• high voltage LED blinker

    From John Larkin@21:1/5 to All on Fri May 27 17:08:44 2022
    https://www.dropbox.com/s/53vtce00svlwur4/Blink_1.jpg?raw=1

    https://www.dropbox.com/s/yn63unaffp6q9sb/Blink_2.jpg?raw=1

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.

    The 1K resistor really helps the brightness.

    --

    If a man will begin with certainties, he shall end with doubts,
    but if he will be content to begin with doubts he shall end in certainties. Francis Bacon

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  • From John Larkin@21:1/5 to jlarkin@highland_atwork_technology. on Fri May 27 17:28:06 2022
    On Fri, 27 May 2022 17:08:44 -0700, John Larkin <jlarkin@highland_atwork_technology.com> wrote:


    https://www.dropbox.com/s/53vtce00svlwur4/Blink_1.jpg?raw=1

    https://www.dropbox.com/s/yn63unaffp6q9sb/Blink_2.jpg?raw=1

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.

    The 1K resistor really helps the brightness.

    No, the top resistor is 2M from 120 vdc, so the current is more like
    50 uA.

    --

    If a man will begin with certainties, he shall end with doubts,
    but if he will be content to begin with doubts he shall end in certainties. Francis Bacon

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  • From Jan Panteltje@21:1/5 to jlarkin@highland_atwork_technology. on Sat May 28 05:14:12 2022
    On a sunny day (Fri, 27 May 2022 17:08:44 -0700) it happened John Larkin <jlarkin@highland_atwork_technology.com> wrote in <elp29hpqj5ddpv65hgsgcmb6ac4u36huoa@4ax.com>:


    https://www.dropbox.com/s/53vtce00svlwur4/Blink_1.jpg?raw=1

    https://www.dropbox.com/s/yn63unaffp6q9sb/Blink_2.jpg?raw=1

    How about a neon bulb with a series resistor and capacitor in parallel?
    Or if it must be a semi-conductor a UJT with a LED in the discharge..
    not sure that b1 b2 resistance is high enough,
    multivibrator with 2 transistors perhap?

    No spice here atm

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  • From Piotr Wyderski@21:1/5 to John Larkin on Sat May 28 07:36:55 2022
    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.

    This is one good option, a neon bulb is another. But are you sure you
    want your discharge current *low*? Mine is set up to 5mA, as it is the
    DMOS SOA should something go wrong and the discharge circuit got
    constantly on.

    Best regards, Piotr

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  • From jlarkin@highlandsniptechnology.com@21:1/5 to pNaonStpealmtje@yahoo.com on Sat May 28 07:09:00 2022
    On Sat, 28 May 2022 05:14:12 GMT, Jan Panteltje
    <pNaonStpealmtje@yahoo.com> wrote:

    On a sunny day (Fri, 27 May 2022 17:08:44 -0700) it happened John Larkin ><jlarkin@highland_atwork_technology.com> wrote in ><elp29hpqj5ddpv65hgsgcmb6ac4u36huoa@4ax.com>:


    https://www.dropbox.com/s/53vtce00svlwur4/Blink_1.jpg?raw=1

    https://www.dropbox.com/s/yn63unaffp6q9sb/Blink_2.jpg?raw=1

    How about a neon bulb with a series resistor and capacitor in parallel?
    Or if it must be a semi-conductor a UJT with a LED in the discharge..
    not sure that b1 b2 resistance is high enough,
    multivibrator with 2 transistors perhap?

    No spice here atm

    One of my first circuits, as a kid, was a neon blinker. But I want a
    lower trip voltage and a surface-mount indicator.

    Popular Electronics had a fun circuit: build a NE2 relaxation
    oscillator with two neons in parallel. The lower breakdown bulb will
    usually flash, but tiny disurbances - light, efields, radiation - will
    shift to the other.

    For some reason I have a bag full of NE2's.

    Diacs are cool. I never used one before. I can imagine off-label uses.
    LT Spice has a diac in the parts library.





    --

    Anybody can count to one.

    - Robert Widlar

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  • From jlarkin@highlandsniptechnology.com@21:1/5 to bombald@protonmail.com on Sat May 28 07:22:08 2022
    On Sat, 28 May 2022 07:36:55 +0200, Piotr Wyderski
    <bombald@protonmail.com> wrote:

    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.

    This is one good option, a neon bulb is another. But are you sure you
    want your discharge current *low*? Mine is set up to 5mA, as it is the
    DMOS SOA should something go wrong and the discharge circuit got
    constantly on.

    Best regards, Piotr

    I built that last-thing Friday, and left when it blinked. I might
    study it more next week.

    The test circuit on the SODDB3T data sheet has it discharging into
    20K, so it has some low shutoff current. My blink looked much brighter
    with the 1K resistor in series with the LED.

    Of course it's brutal inefficient to discharge 32 volts into a 2-volt
    LED. An inductor or transformer would help, at some hassle. There are
    cute multi-junction leds around.

    I don't know how I could simulate the diac function with transistors
    and stuff. There is some semiconductor magic going on inside a diac.



    --

    Anybody can count to one.

    - Robert Widlar

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  • From bitrex@21:1/5 to jlarkin@highlandsniptechnology.com on Sat May 28 13:11:11 2022
    On 5/28/2022 10:22 AM, jlarkin@highlandsniptechnology.com wrote:
    On Sat, 28 May 2022 07:36:55 +0200, Piotr Wyderski
    <bombald@protonmail.com> wrote:

    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.

    This is one good option, a neon bulb is another. But are you sure you
    want your discharge current *low*? Mine is set up to 5mA, as it is the
    DMOS SOA should something go wrong and the discharge circuit got
    constantly on.

    Best regards, Piotr

    I built that last-thing Friday, and left when it blinked. I might
    study it more next week.

    The test circuit on the SODDB3T data sheet has it discharging into
    20K, so it has some low shutoff current. My blink looked much brighter
    with the 1K resistor in series with the LED.

    Of course it's brutal inefficient to discharge 32 volts into a 2-volt
    LED. An inductor or transformer would help, at some hassle. There are
    cute multi-junction leds around.

    I don't know how I could simulate the diac function with transistors
    and stuff. There is some semiconductor magic going on inside a diac.




    These strobe trigger transformers are cheap n cheerful, I think the tend
    to be about 1:10 with a couple mH on the secondary.

    <https://www.amazon.com/AFCN-Flashtube-Transformer-Transformateur-Photographic/dp/B07J2VHKBG>

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  • From jlarkin@highlandsniptechnology.com@21:1/5 to bitrex on Sat May 28 10:30:20 2022
    On Sat, 28 May 2022 13:11:11 -0400, bitrex <user@example.net> wrote:

    On 5/28/2022 10:22 AM, jlarkin@highlandsniptechnology.com wrote:
    On Sat, 28 May 2022 07:36:55 +0200, Piotr Wyderski
    <bombald@protonmail.com> wrote:

    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.

    This is one good option, a neon bulb is another. But are you sure you
    want your discharge current *low*? Mine is set up to 5mA, as it is the
    DMOS SOA should something go wrong and the discharge circuit got
    constantly on.

    Best regards, Piotr

    I built that last-thing Friday, and left when it blinked. I might
    study it more next week.

    The test circuit on the SODDB3T data sheet has it discharging into
    20K, so it has some low shutoff current. My blink looked much brighter
    with the 1K resistor in series with the LED.

    Of course it's brutal inefficient to discharge 32 volts into a 2-volt
    LED. An inductor or transformer would help, at some hassle. There are
    cute multi-junction leds around.

    I don't know how I could simulate the diac function with transistors
    and stuff. There is some semiconductor magic going on inside a diac.




    These strobe trigger transformers are cheap n cheerful, I think the tend
    to be about 1:10 with a couple mH on the secondary.

    <https://www.amazon.com/AFCN-Flashtube-Transformer-Transformateur-Photographic/dp/B07J2VHKBG>

    Just a series L might work, make a sort of single-cycle switching
    power supply.



    --

    Anybody can count to one.

    - Robert Widlar

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  • From whit3rd@21:1/5 to jla...@highlandsniptechnology.com on Sat May 28 12:16:11 2022
    On Saturday, May 28, 2022 at 7:22:18 AM UTC-7, jla...@highlandsniptechnology.com wrote:

    I don't know how I could simulate the diac function with transistors
    and stuff. There is some semiconductor magic going on inside a diac.

    It's basically an SCR with a breakdown that triggers it; two transistors
    makes the SCR, and it triggers by collector-base breakdown

    <https://www.electrical4u.com/two-transistor-model-of-scr/>

    There are variations; GE made a SBS (silicon bilateral switch) with mismatched positive/negative breakdowns, and of course there's BIG CURRENT sidactors

    <https://www.littelfuse.com/~/media/electronics/datasheets/sidactors/littelfuse_sidactor_do_214_datasheet.pdf.pdf>

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  • From boB@21:1/5 to All on Sat May 28 12:36:32 2022
    On Sat, 28 May 2022 07:22:08 -0700, jlarkin@highlandsniptechnology.com
    wrote:

    On Sat, 28 May 2022 07:36:55 +0200, Piotr Wyderski
    <bombald@protonmail.com> wrote:

    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.

    This is one good option, a neon bulb is another. But are you sure you
    want your discharge current *low*? Mine is set up to 5mA, as it is the
    DMOS SOA should something go wrong and the discharge circuit got
    constantly on.

    Best regards, Piotr

    I built that last-thing Friday, and left when it blinked. I might
    study it more next week.

    The test circuit on the SODDB3T data sheet has it discharging into
    20K, so it has some low shutoff current. My blink looked much brighter
    with the 1K resistor in series with the LED.

    Of course it's brutal inefficient to discharge 32 volts into a 2-volt
    LED. An inductor or transformer would help, at some hassle. There are
    cute multi-junction leds around.

    I don't know how I could simulate the diac function with transistors
    and stuff. There is some semiconductor magic going on inside a diac.

    A diiac should just be a triac with a set trigger voltage which
    shouldn't be too difficult to model. I think that there are
    Spice/LTspice models of a diac that can be used.

    I have a product that uses two neon lights but it is from a HV supply
    over 200V.

    I wanted to do something like what you did but as you did, built the
    blinky neon lights many years ago.

    Too bad that the NE-1/NE-2 isn't available in an SMT package though.

    boB

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  • From Phil Hobbs@21:1/5 to Piotr Wyderski on Sat May 28 18:21:53 2022
    Piotr Wyderski wrote:
    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.

    This is one good option, a neon bulb is another. But are you sure you
    want your discharge current *low*? Mine is set up to 5mA, as it is the
    DMOS SOA should something go wrong and the discharge circuit got
    constantly on.

        Best regards, Piotr

    At 1400V, that would waste 7 watts continuously.

    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

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  • From Rich S@21:1/5 to Phil Hobbs on Sat May 28 22:29:30 2022
    On Saturday, May 28, 2022 at 10:22:07 PM UTC, Phil Hobbs wrote:
    Piotr Wyderski wrote:
    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.


    Last time I looked at a diac spec sheet
    (many years ago) I noticed the trigger voltage
    is not exact, has a tolerance like +/-3 volts.
    Not a surprise I think. But I would up your
    cap's voltage rating, just to have more safety
    margin. The cost of 50V over 35V in an Aluminum
    electro is trivial. If youre going to use Tantalum,
    thats a more serious price jump.
    I would also feel better putting a 39V or 47V zener
    or across that cap, just in case a part in the
    LED string fails open, and the cap never gets
    discharged. Exploding caps, even just one,
    are bad for business ;-)
    regards, RS

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  • From Piotr Wyderski@21:1/5 to Piotr Wyderski on Sun May 29 07:53:01 2022
    Piotr Wyderski wrote:

    This is how my discharge circuit works. Basically, a normally-on relay
    minus the contact reliability problems and coil losses. If it were
    supposed to be constantly on, a simple bleeding resistor would do.

    Namely, in addition to the regular DMOS current source with a source
    resistor, there is a diode connected to the gate and then to a tiny 6mm
    OD pulse transformer with <1% duty cycle, powered directly from the MCU
    pins. No pulses (a controller-side failure or intrusion detection) =>
    discharge starts automatically. "Shut up" pulses present => DMOS
    "disappears". 5kV isolation and extreme simplicity thanks to a tiny core
    and 20cm of TIW wire.

    Best regards, Piotr

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  • From Piotr Wyderski@21:1/5 to Phil Hobbs on Sun May 29 07:41:03 2022
    Phil Hobbs wrote:

    At 1400V, that would waste 7 watts continuously.

    IIRC, John mentioned it was a discharge circuit, so it should act fast.
    That's correct: 7W would be dissipated if the DMOS shutdown circuit
    fails and no one notices that, hence me urging to mind the SOA. But the
    power should be essentially 0 watts under normal circumstances, assuming
    there is some indicator of normal operation (an intrusion detection
    switch, low voltage rail presence indicator, you name it).

    This is how my discharge circuit works. Basically, a normally-on relay
    minus the contact reliability problems and coil losses. If it were
    supposed to be constantly on, a simple bleeding resistor would do.

    Best regards, Piotr

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  • From piglet@21:1/5 to jlarkin@highlandsniptechnology.com on Sun May 29 13:24:17 2022
    On 28/05/2022 15:22, jlarkin@highlandsniptechnology.com wrote:


    I don't know how I could simulate the diac function with transistors
    and stuff. There is some semiconductor magic going on inside a diac.



    Glad you tried a diac, have you tried replacing the diac with bipolar transistor (reverse connected and with base open, sometimes called
    negistor)? It is similar effect I think but with breakover about 9V.

    Remember back in the 1960s when diac symbol was like a BJT with two
    emitters and no base connection - that gives a clue to internals.

    I think the semiconductor magic is a combination of emitter-base reverse breakdown, reverse beta and impact ionization? Most diacs are 3 layer
    devices so the negative resistance is not from transistor-transistor
    feedback as in a schockley diode.

    piglet

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  • From jlarkin@highlandsniptechnology.com@21:1/5 to richsulinengineer@gmail.com on Sun May 29 07:11:23 2022
    On Sat, 28 May 2022 22:29:30 -0700 (PDT), Rich S
    <richsulinengineer@gmail.com> wrote:

    On Saturday, May 28, 2022 at 10:22:07 PM UTC, Phil Hobbs wrote:
    Piotr Wyderski wrote:
    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in.

    The 1M resistor would be a string of depletion fets in real life.


    Last time I looked at a diac spec sheet
    (many years ago) I noticed the trigger voltage
    is not exact, has a tolerance like +/-3 volts.
    Not a surprise I think. But I would up your
    cap's voltage rating, just to have more safety
    margin. The cost of 50V over 35V in an Aluminum
    electro is trivial. If youre going to use Tantalum,
    thats a more serious price jump.
    I would also feel better putting a 39V or 47V zener
    or across that cap, just in case a part in the
    LED string fails open, and the cap never gets
    discharged. Exploding caps, even just one,
    are bad for business ;-)
    regards, RS

    Microamps won't explode this cap. Al and tant and even most ceramic
    caps just leak when the voltage gets high. I have seen one brand of
    polymer elec that failed hard without warning at under 2x rated
    voltage, but most seem to just leak more as voltage goes up.

    Small surface-mount tants are 10 cents in quantity. Ceramics lose c as
    voltage goes up, so don't store the expected energy.

    A small Al cap would be OK, more like 5 cents, but might be tricky
    over temperature. In our business, parts cost for passives doesn't
    matter, not when we're lucky to get an FPGA for $200.



    --

    Anybody can count to one.

    - Robert Widlar

    --- SoupGate-Win32 v1.05
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  • From jlarkin@highlandsniptechnology.com@21:1/5 to All on Sun May 29 06:58:41 2022
    On Sun, 29 May 2022 13:24:17 +0100, piglet <erichpwagner@hotmail.com>
    wrote:

    On 28/05/2022 15:22, jlarkin@highlandsniptechnology.com wrote:


    I don't know how I could simulate the diac function with transistors
    and stuff. There is some semiconductor magic going on inside a diac.



    Glad you tried a diac, have you tried replacing the diac with bipolar >transistor (reverse connected and with base open, sometimes called
    negistor)? It is similar effect I think but with breakover about 9V.

    Remember back in the 1960s when diac symbol was like a BJT with two
    emitters and no base connection - that gives a clue to internals.

    I think the semiconductor magic is a combination of emitter-base reverse >breakdown, reverse beta and impact ionization? Most diacs are 3 layer
    devices so the negative resistance is not from transistor-transistor
    feedback as in a schockley diode.

    piglet


    The 32v diac is ideal for this use. It is not specified for holding
    current (stays-on) but that should be OK with my roughly 50 uA
    current-limited source. The academic challenge is to use the energy in
    the cap more efficiently to get a brighter blink on less supply
    current.

    Shockley was obsessed with developing a 4-layer device, rather than
    evolving the transistor. That was one factor in the split:

    https://en.wikipedia.org/wiki/Traitorous_eight



    --

    Anybody can count to one.

    - Robert Widlar

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  • From jlarkin@highlandsniptechnology.com@21:1/5 to bombald@protonmail.com on Sun May 29 07:15:47 2022
    On Sun, 29 May 2022 07:41:03 +0200, Piotr Wyderski
    <bombald@protonmail.com> wrote:

    Phil Hobbs wrote:

    At 1400V, that would waste 7 watts continuously.

    IIRC, John mentioned it was a discharge circuit, so it should act fast. >That's correct: 7W would be dissipated if the DMOS shutdown circuit
    fails and no one notices that, hence me urging to mind the SOA. But the
    power should be essentially 0 watts under normal circumstances, assuming >there is some indicator of normal operation (an intrusion detection
    switch, low voltage rail presence indicator, you name it).

    The blinking LED is the indicator. It blinks until the HV is below
    safe levels, and works even when power is off.


    This is how my discharge circuit works. Basically, a normally-on relay
    minus the contact reliability problems and coil losses. If it were
    supposed to be constantly on, a simple bleeding resistor would do.

    A resistor has a very long exponential delay. The depletion fet
    discharge is linear, much faster, and it blinks!



    --

    Anybody can count to one.

    - Robert Widlar

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  • From bitrex@21:1/5 to jlarkin@highlandsniptechnology.com on Sun May 29 11:04:20 2022
    On 5/29/2022 10:11 AM, jlarkin@highlandsniptechnology.com wrote:
    On Sat, 28 May 2022 22:29:30 -0700 (PDT), Rich S <richsulinengineer@gmail.com> wrote:

    On Saturday, May 28, 2022 at 10:22:07 PM UTC, Phil Hobbs wrote:
    Piotr Wyderski wrote:
    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in. >>>>>
    The 1M resistor would be a string of depletion fets in real life.


    Last time I looked at a diac spec sheet
    (many years ago) I noticed the trigger voltage
    is not exact, has a tolerance like +/-3 volts.
    Not a surprise I think. But I would up your
    cap's voltage rating, just to have more safety
    margin. The cost of 50V over 35V in an Aluminum
    electro is trivial. If youre going to use Tantalum,
    thats a more serious price jump.
    I would also feel better putting a 39V or 47V zener
    or across that cap, just in case a part in the
    LED string fails open, and the cap never gets
    discharged. Exploding caps, even just one,
    are bad for business ;-)
    regards, RS

    Microamps won't explode this cap. Al and tant and even most ceramic
    caps just leak when the voltage gets high. I have seen one brand of
    polymer elec that failed hard without warning at under 2x rated
    voltage, but most seem to just leak more as voltage goes up.

    IIRC MnO2 tantalums are some of the longest-life caps there are once
    they make it out of the first drop in the bathtub curve, the rise at
    "EOL" is very shallow when they're treated right.

    They have a self-healing mechanism, that however can become a
    self-destroying mechanism when they're fed by a low impedance supply and
    2 Meg likely doesn't qualify.

    Small surface-mount tants are 10 cents in quantity. Ceramics lose c as voltage goes up, so don't store the expected energy.

    A small Al cap would be OK, more like 5 cents, but might be tricky
    over temperature. In our business, parts cost for passives doesn't
    matter, not when we're lucky to get an FPGA for $200.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to bitrex on Sun May 29 11:06:11 2022
    On 5/29/2022 11:04 AM, bitrex wrote:
    On 5/29/2022 10:11 AM, jlarkin@highlandsniptechnology.com wrote:
    On Sat, 28 May 2022 22:29:30 -0700 (PDT), Rich S
    <richsulinengineer@gmail.com> wrote:

    On Saturday, May 28, 2022 at 10:22:07 PM UTC, Phil Hobbs wrote:
    Piotr Wyderski wrote:
    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in. >>>>>>
    The 1M resistor would be a string of depletion fets in real life.


    Last time I looked at a diac spec sheet
    (many years ago) I noticed the trigger voltage
    is not exact, has a tolerance like +/-3 volts.
    Not a surprise I think.  But I would up your
    cap's voltage rating, just to have more safety
    margin. The cost of 50V over 35V in an Aluminum
    electro is trivial. If youre going to use Tantalum,
    thats a more serious price jump.
    I would also feel better putting a 39V or 47V zener
    or across that cap, just in case a part in the
    LED string fails open, and the cap never gets
    discharged. Exploding caps, even just one,
    are bad for business ;-)
    regards, RS

    Microamps won't explode this cap. Al and tant and even most ceramic
    caps just leak when the voltage gets high. I have seen one brand of
    polymer elec that failed hard without warning at under 2x rated
    voltage, but most seem to just leak more as voltage goes up.

    IIRC MnO2 tantalums are some of the longest-life caps there are once
    they make it out of the first drop in the bathtub curve, the rise at
    "EOL" is very shallow when they're treated right.

    They have a self-healing mechanism, that however can become a
    self-destroying mechanism when they're fed by a low impedance supply and
    2 Meg likely doesn't qualify.

    Or rather large dv/dt plus low impedance source is bad news for tantalums.

    --- SoupGate-Win32 v1.05
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  • From jlarkin@highlandsniptechnology.com@21:1/5 to bitrex on Sun May 29 09:26:08 2022
    On Sun, 29 May 2022 11:06:11 -0400, bitrex <user@example.net> wrote:

    On 5/29/2022 11:04 AM, bitrex wrote:
    On 5/29/2022 10:11 AM, jlarkin@highlandsniptechnology.com wrote:
    On Sat, 28 May 2022 22:29:30 -0700 (PDT), Rich S
    <richsulinengineer@gmail.com> wrote:

    On Saturday, May 28, 2022 at 10:22:07 PM UTC, Phil Hobbs wrote:
    Piotr Wyderski wrote:
    John Larkin wrote:

    This makes a pretty hunky blink at about 1 Hz with 100 uA coming in. >>>>>>>
    The 1M resistor would be a string of depletion fets in real life. >>>>>>

    Last time I looked at a diac spec sheet
    (many years ago) I noticed the trigger voltage
    is not exact, has a tolerance like +/-3 volts.
    Not a surprise I think. But I would up your
    cap's voltage rating, just to have more safety
    margin. The cost of 50V over 35V in an Aluminum
    electro is trivial. If youre going to use Tantalum,
    thats a more serious price jump.
    I would also feel better putting a 39V or 47V zener
    or across that cap, just in case a part in the
    LED string fails open, and the cap never gets
    discharged. Exploding caps, even just one,
    are bad for business ;-)
    regards, RS

    Microamps won't explode this cap. Al and tant and even most ceramic
    caps just leak when the voltage gets high. I have seen one brand of
    polymer elec that failed hard without warning at under 2x rated
    voltage, but most seem to just leak more as voltage goes up.

    IIRC MnO2 tantalums are some of the longest-life caps there are once
    they make it out of the first drop in the bathtub curve, the rise at
    "EOL" is very shallow when they're treated right.

    They have a self-healing mechanism, that however can become a
    self-destroying mechanism when they're fed by a low impedance supply and
    2 Meg likely doesn't qualify.

    Or rather large dv/dt plus low impedance source is bad news for tantalums.

    Right. They are excellent when used properly. Way better than
    aluminums.





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