high voltage LED blinker...

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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.





--

Anybody can count to one.

- Robert Widlar