1 transistor negative resistance circuit Now working Attenti

J

Jan Panteltje

Guest
1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's diode,
the opto goes off, and only the current through the zeners and R2 R6 remains.
The point where the opto switches off causes the negative dip.
 
Jan Panteltje wrote...
1 transistor negative resistance circuit Now working!
Solution came to me: Opto coupler.
Click to expand...

No fair, that's two active parts! I mean, hey, I'm a
big fan of dual transistors in tiny packages, can those
count as one part? They're often used as if they were.


--
Thanks,
- Win
 
On a sunny day (8 Jul 2019 14:32:33 -0700) it happened Winfield Hill
<winfieldhill@yahoo.com> wrote in <qg0cph02u97@drn.newsguy.com>:

Jan Panteltje wrote...

1 transistor negative resistance circuit Now working!
Solution came to me: Opto coupler.

No fair, that's two active parts!
Click to expand...

OK, maybe I should have written 'one amplifying part',
it is just ONE transistor with Ib controlled by light,
not 'trickety.


I mean, hey, I'm a
big fan of dual transistors in tiny packages, can those
count as one part? They're often used as if they were.
Click to expand...

Na, that is 2 amplifying parts :)




--
Thanks,
- Win
Click to expand...
 
Jan Panteltje wrote:
1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's diode,
the opto goes off, and only the current through the zeners and R2 R6 remains.
The point where the opto switches off causes the negative dip.
Click to expand...
SUPER! Rather inventive, i should say. One active part.
..now..
If i cheat like all hell,
Zero active parts and only one part total,,,,an Esaki diode.
 
On Mon, 08 Jul 2019 19:36:50 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's diode,
the opto goes off, and only the current through the zeners and R2 R6 remains.
The point where the opto switches off causes the negative dip.
Click to expand...

There are those things they use in light dimmers, trigistors and
something else.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
John Larkin wrote...
There are those things they use in light
dimmers, trigistors and something else.
Click to expand...

DIACs. I have some, after one of the profs
came, said he wanted to repair his dimmer,
asked if we had any. Embarrassed, I had to
say no, but I quickly ordered some.


--
Thanks,
- Win
 
On Mon, 08 Jul 2019 19:36:50 +0000, Jan Panteltje wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.
Click to expand...
It appears the LED in the opto is wired backwards, so it will never light
up.

Jon
 
On 2019-07-09 20:30, Jon Elson wrote:
On Mon, 08 Jul 2019 19:36:50 +0000, Jan Panteltje wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

It appears the LED in the opto is wired backwards, so it will never light
up.

Jon
Click to expand...

No. For low voltages R6 and R2 supply the LED current and R7 is switched
in the circuit, loading V1. For higher voltages D2 and D1 draw the
current away from the LED, U1 goes off and R7 'disappears' from the circuit.

For even higher voltages the reverse voltage over the LED will destroy
it, which is also a negative effect.

Arie
 
On a sunny day (Tue, 9 Jul 2019 21:02:39 +0200) it happened Arie de Muynck
<no.spam@no.spam.org> wrote in <5d24e4cf$0$22341$e4fe514c@news.xs4all.nl>:

On 2019-07-09 20:30, Jon Elson wrote:
On Mon, 08 Jul 2019 19:36:50 +0000, Jan Panteltje wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

It appears the LED in the opto is wired backwards, so it will never light
up.

Jon


No. For low voltages R6 and R2 supply the LED current and R7 is switched
in the circuit, loading V1. For higher voltages D2 and D1 draw the
current away from the LED, U1 goes off and R7 'disappears' from the circuit.

For even higher voltages the reverse voltage over the LED will destroy
it, which is also a negative effect.

Arie
Click to expand...

Indeed, and for even higher voltages:
https://www.youtube.com/watch?v=lgaRtqKGNKk
 
On Mon, 08 Jul 2019 19:36:50 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's diode,
the opto goes off, and only the current through the zeners and R2 R6 remains.
The point where the opto switches off causes the negative dip.
Click to expand...

Sort of reminds me of this:

https://www.dropbox.com/s/p52uyap7c31w42i/Ilim_NCSSR.JPG?raw=1



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On 7/9/19 1:25 PM, Winfield Hill wrote:
John Larkin wrote...

There are those things they use in light
dimmers, trigistors and something else.

DIACs. I have some, after one of the profs
came, said he wanted to repair his dimmer,
asked if we had any. Embarrassed, I had to
say no, but I quickly ordered some.
Click to expand...

They're used in CFL ballasts too, to generate the initial trigger pulse
that starts the self-resonant oscillator running
 
On Monday, July 8, 2019 at 2:32:47 PM UTC-7, Winfield Hill wrote:
Jan Panteltje wrote...

1 transistor negative resistance circuit Now working!
Solution came to me: Opto coupler.

No fair, that's two active parts! I mean, hey, I'm a
big fan of dual transistors in tiny packages, can those
count as one part? They're often used as if they were.
Click to expand...

Yeah, and OTAs are just as simple as other (transistor, tube)
items with transconductance. It's just that, like a Darlington
with two transistors, an OTA has...twelve.
 
You can make a macroscopic UJT by wiring an LED to a voltage divider made
with CdS photocells, and pointing the LED at the bottom one. (Latching time
in the 10us range.)

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

"Jan Panteltje" <pNaOnStPeAlMtje@yahoo.com> wrote in message
news:qg060n$ecc$1@dont-email.me...
1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor
loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's
diode,
the opto goes off, and only the current through the zeners and R2 R6
remains.
The point where the opto switches off causes the negative dip.
Click to expand...
 
On a sunny day (Tue, 9 Jul 2019 19:28:51 -0500) it happened "Tim Williams"
<tiwill@seventransistorlabs.com> wrote in <qg3bf5$ge8$1@dont-email.me>:

You can make a macroscopic UJT by wiring an LED to a voltage divider made
with CdS photocells, and pointing the LED at the bottom one. (Latching time
in the 10us range.)

Tim
Click to expand...

Ah yes, I remember seeing that circuit here long ago.
I still have some real UJTs from ebay around.
 
On a sunny day (Tue, 09 Jul 2019 12:59:43 -0700) it happened John Larkin
<jjlarkin@highland_snip_technology.com> wrote in
<6gs9iepm9hi58qc6qh7md1u0sjer4v1vf2@4ax.com>:

On Mon, 08 Jul 2019 19:36:50 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's diode,
the opto goes off, and only the current through the zeners and R2 R6 remains.
The point where the opto switches off causes the negative dip.

Sort of reminds me of this:

https://www.dropbox.com/s/p52uyap7c31w42i/Ilim_NCSSR.JPG?raw=1
Click to expand...

Yes, the idea of a fuses occurred to me,
those that automatically go back to normal
forgot what those are called.

For a one time effect any fuse will do :)

Fuses are slow, and your circuit has many more transistors.

LDR and light bulb and 2 zeners may perhaps work too, also slow.
 
On 7/10/19 10:23 AM, Jan Panteltje wrote:
On a sunny day (Wed, 10 Jul 2019 06:50:52 -0700) it happened John Larkin
jjlarkin@highlandtechnology.com> wrote in
vrqbiedjtivf8rsqe1cj4tnl06a07ahdon@4ax.com>:

On Wed, 10 Jul 2019 05:27:59 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Tue, 09 Jul 2019 12:59:43 -0700) it happened John Larkin
jjlarkin@highland_snip_technology.com> wrote in
6gs9iepm9hi58qc6qh7md1u0sjer4v1vf2@4ax.com>:

On Mon, 08 Jul 2019 19:36:50 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's diode,
the opto goes off, and only the current through the zeners and R2 R6 remains.
The point where the opto switches off causes the negative dip.

Sort of reminds me of this:

https://www.dropbox.com/s/p52uyap7c31w42i/Ilim_NCSSR.JPG?raw=1

Yes, the idea of a fuses occurred to me,
those that automatically go back to normal
forgot what those are called.

For a one time effect any fuse will do :)

Fuses are slow, and your circuit has many more transistors.

LDR and light bulb and 2 zeners may perhaps work too, also slow.

Fusing is a chronic problem for us. Many of our products run off a DC
wall-wart, and a user can potentially give us the wrong voltage or
even polarity.

A real fuse needs to be replaced. Polyfuses are horribly inaccurate.

Ah! That was the word, 'polyfuse', never used one.


e-fuses are IMHO flakey. Polyzens are available in limited ranges. A
polyfuse and a transzorb can be teased.

We generally use a poly and a transzorb and go for 24 volts in,
assuming that warts over 24 volts are rare.

I use a diode against reverse voltage and a LM2596-3.3 for 3.3V
and add a resistor for higher output voltages,
that LM2596 because I got a lot of those from ebay for little.

Most transformer based wallwarts are short circuit protected with a thermal fuse,
switcher types usually will also somehow switch off and / or keep trying periodically in case of overload.


I'm doing some new gadgets that need 3.3 volts internally. I'll run
them from a USB supply, with a USB connector, and assume the input
will never exceed 5 volts, and never get reversed. Maybe have a poly
just in case.

PC USB will switch off power above about 600 mA IIRC,
I do have some Raspberry Pi USB wallwarts that can do a lot more...

I did blow up a WiFi booster by plugging in a 12V wallwart while it only wanted 5V..
Most stuff I have labeled for voltage, not that one..

Just careless.. nothing helps against that :)

The old thyristor and zener crowbar setup should work too?
Click to expand...

When somebody plugs in the wrong supply, you have no idea what is on the
other end of that cord. I sure wouldn't short it to ground unless there
was a fuse in between--it might start a fire someplace.

The SCR crowbar thing really needs something better than a zener to
drive the gate, because as it turns on it steals its own gate drive,
which tends to cause hot spots and reduce the dI/dt capability fairly badly.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On Wed, 10 Jul 2019 05:27:59 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Tue, 09 Jul 2019 12:59:43 -0700) it happened John Larkin
jjlarkin@highland_snip_technology.com> wrote in
6gs9iepm9hi58qc6qh7md1u0sjer4v1vf2@4ax.com>:

On Mon, 08 Jul 2019 19:36:50 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's diode,
the opto goes off, and only the current through the zeners and R2 R6 remains.
The point where the opto switches off causes the negative dip.

Sort of reminds me of this:

https://www.dropbox.com/s/p52uyap7c31w42i/Ilim_NCSSR.JPG?raw=1

Yes, the idea of a fuses occurred to me,
those that automatically go back to normal
forgot what those are called.

For a one time effect any fuse will do :)

Fuses are slow, and your circuit has many more transistors.

LDR and light bulb and 2 zeners may perhaps work too, also slow.
Click to expand...

Fusing is a chronic problem for us. Many of our products run off a DC
wall-wart, and a user can potentially give us the wrong voltage or
even polarity.

A real fuse needs to be replaced. Polyfuses are horribly inaccurate.
e-fuses are IMHO flakey. Polyzens are available in limited ranges. A
polyfuse and a transzorb can be teased.

We generally use a poly and a transzorb and go for 24 volts in,
assuming that warts over 24 volts are rare.

I'm doing some new gadgets that need 3.3 volts internally. I'll run
them from a USB supply, with a USB connector, and assume the input
will never exceed 5 volts, and never get reversed. Maybe have a poly
just in case.






--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On 7/9/19 1:25 PM, Winfield Hill wrote:> John Larkin wrote...
There are those things they use in light
dimmers, trigistors and something else.

DIACs. I have some, after one of the profs
came, said he wanted to repair his dimmer,
asked if we had any. Embarrassed, I had to
say no, but I quickly ordered some.
Click to expand...
Programmable unijunctions too. (Last time I used one of those was in
about 1990, in the interlock circuit of a diode laser controller.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On a sunny day (Wed, 10 Jul 2019 06:50:52 -0700) it happened John Larkin
<jjlarkin@highlandtechnology.com> wrote in
<vrqbiedjtivf8rsqe1cj4tnl06a07ahdon@4ax.com>:

On Wed, 10 Jul 2019 05:27:59 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Tue, 09 Jul 2019 12:59:43 -0700) it happened John Larkin
jjlarkin@highland_snip_technology.com> wrote in
6gs9iepm9hi58qc6qh7md1u0sjer4v1vf2@4ax.com>:

On Mon, 08 Jul 2019 19:36:50 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

1 transistor negative resistance circuit Now working!


http://panteltje.com/pub/neg_res_3.gif
Note the dip around the middle of the screen.

Was wondering 'must be possible'.

Solution came to me: Opto coupler.
Just put in some resistors, you can do better with other values
and other zeners, these are 4.7 V zeners, lowest my spice has.

Normally the opto's diode goes on via R2 and R6, and the opto's transistor loads the supply via R7.
As the voltage rises the zeners reverse the voltage across the opto's diode,
the opto goes off, and only the current through the zeners and R2 R6 remains.
The point where the opto switches off causes the negative dip.

Sort of reminds me of this:

https://www.dropbox.com/s/p52uyap7c31w42i/Ilim_NCSSR.JPG?raw=1

Yes, the idea of a fuses occurred to me,
those that automatically go back to normal
forgot what those are called.

For a one time effect any fuse will do :)

Fuses are slow, and your circuit has many more transistors.

LDR and light bulb and 2 zeners may perhaps work too, also slow.

Fusing is a chronic problem for us. Many of our products run off a DC
wall-wart, and a user can potentially give us the wrong voltage or
even polarity.

A real fuse needs to be replaced. Polyfuses are horribly inaccurate.
Click to expand...

Ah! That was the word, 'polyfuse', never used one.


e-fuses are IMHO flakey. Polyzens are available in limited ranges. A
polyfuse and a transzorb can be teased.

We generally use a poly and a transzorb and go for 24 volts in,
assuming that warts over 24 volts are rare.
Click to expand...

I use a diode against reverse voltage and a LM2596-3.3 for 3.3V
and add a resistor for higher output voltages,
that LM2596 because I got a lot of those from ebay for little.

Most transformer based wallwarts are short circuit protected with a thermal fuse,
switcher types usually will also somehow switch off and / or keep trying periodically in case of overload.


I'm doing some new gadgets that need 3.3 volts internally. I'll run
them from a USB supply, with a USB connector, and assume the input
will never exceed 5 volts, and never get reversed. Maybe have a poly
just in case.
Click to expand...

PC USB will switch off power above about 600 mA IIRC,
I do have some Raspberry Pi USB wallwarts that can do a lot more...

I did blow up a WiFi booster by plugging in a 12V wallwart while it only wanted 5V..
Most stuff I have labeled for voltage, not that one..

Just careless.. nothing helps against that :)

The old thyristor and zener crowbar setup should work too?
 
On a sunny day (Wed, 10 Jul 2019 10:28:17 -0400) it happened Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote in
<2sednWu29cGYa7jAnZ2dnUU7-TfNnZ2d@supernews.com>:

When somebody plugs in the wrong supply, you have no idea what is on the
other end of that cord. I sure wouldn't short it to ground unless there
was a fuse in between--it might start a fire someplace.
Click to expand...

Sure, add a fuse for if they connect it to a 12 V 200 Ah battery :)


The SCR crowbar thing really needs something better than a zener to
drive the gate, because as it turns on it steals its own gate drive,
which tends to cause hot spots and reduce the dI/dt capability fairly badly.
Click to expand...

I have used that circuit and it was standard in some TV sets after the switcher
to protect against the series switcher failing.

Again, NOTHING can protect against carelessness.

Google
"SCR crowbar circuit"

It is a very reliable way of protecting your equipment,
Never mind the rest of the universe...^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H
 
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