Is there a device that...?

[Mark Folsom]

"mike" <spamme0@juno.com> wrote in message news:3FD7AFA5.1010001@juno.com...

Mark Folsom wrote:
[snip]


Ok, so I'm playing 20-questions, reverse engineering a secret design to
help someone who's calling me names.
I think that's called masochism.
But I'm bored, and I really am a nice guy (most of the time), so here
goes.

Interesting little details the 8 amps and 2 ohms.
Would have been nice to have that information in the beginning.

Let's do a back of the envelope approximation.

If your tiny bit of charge is the 5 uA load that takes your caps from
60V to half that in 50 uS, you have about 8.3 pF of capacitance.

I have two 1 uf capacitors. It isn't a 5 uA load that takes it from 60 V to
half that in 50 us. Here's an exact quote of what I wrote in a previous
post:

"I have two capacitors that I am charging in series, with a lot of noise, in
about 50 microseconds--then discharging in parallel. I use some diodes to
allow that to happen--I modeled it and then built it and it works and allows
me to get a lot more energy than I do by charging them from the same source
in parallel. The capacitors then power a custom timer ASIC that draws about
5 microamps. At the end of a programable interval that ranges between 100
and 1000 milliseconds, the circuit switches the remaining charge into a 2
ohm resistance. Any device for this function would have to conduct about 8
amps for a few hundred microseconds and have less than a quarter ohm
resistance when in the on condition.

The diodes that we use to switch from series to parallel seem to have enough
capacitance to keep the output up to the charging voltage until a little
charge is drawn off. It appears to take less than two microseconds to go
from 52 volts to 26 volts when the capacitors are loaded with 12kohm on the
output."

It explicitly says that it goes from 52 to 26 volts in a couple of
microseconds, with a 12 kohm load. It doesn't do that by draining the
charge on the two caps--it drains a much smaller unintended capacitance in
the circuit while changing the effective configuration of the caps from
series to parallel.

When you discharge that into 2 ohms, you have a time constant of
16.6 picoseconds.
So, you need a deivce that can switch 8 amps and get that 16pS time
constant to last a few hundred microseconds.

I expect that's not what you meant. Can you see why some of us might
be more than a little confused by a descrepancy that's 4 orders of
magnitude?

I told you I thought the capacitance that kept the voltage up was the tiny
capacitance of some diodes in the circuit.

So, I guess I am an ignorant jerk that just can't understand what you're
trying to do even after I've read it.

If you're gonna hide the details, at least try to have some consistency
in the numbers you do post. My subscription to the psychic hotline
has expired.

I want a device that blocks current for about 100 microseconds after 50 to
60 volts is applied and then conducts with less than 0.25 ohm resistance for
as long as voltage remains positive. And it needs to draw off a few
nanocoulombs before it switches. And it needs to be tiny. What's
complicated?

Mark Folsom

 

[Boris Mohar]

On Wed, 10 Dec 2003 16:40:46 -0800, "Mark Folsom"
<folsom_snip_man@redshift.com> wrote:

Snip..

I want a device that blocks current for about 100 microseconds after 50 to
60 volts is applied and then conducts with less than 0.25 ohm resistance for
as long as voltage remains positive. And it needs to draw off a few
nanocoulombs before it switches. And it needs to be tiny. What's
complicated?

You are. You are a physicist and you word view apparently excludes subtle
trivialities of tiny electronic devices. I worked with a really brilliant
Piled Higher and Deeper who came to me one day asking why is the clock
oscillator that he was using as a stand alone to drive some gizmo was
getting so hot. When I explained to him that just because that wanted
higher output he could not just crank up the power supply he looked me in
bewilderment and dismay as my world of limitations collided with his
expectations. I ended up building him a two tone FM spectroscopy instrument
which was trivially easy compared to what it took to get the specs out of
him.
What we have here is a failure to communicate. One way to make some headway
is to post the schematic diagram in alt.binaries.schematics.electronic and
post a comprehensive description in sci.electronics.design because it is a
design and not just a part that you need.

--

Boris Mohar

 

[Mark Folsom]

<William P.N. Smith> wrote in message
news:0udftv865v7rh39vti32tkmst15o7i1lkj@4ax.com...

"Mark Folsom" <folsom_snip_man@redshift.com> wrote:
Well, I was told I should use a capacitor, that I should just clamp the
voltage with a zener, that I should use an inductor, etc., etc.
Meanwhile,
I've given more and more detail on how the item would be used, and most
of
the comments I get back offer nothing whatever of use--either you haven't
read what I've posted, or you don't understand what I'm trying to do even
after you've read it. Maybe the vast majority of you don't have a clue
and
you're just jerking me around for your own amusement. Being nice to a
bunch
of ignorant jerks isn't likely to be terribly productive in this context.

Well, if you had given sufficient detail in the first place, you
wouldn't be having this problem. It looks from here like you've been
given a number of ideas which may work, but without a detailed
knowledge of whatit is you are trying to do (which you've said you
won't provide), many of us are just shooting in the dark. The more
detailed your requirements, the more useful will be the [free]
responses you get. In either case, you get what you pay for.

[For instance, if you are looking at the output of a photodiode, maybe
replacing it with a small solar panel would give you enough power to
run your switching circuit...]

I've been given a lot of ideas that won't work which, coincidentally, are
also not what I asked for. If I give a fuller description of everything
that's going on, I will just get more suggestions about things I can't
change, or for things that won't fit. I'm REALLY looking for a device that
blocks current and then conducts after about 100 microseconds. If you've
never heard of anything like that then "I dunno" would be a really good
answer. If I wanted help with a different problem, I would ask for it.

Mark Folsom

 

[William P.N. Smith]

"Mark Folsom" <folsom_snip_man@redshift.com> wrote:

William P.N. Smith> wrote in message
"Mark Folsom" <folsom_snip_man@redshift.com> wrote:
[maybe]
you're just jerking me around for your own amusement. Being nice to a
bunch
of ignorant jerks isn't likely to be terribly productive in this context.

Strangely, insulting the folks who have tried to help you has gotten a
lot of response, and kept this thread going for a lot longer than I
would have expected. Who'da thunk it?

Well, if you had given sufficient detail in the first place, you
wouldn't be having this problem. It looks from here like you've been
given a number of ideas which may work, but without a detailed
knowledge of whatit is you are trying to do (which you've said you
won't provide), many of us are just shooting in the dark. The more
detailed your requirements, the more useful will be the [free]
responses you get. In either case, you get what you pay for.

I've been given a lot of ideas that won't work which, coincidentally, are
also not what I asked for. If I give a fuller description of everything
that's going on, I will just get more suggestions about things I can't
change, or for things that won't fit.

If you think that adding detail to your admittedly sparse description
will make things worse, then no-one is going to be able to help you.
The part you seem to want doesn't seem to exist. Many people here
have offered to help you with the overall problem, but you won't tell
us the grand secret of what you're trying to do.

I'm REALLY looking for a device that
blocks current and then conducts after about 100 microseconds.

It's called a FET plus an appropriate timing device. [But then it
turns out you aren't just looking for that device, you are looking for
one that's tiny, monolithic, and low power, and high current, and all
sorts of other self-contradictory things.]

--
William Smith
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[mike]

Mark Folsom wrote:

"mike" <spamme0@juno.com> wrote in message news:3FD7AFA5.1010001@juno.com...

Mark Folsom wrote:

[snip]

Ok, so I'm playing 20-questions, reverse engineering a secret design to
help someone who's calling me names.
I think that's called masochism.
But I'm bored, and I really am a nice guy (most of the time), so here

goes.

Interesting little details the 8 amps and 2 ohms.
Would have been nice to have that information in the beginning.

Let's do a back of the envelope approximation.

If your tiny bit of charge is the 5 uA load that takes your caps from
60V to half that in 50 uS, you have about 8.3 pF of capacitance.


I have two 1 uf capacitors. It isn't a 5 uA load that takes it from 60 V to
half that in 50 us. Here's an exact quote of what I wrote in a previous
post:

"I have two capacitors that I am charging in series, with a lot of noise, in
about 50 microseconds--then discharging in parallel. I use some diodes to
allow that to happen--I modeled it and then built it and it works and allows
me to get a lot more energy than I do by charging them from the same source
in parallel. The capacitors then power a custom timer ASIC that draws about
5 microamps. At the end of a programable interval that ranges between 100
and 1000 milliseconds, the circuit switches the remaining charge into a 2
ohm resistance. Any device for this function would have to conduct about 8
amps for a few hundred microseconds and have less than a quarter ohm
resistance when in the on condition.

The diodes that we use to switch from series to parallel seem to have enough
capacitance to keep the output up to the charging voltage until a little
charge is drawn off. It appears to take less than two microseconds to go
from 52 volts to 26 volts when the capacitors are loaded with 12kohm on the
output."

It explicitly says that it goes from 52 to 26 volts in a couple of
microseconds, with a 12 kohm load. It doesn't do that by draining the
charge on the two caps--it drains a much smaller unintended capacitance in
the circuit while changing the effective configuration of the caps from
series to parallel.


When you discharge that into 2 ohms, you have a time constant of
16.6 picoseconds.
So, you need a deivce that can switch 8 amps and get that 16pS time
constant to last a few hundred microseconds.

I expect that's not what you meant. Can you see why some of us might
be more than a little confused by a descrepancy that's 4 orders of
magnitude?


I told you I thought the capacitance that kept the voltage up was the tiny
capacitance of some diodes in the circuit.


So, I guess I am an ignorant jerk that just can't understand what you're
trying to do even after I've read it.

If you're gonna hide the details, at least try to have some consistency
in the numbers you do post. My subscription to the psychic hotline
has expired.


I want a device that blocks current for about 100 microseconds after 50 to
60 volts is applied and then conducts with less than 0.25 ohm resistance for
as long as voltage remains positive. And it needs to draw off a few
nanocoulombs before it switches. And it needs to be tiny. What's
complicated?

Mark Folsom

I give up.
You've got enough energy to support 8 amps for microseconds, but you
can't afford to lose the tiny charge stored on diode capacitance.

The answer to your question is, "NO the device you want does NOT exist."
I apologize for wasting your time trying to help.
mike

--
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S
TEK Sampling Sweep Plugin and RM564
Tek 2465 $800, ham radio, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[Mark Folsom]

<William P.N. Smith> wrote in message
news:28lftvs82b5r5p5uomlks49ehppa7mtc94@4ax.com...

"Mark Folsom" <folsom_snip_man@redshift.com> wrote:
William P.N. Smith> wrote in message
"Mark Folsom" <folsom_snip_man@redshift.com> wrote:
[maybe]
you're just jerking me around for your own amusement. Being nice to a
bunch
of ignorant jerks isn't likely to be terribly productive in this
context.

Strangely, insulting the folks who have tried to help you has gotten a
lot of response, and kept this thread going for a lot longer than I
would have expected. Who'da thunk it?

Well, if you had given sufficient detail in the first place, you
wouldn't be having this problem. It looks from here like you've been
given a number of ideas which may work, but without a detailed
knowledge of whatit is you are trying to do (which you've said you
won't provide), many of us are just shooting in the dark. The more
detailed your requirements, the more useful will be the [free]
responses you get. In either case, you get what you pay for.

I've been given a lot of ideas that won't work which, coincidentally, are
also not what I asked for. If I give a fuller description of everything
that's going on, I will just get more suggestions about things I can't
change, or for things that won't fit.

If you think that adding detail to your admittedly sparse description
will make things worse, then no-one is going to be able to help you.
The part you seem to want doesn't seem to exist.

THANK YOU!

Mark Folsom

 

[Mark Folsom]

"Boris Mohar" <borism@sympatico.ca> wrote in message
newspgftvc18jj3k1nosbg55t8hlrskrkgk0o@4ax.com...

On Wed, 10 Dec 2003 16:40:46 -0800, "Mark Folsom"
folsom_snip_man@redshift.com> wrote:

Snip..

I want a device that blocks current for about 100 microseconds after 50
to
60 volts is applied and then conducts with less than 0.25 ohm resistance
for
as long as voltage remains positive. And it needs to draw off a few
nanocoulombs before it switches. And it needs to be tiny. What's
complicated?


You are. You are a physicist and you word view apparently excludes subtle
trivialities of tiny electronic devices.

I'm a mechanical engineer.

I worked with a really brilliant
Piled Higher and Deeper who came to me one day asking why is the clock
oscillator that he was using as a stand alone to drive some gizmo was
getting so hot.

Well, the 125 microjoules that our chip consumes in the first second
probably won't overheat anything.

When I explained to him that just because that wanted
higher output he could not just crank up the power supply he looked me in
bewilderment and dismay as my world of limitations collided with his
expectations.

That's wonderful. It doesn't, however, tell me anything about whether the
device I'm looking for is available.

I ended up building him a two tone FM spectroscopy instrument
which was trivially easy compared to what it took to get the specs out of
him.

I guess you're also wonderful. But I wasn't asking you to design or build
anything for me.

What we have here is a failure to communicate. One way to make some
headway
is to post the schematic diagram in alt.binaries.schematics.electronic and
post a comprehensive description in sci.electronics.design because it is a
design and not just a part that you need.

Says you.

Mark Folsom

 

[Alan]

novatech@eskimo.com (Steven Swift) wrote in message news:<br5njb$tje$1@eskinews.eskimo.com>...

Whoops, in my attempt at "wit" I missed the point. Sorry.


"Mark Folsom" <folsom_snip_man@redshift.com> writes:


Is there a (preferably tiny surface mount) device that starts out
non-conducting and then conducts a short time after a voltage is applied,
like maybe 100 microseconds? If so, what's it called?

Just reading this thread fresh myself, and just have to point out
that it wasn't entirely your fault on misreading this, it wasn't
precise to me either at first, not because I don't get things, but
because it's not worded well for a technical description. Note that
his sentence mentions applying the voltage LAST, even though it's the
first thing that happens, which is a bit sloppy for describing a
technical idea. Note that it's much clearer what he wants if you
actually SAY it as applying the voltage first, then give the rest of
what happens. Time order modifiers like after should be saved for
giving variation to normal speech, not making people have to
de-reference the order in a technical context when trying to initially
describe an idea. Does the after refer to just the nearest (conducts)
part or both that and the earlier (non-conducting) part? It makes
your brain have to quite a bit of extra work while reading it, just to
use the word 'after' and change the order of the sentence. So the
fault wasn't all in your attempt at wit..

I'm not a technical writer btw (although I play one on TV), but do
get enough of it to see that things like this are why even few very
technical people make good technical writings. It must be accurate
and good, in the clearest and fastest to understand order, not varied
like normal speech. That's why most good accurate texts are hard to
read, it's hard to vary your sentences enough to prevent boredom yet
still keep everything in the clearest structure.

Later,
Alan

 

[Alan]

"Mark Folsom" <folsom_snip_man@redshift.com> wrote in message news:<vtf72dobj2jp01@corp.supernews.com>...

Well, I was told I should use a capacitor, that I should just clamp the
voltage with a zener, that I should use an inductor, etc., etc. Meanwhile,
I've given more and more detail on how the item would be used, and most of
the comments I get back offer nothing whatever of use--either you haven't
read what I've posted, or you don't understand what I'm trying to do even
after you've read it. Maybe the vast majority of you don't have a clue and
you're just jerking me around for your own amusement. Being nice to a bunch
of ignorant jerks isn't likely to be terribly productive in this context.

All problems from things that YOU didn't say clearly, that YOU have
already tried but didn't tell us, and that YOU chose to hide to keep
your idea secret. That you YOURSELF are not smart enough to see that
the problems come from YOUR side and the info that you're hiding, and
realizing that finding an answer while only divulging what's necessary
is a STEPWISE process that will take more than a few steps, shows a
CLEAR lack of thinking ability on YOUR, not our, part.

To even suggest that everyone else in here is stupid because of your
poor descriptive abilties when you do describe, and your CHOSEN lack
of description to hide what you're doing, clearly demonstrates your
own stupidity. EVEN if you have need to not disclose, it is still
YOUR fault not ours that you didn't give enough info. You're quite
right that being nice to ingnorant jerks never is productive, but
you're the ignorant jerk in this case.


And counter to the other suggested diagnosis, you have a severe
INFERIORITY complex. Having to assign everyone else as stupid to make
yourself feel smart instead of thinking it through enough to realize
that your own doings are actually at fault, and not then realizing
that you have to live with a slower process if you want to hide info,
is an immediate indicator.

In short, you are a twit.

Also note, since you aren't smart enough to get this on your own
accord, that these newsgroups are archived. ANY FUTURE EMPLOYER that
has an ounce of sense will be doing internet searches, and if they
read this thread and see your clear lack of correct thinking and
blaming it on everyone else, you can bet they'll realize they have
more competent applicants.

I have spoken. And I'm right, ask anyone.

Have a nice day!

Alan