On 10/28/23 3:32 PM, David Higton wrote:
> In message <BuudnQ1ot_sf96H4nZ2dnZfqn_GdnZ2d@earthlink.com>
> "56d.1152" <56d.1152@ztq9.net> wrote:
>
>> On 10/27/23 12:32 AM, The Natural Philosopher wrote:
>>> On 27/10/2023 04:44, 56d.1152 wrote:
>>>
>>>>
>>>>    Solder IS the best.
>>>>
>>> No, actually it often isn't...
>>>
>>> The problem with solder on *stranded* wire is that it wicks up the wire
>>> and reduces it's flexibility by binding the strands together: That
>>> creates a stress concentration where it stops and a likely cause of
>>> fracture failure under vibration. That is why crimps are the choice for
>>> cheaper connections in high stress environments (e.g. automotive) or if
>>> you must solder you absolutely need to mechanically support the wire
>>> upstream of the solder joint.
>>
>> I've had very bad luck with 'crimps' - esp when they are
>> exposed to the weather, but even in higher-vibration
>> environments. Wasted lots of time trying to track down
>> problems related to crimps.
>
> I still remember a very interesting one in the 1980s with a joystick
> for a Sinclair Spectrum.

DID have one ! :-)

> The box proudly proclaimed the use of gold
> plating in the internal connections. They used fully (i.e. not
> selectively) gold plated crimps onto stranded tinned copper wire.
> One of the joints, although completely mechanically sound, was not
> conducting electricity. Yes, that really was the interface between
> the crimp and the wire.
>
> I ran solder in and it was fine.

Yep ... crimps SOUND great - until you hit
the Real World.

Crimps are a cheap quick fix.

> There is a known, but unfortunately not widely known, problem in the
> interface between gold and tin.
>
> The lesson boils down to:
>
> 1) Never mix gold plated and tin plated connectors.
>
> 2) If you're using gold plated connectors, use selectively gold plated
> crimps in them.

Material compatibility IS always important.

Gold MOSTLY works with everything but, by
experience, not ALWAYS

Soldering IS a bigger pain in the ass, no question.
But it's MUCH more sure. It'll last 20-50 YEARS under
really crappy conditions.

My old old HOUSE is mostly SOLDERED electrical
connections - not even sure how they DID that
conveniently back in the day. However I'm NOT
worried about any of those connections - mostly
in the attic/ceiling - overheating like modern
screw-terminal connections that oxidize or
where the copper compresses and becomes loose.

A couple extra hours in 1950 meant 100+
years of reliability. When (likely soon) the
house is destructed the ELECTRIC will still
be 100%

Anyway ... BAD experiences with 'crimps' under
a variety of conditions. Soldered is much more
sure. Solder, add heat-shrink to spread out
the mechanical stress and weatherproof ...
electronic nirvana ! :-)

Sorry, I'm very old-school in this respect.
I really design for 100 years safe service.

On 10/27/23 2:42 AM, Ahem A Rivet's Shot wrote:
> On Thu, 26 Oct 2023 23:44:48 -0400
> "56d.1152" <56d.1152@ztq9.net> wrote:
>
>> But, remember "wire wrap" ? Still have the tools
>> for doing that. The more-extensive wrapping CAN
>> be as reliable as soldered connections.
>
> A good wire wrap connection (done with a power tool - we always
> used Gardner-Denver) is gas tight and extremely reliable as well as being
> faster and easier to modify than soldering.

Yep. Some of those "old world" solutions can
STILL be good solutions !

And, when everything's 100%, you can always
solder the wire-wrap.

As said somewhere, one employer had a *kit* LSI-11
box. It had BASIC, but everything of use was writ
in FORTRAN. They'd worked out all the wiring issues
and soldered the wire-wrap. From there on it was
just a software box. It's STILL around in a
storage spot somewhere, I'll bet on it. And it'll
still WORK - (assuming the 8" floppies can still
be read). Oh, dual 8" Shugart floppy unit ...
weighed about 75 POUNDS, BIG transformer :-)

On Mon, 30 Oct 2023 00:51:14 -0400, 56d.1152 wrote:

>> The other gang that understand interactions between electronics and
>> vibration are model flyers: radio control models, drones and, the most
>> vibration of all, IC powered free flight competition models: a current
>> F1C class model has a 2.5cc engine putting out around 1.3 HP at 30,000
>> rpm and carrying electronic flight timers and a GPS-based radio beacon
>> as a retrieval aid. Free flight models regularly travel 2km or so in
>> the course of a 3 minute flight, especially if the contest is being run
>> on Sculthorpe, an ex-RAF/USAF base in Norfolk,UK. This area is known
>> for its fresh sea breezes.
>
> An actual hydrocarbon-fuel engine WILL create a lot of very buzzy
> vibration - which WILL take its toll on every connection. It's
> amazing how quickly some connections will fail - chips can even work
> their way out of conventional sockets.
>
> And then, if an ignition system is involved, transient electrical
> noise ! :-)
>
High performance model engines have no ignition: they're either diesels
(COMPRESSION IGNITION burning an oil/kerosene/ether mix) or gloplug
ignition (battery heated plug with platinum coil to start, when running
combustion keeps the plug hot and burning methanol/oil mix, sometimes with
added nitromethane for more power.

You quickly learn how to protect in-model electronics and associated
wiring from the engine's vibration - if you don't you'll have lots of more
or less spectacular crashes. An F1C class model can climb vertically to
around 120m with a 3 second engine run.

--

Martin | martin at
Gregorie | gregorie dot org

On 8/11/23 22:33, Jörg Lorenz wrote:
> Am 11.08.23 um 23:07 schrieb The Natural Philosopher:
>> Oh? You think that unsolicited information about Linux and rasberry Pis
>> is spam, in linux and raspberry Pi newsgroups?
>> What on earth do you think that spam acrually IS?
>
> Postings from anonymous Trolls with fake identities.
>
When is an identity real, and when is it fake?

Surely it is only fake if it is pretending to be someone, or something,
it is not.
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Newsgroups: comp.os.linux.misc,comp.sys.raspberry-pi
Subject: Re: Weird code crash
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The Natural Philosopher <tnp@invalid.invalid> writes:
> READ
> ====
> fp=fopen(fullname, "r");
> len=fread(filbuf,1,255,fp); // read entire file

There’s no error checking on the call to fopen, so fp could be a null
pointer when you call fread. So crashes are to be expected, although in
this code fragment a SIGSEGV would be expected rather than SIGABRT.

> WRITE
> =====
> fp=fopen(filename, "w");
> if (fp)
> {
> fprintf(fp,"%s%s\n",filedata,timestamp);
> fclose(fp);
> }
>
> Could this cause a problem?
>
> I tend to suspect some sort of asynchronous timing issue because it is
> such a rare occurrence. I have been utterly unable to make it happen
> on demand...

Investigate properly first (see Theo’s post), guess about the cause
later.

--
https://www.greenend.org.uk/rjk/
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From: Ahem A Rivet's Shot <steveo@eircom.net>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: Limiting the capacity of SD cards for the pi
Date: Wed, 20 Sep 2023 15:40:56 +0100
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On Wed, 20 Sep 2023 16:15:44 +0300
Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:

> On 19.9.2023 13.16, Chris Elvidge wrote:

> > 'su -' needs a password entered (on my system(s))
>
>
> So should all other methods to aquire superuser privileges.

With sudo it depends entirely on what is in /etc/sudoers.

> There seems to be around RaspiOS setups with one user
> permitted in the /etc/sudoers without password.

This is possible sudoers supports a NOPASSWD keyword - this is
mostly useful for automation and laziness.

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
Host: Beautiful Theory meet Inconvenient Fact
Obit: Beautiful Theory died today of factual inconsistency
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From: Theo <theom+news@chiark.greenend.org.uk>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: PCBs available
Date: 13 Oct 2023 13:23:11 +0100 (BST)
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The Natural Philosopher <tnp@invalid.invalid> wrote:
> Since when I did this professionally it was black tape on clear film, I
> ended up using Corel Draw! I started with a 3D modelling program to make
> sure the physical bits fitted, then exported the copper to Corel,
> because I am very fluent in it
>
> I found a CDR to Gerber conversion utility online. That made all the
> difference and it even worked for the legend. The drill file was harder
> but again I found a utility to create that.

Nice. An ex-colleague of mine has a startup which does 'PCB art', ie using
the PCB medium for artistic design that happens to be a functional circuit:
https://boldport.com/

He has a flow that uses Inkscape for the 'artistry' and then turns it into
Gerbers:
https://github.com/boldport/pcbmode

but if you don't need any of the schematic/netlist/ERC/DRC/etc support that
a PCB tool gives you, just hand drawing it in the drawing package works well
enough. It's quite a nice idea for making attractive and not-complicated
boards.

> > I now need to trigger one mains coil from a Pi without exporting mains or
> > putting any DC wiring in the all-mains enclosure (where I can't get good
> > isolation). Current plan is to make a photo-triac triggered by light from
> > an LED on the Pi carried on some optical fibre...
>
> If a discrete optical coupler is a nono that might work.

It's a bit annoying... with no DC in the box and not wanting to risk
exporting mains to the Pi, or making another box with a relay, the obvious
option is an optocoupler, but you can't really ensure good isolation unless
you put it in a good enclosure, which is tricky here because I'm shoving it
in an existing mains box dangling on flying leads.

Aha, I thought, you can get optotriacs to switch AC, so what about if I just
get a phototriac and shine a light at it to trigger the triac instead of
having the LED in the optotriac. Trouble is, phototriacs don't exist as a
discrete component. So the next plan is to use an LDR (photoresistor) to
trigger the gate of a regular triac (street lights use this for the
dawn-to-dusk circuit). Only finding an LDR rated for 339Vpeak is tricky, so
I probably need to voltage divide first...

I suppose I should just bite the bullet with an optotriac, put it in a
little case with wire tail connections, and pot it all with some HV safe
resin. Although the idea of a mains box with just an optical fibre input
does have its appeal...

Theo
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On 05/11/2023 04:33, 56d.1152 wrote:
> Recently replaced a plug socket. Put SOLDER over the
>   ends of the wires and used the SCREW DOWN terminals
>   rather than the "push in" ones. A little extra effort
>   PAYS OFF longer term.

But best practice documents say using soldered/tinned wire in screw
connectors is bad due to differing expansion rates of the brass fitting
and solder. With enough sufficient thermal cycles the connection loosens
causing bad connections.

Obviously the experts should have consulted with you.

On 11/5/23 5:09 AM, mm0fmf wrote:
> On 05/11/2023 04:33, 56d.1152 wrote:
>> Recently replaced a plug socket. Put SOLDER over the
>>    ends of the wires and used the SCREW DOWN terminals
>>    rather than the "push in" ones. A little extra effort
>>    PAYS OFF longer term.
>
> But best practice documents say using soldered/tinned wire in screw
> connectors is bad due to differing expansion rates of the brass fitting
> and solder. With enough sufficient thermal cycles the connection loosens
> causing bad connections.

Don't expect any problems with a microns-thin
solder coating. The main goal there is to shield
the copper from oxidation/corrosion. My environ
IS a bit corrosive. House fires due to older
connections is NOT unheard of. Breakers protect
from overload, but cannot detect a degrading
connection.

Now if you just glob LOTS of solder on there ...

There ARE some kinds of 'goop' that claim to
protect the copper, but I'll stick with what
I know is good. Some of that goop is hydrocarbon
based - basically gasoline if it gets hot. The
silicone-based ... I'd have to see some good
studies as to HOW much that restricts current flow
and whether it can degrade PVC insulation long-term.

> Obviously the experts should have consulted with you.

They should have. I have lots of real-world experience
with marine applications.

56d.1152 <56d.1152@ztq9.net> wrote:
> Recently replaced a plug socket. Put SOLDER over the
> ends of the wires and used the SCREW DOWN terminals
> rather than the "push in" ones. A little extra effort
> PAYS OFF longer term.

Sounds like a recipe for a fire. I've seen screw terminals on 3D-printer
motherboards that were scorched after tinned wires had been put in them, and
they only carried maybe 100-200W at 12-24V.

The proper way to connect stranded wire in a screw terminal is to crimp the
wire in a ferrule or a fork or ring terminal (depending on the screw
terminal type) and then attach it to the terminal. If your crimping tool
isn't working reliably, either you're using it wrong or it's a crappy tool
that should be replaced. (The slip-joint pliers in your tool bag aren't a
proper crimping tool. Long-nose pliers aren't, either.)

Solid copper wire can be safely attached directly to screw terminals.

--
_/_
/ v \ Scott Alfter (remove the obvious to send mail)
(IIGS( https://alfter.us/ Top-posting!
\_^_/ >What's the most annoying thing on Usenet?

In message <UQ92N.38940$sqIa.2684@fx07.iad>
scott@alfter.diespammersdie.us wrote:

>56d.1152 <56d.1152@ztq9.net> wrote:
>> Recently replaced a plug socket. Put SOLDER over the
>> ends of the wires and used the SCREW DOWN terminals
>> rather than the "push in" ones. A little extra effort
>> PAYS OFF longer term.
>
> Sounds like a recipe for a fire. I've seen screw terminals on 3D-printer
> motherboards that were scorched after tinned wires had been put in them,
> and they only carried maybe 100-200W at 12-24V.

Never ever use screw terminals onto stranded wire that you've tinned.
Solder suffers from creep, so the pressure slowly relaxes until the
joint is loose. As stated above, a recipe for a fire.

David

On 11/6/23 4:56 PM, David Higton wrote:
> In message <UQ92N.38940$sqIa.2684@fx07.iad>
> scott@alfter.diespammersdie.us wrote:
>
>> 56d.1152 <56d.1152@ztq9.net> wrote:
>>> Recently replaced a plug socket. Put SOLDER over the
>>> ends of the wires and used the SCREW DOWN terminals
>>> rather than the "push in" ones. A little extra effort
>>> PAYS OFF longer term.
>>
>> Sounds like a recipe for a fire. I've seen screw terminals on 3D-printer
>> motherboards that were scorched after tinned wires had been put in them,
>> and they only carried maybe 100-200W at 12-24V.
>
> Never ever use screw terminals onto stranded wire that you've tinned.
> Solder suffers from creep, so the pressure slowly relaxes until the
> joint is loose. As stated above, a recipe for a fire.

True !

But be aware that electrical-quality copper ALSO 'creeps'.

Had a mystery power prob at my home a few years ago - it
turned out to be that the old screw-down connections in
the MAIN BREAKER had 'crept', loosened, over the years.
The electrician I'd hired put on rubber gloves and
re-tightened everything HOT. Good for another 20 years
I suppose.

For awhile I was responsible for control panels in
20-50 horsepower industrial devices. Once most were
10+ years old I decided to test the old power
connections. They were ALL getting loose - the copper
had 'compressed'.

DO sometimes run into home sockets and such where the
screw-down has a sort of bronze/brass PLATE under it.
Put the wire under the plate. It creates spring-tension
that'll greatly reduce the 'compression' issue.

Note that 'tinning' the stranded wires DOES seem to
slow down the 'creep', if you 'tin' correctly
(meaning JUST enough solder to solidify/bond, not
big blobs). IMHO, house-wiring should be done almost
entirely with SOLID wire though. Alas CORROSION like
you'd get on sea-coasts can STILL ruin things. For
that a VERY thin coat of solder serves well - wipe
on a little flux and LIGHTLY tin and wipe. Just a
few microns.

The most horrible mistake was back when they first
introduced aluminum wiring for homes. The metal in
the sockets/switches/etc were NOT super-compatible.
Esp in 'corrosive' environs the connections would
fail quite early - and start fires.

Remember - breakers protect against SHORTS, but
can NOT detect bad connections - which get hotter
and hotter as the resistance increases.

You get what you pay for. The 'discount' stuff from
Home Despot or whatever will be 'functional', but
for HOW LONG ? Alas, if/when it fails, it really
might burn your house down.

Anyway, enough of Practical Power Electrics in
a Pi group :-)