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'[PIC]: AC mains into PIC pin'
2002\11\04@095101 by Roman Black

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Sean Alcorn - Avion Sydney wrote:
>

> > Well, I don't think you will be able to
> > declare it a good design because that circuit
> > connects the AC mains direct to a PIC pin
> > via a resistor!!!
>
> Are you referring to the power supply, the zero cross detect or both?

The zero cross detect, the power supply is a
capacitve reactance type.

> > There's no way you can convince me it's smart
> > to couple AC mains into a PIC pin with nothing
> > more than one resistor to protect the PIC.
>
> I wasn't trying to convince you, I was asking opinions. And they seem
> to be widely varied.

I know. It's an expression of speech. :o)
Yes opinions vary, we have been discussing this
for months (years?) now on the list with wide
varying opinions.

> > The cost of a capacitor and zener etc are only
> > a few cents.
>
> Again, on the zero cross detect? How would you configure it? Doesn't
> the existing Zener clamp the maximum voltage at 5.6 Volts? Also, the
> minimum voltage is zero volts? Can I ask you Roman, when is the neutral
> ever more than 0 volts?

The PIC doesn't have a zener. It has clamp diodes,
very different story. :o) In the circuit you posted
(yes I know it's not your circuit, sorry if I gave
that impression) the circuit is live to AC mains
active, and the Xc supply and zero cross detect
are driven from the neutral. This has EXACTLY the
same effect as ac mains is, well, ac. :o)

The PIC pin is connected to the AC mains full potential
via just one series resistor.

My reasons for an external zener;
* much larger silicon and testable
* can be physically away from PIC
* WILL clamp 5.1v, even fast spikes

And a capacitor across the zener will give some
spike protection for negative spikes and reduce
zener surge current for all spikes + and -.
These two parts cost a few cents and go some way
to preventing the AC mains killing the PIC. :o)

I've changed the topic as I know lots of people
have their own ideas and may want to add...
Russell has posted a long and detailed post on
the topic recently.
-Roman

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2002\11\04@102154 by Sean Alcorn - Avion Sydney

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Roman,

> The zero cross detect, the power supply is a capacitve reactance type.

You have no issues with these?

> I know. It's an expression of speech. :o)

Yes, I know. But you came across as if I was trying to shove this upon
the list, and that is not what I was trying to do.

> Yes opinions vary, we have been discussing this
> for months (years?) now on the list with wide
> varying opinions.

Sorry. I did not realise it was an old topic. I must have been napping.
I will try to search my archives, then the PIClist.

> The PIC doesn't have a zener.

I was referring to the Zener in Paul Benford's circuit. Isn't it
holding VDD at 5.6 volts relative to "0 volts" connected to VSS? But
then this would also mean that the neutral can swing from zero to
(339.5 - 5.6) as referenced to zero volts right? And that is what you
are getting at. You do not trust the internal clamp diodes to clamp
this off - even when it appears in many Microchip application notes and
those of third parties?

>  It has clamp diodes,
> very different story. :o) In the circuit you posted
> (yes I know it's not your circuit, sorry if I gave
> that impression)

No. I just don't want to be seen to be putting up someone else's work
without giving them the credit - whether it's good or bad! :-)

> the circuit is live to AC mains
> active, and the Xc supply and zero cross detect
> are driven from the neutral. This has EXACTLY the
> same effect as ac mains is, well, ac. :o)

Yes. Agree.

> The PIC pin is connected to the AC mains full potential
> via just one series resistor.

Yes.
>
> My reasons for an external zener;
> * much larger silicon and testable
> * can be physically away from PIC
> * WILL clamp 5.1v, even fast spikes

OK, thanks.

> And a capacitor across the zener will give some
> spike protection for negative spikes and reduce
> zener surge current for all spikes + and -.
> These two parts cost a few cents and go some way
> to preventing the AC mains killing the PIC. :o)

OK, Agreed. I don't care about the PIC as much as I do as making a safe
product and one that will pass standards.

> I've changed the topic as I know lots of people
> have their own ideas and may want to add...

OK

> Russell has posted a long and detailed post on
> the topic recently.

What was the subject? I can not find it on my machine at home. Will
check in the office tomorrow.

Regards,

Sean

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2002\11\07@025545 by john

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the safest way is to use an opto-coupler.

I have vast experience in this field (dimmers in professional lighting field)
and if you only knew what comes down those AC lines...... you'd use an opto
too.
Nicest way of doing it is to put the INT pin via a zener and res after
step-down trafo, separated by a diode from the main storage caps.

Microchip say you can do it with just a resistor, and that it will be ok (
reasoning is: high impedance resistance.. a few megs, capacitance of pin for
slew limit, maximum current through pin is ok and clamps to PSU rail, due to
certain circumstances use 2 diodes to strap the pin to v+ and 0V ). I tend to
agree with them. The diodes internally vary from port type to port type so
BEWARE.

This is also documented in the Microchip AppNotes.

The safest way of doing it is  via an opto-coupler, which needs a reverse
diode accross the internal LED, and suitable current limit resistor so as not
to get too much delay on the sync relative to the 0 point on the wave.

Regards,
John

On Monday 04 November 2002 05:21 pm, you wrote:
{Quote hidden}

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2002\11\07@050447 by Russell McMahon

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> the safest way is to use an opto-coupler.
>
> I have vast experience in this field (dimmers in professional lighting
field)
> and if you only knew what comes down those AC lines...... you'd use an
opto
> too.
> Nicest way of doing it is to put the INT pin via a zener and res after
> step-down trafo, separated by a diode from the main storage caps.
>
> Microchip say you can do it with just a resistor, and that it will be ok (
> reasoning is: high impedance resistance.. a few megs, capacitance of pin
for
> slew limit, maximum current through pin is ok and clamps to PSU rail, due
to
> certain circumstances use 2 diodes to strap the pin to v+ and 0V ). I tend
to
> agree with them. The diodes internally vary from port type to port type so
> BEWARE.

Microchip's mother wears army boots and dresses it funny too, in this
instance.
Although, a laaaaarge enough value resistor approaches reasonableness.
Just because one of the manufacturer's people says it's OK doesn't mean it
is. The same applies if its written in an app note. In the operating
conditions section of a spec sheet SHOULD be different. (In the absolute
maximum section doesn't count).

When they put it in a data-sheet as a guaranteed spec you can *try* and hold
them to it - even then it still won't work if it breaks the laws of physics.

*IF* they actually suggest, as you say they do, that  using external diodes
may be necessary, it proves they have found out by experience that the
internal catch diodes DON'T always work well and take you too near the
ragged edge and are taking you SOMEWHAT further away from the edge.
Consider, the internal diodes are standard silicon devices with a nominal
0.6v forward conduction voltage. Adding another silicon diode in p[arallel
externally MAY reduce internal currents significantly, and may not. Adding
external SCHOTTKY diodes is another story - that will work as the Scottky's
will conduct before the internal silicon diodes. If that is what they are
recommending then I apologise about the army boots comment. Shame about the
clothes though.

> This is also documented in the Microchip AppNotes.

Yeah.

> The safest way of doing it is  via an opto-coupler, which needs a reverse
> diode accross the internal LED, and suitable current limit resistor so as
not
> to get too much delay on the sync relative to the 0 point on the wave.

Yes. Or someother "proper" isolation system. Note that even optos have their
limitations in very high rise time situations, but that's not liable to be
much of a problem here.(very bad input transients may need to be
considered).

It IS possible to design a resistive input mains interface that doesn't
violate IC input specs and which handles reasonably probable transients
well. It may be cheaper than using an opto but will not be safe for human
isolation purposes.



       Russell McMahon

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2002\11\07@053410 by Sean Alcorn - Avion Sydney

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> It IS possible to design a resistive input mains interface that doesn't
> violate IC input specs and which handles reasonably probable transients
> well.

With all this huff and puffing on this subject, has anybody actually
tried it?

> It may be cheaper than using an opto but will not be safe for human
> isolation purposes.

In my case, that was never an issue.

Sean

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2002\11\07@061517 by Vasile Surducan

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someone said:

> > the safest way is to use an opto-coupler.
> >

 I've heard this topic sooo many time it definitely bored me. :(
 The isolation tehnique ( any one would be ) is not necessary if
the final product it's a stand alone ( or it's communicating via
optoisolated i2c, RS485, Rs232 etc ). It's also not necessary even if
the product have a LCD and a keypad and *all* isolation requirements
to the operator's hands and to other commands are fulfilled ( ie plastic
chasis, isolated buttons, optocouplers or transformers for other special
inter-modules connections etc. ) It's also not necessary isolation to
triacs or tyristors gates driving, but sometime boosting it's required.
Think just a little what you'll do when 10 or
20 triacs must be driven. For mains zero cross detection, I'm using
succesfully an external schmitd trigger gate (cmos, CD4093 ) input
directly to main ( 220V -15%...+20% ) via a 220K resistor and one
protective zenner ( 5V1, 4093 supply at 5V ) to ground from the same
input. Optionally a 10nF...100nF can be used for filtering, but usually is
not necessary.
For the system I've described, conecting the system ground to the
neutral or to phase does not change anything in normal functioning
conditions. And this one was tested.

best regards,
Vasile

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2002\11\07@080208 by Russell McMahon

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> > It IS possible to design a resistive input mains interface that doesn't
> > violate IC input specs and which handles reasonably probable transients
> > well.
>
> With all this huff and puffing on this subject, has anybody actually
> tried it?

That question could mean several things, but yes in several cases.

I have used a properly designed resistive input from mains to processor pin
with no problems.

I have had an improper resistive input from RS232 cause severe problems
(using a circuit recommended by a commercial source (not uChip)).

Re "huffing and puffing".
Some while ago I decided to resolutely (read bloody mindedly) address the
use-of-protection-diodes-during-normal-operation issue every time it came up
as it comes up repeatedly and there are ALWAYS people who mislead the
uninitiated by telling them you can violate datasheet specs and be sure to
have no problems. I am well aware of the exceptions, the what if's, the
maybe you can's and the characterise it yourself for your application
arguments. I am aware that you can break the rules and live (or have your
design live) on many occasions. I've just decided to go in to bat on behalf
of the beginners and the less initiated (and that's a large proportion of
those on this list in this area) so that they hear some other voice than the
"just do it, all will be well" brigade :-).

Sometime, when time allows, (probably within the next 50 years) I intend to
do some real world tests injecting current into protection diodes on various
pins and report when observed strange affects do start to arise. I have seen
it happen in real world situations using digital only pins.

Re isolation and protection. I see no problem with using "non isolated"
interfaces; as long as the system level implications are understood and
properly addressed.


       Russell McMahon

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2002\11\07@082049 by Sean Alcorn - Avion Sydney

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Russell,

> I have used a properly designed resistive input from mains to
> processor pin
> with no problems.

Well, based on what you and Roman have input here the following would
work for 240VAC (assuming shitty Australia and New Zealand power);

* Two resistors in series - say 3~4M each
* 5.1V Zener from Pin to GND - only small wattage, I assume is OK
* up to say 100nF Metalised cap (rated at 400V) strapped across Zener

OR

* a pair of Schottky diodes on input pin

Yes?

Ho do you feel about sinking the gate current to a PIC pin through a
single resistor - if maintained at around 5mA?

Regards,

Sean

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2002\11\07@085143 by Olin Lathrop

face picon face
> Well, based on what you and Roman have input here the following would
> work for 240VAC (assuming shitty Australia and New Zealand power);
>
> * Two resistors in series - say 3~4M each
> * up to say 100nF Metalised cap (rated at 400V) strapped across Zener

This will not work for a very different reason that those brought up so
far.  Two "3~4M" resistors in series gets you at least 6M ohms.  6M ohms
and 100nF make quite a low pass filter.  If my quick and dirty
calculations are right, you end up with about +-1.8V from 240V 50Hz mains.
With 6Mohm small leakages that could normally be ignored become
significant.

> * 5.1V Zener from Pin to GND - only small wattage, I assume is OK

The zener leakage won't let the voltage get anywhere near 5V with 6Mohm in
series.


*****************************************************************
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(978) 742-9014, http://www.embedinc.com

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2002\11\07@092728 by Jim

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> > the safest way is to use an opto-coupler.
> >
> > I have vast experience in this field (dimmers in professional
> > lighting field) and if you only knew what comes down those
> > AC lines...... you'd use an opto too.

Has anyone ever seen the sparks that fly from the
plug when un-plugging their shop-vac from the mains
w/o using the normal On/Off power switch?

(As my power switch died some ten years ago - this is
the technique I have been since to 'switch' my shop-
vac on and off.)

THESE are the kinds of transients that your circuits,
intended for public use, need to be 'tested' against
(at the least I would think!).

I would be interested to see how these direct-interface
circuits fare when used (and tested) on the main's line
as a shop-vac is switched "on and off" a few times ...

RF Jim

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2002\11\07@095147 by Sean Alcorn - PIC Stuff

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> Has anyone ever seen the sparks that fly from the
> plug when un-plugging their shop-vac from the mains
> w/o using the normal On/Off power switch?

Um, what's a shop-vac?

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2002\11\07@100258 by Jim

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A generic term that refers to a "wet/dry" vacuum
normally used in the garage or shop -

http://www.shopvac.com/


The Shop-Vac Jet Engine - A LESSON IN VOLITILITY
http://www.delta-9.com/net47/myth/shopvac.html

RF Jim


{Original Message removed}

2002\11\07@100915 by Chris Loiacono

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However....
I just went through troubleshooting a power controller whose gate firing
opto's were being killed by DV/DT. Some are less immune to high DV/DT than
the devices they are used to control or output to....But then again, that
was on the output, or detector side, not the emitter as is being discussed.
I have never seen a properly applied opto used to detect ZC fail probably
because the transient events are so fast that the LED's don't have time to
dim out.

Even slow opto's are fast enough for most AC control apps. There are a
number of parts available with bi-directional LED's also, called AC
optocouplers, I think. Each one protects the other and they provide a nice
quick pulse a +/- the diode voltage - really nice for triacs, a bit of extra
effort to use them with SCR's, though...

Chris

{Quote hidden}

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2002\11\07@105428 by llile

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Do any of you have any standard torture tests that test your products
against common levels of noise and spikes?  I am not interested in formal
EMC testing at a lab, just something that can be homebrewed.   We have a
machine we use that consists of a lamp dimmer with a 100 watt lamp, a
couple of heavy duty contactors that clack each other on and off, and an
electric mixer connected to one of the clacking relays going rrumm rrrumm
rrumm.   It is an extremely crude machine, but pretty effective at making
noise.  I am wondering if anyone else does this sort of testing.



-- Lawrence Lile





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> Has anyone ever seen the sparks that fly from the
> plug when un-plugging their shop-vac from the mains
> w/o using the normal On/Off power switch?

Um, what's a shop-vac?

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2002\11\07@105808 by Spehro Pefhany

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At 09:02 AM 11/7/02 -0600, you wrote:
>A generic term that refers to a "wet/dry" vacuum
>normally used in the garage or shop -
>
>http://www.shopvac.com/

Apparently the name causes confusion in parts of the non-mainland
English-speaking world ;-) where a "shop" is a place that sells
things rather than a workshop.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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2002\11\07@110635 by Spehro Pefhany

picon face
At 09:52 AM 11/7/02 -0600, you wrote:
>Do any of you have any standard torture tests that test your products
>against common levels of noise and spikes?  I am not interested in formal
>EMC testing at a lab, just something that can be homebrewed.   We have a
>machine we use that consists of a lamp dimmer with a 100 watt lamp, a
>couple of heavy duty contactors that clack each other on and off, and an
>electric mixer connected to one of the clacking relays going rrumm rrrumm
>rrumm.   It is an extremely crude machine, but pretty effective at making
>noise.  I am wondering if anyone else does this sort of testing.

I'll admit to it. An old Weller 250W soldering gun, a CB radio at
close range, and I've used a 50 lb transformer with the primary
energized by dragging a wire over a woodworking file. ;-)

It's still hard to predict with 100% confidence what will happen when
100A/480V or 600V is mechanically switched in close proximity to your
circuit, or when  the 300A Lincoln arc welder starts up.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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2002\11\07@111051 by Alan B. Pearce

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> Um, what's a shop-vac?

Is that not what you get the wife to bring round when the shop needs to be
cleaned up ?? :)

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2002\11\07@111428 by Alan B. Pearce

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>I am wondering if anyone else does this sort of testing.

One that I saw used effectively was a small light box containing a couple of
10-15W (or thereabouts) fluorescent tubes with ballast and starters.
Switched off/on rapidly using a small toggle switch produced much mains
bourne noise.

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2002\11\07@120135 by Mark Skeels

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Try wiring a 125VAC relay's coil  in series with it's NC contacts and plug in.

Mark

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2002\11\07@120803 by Chris Loiacono

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The stuff I work with makes it pretty easy. If a thyristor is iether
beinggated falsely by noise or is being falsely commutated, it shows on the
Ac waveform on the scope. When I want to see if it's affecting the
microcontroller or any part of my logic circuitry I connectthe Bitscope. A
favorite test I now have is to use the bitscope with one analog channel on
various points after my 5V (or 3.3V) supply while watching for hiccups like
bit flipping, etc with the digital channels. I suppose checking another
nearby device would be equally as interesting...

It's like the tree falling in the forest thing again....If I can't hear it,
it didn't make (enough) noise.

Chris

{Quote hidden}

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2002\11\07@130803 by Matt Pobursky

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If your device has a transformer on the AC mains, just insert your plug loosely into the AC socket and wiggle it side to side so it makes/breaks contact with the mains voltage. Very similar to the test
you do, also very "real-world".

You'll get some *very* interesting spikes and HF noise on the transformer secondary. I have used this "bench test" on virtually every
consumer electronics device I've designed and find that if it passes this test and doesn't lockup or exhibit weird beahvior, it almost always has no other transient related problems in regulatory agency testing.

I've found that once any line noise gets through to a transformer secondary, it's virtually impossible to get rid of.

Matt Pobursky Maximum Performance Systems
On Thu, 7 Nov 2002 09:52:48 -0600, @spam@llile@spam@spamspam_OUTSALTONUSA.COM wrote:
Do any of you have any standard torture tests that test your products against common levels of noise and spikes?  I am not interested in formal EMC testing at a lab, just something that can be homebrewed.
We have a machine we use that consists of a lamp dimmer with a 100 watt lamp, a couple of heavy duty contactors that clack each other on and off, and an electric mixer connected to one of the clacking relays going rrumm rrrumm rrumm.   It is an extremely crude machine, but pretty effective at making noise.  I am wondering if anyone else does this sort of testing.

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2002\11\07@134523 by llile

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>I've used a 50 lb transformer with the primary
energized by dragging a wire over a woodworking file. ;-)

Sphero, that is the crudest and most un-sophisticated test I have seen in
a while.  My co-workers think I have inhaled laughing gas as I read your
description.  I think I will try it!

We also test units against brownout, or more accurately, brief
interruptions of AC voltage.  We have seen products that freak out when
the line voltage drops out for a fraction of a second.  BTW the test
machine has a PIC in it, a 12C508, so we are still on topic.

-- Lawrence Lile





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I'll admit to it. An old Weller 250W soldering gun, a CB radio at
close range, and I've used a 50 lb transformer with the primary
energized by dragging a wire over a woodworking file. ;-)

It's still hard to predict with 100% confidence what will happen when
100A/480V or 600V is mechanically switched in close proximity to your
circuit, or when  the 300A Lincoln arc welder starts up.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the
reward"
.....speffspamRemoveMEinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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2002\11\07@152255 by Peter L. Peres

picon face
*>>Do any of you have any standard torture tests that test your products
*>>against common levels of noise and spikes?  I am not interested in formal
*>>EMC testing at a lab, just something that can be homebrewed.   We have a

I used a fluorescent fixture ballast without the lamp and with just the
starter and the capacitor across the starter as load. The starters do not
last very long like this, but they are cheap. You can add a VDR across the
starter for extra effect. Makes 0.5 or more Joule pulses at as many volts
as you can think of (remove the input capacitor to the fixture). A spark
gap across the starter could prolong its life also (even better a gas
arrestor at ~400V firing voltage). Testing time is 1 hour or so (or until
the 60W ballast gets too hot to touch, whichever happens first).

For spark susceptibility testing I used a gas ligher piezo element (to
jump sparks into the ground/case), and also an ionizer that made 10kV from
a 9V battery and pulled >10mm sparks. Output caps were 0.01uF I think
(also 0.5J like the coil - the ionizer obviously did not have 0.01uF
output caps - I added them).

I think that if one makes an electronic ignition it should be made to
withstand sparks to ground from the output coil (can be 20J). This is
*hard*. I doubt that most series auto electronics will withstand this in a
modern 'computerised' engine. I'd probably test house alarm systems to the
same standard ...

Peter

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2002\11\07@153246 by Bob Blick

face picon face
> I think that if one makes an electronic ignition it should be made to
> withstand sparks to ground from the output coil (can be 20J). This is
> *hard*. I doubt that most series auto electronics will withstand this in a
> modern 'computerised' engine.


True. Even the electronic ignition systems in new cars (Toyota in
particular) do not survive losing a spark plug wire with engine running.

-Bob

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2002\11\07@154322 by Herbert Graf

flavicon
face
> > Has anyone ever seen the sparks that fly from the
> > plug when un-plugging their shop-vac from the mains
> > w/o using the normal On/Off power switch?
>
> Um, what's a shop-vac?

       Shop-vac is a brand name for a range of wet/dry vaccum clearners. They are
of the "canister" type and are quite durable and powerful.
http://www.shopvac.com. TTYL

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2002\11\07@154913 by Peter L. Peres

picon face
On Thu, 7 Nov 2002, Bob Blick wrote:

*>> I think that if one makes an electronic ignition it should be made to
*>> withstand sparks to ground from the output coil (can be 20J). This is
*>> *hard*. I doubt that most series auto electronics will withstand this in a
*>> modern 'computerised' engine.
*>
*>
*>True. Even the electronic ignition systems in new cars (Toyota in
*>particular) do not survive losing a spark plug wire with engine running.

So what do you do when you adjust them ?! Put on a dummy load ? I've heard
of lead pencils being used for this in a pinch.

Peter

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2002\11\07@162513 by Bob Blick

face picon face
> *>True. Even the electronic ignition systems in new cars (Toyota in
> *>particular) do not survive losing a spark plug wire with engine running.
>
> So what do you do when you adjust them ?! Put on a dummy load ? I've heard
> of lead pencils being used for this in a pinch.

You don't ever disconnect a wire with the engine running. An engine
analyzer will show you weak cylinders, etc. But I do not know the
"backyard mechanic's method" for new cars now that pulling the wires is
not allowed.

-Bob

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2002\11\07@163731 by Peter L. Peres

picon face
On Thu, 7 Nov 2002, Bob Blick wrote:

*>> *>True. Even the electronic ignition systems in new cars (Toyota in
*>> *>particular) do not survive losing a spark plug wire with engine running.
*>>
*>> So what do you do when you adjust them ?! Put on a dummy load ? I've heard
*>> of lead pencils being used for this in a pinch.
*>
*>You don't ever disconnect a wire with the engine running. An engine
*>analyzer will show you weak cylinders, etc. But I do not know the
*>"backyard mechanic's method" for new cars now that pulling the wires is
*>not allowed.

Oh. No pulling wires ? I feel that aircraft engines ignitions are exempt
from this limitation. I once had a Bendix coil that had a built in spark
gap for protection. It was indestructible (used for high voltage
experiments). It must have been 50 years old.

Peter

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2002\11\07@164812 by Russell McMahon

face
flavicon
face
> Well, based on what you and Roman have input here the following would
> work for 240VAC (assuming shitty Australia and New Zealand power);
>
> * Two resistors in series - say 3~4M each
> * 5.1V Zener from Pin to GND - only small wattage, I assume is OK
> * up to say 100nF Metalised cap (rated at 400V) strapped across Zener
>
> OR
>
> * a pair of Schottky diodes on input pin
>
> Yes?


Yes-ish, for positive input.
Add second zener to supply (suitable polarity) for negative input.
Even 5v1 violates spec but can be thought about. (ie it would work :-) ).


> How do you feel about sinking the gate current to a PIC pin through a
> single resistor - if maintained at around 5mA?

I feel very positive about it.
I'm absolutely CERTAIN that it would cause undefined and undefinable
operational problems in some cases.

As a PROTECTIVE system where the cpu was meant to live but not be
guaranteeed to be able to chew gum during OR AFTER mains application it's
fine. CPU would need to be powered down (to under 0.1V on Vdd*) and
restarted after the event to be certain operation would be OK. Resistor
would need to be AT LEAST 2w rated at 5 mA. Resistor would need to be X
rated (a la caps spec) - most small resistors do NOT have suitable voltage
ratings for off mains use, regardless of power dissipated. Transients would
need to be considered separately.

* Based on experience.
Once latchup occurs it can remain until Vdd falls to a very low level. My
experience is that < 0.1V on Vdd removes non-destructive latchup but
voltages above this may not. In many systems Vdd falls to under about 0.5V
rapidly due to junction conduction but then falls much more slowly due to
resistive only loads. The latchup state MAY remain for tens of seconds.
Antibrownout and reset will not cure this.


       Russell McMahon

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2002\11\07@165858 by Dale Botkin

flavicon
face
On Thu, 7 Nov 2002, Peter L. Peres wrote:

> *>True. Even the electronic ignition systems in new cars (Toyota in
> *>particular) do not survive losing a spark plug wire with engine running.
>
> So what do you do when you adjust them ?! Put on a dummy load ? I've heard
> of lead pencils being used for this in a pinch.

Adjust *what*, exactly?  There's pretty much nothing to adjust any more.
No points, no distributor, no rotor, no mixture, if you're lucky maybe an
idle speed adjusting screw.  Mine has timing marks on the flywheel, but no
pointer - since timing is (supposedly) non-adjustable.  If you can/do set
timing, you've got to use a timing light with an inductive pickup.  I
think the new ones probably don't even have degree marks.  Change the
plugs every 60K to 100K miles or so if you feel you ned to, but quite
honestly it's been a long time since I had to lay a wrench on an engine
any newer than 1992 or so.

Dale

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2002\11\07@172018 by Peter L. Peres

picon face
I have used 2 x 510k in series and 1nF to ground into PIC pin from 220 V
mains. The PIC did not use AD. With AD I'd use my clamping circuit. This
configuration (with 1Meg and 1nF) should resist 2kV spikes if and only if
the resistors have proper voltage rating. This was not in a production
circuit and it violates input voltage specs (go below and above gnd and
vdd by more than 0.3V). Nominal protection diode current is 310uA (220V
country). There is a 5V1 zener across the PIC power pins, which is also
the only voltage regulator this circuit has got. The PIC was 16F84 for
prototyping then 12C508A.

Peter

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2002\11\07@192237 by Reginald Neale

picon face
Yes. All of the below. Also a big variable speed electric hand drill
plugged into same power outlet or connected with clip leads to 115VAC
terminals of device being tested. Click on/off, fwd and rev.

And for UNcommon levels, a barbecue igniter. Connect one terminal to
ground plane of circuit board, let other terminal arc to ground
connection in a different place or even to the same connection a mm
or so away. If that doesn't reset your PIC even one time out of a
hundred, you've got a pretty robust design.

Another torture is to wire up a (e.g.) 5V relay as a buzzer and
connect it with clip leads to the 5V supply on the board to be
tested. (Assuming, of course, that there is enough margin in the
supply to drive the relay in addition to the circuit.) Manipulate it
into various orientations w/respect to the PIC, as some of the EMI is
conducted and some radiated.

Reg

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2002\11\07@195355 by Sean Alcorn - Avion SYD

flavicon
face
> A generic term that refers to a "wet/dry" vacuum
> normally used in the garage or shop -

Ah! "generic" as in "US term"

Got it!

Sean

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2002\11\07@195820 by Sean Alcorn - PIC Stuff

flavicon
face
> Apparently the name causes confusion in parts of the non-mainland
> English-speaking world ;-) where a "shop" is a place that sells
> things rather than a workshop.

Hey, downunder we are still trying to come to terms with a "regular"
sized drink!

Sean

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2002\11\07@200017 by Russell McMahon

face
flavicon
face
> Well, based on what you and Roman have input here the following would
> work for 240VAC (assuming shitty Australia and New Zealand power);
>
> * Two resistors in series - say 3~4M each
> * 5.1V Zener from Pin to GND - only small wattage, I assume is OK
> * up to say 100nF Metalised cap (rated at 400V) strapped across Zener
>
> OR
>
> * a pair of Schottky diodes on input pin
>
> Yes?


Yes-ish, for positive input.
Need to check leakage specs, zener bias point and time constants as Olin
says.
Transient behaviour would need to be verified (and found wanting :-) ).

Add second zener to supply (suitable polarity) for negative input.
(Otherwise its just a poor diode (about 0.8v maybe) and you have no negative
cycle protection).

Even 5v1 violates spec but can be thought about. (ie it would work :-) ).


> How do you feel about sinking the gate current to a PIC pin through a
> single resistor - if maintained at around 5mA?

I feel very positive about it.
I'm absolutely CERTAIN that it would cause undefined and undefinable
operational problems in some cases.

As a PROTECTIVE system where the CPU was meant to live but not be
guaranteed to be able to chew gum during OR AFTER mains application it's
fine. CPU would need to be powered down (to under 0.1V on Vdd*) and
restarted after the event to be certain operation would be OK. Resistor
would need to be AT LEAST 2w rated at 5 mA. Resistor would need to be X
rated (a la caps spec) - most small resistors do NOT have suitable voltage
ratings for off mains use, regardless of power dissipated. Transients would
need to be considered separately.

* Based on experience.
Once latchup occurs it can remain until Vdd falls to a very low level. My
experience is that < 0.1V on Vdd removes non-destructive latchup but
voltages above this may not. In many systems Vdd falls to under about 0.5V
rapidly due to junction conduction but then falls much more slowly due to
resistive only loads. The latchup state MAY remain for tens of seconds.
Antibrownout and reset will not cure this.


       Russell McMahon

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2002\11\07@205839 by Russell McMahon

face
flavicon
face
> > A generic term that refers to a "wet/dry" vacuum
> > normally used in the garage or shop -
>
> Ah! "generic" as in "US term"
>
> Got it!

More like "generic" as in brand name that becomes eponymous for the product
with that brand and then synonymous for all competitors semi-equivalent
products.

Similarly used terms with broader application than originally intended:

Cellotape, nugget (shoe polish)(here anyway), skilsaw, coke (all too often
when served some vile and inferior substitute)(as opposed to the vile real
thing :-) , IBM PC, Pentium, Swiss army knife (arguable), Ethernet
(according to its inventor), zip, thermos flask, zippo lighter ?, and, I'm
sure, many more.



       RM

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2002\11\07@211302 by Sean Alcorn - PIC Stuff

flavicon
face
> More like "generic" as in brand name that becomes eponymous for the
> product
> with that brand and then synonymous for all competitors semi-equivalent
> products.

Yes. I know what generic means, and it's not exactly 'generic' in the
true sense of the word. I was simply referring to what may be
considered 'generic' in one part of the world may or may not be used in
others. "Shop-vac" is obviously being a 'generic' in North America. So
you call them shop-vacs in New Zealand?

I am sure you wouldn't place a post referring to "Chilly Bins" or
"Jandals" (sp?) knowing that the rest of the list would not have a clue
what you are talking about.

Regards,

Sean

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2002\11\07@223103 by Russell McMahon

face
flavicon
face
> > More like "generic" as in brand name that becomes eponymous for the
> > product
> > with that brand and then synonymous for all competitors semi-equivalent
> > products.
>
> Yes. I know what generic means,

ah yes, but there's generic, "generic" and 'generic'.  :-)

> and it's not exactly 'generic' in the
> true sense of the word. I was simply referring to what may be
> considered 'generic' in one part of the world may or may not be used in
> others. "Shop-vac" is obviously being a 'generic' in North America. So
> you call them shop-vacs in New Zealand?

There is a shop-vac sold here branded Vax.
I am so used to the term )(probably due to Internet exposaure) that I cannot
say how common it is.
My wife had no idea what a shop-vac woukld be when I asked her just now.

> I am sure you wouldn't place a post referring to "Chilly Bins" or

   Eskies, cobber?

> "Jandals" (sp?)

   Struth mate, yer must mean thongs.

Actually, I would hope that "chilly bin " would translate OK for any
reasonably competent Mentat :-)
Jandal has no useful linguistic content (I think).
Shopvac has quite a lot.
Thong may end up as an Oz bathing suit.


       RM

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2002\11\07@224139 by hard Prosser

flavicon
face
snip...............

> I am sure you wouldn't place a post referring to "Chilly Bins" or

>    Eskies, cobber?

> "Jandals" (sp?)

>    Struth mate, yer must mean thongs.

>Actually, I would hope that "chilly bin " would translate OK for any
>reasonably competent Mentat :-)
>Jandal has no useful linguistic content (I think).
>Shopvac has quite a lot.
>Thong may end up as an Oz bathing suit.


       RM

Bathers ???????


RP

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2002\11\08@045546 by Alan B. Pearce

face picon face
>>I've used a 50 lb transformer with the primary
>energized by dragging a wire over a woodworking file. ;-)

>Sphero, that is the crudest and most un-sophisticated test
>I have seen in a while.  My co-workers think I have inhaled
>laughing gas as I read your description. I think I will try it!

However such tests are often the ones that the equipment will fail under. It
is the sophisticated "shaped waveform" tests that are easiest to pass as the
waveform is often not like a real world thing anyway :))))

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2002\11\08@045747 by Alan B. Pearce

face picon face
>A spark gap across the starter could prolong its life
>also (even better a gas arrestor at ~400V firing voltage).

Hmm, the old style starters that I have come across were a bimetal strip
inside an envelope that was filled with a gas like argon or neon. So I doubt
that an external spark gap would help as the starter itself is already
designed like this.

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2002\11\08@054948 by Russell McMahon

face
flavicon
face
> >Sphero, that is the crudest and most un-sophisticated test
> >I have seen in a while.  My co-workers think I have inhaled
> >laughing gas as I read your description. I think I will try it!

You can buy it as cream whipping gas.

It was the gas you were going to try, wasn't it :-)


       RM

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2002\11\08@080547 by Olin Lathrop

face picon face
> I am sure you wouldn't place a post referring to "Chilly Bins" or
> "Jandals" (sp?) knowing that the rest of the list would not have a clue
> what you are talking about.

Good thing you guys wouldn't, because I have no idea what those are.

However, we're more arrogant and self-centered here in North America that
most of us probably didn't even realize that "shop vac" wasn't a generic
term (I didn't).


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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2002\11\08@081837 by Russell McMahon

face
flavicon
face
FWIW

> > I am sure you wouldn't place a post referring to "Chilly Bins"

Also called "Eskys" by our Oz brethren.
Insulating container for food or drink. Usually kept cold with ice.
Often found to contain (or have contained) beer
Often polystyrene.
I've no idea what our US brothers call these.

or

> > "Jandals"

Casual footwear with a flattish sole and two (usually) rubber (like) straps
extending from a vertical common point at the front to points at each side
about ?70% from the front. The vertical common point fits between the
wearers big and second toe. Foot slips in and out easily. Not recommended
for running in or motorcycling :-(.



       RM

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2002\11\08@100732 by Sean Alcorn - PIC Stuff

flavicon
face
> Casual footwear with a flattish sole and two (usually) rubber (like)
> straps
> extending from a vertical common point at the front to points at each
> side
> about ?70% from the front. The vertical common point fits between the
> wearers big and second toe. Foot slips in and out easily. Not
> recommended
> for running in or motorcycling :-(.

Obviously you have not been to Taiwan! :-)

Sean

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2002\11\08@121432 by Peter L. Peres

picon face
On Fri, 8 Nov 2002, Alan B. Pearce wrote:

*>>A spark gap across the starter could prolong its life
*>>also (even better a gas arrestor at ~400V firing voltage).
*>
*>Hmm, the old style starters that I have come across were a bimetal strip
*>inside an envelope that was filled with a gas like argon or neon. So I doubt
*>that an external spark gap would help as the starter itself is already
*>designed like this.

The opened starter must withstand the ignition voltage of the tube which
is 0.5-1kV-ish after heaters were applied. It does this by only passing a
limited amount of current (it's a constant current discharge tube - not an
arc tube - probably with very low pressure gas fill). And the external
spark gap or vdr is very important if you don't want the poor starter to
plate the glass envelope with its innards before too long. In a normal
fluorescent fixture if the lamp does not catch the starter flashes
brightly. Every time it does that its life is shortened.

Peter

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2002\11\08@195937 by Russell McMahon

face
flavicon
face
> > Casual footwear with a flattish sole and two (usually) rubber (like)
> > straps
>>  Not recommended for running in or motorcycling :-(.

> Obviously you have not been to Taiwan! :-)

I have :-)
STILL not recommended for ................

       RM

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2002\11\10@053826 by Roman Black

flavicon
face
Spehro Pefhany wrote:
>
> At 09:02 AM 11/7/02 -0600, you wrote:
> >A generic term that refers to a "wet/dry" vacuum
> >normally used in the garage or shop -
> >
> >http://www.shopvac.com/
>
> Apparently the name causes confusion in parts of the non-mainland
> English-speaking world ;-) where a "shop" is a place that sells
> things rather than a workshop.


You mean the countries that speak English
rather than arrogantly butcher it? ;o)

I believe the words "shop" and "workshop"
are both valid English words with entirely
different meanings. Maybe 'shop is acceptable
but very ugly.

And don't get me started on "aluminum", darn
how can you remove letters from an element in
the periodic table to suit the pronunciation of
the ignorant masses? Surely American scientists
actually spell the elements correctly even if
aluminum siding salesmen can't??
-Roman

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2002\11\10@060818 by Sean Alcorn - PIC Stuff

flavicon
face
Roman,

> Surely American scientists
> actually spell the elements correctly even if
> aluminum siding salesmen can't??

I wouldn't bet on it. Aluminum is the "correct" spelling according to
an American dictionary. I am sure American scientists and engineers
simply use the spelling they were educated with.

It's always intrigued me why the language had to be "simplified" :-)

Sean

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2002\11\10@065653 by Roman Black

flavicon
face
> > Casual footwear with a flattish sole and two (usually) rubber (like)
> > straps
> > extending from a vertical common point at the front to points at each
> > side
> > about ?70% from the front. The vertical common point fits between the
> > wearers big and second toe. Foot slips in and out easily. Not
> > recommended
> > for running in or motorcycling :-(.


Not for motorcycling?? I do some of my best
lap times wearing Dianese flip flops...
Having bare toes helps feel the shift lever
so much better... ;o)
-Roman

PS. Is this OT yet????

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2002\11\10@080738 by Roman Black

flavicon
face
Sean Alcorn - PIC Stuff wrote:
>
> Roman,
>
> > Surely American scientists
> > actually spell the elements correctly even if
> > aluminum siding salesmen can't??
>
> I wouldn't bet on it. Aluminum is the "correct" spelling according to
> an American dictionary. I am sure American scientists and engineers
> simply use the spelling they were educated with.


Darn, what next?? Hydrijen?? Coppa?
But even those two have the correct number of
syllables...
<sunday night teasing grin>
-Roman

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