem with silicon
BJTs. http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf
Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

In the article he touts the importance of MOSFETs in performing the
work of converting as little as 150mV of source voltage into a nice
5V supply, but in truth this is a simple task given say 8 to 10V to
run the MOSFETs. Damaschke created a 8.5V source for the job, and
that circuit is the real innovation. The tough task of working with
as little as 300mV at startup is provided by a nifty JFET blocking
oscillator, which creates sufficient voltage to start running the 5V
converter. Once the +5V output voltage is well on its way, a MAX630
(RC4193) step-up converter takes over, providing 8.5V for the FETs
If high load conditions on the 5V output drag the input thermopile
down to as low as 150mV, the full converter continues to work.

Damaschke says his blocking oscillator is similar to those used in
pacemakers, which are credited to Wilson Greatbatch's 1958 invention,
http://www.engology.com/eng5greatbatch.htm In Greatbatch's own words,
http://www.winstonbrill.com/bril001/html/article_index/articles/151-200/article190_body.html

Let's examine Damaschke's JFET circuit. At startup the depletion-mode
JFET is on and current starts flowing in the transformer, charging the
1nF cap with a negative voltage. When the current rises sufficiently
to saturate the transformer core, the secondary voltages collapse, and
the JFET gate is forced negative, ending the cycle. A 1M resistor
discharges the 1nF cap, setting the cycle period to about 1200Hz.

| 1:45:65
| +in ,------,
| O--|----, | ,-----|>|----+---- +8.5V
| | # # # |
| | # # # |+
| | # # # ---
| | | | | 1.0nF --- 470uF
| | |-' '-|-+--||--, |
| '->|-, | | | |
| | | '-/\/\-+ |
| J105 | | 1.0M | |
| O-------+---+--------+---+---- gnd

Sadly, Damaschke doesn't have much to say about the critical aspects
of this circuit, e.g. transformer properties or JFET requirements.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

Did you see Greatbatch's AIDS patent 5,324,643 (www.uspto.gov or better
yet, use www.pat2pdf.com)?? Amazing. It actually has the genetic code
for the virus. I treasure your posts, Win.

 

[Watson A.Name \Watt Sun - the Dark Remover\]

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]
Here's a URL for a converter that takes an input of .3VDC and converts
it to 5VDC. It uses FETs to get around the .6V problem with silicon
BJTs. http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf
Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

In the article he touts the importance of MOSFETs in performing the
work of converting as little as 150mV of source voltage into a nice
5V supply, but in truth this is a simple task given say 8 to 10V to
run the MOSFETs. Damaschke created a 8.5V source for the job, and
that circuit is the real innovation. The tough task of working with
as little as 300mV at startup is provided by a nifty JFET blocking
oscillator, which creates sufficient voltage to start running the 5V
converter. Once the +5V output voltage is well on its way, a MAX630
(RC4193) step-up converter takes over, providing 8.5V for the FETs
If high load conditions on the 5V output drag the input thermopile
down to as low as 150mV, the full converter continues to work.

Damaschke says his blocking oscillator is similar to those used in
pacemakers, which are credited to Wilson Greatbatch's 1958 invention,
http://www.engology.com/eng5greatbatch.htm In Greatbatch's own words,
http://www.winstonbrill.com/bril001/html/article_index/articles/151-200/article190_body.html

Let's examine Damaschke's JFET circuit. At startup the depletion-mode
JFET is on and current starts flowing in the transformer, charging the
1nF cap with a negative voltage. When the current rises sufficiently
to saturate the transformer core, the secondary voltages collapse, and
the JFET gate is forced negative, ending the cycle. A 1M resistor
discharges the 1nF cap, setting the cycle period to about 1200Hz.

| 1:45:65
| +in ,------,
| O--|----, | ,-----|>|----+---- +8.5V
| | # # # |
| | # # # |+
| | # # # ---
| | | | | 1.0nF --- 470uF
| | |-' '-|-+--||--, |
| '->|-, | | | |
| | | '-/\/\-+ |
| J105 | | 1.0M | |
| O-------+---+--------+---+---- gnd

Sadly, Damaschke doesn't have much to say about the critical aspects
of this circuit, e.g. transformer properties or JFET requirements.

I used that very same blocking oscillator circuit in my old timer
germanium transistor V boost circuit. It actually works down to .18VDC,
but with the white LED barely visible. At .6V it's going pretty good,
where the usual silicon transistor hasn't even started.

So I got a bunch of LR44 / 357 button cells from Ebay, 50 for 8 bucks.
I used a regular spring clothespin, drilled holes in the clip end and
put two #3 brass screws in them for contacts. I use this as my button
cell holder, and connected my V boost circuit to a LR44 button cell.

It will run for a minute or so, then dim down to nothing. The voltage
sag is very great, from 1.5V open circuit down to only .6V with a few
tens of mA load. The light dims down to nothing after a few tens of
seconds, so I opened the circuit. After a few minutes, the cell
recovers, and I could do another load test, but the cell was much
quicker to dim down to nothing. I can repeat this after an hour of
recovery, and I've done it many times, and the cell seems to come back
from the dead every time. It's getting to the point where the cell is
taking longer to recover and putting out for a much shorter time, so I
guess it's getting 'used up'.

It's quite apparent that the load is too much for this little cell. Yet
many of the laser pens and flashing LED keyfob lights use these button
cells, probably because they're so small and cheap. Just don't expect
them to give light for long enough to do anything serious. Putting a
key into the lock is no problem, tho.

I previously mentioned that I went to Radio Shaft to buy an LR44 button
cell, and found that they want $3.19 apiece for them. Yikes! For four
cells, that's a couple dollars more that what I paid for the LED keyfoib
light, which was only ten bucks _with_ the four LR44 button cells!

Meanwhile, the other day I was walking down the mall, and in the walkway
was a watch and bracelet kiosk. I asked the salesman if he had an LR44
button cell and he said yes, so I asked how much? $9.99, was his
answer, so I asked was that with installation, and he said yes. So I
asked, how much for the cell without installation, an he said $9.99! So
his price is three times as much as Radio Shaft, and 62 times the price
I paid for the LR44s on Ebay, including shipping! Now that's amazing!

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]

Here's a URL for a converter that takes an input of .3VDC and converts
it to 5VDC. It uses FETs to get around the .6V problem with silicon
BJTs. http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf

Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

In the article he touts the importance of MOSFETs in performing the
work of converting as little as 150mV of source voltage into a nice
5V supply, but in truth this is a simple task given say 8 to 10V to
run the MOSFETs. Damaschke created a 8.5V source for the job, and
that circuit is the real innovation. The tough task of working with
as little as 300mV at startup is provided by a nifty JFET blocking
oscillator, which creates sufficient voltage to start running the 5V
converter. Once the +5V output voltage is well on its way, a MAX630
(RC4193) step-up converter takes over, providing 8.5V for the FETs
If high load conditions on the 5V output drag the input thermopile
down to as low as 150mV, the full converter continues to work.

Damaschke says his blocking oscillator is similar to those used in
pacemakers, which are credited to Wilson Greatbatch's 1958 invention,
http://www.engology.com/eng5greatbatch.htm In Greatbatch's own words,http://www.winstonbrill.com/bril001/html/article_index/articles/151-200/
article190_body.html

Let's examine Damaschke's JFET circuit. At startup the depletion-mode
JFET is on and current starts flowing in the transformer, charging the
1nF cap with a negative voltage. When the current rises sufficiently
to saturate the transformer core, the secondary voltages collapse, and
the JFET gate is forced negative, ending the cycle. A 1M resistor
discharges the 1nF cap, setting the cycle period to about 1200Hz.

| 1:45:65
| +in ,------,
| O--|----, | ,-----|>|----+---- +8.5V
| | # # # |
| | # # # |+
| | # # # ---
| | | | | 1.0nF --- 470uF
| | |-' '-|-+--||--, |
| '->|-, | | | |
| | | '-/\/\-+ |
| J105 | | 1.0M | |
| O-------+---+--------+---+---- gnd

Sadly, Damaschke doesn't have much to say about the critical aspects
of this circuit, e.g. transformer properties or JFET requirements.

It says 1:45:65 but I would assume that there's more than one turn on
the primary winding. So if it had ten turns, then the others would have
450 and 650 turns respectively. But then if it had 20 turns... >:-O

 

[Terry Given]

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]

Here's a URL for a converter that takes an input of .3VDC and converts
it to 5VDC. It uses FETs to get around the .6V problem with silicon
BJTs. http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf

Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

In the article he touts the importance of MOSFETs in performing the
work of converting as little as 150mV of source voltage into a nice
5V supply, but in truth this is a simple task given say 8 to 10V to
run the MOSFETs. Damaschke created a 8.5V source for the job, and
that circuit is the real innovation. The tough task of working with
as little as 300mV at startup is provided by a nifty JFET blocking
oscillator, which creates sufficient voltage to start running the 5V
converter. Once the +5V output voltage is well on its way, a MAX630
(RC4193) step-up converter takes over, providing 8.5V for the FETs
If high load conditions on the 5V output drag the input thermopile
down to as low as 150mV, the full converter continues to work.

Damaschke says his blocking oscillator is similar to those used in
pacemakers, which are credited to Wilson Greatbatch's 1958 invention,
http://www.engology.com/eng5greatbatch.htm In Greatbatch's own words,http://www.winstonbrill.com/bril001/html/article_index/articles/151-200/
article190_body.html

Let's examine Damaschke's JFET circuit. At startup the depletion-mode
JFET is on and current starts flowing in the transformer, charging the
1nF cap with a negative voltage. When the current rises sufficiently
to saturate the transformer core, the secondary voltages collapse, and
the JFET gate is forced negative, ending the cycle. A 1M resistor
discharges the 1nF cap, setting the cycle period to about 1200Hz.

| 1:45:65
| +in ,------,
| O--|----, | ,-----|>|----+---- +8.5V
| | # # # |
| | # # # |+
| | # # # ---
| | | | | 1.0nF --- 470uF
| | |-' '-|-+--||--, |
| '->|-, | | | |
| | | '-/\/\-+ |
| J105 | | 1.0M | |
| O-------+---+--------+---+---- gnd

Sadly, Damaschke doesn't have much to say about the critical aspects
of this circuit, e.g. transformer properties or JFET requirements.

It says 1:45:65 but I would assume that there's more than one turn on
the primary winding. So if it had ten turns, then the others would have
450 and 650 turns respectively. But then if it had 20 turns... >:-O

..... your transformer manufacturer will hunt you down and beat you with a
stick

Cheers
Terry

 

[mike]

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]

Here's a URL for a converter that takes an input of .3VDC and
converts

it to 5VDC. It uses FETs to get around the .6V problem with silicon
BJTs. http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf

Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

In the article he touts the importance of MOSFETs in performing the
work of converting as little as 150mV of source voltage into a nice
5V supply, but in truth this is a simple task given say 8 to 10V to
run the MOSFETs. Damaschke created a 8.5V source for the job, and
that circuit is the real innovation. The tough task of working with
as little as 300mV at startup is provided by a nifty JFET blocking
oscillator, which creates sufficient voltage to start running the 5V
converter. Once the +5V output voltage is well on its way, a MAX630
(RC4193) step-up converter takes over, providing 8.5V for the FETs
If high load conditions on the 5V output drag the input thermopile
down to as low as 150mV, the full converter continues to work.

Damaschke says his blocking oscillator is similar to those used in
pacemakers, which are credited to Wilson Greatbatch's 1958 invention,
http://www.engology.com/eng5greatbatch.htm In Greatbatch's own
words,

http://www.winstonbrill.com/bril001/html/article_index/articles/151-200/
article190_body.html

Let's examine Damaschke's JFET circuit. At startup the
depletion-mode

JFET is on and current starts flowing in the transformer, charging
the

1nF cap with a negative voltage. When the current rises sufficiently
to saturate the transformer core, the secondary voltages collapse,
and

the JFET gate is forced negative, ending the cycle. A 1M resistor
discharges the 1nF cap, setting the cycle period to about 1200Hz.

| 1:45:65
| +in ,------,
| O--|----, | ,-----|>|----+---- +8.5V
| | # # # |
| | # # # |+
| | # # # ---
| | | | | 1.0nF --- 470uF
| | |-' '-|-+--||--, |
| '->|-, | | | |
| | | '-/\/\-+ |
| J105 | | 1.0M | |
| O-------+---+--------+---+---- gnd

Sadly, Damaschke doesn't have much to say about the critical aspects
of this circuit, e.g. transformer properties or JFET requirements.

It says 1:45:65 but I would assume that there's more than one turn on
the primary winding. So if it had ten turns, then the others would have
450 and 650 turns respectively. But then if it had 20 turns... >:-O

..... your transformer manufacturer will hunt you down and beat you with a
stick

Cheers
Terry

Why do you need three windings at all? Move the RC to the Gate side????
What am I missing?
mike

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[Watson A.Name \Watt Sun - the Dark Remover\]

in message news:[email protected]...

news:[email protected]...

[snip]

It says 1:45:65 but I would assume that there's more than one turn on
the primary winding. So if it had ten turns, then the others would have
450 and 650 turns respectively. But then if it had 20 turns... >:-O

.... your transformer manufacturer will hunt you down and beat you with a
stick

Besides, why does he use such a high ratio of turns on the feedback
winding? I realize that the input is only a few hundred mV, but why
should the JFET need more than a few volts to switch? They shouldn't be
as demanding as power FETs are for gate voltage.

 

[Jan Panteltje]

in message news:[email protected]...

news:[email protected]...

[snip]

| 1:45:65
| +in ,------,
| O--|----, | ,-----|>|----+---- +8.5V
| | # # # |
| | # # # |+
| | # # # ---
| | | | | 1.0nF --- 470uF
| | |-' '-|-+--||--, |
| '->|-, | | | |
| | | '-/\/\-+ |
| J105 | | 1.0M | |
| O-------+---+--------+---+---- gnd
Sadly, Damaschke doesn't have much to say about the critical aspects
of this circuit, e.g. transformer properties or JFET requirements.
It says 1:45:65 but I would assume that there's more than one turn on
the primary winding. So if it had ten turns, then the others would have
450 and 650 turns respectively. But then if it had 20 turns... >:-O

.... your transformer manufacturer will hunt you down and beat you with a
stick

Besides, why does he use such a high ratio of turns on the feedback
winding? I realize that the input is only a few hundred mV, but why
should the JFET need more than a few volts to switch? They shouldn't be
as demanding as power FETs are for gate voltage.

45 x 150mV = 6.75V, you want the FET to 100% cut off.
JP

 

[Kevin Aylward]

"Watson A.Name - "Watt Sun, the Dark Remover""

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote...

I putzed around with an old germanium transistor ... [ snip ]

Here's a URL for a converter that takes an input of .3VDC and converts
it to 5VDC. It uses FETs to get around the .6V problem with
silicon BJTs.
http://www.ece.uvic.ca/~jbornema/Journals/064a-97ia-jmd.pdf

Can anyone tell off the top of their head, what the output voltage
is for those thermocouples that are used in furnaces? This might
run off one of them.

Perhaps someone else can answer the furnace-thermopile question.

John Damaschke's 100mW 300mV-to-5V dc-dc converter is interesting.

In the article he touts the importance of MOSFETs in performing the
work of converting as little as 150mV of source voltage into a nice
5V supply, but in truth this is a simple task given say 8 to 10V to
run the MOSFETs. Damaschke created a 8.5V source for the job, and
that circuit is the real innovation. The tough task of working
with as little as 300mV at startup is provided by a nifty JFET
blocking oscillator, which creates sufficient voltage to start
running the 5V converter. Once the +5V output voltage is well on
its way, a MAX630 (RC4193) step-up converter takes over, providing
8.5V for the FETs If high load conditions on the 5V output drag
the input thermopile down to as low as 150mV, the full converter
continues to work.

Damaschke says his blocking oscillator is similar to those used in
pacemakers, which are credited to Wilson Greatbatch's 1958
invention, http://www.engology.com/eng5greatbatch.htm In
Greatbatch's own words,

http://www.winstonbrill.com/bril001/html/article_index/articles/151-200/
article190_body.html

Let's examine Damaschke's JFET circuit. At startup the depletion-mode
JFET is on and current starts flowing in the transformer, charging the
1nF cap with a negative voltage. When the current rises
sufficiently to saturate the transformer core, the secondary
voltages collapse, and
the JFET gate is forced negative, ending the cycle. A 1M resistor
discharges the 1nF cap, setting the cycle period to about 1200Hz.

1:45:65
+in ,------,
O--|----, | ,-----|>|----+---- +8.5V
| # # # |
| # # # |+
| # # # ---
| | | | 1.0nF --- 470uF
| |-' '-|-+--||--, |
'->|-, | | | |
| | '-/\/\-+ |
J105 | | 1.0M | |
O-------+---+--------+---+---- gnd

Sadly, Damaschke doesn't have much to say about the critical
aspects of this circuit, e.g. transformer properties or JFET
requirements.

Ensure that Idss > I saturation of the transformer. This will result in
the transformer requiring quite a lot of turns when this is in the few
ma range.

Lots of turns so that it satuates at low I.

.... your transformer manufacturer will hunt you down and beat you
with a stick

Well, I was quite intrigued by this, so I have now updated SS with an
example oscillator of this type (LVBlockingOsc.sss,
http://www.anasoft.co.uk/LVBlockingOsc.GIF
, ignore the update date). It runs from about 150mv upwards.

The "design" is pretty simple. I only used a transformer with 2 windings
to try and minimise space. It uses my newly added hysteretic non-linear
core model (thanks for the core idea Mike).

Its quite subtle really, it just looks like a normal oscillator circuit.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Winfield Hill]

Kevin Aylward wrote...

Ensure that Idss > I saturation of the transformer. This will result
in the transformer requiring quite a lot of turns when this is in the
few ma range.

Well, I was quite intrigued by this, so I have now updated SS with
an example oscillator of this type (LVBlockingOsc.sss,
http://www.anasoft.co.uk/LVBlockingOsc.GIF
ignore the update date). It runs from about 150mv upwards.

The "design" is pretty simple. I only used a transformer with 2 windings
to try and minimise space. It uses my newly added hysteretic non-linear
core model (thanks for the core idea Mike).

Its quite subtle really, it just looks like a normal oscillator circuit.

You used a J109, which has Idss = 40mA (min), whereas Damaschke used a
J105, with Idss = 500mA (min, at 15V vds). That's quite a difference.
At 300mV (Damaschke's specified minimum startup voltage) the J105 with
Rdss = 3 ohms (max), the minimum peak current will be 100mA, assuming
a minimal transformer winding resistance of course.

The thing that worries me about Damaschke's proposal to use this circuit
with a low-voltage furnace thermopile is the *very slow* risetime of the
300mV input whenever the furnace starts. Won't this completely fail to
start the blocking oscillator? Other low-voltage applications, like
seawater rope batteries, may also have this problem.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Stefan Heinzmann]

The thing that worries me about Damaschke's proposal to use this circuit
with a low-voltage furnace thermopile is the *very slow* risetime of the
300mV input whenever the furnace starts. Won't this completely fail to
start the blocking oscillator? Other low-voltage applications, like
seawater rope batteries, may also have this problem.

That's what I was worrying about since I saw your original Damaschke
reference: Is the circuit going to start up reliably? If not, can
anything be done about it?

 

[Jan Panteltje]

The thing that worries me about Damaschke's proposal to use this circuit
with a low-voltage furnace thermopile is the *very slow* risetime of the
300mV input whenever the furnace starts. Won't this completely fail to
start the blocking oscillator? Other low-voltage applications, like
seawater rope batteries, may also have this problem.

Noise, in the linear range it will be amplified?
JP

 

[Winfield Hill]

Stefan Heinzmann wrote...

That's what I was worrying about since I saw your original Damaschke
reference: Is the circuit going to start up reliably? If not, can
anything be done about it?

Yes, of course, toss the whole silly business. The task of converting
100mV or whatever up to 5V is trivial, given the fantastic low R_on of
modern power MOSFETs. Assuming, of course, a power supply is available
to power the FET gate-drive circuits. Under normal operation this can
be provided from the 5V output, as in Damaschke's circuit. But during
startup or load-fault conditions this is provided from a small battery,
eliminating clever and painful low-voltage converters. A simple low-
power 150mV comparator circuit can be used to disable the power-hungry
conversion circuitry from draining the battery whenever an inadequate
input voltage is present.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Terry Given]

Stefan Heinzmann wrote...

Yes, of course, toss the whole silly business. The task of converting
100mV or whatever up to 5V is trivial, given the fantastic low R_on of
modern power MOSFETs. Assuming, of course, a power supply is available
to power the FET gate-drive circuits. Under normal operation this can
be provided from the 5V output, as in Damaschke's circuit. But during
startup or load-fault conditions this is provided from a small battery,
eliminating clever and painful low-voltage converters. A simple low-
power 150mV comparator circuit can be used to disable the power-hungry
conversion circuitry from draining the battery whenever an inadequate
input voltage is present.

Thanks,
- Win

nice. There are plenty of ways of skinning cats....

I bought a digital micrometer a while ago. No off button - the battery lasts
for 3-4 years, so why bother.

Cheers
Terry

 

[Joel Kolstad]

Yes, of course, toss the whole silly business. The task of converting
100mV or whatever up to 5V is trivial, given the fantastic low R_on of
modern power MOSFETs. Assuming, of course, a power supply is available
to power the FET gate-drive circuits.

Yes, but it still seems to me like there's a place for the
'ultra-low-voltage/low-power input to super cap' converter chip out there,
even if it is just to provide the start-up voltage for a much better (more
efficient) power converter. That way I'd think you could realistically
expect equipment (I'm thinking solar powered here) that would keep working
for perhaps a decade without maintenance, whereas with a battery you'd have
to replace it every 2-3 years if rechargeable.

Although you might convince me that with a lithium battery you could still
get ten years...

 

[Kevin Aylward]

Kevin Aylward wrote...

You used a J109, which has Idss = 40mA (min), whereas Damaschke used
a J105, with Idss = 500mA (min, at 15V vds). That's quite a
difference.

I just used whatever was in my SS lib. It was only a proof of concept
thing. One alternative would be to use a depletion mode power mosfet.
There are some, but I couldn't be bothered setting up a model for the
one that I found.

At 300mV (Damaschke's specified minimum startup voltage)
the J105 with Rdss = 3 ohms (max), the minimum peak current will be
100mA, assuming a minimal transformer winding resistance of course.

The thing that worries me about Damaschke's proposal to use this
circuit with a low-voltage furnace thermopile is the *very slow*
risetime of the 300mV input whenever the furnace starts. Won't this
completely fail to start the blocking oscillator? Other low-voltage
applications, like seawater rope batteries, may also have this
problem.

This could be an issue. I did try a 10sec ramp, and this seemed to work
ok though. The output stays at 0V through the ramp up, then collapses
quite fast (to -15V) at the saturation point of the transformer, forcing
the ocilator to start. I suppose one could use a realy attached to the
300mv so that it switchs the voltage at the appropiate point.

I'm also never happy with circuits that only work dynamically. i.e. have
more then one stable state.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Winfield Hill]

Terry Given wrote...

I bought a digital micrometer a while ago. No off button - the
battery lasts for 3-4 years, so why bother.

After 3-4 years goes by and it no longer works, you'll be thinking
about that off button as you make the trek to Radio Shack for the
hearing-aid battery. After 6-8 years has gone by you'll be sorely
missing that off button when it fails again. After 9-12 years...

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Winfield Hill]

Kevin Aylward wrote...

I just used whatever was in my SS lib. It was only a proof of concept
thing. One alternative would be to use a depletion mode power mosfet.
There are some, but I couldn't be bothered setting up a model for the
one that I found.

Yep, the J105 is better, you should add it to your library. $1.22 qty
25 at Newark, #38C7317, http://www.fairchildsemi.com/ds/J1/J105.pdf

This could be an issue. I did try a 10sec ramp, and this seemed to
work ok though. The output stays at 0V through the ramp up, then
collapses quite fast (to -15V) at the saturation point of the
transformer, forcing the oscillator to start.

I suspect your transformer model. Real transformers don't have the
square loops I remember from your model, IIRC, and their saturation
is gradual. A slow 30mV/sec ramp wouldn't create enough secondary
voltage with a real transformer to negatively charge the 1.0nF cap
in Damaschke's circuit above, providing a way to turn off the JFET.

I suppose one could use a relay attached to the 300mv so that it
switches the voltage at the appropiate point.

But the relay circuit would have to operate on 300mV. :>(

I'm also never happy with circuits that only work dynamically.
i.e. have more then one stable state.

Indeed, one wakes up at night worrying about the extra non-operating
state. But if circuitry was added to detect this state and kick the
oscillator, then the benefit of simplicity is lost.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)