Driver to drive?

[Frank Bemelman]

"John Smith" <kd5yikes@mindspring.com> schreef in bericht
news:iyybd.3079$6k2.2170@newsread3.news.pas.earthlink.net...

Hi -

I bought a Tek 468 which I returned today. I thought it had a problem, but
the seller disagreed. I would like to know if I am wrong.

The 468 is an analog/digital scope. In the digital mode, I noticed that
the
trace had rectangular pulses on it of about .1 cm amplitude and apparently
random in frequency and width. This was with the inputs grounded using the
switch on the front panel. The amplitude of these pulses did not change
when
I changed the attenuator setting except at the three most sensitive
settings
of the attenuator (2 mV, 1 mV and .5 mV). Those three most sensitive
settings were active for digital storage operation only and were
non-functional in the analog mode.

When I complained about it, the seller said that it was caused by
quantization, it met Tek's specifications, and that .1 cm was entirely
reasonable. I disagreed because all waveforms appeared noisy so one would
never be able to tell whether the observed waveform was at fault or the
scope was at fault. In addition, .1 cm is 1 part in 80 for the vertical
displacement (8 cm vertical grid). It didn't seem right that maximum
resolution would be 1 in 80 or even 1 in 100. Logically, I felt that the
resolution would be 1 in 256 so that quantization noise would be much less
than actually observed.

It is normal. The ADC's span is bigger than the 8 squares on the grid.
One-tenth of a grid square 'uncertainy' doesn't sound alarming. Of course
that 1-bit noise rides on top of everything. You also see this very clear
on a new LCD scope like a TDS220 or something. Perhaps less annoying with
these scopes, because it's fast realtime update tends to average it out,
sort of. But when you stop the aqcuisition, it is all over the place.

Maybe I understand nothing about scopes and digital stuff. But, I could
not
believe that Tek would sell such a product. Am I wrong?

Tek has sold more rubbish TAS220 for instance.

--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

 

[Goran Larsson]

In article <T5mdnTo2SJGTPfPcRVn-sg@rcn.net>,
HoloBarreŠŽ <physical@erols.com> wrote:

The only long term stable
solution I can think of right now, would be to place flow sensors in the
out going and return lines of the tank and do the math there.

Why are you ignoring any long term instability in the flow sensors?

Many years ago I wrote software for a fuel consumption display for a
fishing boat. The hardware had flow sensors (feed and return) and at
slow speed most of the feed fuel was returned unused. In this situation
you had two sensors that had some tolerance and also reduced precision
due to vibrations. Taking the difference between the two sensors
resulted in what looked like noise, so much noise that the fuel
consumtion sometines was negative. It required lots of filtering
(software) to get any useful fuel consumption numbers out of that
hardware installation.

I much prefer how it is done in the cars I have owned, basing the
consumption calculations on the time the fuel injectors are open.

--
Göran Larsson http://www.mitt-eget.com/

 

[Paul Burridge]

On Thu, 14 Oct 2004 10:36:53 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

On Thu, 14 Oct 2004 14:56:53 +0100, the renowned Paul Burridge
pb@notthisbit.osiris1.co.uk> wrote:

On 14 Oct 2004 06:09:07 -0700, photo@metrodiapo.com (Pol Guerin Ph.D)
wrote:

Dearest photographers,

Metroscope research group is inviting photographers to submit any
image of metros from around the world.

What's a "metro"?

Subway. Err..."Underground"/"Tube".

Oh. Can't help, then, I'm afraid. Taking pickshures of the London
Underground is prohibiited for some strange reason.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Paul Burridge]

On Thu, 14 Oct 2004 10:57:56 -0700, John Larkin
<jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:

I have a TDS2012 on my desk, displaying RS232 poll/reply sequences for
a uP thing I'm testing. With no input, it has about 0.1 cm p-p noise
at most gain settings, increasing to 0.5 cm p-p at 2 mv/cm. The noise
appears, to me, to be a mixture of real front-end analog noise, adc
quantization, and lcd pixellization. Welcome to the digital age!

Sounds like a heap of shit. Why don't you use a good ol' classic
analogue scope like this one I rescued from a dumpster and shoved into
my garage for posterity:

http://www.burridge8333.fsbusiness.co.uk/oscilloscope.jpg

No quantization noise guaranteed!
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Joerg]

Hi Chris,

That looks like the usual chicken and egg scenario. Solar, for example,
never really gets off the ground because the stuff is cost prohibitive
to anybody but the most dedicated environmentalists. The inverters are
one of the reasons. If they weren't so expensive, they'd sell a lot
more, amortizing the R&D faster.




Well no, I don't think that's correct. How many people have a use for a DVD
player? How many have a use for an inverter?


While the market would never even reach a percent of the DVD sales there

is a huge potential to grow the inverter market. And I mean not just a
few percent. For example, here in California solar power would be a
tremendous relief for an overburdened and long neglected electric energy
situation. Two factors are keeping a tight lid on that: The cost of
solar panels and the cost of the "control hardware", the latter
including the inverter. The math is simple. Most people including myself
would consider an installation that amortizes over 5-7 years something
to ponder. But when amortization requires way more than 10 years the
majority of potential customers lose interest.

Inverter manufacturers and solar panel producers would have to sit down
and see whether there is a longer term business model they could agree
on. However, they'd have to give up concentrating on how to make next
quarter's results look good.

There is another problem too. I know this from experience. 80% of *first time*
inverter users connect it up wrong and blow it up. The manufacturers have to
account for these "warranty" claims in the cost. The result being that they
have to still make a profit by giving one away for each unit sold.


That is either lack of consumer education or lack of circuit safeguards,

or both. What can you do wrong with an inverter? After all, an inverter
only has two ports.

Reverse input polarity? How many people place a car battery in
backwards? A nice big diode across and a breaker should be able to
handle that.

Yes, I have heard of people using inverters as transformers, hooking up
the output to mains and expecting 12V to come out the other side. Lack
of consumer education. This can also be handled with some failsafe
circuitry.

A 1000 watt inverter for 90 bucks is *not* the market price. That's a surplus,
job lot price, probably end of run or bankrupt stock. It isn't even close to
the true price.


Costco sold these all summer. I believe that was similar in previous

years and Sam's Club had inverters in that range, too. Xantrex and
others. Usually those wholesalers don't deal in surplus, except when it
is their own overstock and then they display the regular price and the
sale price. That happens very rarely though.

They also had lots of smaller models, like one 400W "brick" plus a
50-100W plug-in sold at a similar price in combo packs. The little
emergency pack I bought was about $100 five years ago when we had all
these rolling blackouts. It has a 300W inverter and a lead acid battery
in a handy mini-suitcase and came with a charger, cables for the car,
for hooking up a larger marine battery and all.

If your TV breaks it's no big deal. If your inverter breaks (I'm talking about
units used to power remote homes or boats here) it can be a real problem yet
people still go out and buy the cheapest one they can find. Seems rather silly
to me.


That's why I would always buy two units if it was really critical. That

results in great peace of mind, in the same way that I would never run a
business with one computer alone (although some people do that...).

Even Xantrex are now marketing some rubbish as well as their *real* units.


That would be dangerous. One big problem and a good reputation might be

toast. It can be hard to nearly impossible to recover.

An old reg on this NG used to work for Statpower and was heavily involved in
development of the ProSine. That unit took a team of 20 engineers over 18
months to develop. That is a *lot* of money to get back in sales. And they
can't do it by selling them at 5 bucks profit per unit because they still
wouldn't sell any more.


Agree. But sometimes I think that concentrating on just the top tier

segment of a market can stifle overall revenue. My background is mostly
medical electronics and there it is often the same. Marketeers want a
better machine than the competition. In fact, often they want the best
machine that current technology can yield. Time and time again I try to
preach low cost approaches. In the end the market always shows where
companies flourish in the long term, by making technology available to
the broadest audience possible. In our case down to the lone doctor in a
rural practice where the majority of his or her clients is unable to
foot a huge medical bill. They need low cost equipment. My mantra is
that if we don't provide that, somebody else will and ultimately blow
the others out of the water. This is not based on my dousing rod or
something, I have seen many companies that went for too lofty goals
disappear.

Maybe I am too different but I experience the most fun not in designing
that super duper top notch golden machine. My fun is in designing
something that most of the market can afford.

Regards, Joerg

http://www.analogconsultants.com

 

[Frank Bemelman]

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> schreef in bericht
news:fehtm0p011lqnriv09geb7iionsr0pfhhs@4ax.com...

On Thu, 14 Oct 2004 10:57:56 -0700, John Larkin
jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:

I have a TDS2012 on my desk, displaying RS232 poll/reply sequences for
a uP thing I'm testing. With no input, it has about 0.1 cm p-p noise
at most gain settings, increasing to 0.5 cm p-p at 2 mv/cm. The noise
appears, to me, to be a mixture of real front-end analog noise, adc
quantization, and lcd pixellization. Welcome to the digital age!

Sounds like a heap of shit. Why don't you use a good ol' classic
analogue scope like this one I rescued from a dumpster and shoved into
my garage for posterity:

http://www.burridge8333.fsbusiness.co.uk/oscilloscope.jpg

No quantization noise guaranteed!

You need to be a bit more convincing to make John want to
swap oscilloscopes with you

--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

 

[Georg Acher]

John Larkin <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> writes:
<scope noise>

I have a TDS2012 on my desk, displaying RS232 poll/reply sequences for
a uP thing I'm testing. With no input, it has about 0.1 cm p-p noise
at most gain settings, increasing to 0.5 cm p-p at 2 mv/cm. The noise
appears, to me, to be a mixture of real front-end analog noise, adc
quantization, and lcd pixellization. Welcome to the digital age!

The "cheaper" scopes use CCD shift registers and multiple ADCs for
sampling. That saves the exponentially increasing price for faster ADCs, but
introduces additional noise and common mode problems...

--
Georg Acher, acher@in.tum.de
http://wwwbode.in.tum.de/~acher
"Oh no, not again !" The bowl of petunias

 

[John Smith]

"Frank Bemelman" <f.bemelmanx@xs4all.invalid.nl> wrote in message
news:416eba55$0$10528$e4fe514c@news.xs4all.nl...

"John Smith" <kd5yikes@mindspring.com> schreef in bericht
news:iyybd.3079$6k2.2170@newsread3.news.pas.earthlink.net...
Hi -

I bought a Tek 468 which I returned today. I thought it had a problem,
but
the seller disagreed. I would like to know if I am wrong.

The 468 is an analog/digital scope. In the digital mode, I noticed that
the
trace had rectangular pulses on it of about .1 cm amplitude and
apparently
random in frequency and width. This was with the inputs grounded using
the
switch on the front panel. The amplitude of these pulses did not change
when
I changed the attenuator setting except at the three most sensitive
settings
of the attenuator (2 mV, 1 mV and .5 mV). Those three most sensitive
settings were active for digital storage operation only and were
non-functional in the analog mode.

When I complained about it, the seller said that it was caused by
quantization, it met Tek's specifications, and that .1 cm was entirely
reasonable. I disagreed because all waveforms appeared noisy so one would
never be able to tell whether the observed waveform was at fault or the
scope was at fault. In addition, .1 cm is 1 part in 80 for the vertical
displacement (8 cm vertical grid). It didn't seem right that maximum
resolution would be 1 in 80 or even 1 in 100. Logically, I felt that the
resolution would be 1 in 256 so that quantization noise would be much
less
than actually observed.

It is normal. The ADC's span is bigger than the 8 squares on the grid.
One-tenth of a grid square 'uncertainy' doesn't sound alarming. Of course
that 1-bit noise rides on top of everything. You also see this very clear
on a new LCD scope like a TDS220 or something. Perhaps less annoying with
these scopes, because it's fast realtime update tends to average it out,
sort of. But when you stop the aqcuisition, it is all over the place.


Maybe I understand nothing about scopes and digital stuff. But, I could
not
believe that Tek would sell such a product. Am I wrong?

Tek has sold more rubbish TAS220 for instance.

--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

It is disappointing to learn they produced such a piece of equipment.
Thanks, Frank, for the information.

John

 

[Clarence]

"Pol Guerin Ph.D" <photo@metrodiapo.com> wrote in message
news:434c7f63.0410140509.4fd4dd13@posting.google.com...

Dearest photographers,

Metroscope research group is inviting photographers to submit any
image of metros from around the world.

This is a great opportunity to get published since thousands of
images are required for the final publication.

for information info@metrodiapo.com

submission of images photo@metrodiapo.com

How much do you pay?

-----------------------
Only a fool works free!

 

[Clarence]

"Winfield Hill" <Winfield_member@newsguy.com> wrote in message
news:ckll0202fba@drn.newsguy.com...

xray wrote...
snip
I'd call this one close to a draw.

That's because you couldn't see GWB's stupid smirks, "grins" and drools.

Because there weren't any. But you didn't watch the debate did you?

Consensus of the media people who were in the hall was that Bush was "clearly
the winner" of this debate.

Not that it matters, in a poll before the first debate 90% of those polled said
the debates would not change their vote. It was a show, and not a very good
one!

 

[Rich Grise]

On Thu, 14 Oct 2004 10:36:53 -0400, Spehro Pefhany wrote:

On Thu, 14 Oct 2004 14:56:53 +0100, the renowned Paul Burridge
pb@notthisbit.osiris1.co.uk> wrote:

On 14 Oct 2004 06:09:07 -0700, photo@metrodiapo.com (Pol Guerin Ph.D)
wrote:

Dearest photographers,

Metroscope research group is inviting photographers to submit any
image of metros from around the world.

What's a "metro"?

Subway. Err..."Underground"/"Tube".

In some parts of the US, the Metro is buses or trolleys, or both.

When I was in the AF, a Metro was a blue bread truck.
In France, isn't it the sewer or something?

Cheers!
Rich

 

[CFoley1064]

I believe this is something close to what Mr. Pefhany is talking about.
Unless
you want to change something else, this should do the job (view in fixed font
or M$ Notepad):



+5V
|
.-. +5V
| | | +5V 1/4 4066
| | .-. | .-----.
'-' 1/2 LM393| | | | |
| +5V| | '---oI Oo-.
.-. |\| '-' | C | |
| |<--------|-\ | '--o--' |
___ | | | >-o-----------' |
.--|___|----. '-' .-----|+/ |
| +5V | | | |/| |
| | | | | -5V o--o
| |\ | | | | |
.---o---|H>O----' o-----------o +5V | |
| | |/ | | | | 1/4 4066 | .-.
| | | | | | .-. .-----. | | |
| --- | | .----o | | | | | | | |
| --- -5V | | | | +5V| | .--oI Oo-' '-'
| | 1/6 74C14 | | .-. | |\| '-' | | C | |
| | |=== | |<--|-----|-\ | | '--o--' ===
| | |GND | | | | >-o-----|-----' GND
| -5V | '-' '-----|+/ |
| | | |/| |
|------------------' .-. -5V -5V
| | 1/2 LM393
| |
'-'
|
-5V
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

Not elegant at all, but it will do the job. Split supplies, matched +/-5V.
H
is 1/6 of a 74C14, which should oscillate at the frequency you determine with
the R and C. DC level of oscillations should be nearly 0V. Amplitude of
oscillation with +--5V supplies with a C14 (don't use a 40106 or other CMOS
schmitt trigger IC -- they're made differently and have lower hysteresis
voltage and less precise switching points) should be about +2V to -2V. The
two
comparators pick off the signal from the cap, and are compared with the pot
settings. You can use those pots to set the time for +5V out (up to 50%) and
-5V out (up to 50%). These outputs go to half a 4052 or 4066, which are
analog
switches that turn on the +5V or -5V output. When neither is on, you have 0V
(resistor to GND).

One immediately apparent way to make this better would be to use a quad op
amp
instead of the dual comparator and the C14, to ensure symmetry around GND for
the oscillator and design in a fixed amplitude even if the supplies are not
matched. The OP is talking about a couple of KHz, so the rise time of a good
op amp shouldn't be too significant here. Use two of the other 4 op amps as
comparators, and lose the pullup resistors.

And, if you want the + part to be able to go to 100% or the - part to be able
to go to 100%, you'll have to play with the pots a little. This is the basic
idea, though. Oh, yes. As always, you can use a PIC to drive these outputs at
any duty cycle you choose. If you need some power, just connect a rail-to-rail
op amp as a voltage follower at the output.

Chris

 

[ChrisGibboGibson]

Joerg wrote:

[large snips}

Inverter manufacturers and solar panel producers would have to sit down
and see whether there is a longer term business model they could agree
on. However, they'd have to give up concentrating on how to make next
quarter's results look good.

Keep your eyes on Trace Engineering (yet another now part of Xantrex)

There is another problem too. I know this from experience. 80% of *first
time*
inverter users connect it up wrong and blow it up. The manufacturers have to
account for these "warranty" claims in the cost. The result being that they
have to still make a profit by giving one away for each unit sold.


That is either lack of consumer education or lack of circuit safeguards,
or both.

Well the owners manual stresses about reverse battery polarity on just about
every page so it can't be that! It still doesn't stop them doing it.

Warnings on battery cables, in the manual, red and black cables. They *still*
do it.

What can you do wrong with an inverter? After all, an inverter
only has two ports.

Plus remote sockets, cascade sockets, temperature sensor sockets. You have no
idea of the damage I have seen caused by some users.

Reverse input polarity? How many people place a car battery in
backwards? A nice big diode across and a breaker should be able to
handle that.

That's one of those solutions that seems simple. You should try that trick with
a 3kW inverter. It just don't work.

What spec diode (or rather bank of diodes) would you need to guarantee no
reverse voltage at the inverter greater than the body diode in the mosfets for
the time it would take to blow a fuse or circuit breaker on a 3kW inverter with
a surge rating of 9kW ?

That means the inline fuse (if correctely sized) must be able to pass about
1000 amps for 10 seconds.

How big would this "idiot"diode" (as we call them) be? Similar size to the
inverter? Bigger?

Yes, I have heard of people using inverters as transformers, hooking up
the output to mains and expecting 12V to come out the other side. Lack
of consumer education.

Known as a backfeed

This can also be handled with some failsafe
circuitry.

Which kinda answers my previous point.

The Prosine is protected against AC backfeed, but it's expensive, so people buy
the cheap ones which are not protected! Then complain when it blows up when
they backfeed it.

A 1000 watt inverter for 90 bucks is *not* the market price. That's a
surplus,
job lot price, probably end of run or bankrupt stock. It isn't even close to
the true price.


Costco sold these all summer. I believe that was similar in previous
years and Sam's Club had inverters in that range, too. Xantrex and
others. Usually those wholesalers don't deal in surplus, except when it
is their own overstock and then they display the regular price and the
sale price. That happens very rarely though.

Well I know what the real distributor price is from Xantrex and the price you
quote is well below it.

They also had lots of smaller models, like one 400W "brick" plus a
50-100W plug-in sold at a similar price in combo packs. The little
emergency pack I bought was about $100 five years ago when we had all
these rolling blackouts. It has a 300W inverter and a lead acid battery
in a handy mini-suitcase and came with a charger, cables for the car,
for hooking up a larger marine battery and all.

If your TV breaks it's no big deal. If your inverter breaks (I'm talking
about
units used to power remote homes or boats here) it can be a real problem yet
people still go out and buy the cheapest one they can find. Seems rather
silly
to me.


That's why I would always buy two units if it was really critical. That
results in great peace of mind, in the same way that I would never run a
business with one computer alone (although some people do that...).

Or buy an expensive inverter in the first place which has less chance of
failing!

Even Xantrex are now marketing some rubbish as well as their *real* units.


That would be dangerous. One big problem and a good reputation might be
toast. It can be hard to nearly impossible to recover.

I'd normally agree with that statement. But in the case of inverters, as you
yourself seem to agree, people buy the cheapest (including yourself).
Consequently it has become accepted that inverters blow up all the time. Only
the cheap ones do that.

An old reg on this NG used to work for Statpower and was heavily involved in
development of the ProSine. That unit took a team of 20 engineers over 18
months to develop. That is a *lot* of money to get back in sales. And they
can't do it by selling them at 5 bucks profit per unit because they still
wouldn't sell any more.


Agree. But sometimes I think that concentrating on just the top tier
segment of a market can stifle overall revenue.

Which is why they are now also selling junk.

My background is mostly
medical electronics and there it is often the same. Marketeers want a
better machine than the competition. In fact, often they want the best
machine that current technology can yield. Time and time again I try to
preach low cost approaches. In the end the market always shows where
companies flourish in the long term, by making technology available to
the broadest audience possible. In our case down to the lone doctor in a
rural practice where the majority of his or her clients is unable to
foot a huge medical bill. They need low cost equipment. My mantra is
that if we don't provide that, somebody else will and ultimately blow
the others out of the water. This is not based on my dousing rod or
something, I have seen many companies that went for too lofty goals
disappear.

Maybe I am too different but I experience the most fun not in designing
that super duper top notch golden machine. My fun is in designing
something that most of the market can afford.

Me too. The problem with inverters, and you have more or less borne this out,
is as follows..

People buy the cheap ones. They blow up.

They then complain that they should be protected against all sorts of user
abuse, then when a company produces such a device, customers ask "why are they
so expensive ?"

You see my point ?

Gibbo

 

[John Larkin]

On Thu, 14 Oct 2004 20:22:39 GMT, Bob Stephens
<stephensyomamadigital@earthlink.net> wrote:

I have a TDS2012 on my desk, displaying RS232 poll/reply sequences for
a uP thing I'm testing. With no input, it has about 0.1 cm p-p noise
at most gain settings, increasing to 0.5 cm p-p at 2 mv/cm. The noise
appears, to me, to be a mixture of real front-end analog noise, adc
quantization, and lcd pixellization. Welcome to the digital age!

John

I had a TDS2012 on my desk and the quiescent noise was so bad I called up
the metrology lab we use for a repair quote. They said that this is a known
problem with this series of 'scopes and that no one including Tektronix
will fix them. He maintained that it is a condition that worsens with age
rather than an inherent design flaw.

Bob

This one is a couple of years old, and I haven't noticed the noise
increasing. 1 mv p-p noise ain't at all bad for a 100 MHz scope; it
*does* go down to 2 mv/cm, which few analog bench scopes will do.
Heck, a cheap analog scope won't focus to better than 0.1 cm, and the
Tek will signal average up to x128, too.

I like it, anyhow.

John

 

[ChrisGibboGibson]

Joerg wrote:

Yes, same in medical. After all, doctors are not engineers and are

Ah well that's a help. Most of the people who use inverters *think* they are
engineers and they are the worst type of all for blowing things up.

usually under a lot of stress. So we anticipate all the abuse that we
ever heard of from the Service and QC folks and then redesign in
safeguards.

Which adds to the cost

Re the fuse....

No, it can blow and it should. But it needs to indicate that it did so
and spares must be available. Ideally versions you can by at the local
auto parts store.

You missed the point. In order for this hypothetical inverter to operate to
it's full spec, it's battery fuse must be able to pass 1000 amps for 10
seconds. Now what diode do you propose to use that will blow that fuse and
*never*, not even for 1 pS allow the voltage across it to exceed the voltage
drop of the body diodes in the inverter?

How big would this "idiot"diode" (as we call them) be? Similar size to the
inverter? Bigger?


It could also be a "sacrificial diode". As long as it can be purchased
as a spare at reasonable cost.

Refer to the above and show me one at reasonable cost that will pass 1000 amps
with less voltage drop than the mosfet body diodes for long enough to blow the
fuse.

Now that will add to the product cost
since the contact areas need to be rather huge.

The Prosine is protected against AC backfeed, but it's expensive, so people
buy
the cheap ones which are not protected! Then complain when it blows up when
they backfeed it.


Why is that so expensive? Can't it be a fast sense circuit which rapidly
opens the H-bridge?

Which is indeed what it is in the ProSine. In actual fact protection against
backfeed is almost inherent in this type of inverter and doesn't require *that*
much extra.

But in this case there is very large inductance between the IGBTs and the
output port which thereby slows the voltage rise time as seen by the IGBTs when
it is backfed.

That isn't the case in a modified sinewave inverter so no matter *how* fast you
make the sense circuit, the overcurrent on the IGBTs is instant. They blow at
the same time as the overcurrent circuit senses the problem.

The only way this can work is to increase the output impedance of the voltage
up converter, which thereby reduces the efficiency.

All these suggestions to protect the units are things we looked at 20 years
ago. There is *nothing* that hasn't been suggested, analysed, tried and then
finally rejected!

It took a while but meantime most RF transmitters
are pretty well protected against a sudden loss of antenna connection,

Again you have inductance to help.

It would be somehwhat more difficult to protect the transmitter output against
someone connecting it to another transmitter output with 100 times the power
capability, the same output voltage and an output impedance of about 1 ohm.
Which is a fair analogy to an AC backfeed.

Now think how much more dificult it would be if the original transmitter was
operating in class D.

Or buy an expensive inverter in the first place which has less chance of
failing!


Well, even the most sophisticated equipment can fail. If failure can
cause great harm or losses then I'd always want a spare. Just as I don't
go over a mountain pass, or pretty much anywhere, without a spare tire.
Murphy says that even the best inverter could fail and that if it ever
does it will be on a Saturday afternoon.

Indeed. Which is why have 2 on my boat!

I'd normally agree with that statement. But in the case of inverters, as you
yourself seem to agree, people buy the cheapest (including yourself).


Guilty.

Consequently it has become accepted that inverters blow up all the time.
Only
the cheap ones do that.


I never had one blow up.

But you're not likely to connect it to the batteries the wrong way round, or
backfeed it, or connect a heart interface remote panel to a prosine. Or plug a
temperature sensor into the remote panel, or fill it with salt water etc etc
etc

These are things that get done.

Try a *variable speed* electric drill on it. Don't come asking me to help when
it blows up

I see the point. But the cost delta between high end and low end does
not have to be more than 10dB ;-)

It will remain so as long as customers in general buy the cheap ones. When they
finally realise that the expensive ones *are* better the prices will fall even
faster than they already are doing.

I personally would prefer 20dB difference

Gibbo

 

[john jardine]

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message

Sounds like a heap of shit. Why don't you use a good ol' classic
analogue scope like this one I rescued from a dumpster and shoved into
my garage for posterity:

Looks like the same one I threw in 10 years ago
regards
john

 

[Ken Smith]

In article <ck9gtm$2hvl$10@news.iquest.net>,
John S. Dyson <toor@iquest.net> wrote:

In article <ck9022$q9g$5@blue.rahul.net>,
kensmith@green.rahul.net (Ken Smith) writes:
In article <ck7mus$21bn$1@news.iquest.net>,
John S. Dyson <toor@iquest.net> wrote:
[...]
paying an emotional price for their support of the very lousy traitor
against America, John Kerry.

Please define how you can consider Kerry a traitor and not Bush.

Kerrys', actual personal participation in war crimes and telling lies against
military people.

Site please! I'd love to see you try to prove that this is anything but
more BS spread by the right wing nuts. Go read the actual word Kerry said
and the actual record and you will find something very startling.

There is no evidence against Bush.

So you dispute the existance of the Robert Novak article where he stated
the name of the CIA agent and where he got it. Do I have to spell it out
for you?

Kerry has personally
provided enough evidence that he should be disgraced in jail.

Kerry made statements that when taken completely out of contexted you
could perhaps consider such evidence. If you see what he really said and
the surounding context you will find that this claim that the right wing
nut cases keep bringing up is totally bogus.


--
--
kensmith@rahul.net forging knowledge

 

[Clarence]

"Winfield Hill" <Winfield_member@newsguy.com> wrote in message
news:ckm0t10ghd@drn.newsguy.com...

Fred Bloggs wrote...

Once again- another HUGE group, instrumental in government policy
making, warns America to oust Bush:


October, 2004

An Open Letter to the American People:

We, a nonpartisan group of foreign affairs specialists [ snip ]

Now it's "Non-Partisan!

Like anyone cares what a bunch of partisans say.

 

[Dirk Bruere at Neopax]

Scott Stephens wrote:

Dirk Bruere at Neopax wrote:

Rich Grise wrote:


I'd even take a mere moronic fuckup. There's intentional death and
destruction going on, and GWB seems to be the figurehead. I'm really
saddened that doublethink has got so bad that people can convince
themselves that long-distance murder has anything to do with "defense."



Half the population is below average intelligence, and the other half
are mostly fools. They are busy building the future they deserve.


The history of the human race is that of one armed nation taking what
they want from a weaker nation. "The strong do as they will, the weak
suffer what they must".

Our government makes cheap excuses about WMD and such, but its about oil
and military dominance of where oil comes from.

And the reason we peasants are not informed of this fact, is because the
class-structure is based on an aristocracy which keeps its peasants
enslaved with altruistic lies about "freedom", "morality", "human
rights", "God".

Right. Dummies and fools getting what they deserve.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[mike]

Durall wrote:

I understand that a flip-flop will toggle between states when a button
is pressed. I'd like to know though, will it hold state with NO power?

I have an led that I'd like to power with 4 'D' batteries. The first
time that I push the button, I'd like the LED to stay on. The second
time that I push the button the LED will go off. The Flip-flop circuit
will lose power too. The next time I push the button, I'd like the LED
to flash, say 3 times/second. 4th Push, off again. Circuit loses power
again. Goto first push.

Should I just step away from the soldering iron and get some fresh
air?

Gotta have some memory somewhere. Mechanical switch memory,
semiconductor memory, past-life memory...
Use a low power flip-flop and leave it powered on all the time.
Use a PIC processor or similar. One part, got the memory and everything
you need except the light driver.
mike

--
Return address is VALID.
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
http://www.geocities.com/SiliconValley/Monitor/4710/