Driver to drive?

[Spehro Pefhany]

On Fri, 15 Feb 2013 17:14:12 -0500, the renowned Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Pournelle's Law still applies too: "The computer you want is always
$5000." Still true for me!

Cheers

Phil Hobbs

Yup, me two (or is it three).

A corollary is that no matter what you might consider buying
(including computers) you can imagine spending about 3x as much
without straining much.

2nd corollary is that when you make up your mind what you want, you
should look at spending about 20% more. It often makes the difference
between pretty good and great.


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

 

[josephkk]

On Thu, 14 Feb 2013 19:11:35 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

rickman wrote:

On 2/12/2013 12:25 PM, Michael A. Terrell wrote:

radams2000@gmail.com wrote:

Long ago I learned a painful lesson about video frequency accuracy. I assumed that getting a crystal within 100ppm of tbe ideal frequency should be just fine. But when we tried to send that signal through a satellite, it wouldn't go because the frequency accuracy was too poor.

I think the issue is that VCXO's are often used for clock recovery and they can't be pulled very far. Or maybe they just rely on absolute accuracy, and when things drift between the source and the sync, you just drop or repeat a frame. Not sure.


NTSC color calls for +/- 10 Hz for the 3,579,545 burst frequency.

Hmmm... ą3 ppm. Did they have much luck finding crystals that would
provide this? I expect there is more than just a crystal in this
circuit. I seem to recall that the color burst *is* a reference that
lets the local TV oscillator sync up on every frame. Maybe the camera
has a ą3 ppm oscillator in it, but I seriously doubt TVs do.


Apparently you've never looked at the schematic of a color TV or
monitor or the RS-170A standard.

"Color Burst" is SEVEN cycyles of 3.57945 HZ in every line of video
to phase lock the crystal in the display, not every frame, or even every
field. The 'Tint' control trims the phase of the internal Chroma
oscillator, and it only takes a slight change in phase to make faces go
from green to purple. If it was off more than a cycle the chroma
unlocks, and you see slowly swirling color crap on the screen. Go more
than the 10 cycle limit and it triggers the 'color killer' circuit which
turns it to a mono display.

That was changed to 8 about 1970 or so.

Ever heard of oven controlled crystal oscillators? The master sync
generator uses one, then 'Blackburst' is sent to every camera, VTR or
effects unit to provide the reference signal. They are powered
24/7/265.25 Even the series 300 Grass Valley group I used back in the
early '70s had dual generators with genlock and active failover.

All this was understood 60 years ago when NTSC approved the use of
Color TV in the US. They designed the system so the expensive hardware
was only needed at the station, and even that left the TVs at $1000+ in
the first couple years. Specially designed tubes allowed simpler
designs and fewer stages which helped, and that drop spurred more sales.
A nice color TV was still around $600 in the mid to late '60s.

 

[josephkk]

On Fri, 15 Feb 2013 17:14:12 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

All this was understood 60 years ago when NTSC approved the use of
Color TV in the US. They designed the system so the expensive hardware
was only needed at the station, and even that left the TVs at $1000+ in
the first couple years. Specially designed tubes allowed simpler
designs and fewer stages which helped, and that drop spurred more sales.
A nice color TV was still around $600 in the mid to late '60s.

A nice color TV is still around $600. ;-) ...and probably always will
be.


Pournelle's Law still applies too: "The computer you want is always
$5000." Still true for me!

Cheers

Phil Hobbs

Long before you posted the general description of your big simulation
number cruncher i was jonesing for something like that, but it was about
$30,000. I now have a laptop that seems to be the fastest that i have for
under a grand, and i have an AMD 1075T box and a FX6100 box, both about
the same speed.

?-)

 

[Michael A. Terrell]

josephkk wrote:

On Thu, 14 Feb 2013 19:11:35 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


rickman wrote:

On 2/12/2013 12:25 PM, Michael A. Terrell wrote:

radams2000@gmail.com wrote:

Long ago I learned a painful lesson about video frequency accuracy. I assumed that getting a crystal within 100ppm of tbe ideal frequency should be just fine. But when we tried to send that signal through a satellite, it wouldn't go because the frequency accuracy was too poor.

I think the issue is that VCXO's are often used for clock recovery and they can't be pulled very far. Or maybe they just rely on absolute accuracy, and when things drift between the source and the sync, you just drop or repeat a frame. Not sure.


NTSC color calls for +/- 10 Hz for the 3,579,545 burst frequency.

Hmmm... ą3 ppm. Did they have much luck finding crystals that would
provide this? I expect there is more than just a crystal in this
circuit. I seem to recall that the color burst *is* a reference that
lets the local TV oscillator sync up on every frame. Maybe the camera
has a ą3 ppm oscillator in it, but I seriously doubt TVs do.


Apparently you've never looked at the schematic of a color TV or
monitor or the RS-170A standard.

"Color Burst" is SEVEN cycyles of 3.57945 HZ in every line of video
to phase lock the crystal in the display, not every frame, or even every
field. The 'Tint' control trims the phase of the internal Chroma
oscillator, and it only takes a slight change in phase to make faces go
from green to purple. If it was off more than a cycle the chroma
unlocks, and you see slowly swirling color crap on the screen. Go more
than the 10 cycle limit and it triggers the 'color killer' circuit which
turns it to a mono display.

That was changed to 8 about 1970 or so.

The crystal would have to be defective not to be pulled into lock, if
the chroma demodulator was aligned properly. Let it run free and adust
it as close as possible, usually with a variable inductor. Most
manufacturers literature told you where to short the incoming burst to
ground to do the alignment which consisted of turning the slug till the
color was almost locked without the burst signal. You would go from
colored stripes, to slowly drifting tint. That was a rarely needed
procedure. Usually only if some geek, or the owner got into the
alignment. The others were when the burst crystal failed.


I've only seen one pair of sync generators without an oven. They
were very early Grass Valley, at a monochome TV station. Did I ever
mention that I hate RTL ICs? They didn't have a lot of faith, since
there were two generators and a fail over switch. I think they were 300
series, and installed around 1970. A station in Fairbanks still had the
original RCA tube type that filled a third of a relay rack. They still
had a color video monitor built on the 1954 RCA CTC4 (Color TV Chassis)
for their master monitor. It took them anywhere from 90 minutes to four
hours to set up that old junk every day. Luckily, the one electronics
parts house in town was only a couple blocks away.

 

Tim Wescott <tim@seemywebsite.com> wrote:

Does anyone even _make_ RPN calculators any more?

I know I'm a little late, but: HP 48G / GX / G+. They seem to go for
$30 to $70 on Ebay. Not quite sure what the differences are, but those
were the last models of the "classic" 48. My 48SX from circa 1991 is
still chugging along; it's on maybe its third or fourth set of AAAs.
They are from before the clue fire went out at HP, so they will keep
working for a long time.

I used it at work two years ago to figure out a problem that required a
48-bit word size; a 48-bit number was coming out of an FPGA and then
being (incorrectly) converted to a 64-bit number in C. None of the
"desktop" calculators I tried, Linux and Windows, 32 or 64 bit, could
handle this correctly. The HP can do anything from 1 to 64 bit word
size; mine helped me confir that the program was indeed screwing up and
what the fix was.

Matt Roberds

 

On Thu, 14 Feb 2013 15:40:15 -0500, rickman <gnuarm@gmail.com> wrote:

On 2/12/2013 12:25 PM, Michael A. Terrell wrote:

radams2000@gmail.com wrote:

Long ago I learned a painful lesson about video frequency accuracy. I assumed that getting a crystal within 100ppm of tbe ideal frequency should be just fine. But when we tried to send that signal through a satellite, it wouldn't go because the frequency accuracy was too poor.

I think the issue is that VCXO's are often used for clock recovery and they can't be pulled very far. Or maybe they just rely on absolute accuracy, and when things drift between the source and the sync, you just drop or repeat a frame. Not sure.


NTSC color calls for +/- 10 Hz for the 3,579,545 burst frequency.

That would be +/-3600 degrees/s phase error, so from the colour burst
to the end of the visible line (about 60 us) that would be only be
less than 0.2 degree phase error. Why is the requirement that tight ?

Hmmm... ą3 ppm. Did they have much luck finding crystals that would
provide this? I expect there is more than just a crystal in this
circuit. I seem to recall that the color burst *is* a reference that
lets the local TV oscillator sync up on every frame. Maybe the camera
has a ą3 ppm oscillator in it, but I seriously doubt TVs do.

IIRC, in 1960/70's in comparisons between NTSC and PAL one significant
drawback listed against NTSC was the need for a high quality
(expensive) crystal oscillator, compared to PAL.

 

On Sat, 16 Feb 2013 09:33:40 +0000 (UTC), mroberds@att.net wrote:

Tim Wescott <tim@seemywebsite.com> wrote:
Does anyone even _make_ RPN calculators any more?

I know I'm a little late, but: HP 48G / GX / G+. They seem to go for
$30 to $70 on Ebay. Not quite sure what the differences are, but those
were the last models of the "classic" 48. My 48SX from circa 1991 is
still chugging along; it's on maybe its third or fourth set of AAAs.
They are from before the clue fire went out at HP, so they will keep
working for a long time.

The 'X' models had expandable memory and the '+' had more memory on
board, according to Wiki. I may investigate eBay. Thanks.

I used it at work two years ago to figure out a problem that required a
48-bit word size; a 48-bit number was coming out of an FPGA and then
being (incorrectly) converted to a 64-bit number in C. None of the
"desktop" calculators I tried, Linux and Windows, 32 or 64 bit, could
handle this correctly. The HP can do anything from 1 to 64 bit word
size; mine helped me confir that the program was indeed screwing up and
what the fix was.

I had a problem with binary calculators when doing some 2-D filters in

an FPGA. None handled binary fractions properly, with the exception
of one app for a Palm Pilot and it wasn't RPN. :-(

 

[Fred Abse]

On Wed, 13 Feb 2013 19:13:18 -0800, josephkk wrote:

On 13 Feb 2013 10:57:17 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2013-02-13, josephkk <joseph_barrett@sbcglobal.net> wrote:

I run Agent in wine. Works pretty well without any fuss to install and
get it running. Help doesn't work properly though.

hve you installed "xchm" or is help broken in lyspice+wine too?

I have tried installing xchm and both are still broken. It is very
possible i did something wrong though.

I used chm2pdf to convert the LTspice help into a nice indexed PDF.

Better, in fact than LT's own PDF offering.

Xchm doesn't always work with some later editions, beyond the first page.


--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

On Sunday, 3 February 2013 14:20:23 UTC, Lasse Langwadt Christensen wrote:

On Feb 3, 5:31 am, "Michael A. Terrell" <mike.terr...@earthlink.net> wrote: > "langw...@fonz.dk" wrote: > > > On Feb 3, 4:00 am, Jamie > > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote: > > > Jasen Betts wrote: > > > > On 2013-02-01, Robert Macy <robert.a.m...@gmail.com> wrote: > > > > >>First place I'd look... > > > >>Electronic ballasts require an EMI filter in front of them to prevent > > > >>the conducted emanations. What you have there is a capacitor across > > > >>the AC mains followed by some husky inductance. That makes the load > > > >>look incredibly inductive, not capacitive - with main impact as you > > > >>turn it off. To envision, simply unplug your PC very slowly from the > > > >>AC outlet. Even with it turned off, you'll draw an impressive arc. All > > > >>due to the stored energy in the EMI filter. I suspect it is THAT > > > >>energy that is welding the contacts together. > > > > > contacts can't weld closed while they are open. > > > > therfore the damage is occurring when they close > > > > capacitor derived surge current through the bouncing > > > > contacts heats them up to melting and the weld closed. > > > >   They most certainly can weld together while they are in > > > the process of opening with induction loads. Which is why > > > special designs are out there just for handling induction > > > loads. > > > I have hard time seeing how it can happen when opening, arc > > start when they are already moving apart so unless you close them > > instantly after being melted by the opening arc I don't see how > > they could weld > > > at closing it is more like spot welding, melt and press together > > > >    If you don't use the correct contact design for these types > > > of loads, the relay will not last long. > > > > Jamie > > > sure arcing at opening will eat the contacts, but that is different > > > -Lasse > >    You've never done any arc welding, have you? I have done plenty of welding, stick and tig have you ever got the rod stuck while pulling it off? -Lasse

Hello there. I think modern HF flourescent light fittings probably use high voltage mosfets (500-900volts)electronic balasts probably presenting an operating reactive load that is similar to switched mode PSUs (Transmitters,telecoms,server bank PCs) which calls for a substantual derating of your relay in question. 16A resistive(heating element load) but only 2A reactive load is typical of external integral halogen lamp PIR controller or 5-6A max reactive for seperate PIR module. Probably call for the 15A (600-800mW) or 25A (30/20A DPDT Finder) (1-2W) for conventional mechanical relay from Maplin (or rapidonline.com). There are also 25A electronic relay modules (farnell.com) that use triac switching (might NOT be suitable).

 

[Michael A. Terrell]

varient412@yahoo.co.uk wrote:

On Sunday, 3 February 2013 14:20:23 UTC, Lasse Langwadt Christensen wrote:
On Feb 3, 5:31 am, "Michael A. Terrell" <mike.terr...@earthlink.net> wrote: > "langw...@fonz.dk" wrote: > > > On Feb 3, 4:00 am, Jamie > > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote: > > > Jasen Betts wrote: > > > > On 2013-02-01, Robert Macy <robert.a.m...@gmail.com> wrote: > > > > >>First place I'd look... > > > >>Electronic ballasts require an EMI filter in front of them to prevent > > > >>the conducted emanations. What you have there is a capacitor across > > > >>the AC mains followed by some husky inductance. That makes the load > > > >>look incredibly inductive, not capacitive - with main impact as you > > > >>turn it off. To envision, simply unplug your PC very slowly from the > > > >>AC outlet. Even with it turned off, you'll draw an impressive arc. All > > > >>due to the stored energy in the EMI filter. I suspect it is THAT > > > >>energy that is welding the contacts together. > > > > > contacts can't weld closed while they are open. > > > > therfore the
damage is occurring when they close > > > > capacitor derived surge current through the bouncing > > > > contacts heats them up to melting and the weld closed. > > > > They most certainly can weld together while they are in > > > the process of opening with induction loads. Which is why > > > special designs are out there just for handling induction > > > loads. > > > I have hard time seeing how it can happen when opening, arc > > start when they are already moving apart so unless you close them > > instantly after being melted by the opening arc I don't see how > > they could weld > > > at closing it is more like spot welding, melt and press together > > > > If you don't use the correct contact design for these types > > > of loads, the relay will not last long. > > > > Jamie > > > sure arcing at opening will eat the contacts, but that is different > > > -Lasse > > You've never done any arc welding, have you? I have done plenty of welding, stick and tig have you ever got
the rod stuck while pulling it off? -Lasse

Hello there. I think modern HF flourescent light fittings probably use high voltage mosfets (500-900volts)electronic balasts probably presenting an operating reactive load that is similar to switched mode PSUs (Transmitters,telecoms,server bank PCs) which calls for a substantual derating of your relay in question. 16A resistive(heating element load) but only 2A reactive load is typical of external integral halogen lamp PIR controller or 5-6A max reactive for seperate PIR module. Probably call for the 15A (600-800mW) or 25A (30/20A DPDT Finder) (1-2W) for conventional mechanical relay from Maplin (or rapidonline.com). There are also 25A electronic relay modules (farnell.com) that use triac switching (might NOT be suitable).

What the hell are you posting with? It completely destroys the
messages in your reply.

 

[P E Schoen]

"Michael A. Terrell" wrote in message
news:A7SdnXhHCdCn6rrMnZ2dnUVZ_tCdnZ2d@earthlink.com...

What the hell are you posting with? It completely destroys the
messages in your reply.

It says User Agent G2/1.0 which appears to be Google Groups. They probably
made another "improvement".
https://wiki.mozilla.org/Discussion_Forums/Request_For_Comment

Paul

 

[josephkk]

On Fri, 22 Feb 2013 08:48:26 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

varient412@yahoo.co.uk wrote:

On Sunday, 3 February 2013 14:20:23 UTC, Lasse Langwadt Christensen wrote:
On Feb 3, 5:31 am, "Michael A. Terrell" <mike.terr...@earthlink.net> wrote: > "langw...@fonz.dk" wrote: > > > On Feb 3, 4:00 am, Jamie > > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote: > > > Jasen Betts wrote: > > > > On 2013-02-01, Robert Macy <robert.a.m...@gmail.com> wrote: > > > > >>First place I'd look... > > > >>Electronic ballasts require an EMI filter in front of them to prevent > > > >>the conducted emanations. What you have there is a capacitor across > > > >>the AC mains followed by some husky inductance. That makes the load > > > >>look incredibly inductive, not capacitive - with main impact as you > > > >>turn it off. To envision, simply unplug your PC very slowly from the > > > >>AC outlet. Even with it turned off, you'll draw an impressive arc. All > > > >>due to the stored energy in the EMI filter. I suspect it is THAT > > > >>energy that is welding the contacts together. > > > > > contacts can't weld closed while they are open. > > > > therfore the
damage is occurring when they close > > > > capacitor derived surge current through the bouncing > > > > contacts heats them up to melting and the weld closed. > > > > They most certainly can weld together while they are in > > > the process of opening with induction loads. Which is why > > > special designs are out there just for handling induction > > > loads. > > > I have hard time seeing how it can happen when opening, arc > > start when they are already moving apart so unless you close them > > instantly after being melted by the opening arc I don't see how > > they could weld > > > at closing it is more like spot welding, melt and press together > > > > If you don't use the correct contact design for these types > > > of loads, the relay will not last long. > > > > Jamie > > > sure arcing at opening will eat the contacts, but that is different > > > -Lasse > > You've never done any arc welding, have you? I have done plenty of welding, stick and tig have you ever got
the rod stuck while pulling it off? -Lasse

Hello there. I think modern HF flourescent light fittings probably use high voltage mosfets (500-900volts)electronic balasts probably presenting an operating reactive load that is similar to switched mode PSUs (Transmitters,telecoms,server bank PCs) which calls for a substantual derating of your relay in question. 16A resistive(heating element load) but only 2A reactive load is typical of external integral halogen lamp PIR controller or 5-6A max reactive for seperate PIR module. Probably call for the 15A (600-800mW) or 25A (30/20A DPDT Finder) (1-2W) for conventional mechanical relay from Maplin (or rapidonline.com). There are also 25A electronic relay modules (farnell.com) that use triac switching (might NOT be suitable).


What the hell are you posting with? It completely destroys the
messages in your reply.

It looks like varient412 is using Netscape 4.8 with very messed up
settings. He seems to be doing an Earthlike - giganews cha-cha as well.

?-)

 

[Michael A. Terrell]

josephkk wrote:

On Fri, 22 Feb 2013 08:48:26 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


varient412@yahoo.co.uk wrote:

On Sunday, 3 February 2013 14:20:23 UTC, Lasse Langwadt Christensen wrote:
On Feb 3, 5:31 am, "Michael A. Terrell" <mike.terr...@earthlink.net> wrote: > "langw...@fonz.dk" wrote: > > > On Feb 3, 4:00 am, Jamie > > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote: > > > Jasen Betts wrote: > > > > On 2013-02-01, Robert Macy <robert.a.m...@gmail.com> wrote: > > > > >>First place I'd look... > > > >>Electronic ballasts require an EMI filter in front of them to prevent > > > >>the conducted emanations. What you have there is a capacitor across > > > >>the AC mains followed by some husky inductance. That makes the load > > > >>look incredibly inductive, not capacitive - with main impact as you > > > >>turn it off. To envision, simply unplug your PC very slowly from the > > > >>AC outlet. Even with it turned off, you'll draw an impressive arc. All > > > >>due to the stored energy in the EMI filter. I suspect it is THAT > > > >>energy that is welding the contacts together. > > > > > contacts can't weld closed while they are open. > > > > therfore the
damage is occurring when they close > > > > capacitor derived surge current through the bouncing > > > > contacts heats them up to melting and the weld closed. > > > > They most certainly can weld together while they are in > > > the process of opening with induction loads. Which is why > > > special designs are out there just for handling induction > > > loads. > > > I have hard time seeing how it can happen when opening, arc > > start when they are already moving apart so unless you close them > > instantly after being melted by the opening arc I don't see how > > they could weld > > > at closing it is more like spot welding, melt and press together > > > > If you don't use the correct contact design for these types > > > of loads, the relay will not last long. > > > > Jamie > > > sure arcing at opening will eat the contacts, but that is different > > > -Lasse > > You've never done any arc welding, have you? I have done plenty of welding, stick and tig have you ever got
the rod stuck while pulling it off? -Lasse

Hello there. I think modern HF flourescent light fittings probably use high voltage mosfets (500-900volts)electronic balasts probably presenting an operating reactive load that is similar to switched mode PSUs (Transmitters,telecoms,server bank PCs) which calls for a substantual derating of your relay in question. 16A resistive(heating element load) but only 2A reactive load is typical of external integral halogen lamp PIR controller or 5-6A max reactive for seperate PIR module. Probably call for the 15A (600-800mW) or 25A (30/20A DPDT Finder) (1-2W) for conventional mechanical relay from Maplin (or rapidonline.com). There are also 25A electronic relay modules (farnell.com) that use triac switching (might NOT be suitable).


What the hell are you posting with? It completely destroys the
messages in your reply.

It looks like varient412 is using Netscape 4.8 with very messed up
settings. He seems to be doing an Earthlike - giganews cha-cha as well.

I think you looked at my headers.

His looks like another 'Google Groups' change.


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Newsgroups: sci.electronics.design

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Subject: Re: Relay failures in lighting controller

From: varient412@yahoo.co.uk

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Or he could be an alien using FTL communications in an attempt to
destroy Usenet. ;-)

 

[Phil Allison]

<varient412@yahoo.co.uk

I think modern HF flourescent light fittings probably use high voltage
mosfets (500-900volts)electronic balasts probably presenting an operating
reactive load that is similar to switched mode PSUs


** SMPS do not present a reactive load.

Why does this idiotic myth persist for so long ??

It's harder to kill than the AGW myth ....


16A resistive(heating element load) but only 2A reactive load is typical of
external integral halogen lamp PIR controller or 5-6A max reactive for
seperate PIR module.


** Fuck knows what this total dill is on about - but some folk consider
transformers to be "reactive loads" and a 2Amp nominal transformer can have
a big inrush surge particularly when loaded with halogen lamps.

Not one bit reactive.


.... Phil

 

[SoothSayer]

On Sun, 24 Feb 2013 05:12:28 -0800, dave <ricketzz@earthlink.net> wrote:

On 02/24/2013 12:30 AM, Mike Cook wrote:
The gel cell is 12v.


Most lead acid batteries are ca. 13.6 Vdc

No most 12 volt car battery chargers operate at 13.6 VDC. That is the
CHARGE Voltage, not the voltage the battery ends up carrying. In order
to charge a battery, one must apply a higher voltage than the battery
operates at.

If your car battery ever got
down to 12 Vdc the car would have trouble starting.

You're an idiot. A car battery or 12V gel cell that reads 12volts IS
fully charged and will put out its declared rate.

Lead acid cells are
about 2.22 Vdc.

You're an idiot. Perhaps you should provide a wiki citation or such.
Right now you appear as a joke.



Cross posting fucking retards.

 

[SoothSayer]

On Sun, 24 Feb 2013 05:17:53 -0800, dave <ricketzz@earthlink.net> wrote:

On 02/24/2013 05:14 AM, Phil Allison wrote:
"dave"

You answered your own question. As long as the battery doesn't heat up on
a big charge you're probably OK.


** SLA or "gel cells" are prone to gassing when overcharged.

The pressure builds up inside until something gives - then you have bits
of battery and acid all over the place.

Voltage & current limited charging is the only safe and sensible way.



... Phil



They have vents.

Which are NOT meant for overcharge relief.

 

Hello all (after many years), Frank Miles' equation is exact and it becomes even simpler if A approaches infinity (ideal OpAmp), so:

((R3 + R4) * R1)
Rin = ------------------
(R3 + R4 - m * R4)

which gives correct values, too. If m = 2, Rin is (almost) infinity and if m > 2, Rin appears to be negative meaning that output phase reverses. Take positive value only. However, if inputs are in quadrature, other equation could be found (but not necessary). Anyway, the original purpose of discussion seems to be solved.

Kindly, EePee (OH2NFI).

 

Do not connect a capasitor. Firstly, you would need a FARAD- ranged unit, not in microFarad range, as the battery is very low-impedance load. Secondly, the charger's no-load voltage with capasitor can be much over 15 volts.

In typical chargers there is usually only a full-wave bridge rectifier in transformer's secondary circuit (and often an inaccurate AC current meter), so current comes in peaks; you should have an RMS current meter to get correct readings. Voltage is best checked without charger, as mentioned. If no-load voltage is over 13.8 volts (typical floating charge value), the lead-acid battery is probably fully charged. - EePee.

 

[dave]

On 02/24/2013 05:37 AM, SoothSayer wrote:

On Sun, 24 Feb 2013 05:17:53 -0800, dave <ricketzz@earthlink.net> wrote:

On 02/24/2013 05:14 AM, Phil Allison wrote:
"dave"

You answered your own question. As long as the battery doesn't heat up on
a big charge you're probably OK.


** SLA or "gel cells" are prone to gassing when overcharged.

The pressure builds up inside until something gives - then you have bits
of battery and acid all over the place.

Voltage & current limited charging is the only safe and sensible way.



... Phil



They have vents.

Which are NOT meant for overcharge relief.

I didn't say they were. I was speaking to the "bits of battery and acid"
prediction above.

 

[dave]

On 02/24/2013 05:35 AM, SoothSayer wrote:

On Sun, 24 Feb 2013 05:12:28 -0800, dave <ricketzz@earthlink.net> wrote:

On 02/24/2013 12:30 AM, Mike Cook wrote:
The gel cell is 12v.


Most lead acid batteries are ca. 13.6 Vdc

No most 12 volt car battery chargers operate at 13.6 VDC. That is the
CHARGE Voltage, not the voltage the battery ends up carrying. In order
to charge a battery, one must apply a higher voltage than the battery
operates at.

If your car battery ever got
down to 12 Vdc the car would have trouble starting.

You're an idiot. A car battery or 12V gel cell that reads 12volts IS
fully charged and will put out its declared rate.

Lead acid cells are
about 2.22 Vdc.

You're an idiot. Perhaps you should provide a wiki citation or such.
Right now you appear as a joke.



Cross posting fucking retards.

13.6 Vdc is the float voltage. Virtually all amateur radio equipment,
most mobile communications equipment and power supplies (for above) are
rated at 13.6 Vdc, the nominal Voltage of a 6 cell lead acid battery.
That is a fact, no matter how rude you become.

Here's another flash, your 1.5 V "AA" NiCads are only putting out 1.2 Vdc.