Driver to drive?

[Paul Burke]

Frank Bemelman wrote:

I was afraid someone would suggest that. Thank heavens it
is not very important. For some silly reason, I don't like
555's. There no explanation, alas.

Hear, hear! Along with PICs- the number of jobs I lost eight or ten
years ago because I quoted a "proper" micro, when the opposition quoted
a PIC- the fact that the end result didn't do the job was no help, the
customer had spent the budget by then!

But 555's- I think I've told you about the Electronics GCSE (16 year
olds' exam) - two papers ALL concerning 555s- they didn't expect you to
know Ohm's Law, but you DID have to know the 555 equations!

Paul Burke

 

[Frank Bemelman]

"Clarence" <no@No.com> schreef in bericht
news:Ujidd.16248$nj.15005@newssvr13.news.prodigy.com...

Hassan wrote:
Hello;
I want to design a switching power supply with:
Vin=24 Vdc and Vo=15V @ 7A

Did you get my schematic?
Is it along the lines of what you wanted?

Of course it isn't what he wanted. He wanted:

I am looking for a switcher IC something like LM2678 with integrated
controller and Power Mosfet. But LM2678 has a maximum current
limitation of 5A. Does any body know an IC which I can use for this
project? I mean something with a controller and power Mosfet just
in a package.

For a better understanding, just look at these lines:

project? I mean something with a controller and power Mosfet just
in a package.

Notice the important part:

controller and power Mosfet just in a package.

Which probably means:

"just in one package".

"one" as in "single".

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

 

[Tony Williams]

In article <2tmi34F21dppeU1@uni-berlin.de>,
Paul Burke <paul@scazon.com> wrote:

Frank Bemelman wrote:
I was afraid someone would suggest that. Thank heavens it
is not very important. For some silly reason, I don't like
555's. There no explanation, alas.

[snip]

But 555's- I think I've told you about the Electronics GCSE (16
year olds' exam) - two papers ALL concerning 555s- they didn't
expect you to know Ohm's Law, but you DID have to know the 555
equations!

Come on chaps...... there's no shame in using a 555, and
it was designed to do exactly the sort of thing that Frank
needs to do.

Frank is muttering about using a comparator, etc. Come
on now, there's a comparator built into the 555, complete
with a 2/3Vcc Vref, R-S flip-flop for clean switching, and
an output stage. What more could you want?

--
Tony Williams.

 

[James Arthur]

On 10/15/04, Jonathan Kirwan jkirwan@easystreet.com wrote:

On 15 Oct 2004 16:56:43 -0700, soar2morrow@yahoo.com (Tom Seim) wrote:

Kerry either committed war crimes, as he testified to and makes him a
war criminal; or he didn't, in, which case, he lied under oath
(another crime).

Your assumption is wrong, your logic unsound, your conclusion meaningless.

John Kerry spoke to the Senate Committee of Foreign Relations on April 23rd,
1971, speaking as a representative of the Vietnam Veterans Against the War.
He
was selected as their representative.

His testimony is here:


http://lists.village.virginia.edu/sixties/HTML_docs/Resources/Primary/Man
ifestos/VVAW_Kerry_Senate.html

Feel free to find where he makes a personal admission about committing war
crimes or otherwise violates an oath to tell the truth. (An oath, by the
way,
that G. Bush and Cheney recently both refused to take, while others
testifying
had to.) He spoke as the VVAW representative and spoke in the collective
'we.'
Something that is patently obvious when you read his testimony and was
similarly
obvious to those listening at the time (as I was.)

He did not testify to committing war crimes. Without some other evidence
(which
you do not present), he hasn't admitted to being a war criminal. I've seen
no
evidence presented by you that he lied under oath, either. Sadly, this kind
of
poor thinking process of yours is too often taken for rationality. It's not.

I'd recommend that you present some other evidence to make your point,
because
your comment is quite simply unsound as it stands.

Jon

It wasn't testimony, but I suspect the poster(s) are referring to John
Kerry's
4/18/04 appearance on Meet The Press:
http://msnbc.msn.com/id/4772030

Searching the transcript for "videotape" will call up the relevant remarks.

Either this, or perhaps his 6/30/71 debate with John O'Neill:
rtsp://video.c-span.org/project/c04/c04_rwh081504.rm

James

 

[Klaus Vestergaard Kragelu]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:96_cd.32220$QJ3.13449@newssvr21.news.prodigy.com...

Hi Genome,

There used to also be a "CMOS cook book", similar to the TTL cook book
but I never had a copy myself. That had tons of tricks with CD chips in
there. An application note that might interest you would be National's
old AN-88. It explains the use of CMOS logic chips (not Schmitts, of
course) for linear amplification purposes. I believe it's not on their
server anymore but probably TI, ON Semi or Fairchild have similar app
notes.

This old 4000 logic series is marvelous when the task is to drive some
circuitry to rock bottom cost. It also enjoys a great longevity and
might even surpass the VW Beatle since they recently came out with tiny
packages a little over half the SO footprint.

Yes - they have been launched in the TSSOP footprint (5x6mm).

Sorry to say my favorite low price part, the CD4093 is only available from
TI in this package. The other manufactors still use SO14. I asked them and
they said the die was too large to fit inside the TSSOP. Maybe TI has some
"shrinking" equipment they havent

Cheers

Klaus

 

[legg]

On 18 Oct 2004 20:57:18 GMT, bobgardner@aol.comma (BobGardner) wrote:

They always told me 'there is no such thing as peak to peak voltage'. At one
instant, there is a positive peak voltage, and at some other instant, there is
a negative peak voltage, but the voltage is a function, and only has one value
at an instant in time. Now lets argue about whether the product of rms voltage
and rms current is rms power or average power.....

non sequitur

Look it up the definition.

Also check "peak and random deviation" (PARD).

RL

 

[HoloBarreŠŽ]

"James Beck" <jim@reallykillersystems.com> wrote in message
news:MPG.1bd85b93336243fc989a2a@news.west.earthlink.net...
In article <ckloqo$ftq$1@nrc-news.nrc.ca>, pat.ford@nrc.ca says...

"HoloBarreŠŽ" <physical@erols.com> wrote in message
news:bPSdnU44tcV-bvDcRVn-og@rcn.net...
All--

I'm interested in measuring vehicle miles per gallon, based on
the
odometer signal and the fuel injector signals, which are all available
at
the engine's ECM (electronic control module). Flowmeters are the
benchmark
for such measurements, but for multi-cylinder vehicles, a real invasive
(plumbing) nightmare.
One representative fuel injector's signal would seem to be the
best
and least invasive compromise--not an absolute measure of true mpg's,
but
likely a very accurate "relative" indicator, good enough for my
purposes,
which could be pretty well calibrated over time.
I presume I would need some spec's from the auto mfr (nissan,
in
this case), but it's tough getting past Customer ""Service"".
Any ideas on how to obtain specs? To proceed in general? I
don't
think the workshop manual would help w/ this type of info, but then....
Knowing the array of diagnositc equipment for a vehicle might
help, so maybe a well-equipped svc. dept might help.
Any leads would be greatly appreciated.
----------------------------
Mr. P.V.'d



try asking on some of the Nissan tech lists about the #per hour of the
injectors ( or CC/minute) count the on time of the injector. Multiply the
two to get comsumption per time, then get the speed ( tap into the speed
ref
for the cruise control)
Pat

That will work as long as his fuel pressure regulator is exactly within

spec. The injectors are going to be rated at VOL/TIME @ a specific fuel
pressure. I guess you might come pretty close, but as the regulator
ages and the pressure drifts, it is anyones guess. Also, as the
injectors age and get worn and dirty the computer will adjust the on
time to keep the mix correct as far as emmisions are concerned, that
will cause errors if just on time is used. Once again, I have never
tried it, so the data might be close enough. 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.

Jim
-----------------------

Even here, you are calculating a relatively small flow *difference*
from relatively large flows--from what I've read. If a clear fuel line "tap"
was evident, then you could use just one flowmeter. And flowmeters are not
cheap! And the plumbing is still considerable.
What you say about injectors is exactly true, but likely still the
best compromise. Thus, tapping off existing ports seems to be the
expeditious way to go.
I appreciate everyones' insights!

However, as I barely grokked the theory of tube amps, I would need
someone skilled in the nitty gritty of counters, PICs, etc. to do this--on
my car. Would local EE grads/undergrads be capable of undertaking this?

Would there be advantages, either way, to taking the odometer
pulses before the processor (right off the wheel), or the signal after the
processor (on its way to the LCD)?

FYI, according to Nissan, they calc THEIR mpgs by sensing the
height level in the fuel tank!! Flow sensor indeed!!!!
----------------------------
Mr. P.V.'d

 

[James Arthur]

I wrote:

Either this, or perhaps his 6/30/71 debate with John O'Neill:
rtsp://video.c-span.org/project/c04/c04_rwh081504.rm

Warning: this is a link to a *very long* video of the Dick Cavett Show of that
date.

O'Neill indicates that he feels Vietnam vets had been defamed,
unjustly accused by Kerry of war crimes, and tries to make the
case that by his participation Kerry himself ought then be guilty
of the same. No frank admissions thereof were forthcoming,
however -- Kerry was unclear.

Much time could be saved by Googling for the transcripts,
although these are not as informative -- significant emphases
and inflections are lost.

James

 

[Frank Bemelman]

"Tony Williams" <tonyw@ledelec.demon.co.uk> schreef in bericht
news:4d00c029cftonyw@ledelec.demon.co.uk...

In article <2tmi34F21dppeU1@uni-berlin.de>,
Paul Burke <paul@scazon.com> wrote:

Frank Bemelman wrote:
I was afraid someone would suggest that. Thank heavens it
is not very important. For some silly reason, I don't like
555's. There no explanation, alas.

[snip]
But 555's- I think I've told you about the Electronics GCSE (16
year olds' exam) - two papers ALL concerning 555s- they didn't
expect you to know Ohm's Law, but you DID have to know the 555
equations!

Come on chaps...... there's no shame in using a 555, and
it was designed to do exactly the sort of thing that Frank
needs to do.

Frank is muttering about using a comparator, etc. Come
on now, there's a comparator built into the 555, complete
with a 2/3Vcc Vref, R-S flip-flop for clean switching, and
an output stage. What more could you want?

You are absolutely right of course. It's not a matter of shame,
if it were, I would sand off the number There are two parts
that I don't like. 555's and zeners. I fully admit that such is
utterly stupid.

Now I have to look at the circuit made by Fred.

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

 

[James Beck]

In article <T5mdnTo2SJGTPfPcRVn-sg@rcn.net>, physical@erols.com says...

-----------------------

Even here, you are calculating a relatively small flow *difference*
from relatively large flows--from what I've read. If a clear fuel line "tap"
was evident, then you could use just one flowmeter. And flowmeters are not
cheap! And the plumbing is still considerable.
What you say about injectors is exactly true, but likely still the
best compromise. Thus, tapping off existing ports seems to be the
expeditious way to go.
I appreciate everyones' insights!

However, as I barely grokked the theory of tube amps, I would need
someone skilled in the nitty gritty of counters, PICs, etc. to do this--on
my car. Would local EE grads/undergrads be capable of undertaking this?

Would there be advantages, either way, to taking the odometer
pulses before the processor (right off the wheel), or the signal after the
processor (on its way to the LCD)?

FYI, according to Nissan, they calc THEIR mpgs by sensing the
height level in the fuel tank!! Flow sensor indeed!!!!
----------------------------
Mr. P.V.'d


My wifes car does a similar thing with MPG and Range estimations.

I have found that they REALLY stretch the estimation at times.
If that kind of accuracy is OK then go with it. You never mentioned any
design accuracy constraints, so I was just going with what I thought the
most accurate way was that wasn't going to be too affected by outside
factors.

Jim

 

[John Larkin]

On Thu, 14 Oct 2004 19:37:49 +0100, Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote:

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!

Why not?

Color
Infinite storage
Expansion and panning of stored traces
Measurement cursors
A 545 wouldn't fit on my desk
A 545 would be hard to carry up the stairs
It's warm in my office already

I like the 545B. I have one or two, I forget. It's a classic 545 with
transistors replacing many of the tubes, especially the vertical
distributed amplifier.

See pic in abse.

John

 

[Winfield Hill]

John S. Dyson wrote...

Actually, Carter wasn't really as much a mass murderer as incompetent
as president. Re-electing him would have no justification. Otherwise,
there has been no 'religious' freak as president in recent years. (Of course,
there are those, like Bush, who aren't shy about their religion, but also
who don't advocate other people having the same religion as him.) If
anything, there is apparently a movement to REPRESS Bush by condemning him
almost whenever he mentions his faith. (When someone mentions that they
pray for guidance, that shouldn't be deemed as being an imposition on you --
unless you are overly sensitive.) The biggest 'evangelist' group here
in the US appears to be those who are 'evangelizing' against religion.

This one appears to be a special case.
http://www.nytimes.com/2004/10/17/magazine/17BUSH.html


--
Thanks,
- Win

(email: use hill_at_rowland-dotties-org for now)

 

[Frank Bemelman]

"Fred Bartoli"
<fred._canxxxel_this_bartoli@RemoveThatAlso_free.fr_AndThisToo> schreef in
bericht news:417628ce$0$29540$626a14ce@news.free.fr...

"Frank Bemelman" <f.bemelmanx@xs4all.invalid.nl> a écrit dans le message
de

I figured the capacitors would avoid sporadic actions. But I think
I forget the entire circuit. I knew I am not good with discrete
transistor stuff, and now I know it again


Hi Frank,

Why not this simpler one ?

OPTO
SW ___
.---o/o---+---------+---------|___|--.
| | | |
| | --- |
| | --- 100n |
| | | |
| | | ||-+
--- | | ||<-
- 9V | +------+------||-+ 2N7000/7002
| | | | |
| .-. | .-. |
| | | Z | | |
| | | 12V ^ | | 470K |
| '-' | '-' |
| | | | |
| | | | |
=== === === === ===
GND GND GND GND GND

created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

The RC time constant with the mos threshold gives you the pulse width.

That doesn't look bad at all. I think I can replace the zener with
a diode. I just confessed a minute ago that I hate zeners I'll
try it with this one, thanks!

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

 

[CFoley1064]

Subject: Re: Want independant pulse width variation on + and - side of
gnd;square wave of about 1kHz
From: Spehro Pefhany speffSNIP@interlogDOTyou.knowwhat
Date: 10/14/2004 1:58 PM Central Daylight Time
Message-id: <j4htm09e04voj3s78495417k3ip0o5sd47@4ax.com

<snip>

Yes, but how would I get a (say) drop from ground to -5V lasting for
1/4000th second , returning to 0V for 1/4000th second (1/2 cycle of 1kHz at
50%) followed by (say) a rise from 0V to +5V lasting for 1/8000th second,
returning to 0V for 3/8000ths of a scond (1/2 cycle of 1Khz at 25%)?

Okay. If you use a single 555 in astable mode you can steer the
currents through both ends of your two pots to get this effect by
using a FF (eg. 1/2 4013) and 2 complimentary pairs of transistors.

Driving the output to the 3 levels depends on how much drive you need.
One possibility would be to use 1/2 of a 4052. It could also be done
with discretes.


Best regards,
Spehro Pefhany

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.

Oh, yes, and would you like fries with that?

(Note the trouble you can get yourself into on newsgroups while you're waiting
for a customer to call.)

Good luck
Chris

 

[Clarence]

"Frank Bemelman" <f.bemelmanx@xs4all.nl> wrote in message
news:4176182c$0$34762$e4fe514c@news.xs4all.nl...

"Clarence" <no@No.com> schreef in bericht
news:Ujidd.16248$nj.15005@newssvr13.news.prodigy.com...

Hassan wrote:
Hello;
I want to design a switching power supply with:
Vin=24 Vdc and Vo=15V @ 7A

Did you get my schematic?
Is it along the lines of what you wanted?

Of course it isn't what he wanted. He wanted:
I am looking for a switcher IC something like LM2678 with integrated
controller and Power Mosfet. But LM2678 has a maximum current
limitation of 5A. Does any body know an IC which I can use for this
project? I mean something with a controller and power Mosfet just
in a package.

For a better understanding, just look at these lines:

project? I mean something with a controller and power Mosfet just
in a package.

Notice the important part:

controller and power Mosfet just in a package.
Which probably means:
"just in one package".
"one" as in "single".

Gee, I thought he wanted something that worked! The circuit meets the
electrical specification.

But the circuit from Linear CAN be put in ONE package! At 95% efficiency
(predicted) makes it reasonable to put it in a rather small foot print. Also,
he will still need the support circuitry and filter Caps so it is not a lot
different.

Since you are not an Engineer I guess you wouldn't know there are few to none
which can handle a 14 ampere bilateral switch in one IC package. Cost and
power are both high.

I'll wait for the OP to decide.

BTW, I have used a lot of LM2678's.

 

[Fred Bartoli]

"Frank Bemelman" <f.bemelmanx@xs4all.invalid.nl> a écrit dans le message de
news:41763f2c$0$78753$e4fe514c@news.xs4all.nl...

"Fred Bartoli"
fred._canxxxel_this_bartoli@RemoveThatAlso_free.fr_AndThisToo> schreef in
bericht news:417628ce$0$29540$626a14ce@news.free.fr...

"Frank Bemelman" <f.bemelmanx@xs4all.invalid.nl> a écrit dans le message
de

I figured the capacitors would avoid sporadic actions. But I think
I forget the entire circuit. I knew I am not good with discrete
transistor stuff, and now I know it again


Hi Frank,

Why not this simpler one ?

OPTO
SW ___
.---o/o---+---------+---------|___|--.
| | | |
| | --- |
| | --- 100n |
| | | |
| | | ||-+
--- | | ||<-
- 9V | +------+------||-+ 2N7000/7002
| | | | |
| .-. | .-. |
| | | Z | | |
| | | 12V ^ | | 470K |
| '-' | '-' |
| | | | |
| | | | |
=== === === === ===
GND GND GND GND GND

created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

The RC time constant with the mos threshold gives you the pulse width.

That doesn't look bad at all. I think I can replace the zener with
a diode. I just confessed a minute ago that I hate zeners I'll
try it with this one, thanks!

Try to overcome your gut feels about zeners. Here, it prevents you from
zapping the Mosfet grid with ESD.

Oh, I could have added a series resistor to improve ESD handling.

OPTO
SW ___
.---o/o---+---------+---------|___|--.
| | | |
| | --- |
| | --- 100n |
| | | |
| | | ||-+
--- | | ||<-
- 9V | +-10K--+------||-+ 2N7000/7002
| | | | |
| .-. .-. | |
| | | | | Z 12V |
| | | | | ^ |
| '-' '-| | |
| | | | |
| | | | |
=== === === === ===
GND GND GND GND GND

--
Thanks,
Fred.

 

[Joerg]

Hi Chris,

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.


That's true. Also, most people's confidence level is usually

proportional to the blood alcohol content. Especially when out in the
woods where being macho is cool ;-)

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


Not always if we think out of the box. Isolation barriers are an

example, in case somebody applies a defibrillator without disconnecting
diagnostic equipment. I'd consider that a panic reaction which must be
expected. If provided that used to be done with terribly expensive iso
amps. Then I convinced a client to roll our own and it went from way
over a hundred Dollars to just a few.

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?


If you provide some LC, just a little, maybe you don't need a picosecond.

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.


It's been too long ago that I used big Schottkys. One was I believe from

Ixys' DSS series. A monster of a diode that came in a flat pack and
needed to be bolted down. I think it was 400A and had two diodes. But it
may be too expensive here. One of the guys actually commented that it
was "puny". He had worked in surge protection for power plants...

I don't know if this can be done: A crowbar solution around the LTC4412
power path controller? The challenge would be to supply it fast enough
though and that alone might rule it out in an inverter.

Ok, how about this low-tech solution: A sizeable automotive relay. Wrong
polarity - no turn on. It could even light an LED, telling the user that
it would be nice to swap the leads A few hundred amps over a relay is no
big deal and they aren't even that voluminous. It should beat the
Schottky in terms of cost.

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.


But a little inductance should not cost that much since this is the low

current side. Then again in modified sinewave every penny counts.

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.


Usually there is just that big toriod push-pull transformer. Not much

inductance there. But you are right, feeding RF power into a turned off
unit will probably cause an impressive kablouie.

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


They were usually class C.

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.


Well, I try to treat it with the same respect as my car. I don't throw

that into 2nd gear either when doing 65mph.

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


Actually, I did run a variable speed Milwaukee Sawzall for quite some

time on a mod-sine unit. I held my breath for the first few seconds but
I had no choice. The only problem was that the overload tripped whenever
I pushed too hard on the blade because the inverter wasn't quite rated
for that big saw.

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.


The two sides have to meet somewhere in the middle. Then there needs to

be some education in the advertising material, plus other publicity.
That's how Honda or Toyota got to command a much higher price for a
sedan than some other brands. People realized that you do get what you
pay for, that there are no free lunches.

Regards, Joerg

http://www.analogconsultants.com

 

[Paul Burridge]

On Tue, 19 Oct 2004 22:06:58 -0700, "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

I was thinking of using the common HAM method of winding a wideband RF
transformer, bifilar to give 4:1, but turn it so that it's 12.5 ohms
load on the output stage. Like this.
http://www.g3ycc.karoo.net/linear1.htm
More of his stuff here
http://w1.859.telia.com/~u85920178/

Here's another cheap RF transistor:
http://members.tripod.com/~malzev/comp/2sc1971.htm

That's one of those old CB PA trannies, isn't it? Is it really good
for 6W @ 175Mhz? The 2SC1972 looks nice, too. Bit more guts.
--

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

 

[Rich Grise]

On Thu, 14 Oct 2004 11:22:33 +0100, Paul Burridge wrote:

On Thu, 14 Oct 2004 07:51:32 GMT, Rich Grise <null@example.net> wrote:

Um, please don't slap me, but I think the ampersand means, "and", and the
"in parallel" sign means "in parallel". It's a sentence, telling you that
the voltage at Vin is voltage-divided from Vcc by R1 and R2, and the
effective base input resistance for the signal is the value of the two
resistors in parallel, because from the signal's POV, Vcc and ground are
the same point. This would be the "input impedance" of the circuit, which
is the load seen by the driving source.

Rich, I may be full of sh*t (it has been known) but AIUI (or not) the
overall input impedance of the stage is R1||R2||ZQ where the last term
is the input impedance of the tranny (approximately Beta x Re+RE)
where Re is the dynamic resistance of the B/E junction and RE is the
emitter resistor (where used). Of course, I stand to be corrected (as
usual).

Yes, you're absolutely right. I'm real shaky in that aspect of knowing
what a circuit is doing; to me it's kind of a "black box." But yes,
the input impedance is as you've said; maybe Rb then only means the
effective base bias resistance, or something like that. Like in almost
everything else, I've learned just enough to sling some bullshit and
get in trouble. ;-)

Cheers!
Rich

 

[Dirk Bruere at Neopax]

Mochuelo wrote:

On Thu, 14 Oct 2004 19:40:54 -0700, "Tom" <tom_cip_nospam@msn.com
wrote:


Hi,

Sorry for the off topic post, but I have been a EE for almost 25 years and I
figured that someone at this NG would have an answer. I pretty much don't
even look at other NGs.

I would like to use software for p2p file sharing. However, my experience
with the software that I have used is very negative. I made the serious
mistake of using Kazaa, through which I downloaded "Limewire". This turned
out to be one of the biggest mistakes of my life.....right up there with my
first wife. Not only could I not download anything, spyware and viruses were
downloaded to my machine faster than my antivirus software could eradicate
them. What a fiasco. I then tried KazaaGold, which did not have the spyware
but again, I was unable to download any of the programs that it supposedly
found.

There must be some decent file sharing software out there. Please send some
recommendations.

Thank You
Tom

tom_cip_11551@hotmail.com





eMule is the best one I've ever used. No spyware/adware/crapware, and
it is free.
http://www.emule-project.net

Or fully encrypted with http://freenet.sourceforge.net/

--
Dirk

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