Driver to drive?

[Pooh Bear]

Neil Preston wrote:

How might I ascertain the optimum power rating of the resistor in a triac
snubber with an inductive load?

You've decided on a value ?

Try a few and check temperature rise. Probably wise to err on the generous side.

Pulse ratings vary a lot on vendor for power film types.


Graham

 

[Terry Given]

John Smith wrote:

"Terry Given" <my_name@ieee.org> wrote in message
news:5a8qd.14297$9A.276874@news.xtra.co.nz...

John Smith wrote:


"Terry Given" <my_name@ieee.org> wrote in message
news:e20qd.14186$9A.271659@news.xtra.co.nz...


Arie de Muynck wrote:


"Neil Preston" ...



So, how would typical resistors react to such a pulse? (In this

application,



it might occur as often as once per second.) Would a 1 watt resistor be
sufficient?
Would it be subject to internal arcing or other degradation?
Would there be any performance/reliability difference in various types

such



as carbon comp, carbon film, metal film, MOX flame proof, wirewound,
etc?
Is there a rule of thumb for the ratio of the power rating to the

intensity



of the energy pulse?


I've once made the mistake of just calculating the power dissipation and
using a film resistor (triac, inductive load, snubber use). They showed
beautiful little sparks after a year of 1 Hz switching. Replacing them
with
(cheaper) carbon composite resistors solved the problem.
Lesson: never ignore the PEAK dissipation and current that may occur,
and
check the datasheet of even a simple item like a $0.03 resistor.

Regards,
Arie de Muynck

Hell yes. I learned this very early on, when placing damping resistors in
series with Y caps in big EMI filters. One day we noticed a flash of
light when we switched the prototype on. We switched it off, pronto. A
thorough set of diagnostics found no problem, but we weren't
hallucinating so kept looking. And the 1R 2W PR02 resistor I had in
series with the 100nF Y cap was open circuit. As were ALL of them, in all
of the prototypes. We then asked the peak-power question, which was
something like (400V*1.41)^2/1R = oh fuck, 314kW. And a
carbon-composition resistor solved the problem. HVR make some real good
ones

Cheers
Terry


Our three-phase, 460VAC, thyristor-controlled, DC and AC motor speed
controllers had snubbers and MOV transient suppressors. All our
controllers used the same snubber values. In two different sites (Denver
and Puerto Rico), one of the MOVs would explode and the customer would
send the unit back for repair. After noticing that the same unit had been
returned more than once for the same problem, we got to looking into the
cause more closely.

It turns out that the firing of the thyristors in conjunction with the
snubber values and line inductance can _create_ a transient, and
repetitive transients will destroy MOVs eventually. The controllers would
operate fine for a day or three, then fail. Simulation showed that we
needed to change the snubber values based on the controller model current
rating.

We had no hard data showing that the line impedance in Denver and Puerto
Rico was higher than in other places, but, as I recall, simulation showed
that it most certainly could be the cause.

Pardon me for posting a little off-topic, but I thought it might be
useful information.

John

Hi John,

Thats a sneaky one. Heres a far less subtle problem:

I had a 2am call from Germany a few years back. One of our 400kW drives
kept blowing up - the Germans built it into a machine, which they sent to
Korea (IIRC), whereupon it promptly blew the hell out of the VDR board.
They replaced it and boom. They replaced it and boom. They called me.
Turns out Korea had some whacked form of 3-phase power distribution (open
delta? I forget - I used to have a power systems of the world book) in
which the phase-earth voltage was equal to, not 1/sqrt(3) of, the
phase-phase voltage. Poor old mr VDR lasted a few seconds then pop. The
solution - sidecutters and no VDR.

Cheers
Terry



I had similar problems in west Texas with some irrigation machines. You run
into all sorts of things when you work with 3-phase power. I hated it.

John

Most common of which was "component no longer there" type errors.

Cheers
Terry

 

[Robert Baer]

Joel Kolstad wrote:

"Robert Baer" <robertbaer@earthlink.net> wrote in message
news:41A7EFC2.3152EF15@earthlink.net...
Exactly. QNX appears to be the only OS that is bug-free and crashless.

It's a lot easier to keep a 40kB kernel bug free than one that's tens?
hundreds? of megabytes as Windows, Linux, etc. are these days. The bigger
OSes provide more features of course, but in many applications you may not
need them. Moral of the story: Don't buy a bigger OS than you need?

...and if one needs to add features to a small, bug-free OS, it is
just another program running in the task list,
Pick what you need when you need, and drop when done.

 

[Mike Diack]

bill.sloman@ieee.org (Bill Sloman) wrote in
news:7c584d27.0411271516.5d8dab21@posting.google.com:

Some humans.

As Fred Bloggs has pointed out, some African Grey parrots seem to be
able to outperform ostensibly human posters on this user-group.

------
Bill Sloman, Nijmegen

That's all very well, but how many newsgroup inhabitants could you say have

"lovely plumage" ?
M

 

[Clifford Heath]

Rich Grise wrote:

For no apparent reason, unless I had "powerup on LAN" and somebody
tried to probe it.
I decided poltergeists, but I think they're more lonely than dangerous. ;-)

I'd go with the poltergeist, seems more likely than someone
guessing your MAC address. Poltergeists, OTOH, tend to
inhabit the frozen smoke that chips are made of - as I'm sure
many folk here will attest.

 

[justin]

In article <cda1cf0d.0411271726.5e19d7dd@posting.google.com>, Simon
Schneiter <seimens@gmx.ch> wrote:

rolavine@aol.com (Rolavine) wrote in message
news:<20041126204148.14229.00001210@mb-m13.aol.com>...
From: seimens@gmx.ch (Simon Schneiter)

You don't need gain, you don't need an op amp. To impedance-buffer
piezo pu use a J201 FET with 2k21 drain to ground, 3M3 gate to ground
and 47ľ drain to output. At Vss=9V, Id Ĺ500ľA, linear headroom is
Ĺ2Vpp. If overdriven It will saturate gracefully but if you are
digitizing the signal for the DSP purposes the TDH is irrelevant
anyway.

j.

 

[Clifford Heath]

Simon Schneiter wrote:

My thought was to make sure I get enough headroom to avoid clipping.
But I sure will mesure the actual output as soon as I get the piezos
delivered.

You might *want* clipping. I used piezo wafers as percussion triggers,
and when glued on 1/8" plywood under a rubber pad, a medium whack
with the handle of a screwdriver yielded pulses of several hundred
volts (with no load of course, just a high-impedance oscilloscope
probe). Make sure you have sufficiently low input impedance!

Clifford Heath.

 

[Sean Bartholomew]

thanks guys.
i like the zener diode idea. how can i ensure that the + current
remains greater than the negative current? a 10k R?
if everything else falls short my plan with the 2 regs can work.
incidentally, the diagram shows a 7805. but i need FOUR volts to get a
+5V supply. remember, 9-5=4. thats why im using a 337T cause the 7904
doesnt exist. i wish it did though.

 

[Terry Given]

Guy Macon wrote:

Robert Baer wrote:


Exactly. QNX appears to be the only OS that is bug-free and crashless.


QNX and a few other real-time OSs.

You can actually upgrade to a new version of QNX without rebooting.
You can also have your hot-swap video card die, crashing the video
driver, put in a new card of a different brand, tell QNX over the
network to terminate the video driver and start up a different
video driver, and continue - all without rebooting and all while
continuously running a robotic assembly line.

Wow. Thats impressive.

Cheers
Terry

 

[Pooh Bear]

Rolavine wrote:

From: seimens@gmx.ch (Simon Schneiter)

I've designed a circuit using single-rail supply, since the
A/D-converter requires the signal to be between 1V and 4V. I assumed
the peak output voltages of the piezo to be at +10V respectively -10V.

I think your way too high there on your assumption, I've fed Piezo guitar
pickups, both buffered and unbuffered into a mixer board, my guess is between 1
volt and 100 mv max rms output.

I'm a graduate student in electrical engeneering, but not experienced
with anlog stuff.

Wait, how is that possible? And in this case it is just a simple ac coupled
single supply op amp circuit with a gain of about 5, sheesh! What the hell are
they teaching you these days?

It's a mystery to me too.

Should mean I'll be handy for anyone needing competent analogue design. It just
doesn't seem to be taught any more. And certainly not well.


Graham

 

[Hal Murray]

Umm... that's still well over an order of magnitude more than QNX, and
presumably a more typical kernel on a desktop PC would easily be two orders
of magnitude at 4MB, no?

The kernel I'm using is:
-rw-r--r-- 1 root root 840157 Aug 24 2002 vmlinuz
That includes drivers for all the hardware on this box.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.

 

[Joel Kolstad]

Hal,

"Hal Murray" <hmurray@suespammers.org> wrote in message
news:gdqdne9Lib0eEjTcRVn-sg@megapath.net...

The kernel I'm using is:
-rw-r--r-- 1 root root 840157 Aug 24 2002 vmlinuz
That includes drivers for all the hardware on this box.

That is impressively small. Do you happen to know how larger the video
drivers for, e.g., nVidia cards are (including 3D support for OpenGL)?
They're pretty large on Windows boxes...

 

[Kevin Aylward]

lemonjuice wrote:

On Wed, 24 Nov 2004 03:43:02 GMT, Rich Grise <rich@example.net> wrote:

On Wed, 24 Nov 2004 00:02:52 +0000, Paul Burridge wrote:

On Tue, 23 Nov 2004 21:44:01 GMT, Rich Grise <rich@example.net
wrote:

I don't know what his point is, but I just simply would like to
present a
way that some people have been looking at this base voltage/base
current
issue. Yes, the application of base voltage does ultimately result
in an
effect on the collector current. But how many designs have you ever
seen
where the designer relies on a particular Vbe drop to give the
right answer? I've _never_ seen a circuit like that, other than
things
like
current mirrors, and in that case, the Vbe is taken into
consideration
either as an almost-constant, a la diode drop, or simply to be as
equal as
is practicable to its partner in the circuit. But the easiest way
I've
ever seen presented of doing the circuit analysis uses base current
and
beta, with Vbe being a secondary (or less) consideration.

This is the only bone I have to pick here with you. If you want to
call it
"voltage controlled", then fine, go ahead, but I know that every
time I've
copied a circuit out of a book or whatever, the operative parameter
has
been base current.

The Vbe/Ic way of looking at it works accurately over a much greater
range than the Ic/Ib relationship, Rich. Even *I* know that!

OK. I lose.

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/comp/active/BiPolar/bpcur.html

Kevin Aylward has been corroborated by The Internet. ;-)

Cheers!
Rich

Mmmmmm Here is a website that says a transistor is a charge
controlled device
http://encyclobeamia.solarbotics.net/articles/transistor.html

I already addressed this in another post.

Noting that the "charge controlled model" is a naming misnomer. This
model describes charge as a function of applied controlling voltages. It
don't mean that charge is controlling anything. Charge is the
*dependant* variable in the "charge controlled model".

The web site also state the transistor is "a curent controlled device".
So what, its wrong. I have explained many times why it is a voltage
controlled. Its basic physics and trivial.

F = q(E + vXB)

Electric fields make charges move. Period. End of story.


Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Nico Coesel]

Joerg <notthisjoergsch@removethispacbell.net> wrote:

Hi All,

What is a good multi function laser printer? You know, the ones that can
laser print but also copy, scan and fax. This avoids cluttering the
office with individual units. It also avoids the occasional cussing that
follows when the copier heater came on while the printer was going and
tripped the breaker.

Go for an HP.

Also, if you happen to have a recommendation for a small and cheap
(meaning low cartridge cost) color inkjet I'd appreciate that. That one
should be able to print circuit board pictures, scope screen shots etc.

AFAIK there are no cheap inkjet printers. If you want to print in
color and keep your money in your wallet, get a color laser printer.
The prices of these machines go down very rapidly.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

 

[Winfield Hill]

Hal Murray wrote...

Umm... that's still well over an order of magnitude more than QNX,
and presumably a more typical kernel on a desktop PC would easily
be two orders of magnitude at 4MB, no?

The kernel I'm using is:
-rw-r--r-- 1 root root 840157 Aug 24 2002 vmlinuz
That includes drivers for all the hardware on this box.

Poking around with Google:

'vmlinuz' The kernel binary on AT&T versions, the original boot on
PDP-11, was called 'unix'. When Berkeley wrote a new kernel with
virtual memory, they called it 'vmunix'. So naturally the Linux
kernel is 'vmlinux' and the compressed version is 'vmlinuz'
(compressed files have a Z or gz extension)...

vmlinuz is a compressed file of vmlinux, with the gzip decompressor
code built in at the beginning. The kernel usually makes a bzImage,
and stores it in arch/i386/boot, and it is up to the user to copy it
to /boot and configure GRUB or LILO.

http://linux-universe.com/HOWTO/Kernel-HOWTO/kernel_files_info.html


--
Thanks,
- Win

 

[Guy Macon]

Chaos Master wrote:

classd101 wrote:

So what came first? Was it the faster/higher capacity hardware or the
bloated software?

The faster hardware moved manufacturers into making more bloated
software.

Indeed. To go into more detail, it works like this:

Certain users (3D cad users, gamers, people setting up servers)
want faster/higher capacity hardware to handle today's software.

Manufacturers make the faster/higher capacity hardware, and
the high-performance users snap up the first batch.

Microsoft (but not Linux or BSD) makes an OS that requires the
faster/higher capacity hardware to do the things ordinary users
like to do, and thows in some incompatability.

Ordinary users have to upgrade to the faster/higher capacity
hardware to run the new OS.

The 3D cad and game vendors make new versions that are even
more capable.

Repeat.

BTW, all these players own stock in each other, thus giving each
a motive to make it so that the others can sell new products
that will drive the next cycle.

 

[Guy Macon]

Joel Kolstad wrote:

"Rich Grise" <rich@example.net> wrote...

You can still compile a kernel that'll fit on a couple of
1.4MB floppies, if you don't want to load it all up
with modules.

Umm... that's still well over an order of magnitude more than QNX,

With QNX you can fit the entire OS with drivers for a wide variety
of hardware, dialup and Ethernet support, a full-featured web
browser, plus various other programs, all on ONE 1.44MB floppy.

Last I heard, some distributions of Linux still re-compile the Kernel during
installation -- something that should never be needed in a 'modern' OS.

That's a deliberate design decision, based on the fact that a kernal
that uses extra CPU features such as MMX or optimizes for the pipeline
in some of the new CPUs runs faster. Other OSs either have to restrict
the code to what runs on a 386 or have a bunch of different kernel
versions for different systems.

 

[Fred Bloggs]

Sean Bartholomew wrote:

thanks guys.
i like the zener diode idea. how can i ensure that the + current
remains greater than the negative current? a 10k R?

If you are talking about the 7805 and 4.7V zener combination, then the
COMMON terminal of the 7805 will supply enough bias current for the
zener. Keep in mind that the zener will sink this current plus the +5V
load current minus the 4V load current.

 

[Phil Hobbs]

Guy Macon wrote:

One of the fellows working for me designed this:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3856393230

It's a simple product, but any comments on the design of it
would be most appreciated.


Looks useful in principle but (unless I miss my guess) not so useful in

practice. The major problem I see is the dip switches--typically these
aren't designed for repetitive use, so I'd worry that they'd become flaky
quite rapidly.

Those DIP switches are SPST, I gather, so all your Rs and Cs are wired in
series, with a DIP switch in shunt with each one. This makes the flakiness
problem significantly worse, since instead of 2 contacts (for a rotary DPNT
wafer switch) you've got N contacts in series.


Capacitor tolerance is another issue--those are mostly ceramic discs. What
capacitance tolerance and tempco are they? And what about the inductance and
capacitance of all those traces?

Cheers,

Phil Hobbs

 

[Boris Mohar]

On Sun, 28 Nov 2004 13:44:04 +0000, Guy Macon <http://www.guymacon.com>
wrote:

One of the fellows working for me designed this:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3856393230

It's a simple product, but any comments on the design of it
would be most appreciated.

Switches will be a pain. Hard to set and will not last long. Changing
capacitance values in some live circuits will be particularly hard on the
switches.

--

Boris Mohar