开云体育

The ESD is a narrow pulse, so it is dim. A small capacitor across the LED
might help. You can also use a string of regular diodes to clamp the
pulse's voltage. They have to total more than the forward voltage of the
LED so a resistor can limit the pulse current to a safe range.

On Thu, May 9, 2024 at 9:14?PM Ed Breya via groups.io <edbreya=
[email protected]> wrote:

I wrote a nice story earlier about experiments with LEDs as ESD
indicators, but it disappeared, so here's a short summary, then I'm done.

The LED survived many HBM discharges at 27 kV, the highest I could get my
ESD tester up to. The LED light was very poor though, just barely visible
in the dark. Need to try high efficiency type LEDs. Also, the neon lamp
suggestion someone suggested could be good alternative.

I will try some more experiments just for fun.

Ed

I tend to agree, although I haven't catalogued all the things that are worse now, after the re-write.

As a retired engineer who has written a lot of code, including HDLs, I have never liked "improvements" that cannot be linked to user requiements, either formal or informal. It is quite frustrating. And, of course, this characteristic is ubiquitous; most of the software programs that I use on the internef (to look for products from a vendor with which I have used for decades, or to pay bills online, etc., etc.) keep changing so that I often have to spend extra time figuring out how to do things using the new and "improved" website that I used to be able to do without a lot of thought using the previous version.

Ok, rant finished.

One specific note: I almost never use the web or mobile versions of groups.io to read and write posts; I pretty much always use my email client (Thunderbird).

DaveD
KC0WJN

Type your reply in Notepad or Wordpad as plain text, then copy and paste it.
Are you zoomed in on the website? Some web pages only work properly at 100*

On Thu, May 9, 2024 at 9:06?PM Ed Breya via groups.io <edbreya=
[email protected]> wrote:

I don't know if it's just me, but to me, the user interface sucks now. I
just lost another long message I was trying to post - it just disappeared
when I hit SEND. The navigation doesn't work right, either - clicking
stuff is often unresponsive, or does something different each time. There
top blue bar in the window is now twice its previous height, and it
obscures important things like the "HOME" button, which is essential to me
anyway, for jumping around. I am disgusted with it.

I suppose it could be due to using WinXP - maybe it's now incompatible. I
don't know. I do know that it worked just fine before, and now it sucks, so
I've had it, and will soon quit posting any messages. Even looking at
messages is difficult now.

I'd like to hear if anyone else is having these kind of troubles - maybe
it is just me, but I have to rant anyway.

I will send this message and hopefully it gets through - I'll copy it so I
can try again if not. Another symptom is that sometimes it goes through
just fine right away, sometimes it opens an error window with a cryptic set
of characters, and sometimes it just disappears.

I'll work hard to get this one posted, then one more short version about
the shopping cart story, and then that's it for me.

Ed

On 5/9/2024 9:05 PM, Ed Breya wrote:

I suppose it could be due to using WinXP - maybe it's now incompatible

That is an entirely possible, as WinXP is pretty Jurassic nowadays. I am always running one version late - now that Win11 is out I am still running Win10.

You might be able to eliminate some problems by using an email client. I don't do email on web sites - I use Thunderbird to aggregate my 32 email accounts (I like many accounts through four domains to combat spam). With one click I can download new email from all 32 accounts, including maybe 40 reflectors and email posted from my hundreds of web pages in my two private domains.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA

I wrote a nice story earlier about experiments with LEDs as ESD indicators, but it disappeared, so here's a short summary, then I'm done.

The LED survived many HBM discharges at 27 kV, the highest I could get my ESD tester up to. The LED light was very poor though, just barely visible in the dark. Need to try high efficiency type LEDs. Also, the neon lamp suggestion someone suggested could be good alternative.

I will try some more experiments just for fun.

Ed

Tried to confirm it worked fine, then the confirmation went to error and disappeared. Will try again.

I don't know if it's just me, but to me, the user interface sucks now. I just lost another long message I was trying to post - it just disappeared when I hit SEND. The navigation doesn't work right, either - clicking stuff is often unresponsive, or does something different each time. There top blue bar in the window is now twice its previous height, and it obscures important things like the "HOME" button, which is essential to me anyway, for jumping around. I am disgusted with it.

I suppose it could be due to using WinXP - maybe it's now incompatible. I don't know. I do know that it worked just fine before, and now it sucks, so I've had it, and will soon quit posting any messages. Even looking at messages is difficult now.

I'd like to hear if anyone else is having these kind of troubles - maybe it is just me, but I have to rant anyway.

I will send this message and hopefully it gets through - I'll copy it so I can try again if not. Another symptom is that sometimes it goes through just fine right away, sometimes it opens an error window with a cryptic set of characters, and sometimes it just disappears.

I'll work hard to get this one posted, then one more short version about the shopping cart story, and then that's it for me.

Ed

I use a regular hacksaw.
If the cut turns out to be irregular, it is easy to straighten it with a file.

On Wed, May 8, 2024 at 09:41 PM, Glydeck wrote:

Very nice. How do you get such a smooth cut of the can?

Here's how I manage it:

/g/TekScopes/album?id=294969

A shopping cart that accumulates a static charge fits the Charged Device
Model (CDM). It doesn't really matter which direction or polarity the
charge represents from a perspective of being shocked. Unfortunately the
initial discharge pulse would probably blow open an LED with the several
amps of discharge current that occurs. The user and the shopping cart
represent several thousand picofarads of capacitance. And depending on the
type of dielectric material used in the cart wheels and the user's shoes,
the charge can reach many thousands of volts. And it's made worse with
waxed floors. About the only thing you can do is to touch the cart to a
grounded item like a freezer or refrigerator to discharge it and yourself.

In an electronics manufacturing facility we'd use special ESD floor tiles
and carts with drag chains to continuously discharge carts as they were
moved. The entrance to those areas had a sign on the tile floors clearly
saying NO WAX so the housekeeping folks wouldn't defeat the ESD dissipative
floor tiles with a wax coating. But when the carts were used in the common
hallways with non-ESD tiles and waxed floors to use the elevator, we had to
touch the cart to the frame of the elevator door to discharge us and the
cart before we pushed the elevator button.

In our lab, a coworker had sneakers that were really bad about building up
a triboelectric charge and he would draw a 6" to 8" long spark from his arm
or shoulder when he turned the corner (with a grounded wall) into his
cubicle. And that didn't involve a cart. But it clearly exceeded the energy
expected in the Human Body Model of ESD control.

Depends upon the manufacturer. I’ve seen both.

Phenolic is also suitable since it is usually strengthened by application of a mesh to both sides of the material.

Greg


Wed, 08 May 2024 23:57:14 MST Michael A. Terrell wrote:

The insulator is fiber, not Phenolic.

All Caigslist listings give the nearest city in their URL. Ann Arbor is in
Michigan.

On Thu, May 9, 2024 at 2:34?AM David via groups.io <vexorg.calibra=
[email protected]> wrote:

It would really help if people put an approximate location on ads.

Though it seems no location means the seller must be American as they are
the ones that don't bother saying where they live (and not adding to the
stereotype that Americans see themselves as the only place in the world...)

The insulator is fiber, not Phenolic.

On Wed, May 8, 2024 at 3:54?PM radiobero.bb via groups.io <radiobero.bb=
[email protected]> wrote:

This is probably familiar to most people who have ever tried to replace an
old electrolytic capacitor.
It is very easy to make an adapter, at no cost.
It is enough to cut off the edge of the old electrolyte, approximately 3
millimeters from the edge.
You will get an outer ring that fits perfectly back to where it was, and
the bakelite center will serve perfectly to place a modern electrolyte on
it.

Here are pictures of how I usually do it:

/g/TekScopes/album?id=294954

I would suspect their choice of floor wax and the material the cart's
wheels are made from. The equipment is all grounded, so you have to
generate the charge. There are floor waxes made to prevent this, and is
used in Electronics factories. Synthetic rubber and long life plastic
wheels generate static, so together they can cause this problem. Rubbing
two insulators together is the problem. There are ESD ground sraps for your
shoes to help bleed away sartic from your body.

On Sat, May 4, 2024 at 12:31?PM cheater cheater via groups.io
<cheater00social@...> wrote:

Hi all,
I frequent a large grocery market nearby and inevitably every time I
go there I get electrical shocks. I walk around with a cart and often
if I touch a metal fixture (fridge, mesh rack) I get a painful shock.
Sometimes I get a shock if I leave the cart for a few seconds and then
touch its metal mesh.

I was wondering what everyone thought. At first I thought it would be
ESD, but why would it be so extreme? It happens every time. I live in
a place that's pretty dry - RH goes under 20% regularly - and being on
a plain it has a lot of wind, which could create triboelectric
charging. But I'm not really sure about this.

I don't know which way the ESD happens. Is my body discharging into
the cart? Is the cart discharging into my body? Is my body discharging
into the racks or vice versa? How can one check the directionality of
ESD?

One theory about ESD I have is that the fixtures get charged and my
body gets the charge applied to it. This however isn't necessarily
true to me because eg today I got a painful shock from touching the
inside metal surface of a fridge, and that's supposed to be earthed.

Another theory is that as I walk around in the store, as I move around
with the cart, that charges my body. I wear rubber sandals and the
cart has rubber wheels. That would mean I'm a conductor, attached to a
large antenna (the cart's mesh frame), moving through dry air,
insulated from the ground. The ground is made out of some sort of high
impact ceramic-ish tile. But then why would my own cart shock me just
mere seconds after letting go of it? I was unloading my groceries for
the cashier.

My third theory is that this whole facility has a lifted earth
potential. There's an industrial area nearby and they may be dumping a
lot of current into earth which would create a situation where walking
on the ground charges you, and then touching something that's low-Z to
neutral discharges your body (in this case this would be the earthed
fridges etc).

I was wondering how people would approach diagnosing this problem, and
how you would fix it if you had the ability to change anything about
the facility at hand - more as a thought exercise, but if I figure out
what's going on I'm going to write to the company.

Thanks

It would really help if people put an approximate location on ads.

Though it seems no location means the seller must be American as they are the ones that don't bother saying where they live (and not adding to the stereotype that Americans see themselves as the only place in the world...)

Try posting on the Logic Analyzers forum on groups.io.

If you're looking for direction, you'll need two of them

I'd be tempted to use a resistor and neon with a one KV diode in series with the neon.? The neon will limit the maximum voltage to about 100 volts or so.

so:? resistor connected to a neon with a series diode, connecting both across each other, and the diodes reversed.

Might be a good idea.

Harvey

Could you use a small (NE-2) neon bulb for this? I recall holding the lead
of one and shuffling across a carpet. I got the bulb to flash.

Steve H.

On Wed, May 8, 2024 at 21:03 Ed Breya via groups.io <edbreya=
[email protected]> wrote:

The LEDs would protect each other from reverse breakdown. They should be
stout enough to take the forward hit and flash. If not, you can put some C
across them or R in series to soften things up (which would also stretch
the pulse for better visibility). Try it and see.

What's really needed to assess part durability is a power rating and an
energy rating. You won't find energy rating for LEDs, so have to
experiment. If you study the HBM you'll have an idea of the energy
available from your own spark. Unfortunately, I don't think there's a spec
for SCM, but you can be sure it would be quite a bit more C, and nearly
zero R. Good luck.

Ed

Very nice. How do you get such a smooth cut of the can?

George KD6NEW

Yes indeed, Steve gets the prize. That's what it would be called if such a thing existed.

Ed