1 transistor negative resistance circuit Now working Attenti

[John Larkin]

On Wed, 10 Jul 2019 10:12:50 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

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.


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

PUTs were cool, back in the days of expensive TTL parts and hairball
async logic.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Wednesday, 10 July 2019 14:51:01 UTC+1, John Larkin wrote:

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.
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.

There's mil spec gear out there that can run on anything from 5vdc to 240v ac on the same input. It's certainly doable, just a question of resources & efficiency.

If V drop weren't critical I might look at current limiting with thermal shutdown for a cheap & simple option.


NT

 

On Wednesday, 10 July 2019 21:07:58 UTC+1, Robert Baer wrote:

Jan Panteltje wrote:

Most transformer based wallwarts are short circuit protected with a thermal fuse,
* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

Re mains frequency transformer types:
A minority have short-proof transformers. Most have a fuse or thermal fuse.


NT

 

[Robert Baer]

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,

* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

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?

 

[John Larkin]

On Wed, 10 Jul 2019 13:08:04 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

Most transformer based wallwarts are short circuit protected with a thermal fuse,
* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

Some are "impedance limited" which means they are wound with such thin
wire that they can't deliver much current. That *reduces* the cost!


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

On Wed, 10 Jul 2019 06:50:52 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

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.
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.

A schottky wouldn't hurt either.

 

[Jan Panteltje]

On a sunny day (Wed, 10 Jul 2019 13:08:04 -0800) it happened Robert Baer
<robertbaer@localnet.com> wrote in <uArVE.27492$lH5.21808@fx05.iad>:

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,
* ALL transformer-based wallwarts that i have seen have ZERO

Watch closely, there may be a thermal fuse mounted under the transformer,
or even wound in it.

Maybe I was lucky, I have some transformer based going back to the eighties in use 24/7 to
power an antenna pre-amp.
And an other to power a MP3 player, and an other to power a camera ?

In any case in relation to using the SCR crowbar as overvoltage protection,
a series fuse will not always blow when powered from a wallwart,
it should be there though.
And in that case you will depend on that thermal protection.
And I use fuses with wires, like these:
https://www.ebay.com/itm/371707810914
no problems with fuse holders, and a blown fuse almost never happens, and if it does
it should be replaced by somebody who knows about 'trickety,
not like that audio amp I got for repair that had nails in the fuse holders...


>protection; that would raise the cost of manufacture...

Sure, by 23 cents?
https://www.ebay.com/itm/223085851577

OK, you got a point, I do not have any recent transformer based wallwarts from China.
Are those still made? From China all switchers here,
mostly big 12V several amps LED strip supplies,
usefull for many things.

 

On Wednesday, 10 July 2019 22:57:37 UTC+1, John Larkin wrote:

On Wed, 10 Jul 2019 13:08:04 -0800, Robert Baer
robertbaer@localnet.com> wrote:


Most transformer based wallwarts are short circuit protected with a thermal fuse,
* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

Some are "impedance limited" which means they are wound with such thin
wire that they can't deliver much current. That *reduces* the cost!

OTOH they drop so much in action that they need to be rated for more VA. Hence only done for tiny transformers.


NT

 

[Phil Hobbs]

On 7/11/19 9:56 AM, John Larkin wrote:

On Thu, 11 Jul 2019 04:30:57 -0700 (PDT), tabbypurr@gmail.com wrote:

On Wednesday, 10 July 2019 22:57:37 UTC+1, John Larkin wrote:
On Wed, 10 Jul 2019 13:08:04 -0800, Robert Baer
robertbaer@localnet.com> wrote:


Most transformer based wallwarts are short circuit protected with a thermal fuse,
* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

Some are "impedance limited" which means they are wound with such thin
wire that they can't deliver much current. That *reduces* the cost!

OTOH they drop so much in action that they need to be rated for more VA. Hence only done for tiny transformers.


NT

It's common for doorbell transformers that can legally be wired
directly to the AC line without fusing. They may use some inductive
current limiting too... less core materials is cheaper too!

A lot of domestic electric fans are "impedance protected", i.e. they
won't catch fire if the rotor seizes up.

Cheers

Phil Hobbs

(Who has one of those in the kitchen that needs to be overhauled again.)

--
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

 

[John Larkin]

On Thu, 11 Jul 2019 04:30:57 -0700 (PDT), tabbypurr@gmail.com wrote:

On Wednesday, 10 July 2019 22:57:37 UTC+1, John Larkin wrote:
On Wed, 10 Jul 2019 13:08:04 -0800, Robert Baer
robertbaer@localnet.com> wrote:


Most transformer based wallwarts are short circuit protected with a thermal fuse,
* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

Some are "impedance limited" which means they are wound with such thin
wire that they can't deliver much current. That *reduces* the cost!

OTOH they drop so much in action that they need to be rated for more VA. Hence only done for tiny transformers.


NT

It's common for doorbell transformers that can legally be wired
directly to the AC line without fusing. They may use some inductive
current limiting too... less core materials is cheaper too!


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Phil Hobbs]

On 7/11/19 11:27 AM, John Larkin wrote:

On Thu, 11 Jul 2019 10:28:51 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 7/11/19 9:56 AM, John Larkin wrote:
On Thu, 11 Jul 2019 04:30:57 -0700 (PDT), tabbypurr@gmail.com wrote:

On Wednesday, 10 July 2019 22:57:37 UTC+1, John Larkin wrote:
On Wed, 10 Jul 2019 13:08:04 -0800, Robert Baer
robertbaer@localnet.com> wrote:


Most transformer based wallwarts are short circuit protected with a thermal fuse,
* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

Some are "impedance limited" which means they are wound with such thin
wire that they can't deliver much current. That *reduces* the cost!

OTOH they drop so much in action that they need to be rated for more VA. Hence only done for tiny transformers.


NT

It's common for doorbell transformers that can legally be wired
directly to the AC line without fusing. They may use some inductive
current limiting too... less core materials is cheaper too!


A lot of domestic electric fans are "impedance protected", i.e. they
won't catch fire if the rotor seizes up.

Cheers

Phil Hobbs

(Who has one of those in the kitchen that needs to be overhauled again.)


Usually the cheap bronze bearings gunk up. Often a solvent clean and
moly re-lube fixes them for a few years.

Yup. This one is mounted in an 8-inch long by 10 inch diameter duct,
right over the cooktop, and has been in use since 1960. I last
overhauled it ten years or so ago, and there's been a lot of bacon
grease through there since.

Shaded-pole motors usually don't mind being stalled.

Well, they come with a shorted turn, no extra charge.

I'm reading a Tesla book. Stuff that seems perfectly obvious to us
now, like making a rotating magnetic field, wasn't.

You and Niki are homeys. I find him a bit like Mary Queen of
Scots--interesting character, but no surprises in the story at this
point, and way too many books written.

Maybe he's tapping into the Great Oz--there are superficial similarities
there too.

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

 

[John Larkin]

On Thu, 11 Jul 2019 10:28:51 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 7/11/19 9:56 AM, John Larkin wrote:
On Thu, 11 Jul 2019 04:30:57 -0700 (PDT), tabbypurr@gmail.com wrote:

On Wednesday, 10 July 2019 22:57:37 UTC+1, John Larkin wrote:
On Wed, 10 Jul 2019 13:08:04 -0800, Robert Baer
robertbaer@localnet.com> wrote:


Most transformer based wallwarts are short circuit protected with a thermal fuse,
* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

Some are "impedance limited" which means they are wound with such thin
wire that they can't deliver much current. That *reduces* the cost!

OTOH they drop so much in action that they need to be rated for more VA. Hence only done for tiny transformers.


NT

It's common for doorbell transformers that can legally be wired
directly to the AC line without fusing. They may use some inductive
current limiting too... less core materials is cheaper too!


A lot of domestic electric fans are "impedance protected", i.e. they
won't catch fire if the rotor seizes up.

Cheers

Phil Hobbs

(Who has one of those in the kitchen that needs to be overhauled again.)

Usually the cheap bronze bearings gunk up. Often a solvent clean and
moly re-lube fixes them for a few years.

Shaded-pole motors usually don't mind being stalled.

I'm reading a Tesla book. Stuff that seems perfectly obvious to us
now, like making a rotating magnetic field, wasn't.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Larkin]

On Thu, 11 Jul 2019 11:33:59 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 7/11/19 11:27 AM, John Larkin wrote:
On Thu, 11 Jul 2019 10:28:51 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 7/11/19 9:56 AM, John Larkin wrote:
On Thu, 11 Jul 2019 04:30:57 -0700 (PDT), tabbypurr@gmail.com wrote:

On Wednesday, 10 July 2019 22:57:37 UTC+1, John Larkin wrote:
On Wed, 10 Jul 2019 13:08:04 -0800, Robert Baer
robertbaer@localnet.com> wrote:


Most transformer based wallwarts are short circuit protected with a thermal fuse,
* ALL transformer-based wallwarts that i have seen have ZERO
protection; that would raise the cost of manufacture...

Some are "impedance limited" which means they are wound with such thin
wire that they can't deliver much current. That *reduces* the cost!

OTOH they drop so much in action that they need to be rated for more VA. Hence only done for tiny transformers.


NT

It's common for doorbell transformers that can legally be wired
directly to the AC line without fusing. They may use some inductive
current limiting too... less core materials is cheaper too!


A lot of domestic electric fans are "impedance protected", i.e. they
won't catch fire if the rotor seizes up.

Cheers

Phil Hobbs

(Who has one of those in the kitchen that needs to be overhauled again.)


Usually the cheap bronze bearings gunk up. Often a solvent clean and
moly re-lube fixes them for a few years.

Yup. This one is mounted in an 8-inch long by 10 inch diameter duct,
right over the cooktop, and has been in use since 1960. I last
overhauled it ten years or so ago, and there's been a lot of bacon
grease through there since.


Shaded-pole motors usually don't mind being stalled.

Well, they come with a shorted turn, no extra charge.


I'm reading a Tesla book. Stuff that seems perfectly obvious to us
now, like making a rotating magnetic field, wasn't.

You and Niki are homeys. I find him a bit like Mary Queen of
Scots--interesting character, but no surprises in the story at this
point, and way too many books written.

He had some good instincts and not much in the way of theory or
quantitative judgement. I sure hope I don't get crazy in later life
like he did.

This book includes some history, Westinghouse and Edison and GE and
Siemens and Niagra Falls and such. And fat cats with money.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics