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Sine to square wave converter
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Stanislaw Flatto
electronics forum addict


Joined: 10 Sep 2005
Posts: 74

PostPosted: Mon Aug 21, 2006 7:21 pm    Post subject: Re: 240V relay contact suppression Reply with quote

MarkMc wrote:
Quote:
Hi

I'm using a relay with 240VAC coil and 240VAC contacts. From what I've
been advised before with relays (not 240VAC), I understand it's a good
idea to protect the contacts with a capacitor and possibly a MOV like
below;

Is this required for AC and is it a good idea to have a MOV?

If the relay is just replacement of manual switch for equipment designed
for line supply then don't improve on it. If the load is sensitive then
add whatever is needed.
Quote:

Also, I assume I need do nothing on the coil side, seeing as it's AC?

Right.

Quote:
Normally, I'd expect a reverse biased diode in there somewhere.

What is "normally"? On DC the diode allows (shorts) the magnetic field
for faster collapse and faster opening of the contacts to eliminate
"welder" spark between them. On AC the spark can at max be 10msec.(50Hz)
till next zero voltage crossing of the line.
Quote:

Regards,
Mark

Cheers

Stanislaw
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Don Bruder
electronics forum Guru Wannabe


Joined: 03 May 2005
Posts: 190

PostPosted: Mon Aug 21, 2006 7:21 pm    Post subject: Re: Transmitter Reply with quote

In article <1156174020.849603.234990@75g2000cwc.googlegroups.com>,
"Chris" <cfoley1064@yahoo.com> wrote:

Quote:
Don Bruder wrote:
Not a phase modulator, Pinky, A Uranium Q-38 Explosive Space Modulator!
There'll be such an Earth-shattering KABOOM, we'll finally be able to
TAKE OVER THE WORLD!

Uh... Sounds good, Brain, but how are we gonna get the fish into those
little-bitty rubber pants?

--
Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my
whitelist,
or the subject of the message doesn't contain the exact text
"PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without
my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more
info

Hi, Don. It's an Illudium Q-36 Explosive Space Modulator .

Only on Mars, ya sawed off little twerp! Down here on earth, we long ago
abandoned that primitive technology. Sheesh... Get with the times,
wouldja???

Quote:
That makes me sooooo angry! Smile

Anger-management classes will help that, I'm told... And if something
like that gets yer cute lil' iron panties in a wad, stay away from
wascally wabbits! They'll make ya blow a gasket fer sure! :)

--
Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info
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Eeyore
electronics forum Guru


Joined: 22 Jun 2006
Posts: 642

PostPosted: Mon Aug 21, 2006 8:13 pm    Post subject: Re: Tape heads, how do they work Reply with quote

"Michael A. Terrell" wrote:

Quote:
Eeyore wrote:


These machines used DC bias.

That would make the frequency response even worse.

It was miserable anyway.

Graham
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Abstract Dissonance
electronics forum Guru


Joined: 22 Dec 2005
Posts: 380

PostPosted: Mon Aug 21, 2006 10:20 pm    Post subject: Re: +/- supply frm single chip Reply with quote

<aaryaluv@gmail.com> wrote in message
news:1155971157.258232.25390@i3g2000cwc.googlegroups.com...
Quote:
i m doin 1 project where i need 2 supply power 2 ADC AD677 ... i need
+/- 5/12 volts..i want this all frm single chip instead of using
7805,7812,7905 & 7912.

can u help me


I'm curious. Would it be possible to use a voltage divider and an
optoisolator to get the +/- supply?
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default
electronics forum Guru Wannabe


Joined: 03 May 2005
Posts: 175

PostPosted: Mon Aug 21, 2006 10:42 pm    Post subject: Re: Trouble With A Very Simple MOSFET Amplifier Reply with quote

On 20 Aug 2006 13:44:45 -0700, "phaeton" <blahbleh666@hotmail.com>
wrote:

Quote:
Well, ok...

Turns out it *does* work with the IRF510. However, it's just not
powerful enough to drive a speaker. After switching a few speakers
around (went from 8ohm to 4ohm) i got brave and plugged a set of
headphones into it. It amplifies, but it's only 'audible' with
headphones. I put a single BJT booster stage in front of it, and while
it distorted a little bit, it didn't really get any louder, so it's a
'headroom' thing, i presume.

Would increasing the supply voltage from 9V up to say, 12V or 18V give
it more 'power', or should I look elsewhere? Will higher voltages
change the biasing requirements?

I expected this to be roughly the same volume level as the LM386 1/2W
chipamp (a fun little device, IMHO). Is that about right?

Thanks.

-Phaeton

There are much better designs than that one. You can't just keep
pushing more DC current through a speaker and expect it to sound good.

In addition to the LM386, National has several higher power amps that
aren't too hard to apply, and at least one or two TO220 case five lead
power op amps with pretty good specs (lots of gain and power output).

I believe a one or two transistor device could easily amplify your 100
mv signal - but with single ended class A you need to match the
impedance to the speaker better (like with a stepdown transformer -
which also keeps the DC off it) or at least a design that uses a
coupling cap to keep DC off the speaker.



----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
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mea305
electronics forum beginner


Joined: 21 Aug 2006
Posts: 15

PostPosted: Mon Aug 21, 2006 10:44 pm    Post subject: Will a Gas Operated Generator Work? Reply with quote

Concerning the use of the macerator, would a gas-powered generator
work? There is a receptacle for 12 VDC, and on the bottom of the
outlet, it appears that the outlet produces 8Amps (designated with 8A).
If this unit works, will it be safer than using the DC power supply
with an automotive battery?

Thanks,

Mark
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Stanislaw Flatto
electronics forum addict


Joined: 10 Sep 2005
Posts: 74

PostPosted: Mon Aug 21, 2006 10:44 pm    Post subject: Re: 240V relay contact suppression Reply with quote

John Fields wrote:

Quote:
Actually, no.

The diode provides a path to Vcc for the high-voltage spike
generated when the relay driver turns off, in order to protect the
driver. The price, though, is that the current won't only flow
through the diode, it'll also flow through the coil (since that's
where it comes from) until it's dissipated to the point where it can
no longer hold the armature closed. That means that the relay will
stay closed longer than if the diode wasn't there, but the driver
won't be destroyed.



Too modern for me. What "driver"?
~1960 AD working on telephone exchanges, relay technology, diodes(?),
were called rectifiers then, selenium plates, and were used (rarely!)
to improve responses by allowing faster collapse of the magnetic field.
Anything changed since?

Have fun

Stanislaw
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Eeyore
electronics forum Guru


Joined: 22 Jun 2006
Posts: 642

PostPosted: Mon Aug 21, 2006 10:49 pm    Post subject: Re: +/- supply frm single chip Reply with quote

Abstract Dissonance wrote:

Quote:
aaryaluv@gmail.com> wrote in message
news:1155971157.258232.25390@i3g2000cwc.googlegroups.com...
i m doin 1 project where i need 2 supply power 2 ADC AD677 ... i need
+/- 5/12 volts..i want this all frm single chip instead of using
7805,7812,7905 & 7912.

can u help me


I'm curious. Would it be possible to use a voltage divider and an
optoisolator to get the +/- supply?

NO
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tombiasi
electronics forum beginner


Joined: 13 May 2006
Posts: 45

PostPosted: Mon Aug 21, 2006 10:55 pm    Post subject: Re: Will a Gas Operated Generator Work? Reply with quote

"mea305" <mea305@aol.com> wrote in message
news:1156200270.172756.30680@h48g2000cwc.googlegroups.com...
Quote:
Concerning the use of the macerator, would a gas-powered generator
work? There is a receptacle for 12 VDC, and on the bottom of the
outlet, it appears that the outlet produces 8Amps (designated with 8A).
If this unit works, will it be safer than using the DC power supply
with an automotive battery?

Thanks,

Mark


If the output states "For Battery Charging Only" they tend to 'play' with
the rating.
The macerator will draw large surges (depending on what you ate Smile ). I
would use the battery.

Tom
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Randy Day
electronics forum beginner


Joined: 28 May 2005
Posts: 29

PostPosted: Mon Aug 21, 2006 11:17 pm    Post subject: Re: PIC18F A/D Reply with quote

Mark Fortune wrote:

[snip]

Quote:
BCF ADCON0,0 ; turn off A/D
RETURN

; in the main program
MOVLW 0x00 ; tell ADC to read AN0
CALL ADCREAD


I dont know an awful lots about the 18F2455, in fact i've only just
learnt how to program the 18F1320. Altho I cant see where you are
reading the ADC, is it stored in its own special register like the 1320
(which uses ADRESH:ADRESL). One thing I did notice about the 1320 is

Yes.

Quote:
that if I turned the ADC off before reading ADRESx into a register I
often got wierd results... maybe it's the same for the 2455?

Hmm. I hadn't considered that; I just treated
ADRESx as normal registers, and let other
routines read from it. I'll try transferring
them before turning it off.
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w2aew
electronics forum beginner


Joined: 28 Jun 2005
Posts: 48

PostPosted: Tue Aug 22, 2006 1:10 am    Post subject: Re: Self-Resonant Frequency and Resonant Frequency Reply with quote

quanghoc@gmail.com wrote:
Quote:
I searched both terms on Wiki

http://en.wikipedia.org/wiki/Self-Resonant_Frequency
and
http://en.wikipedia.org/wiki/Resonant_frequency

I still don't understand what is the difference between them. Let says,
what is the meaning of Self-Resonant Frequency in an Inductor compare
to Resonant Frequency of a Transducer?

Thanks.

Resonance (in electrical parlance) refers to the frequency where the
capacitive reactance is equal to the inductive reactance. At this
point, the phases cancel and you get a sharp change in the overall
impedance. For example, a parallel LC circuit (capacitor in parallel
with an inductor) will be in resonance at a frequency where 2*pi*f*L =
1/(2*pi*f*C). At this frequency, the impedance of this parallel LC
circuit will be extremely high due to the phase combination.

Normally, the term "self-resonant" frequency refers to the resonant
frequency of a component due to the parasitic characteristics of the
component. For example, the physical construction of a capacitor will
determine the parasitic inductance of the leads/connections to the cap.
The frequency where the capacitive reactance of the cap and the
inductive reactance of the lead's parasitic inductance, is the
self-resonant frequency. It is a property of the physical
characteristics of the device - and to some extent, defines where the
cap no longer behaves like a cap, but begins to behave like an
inductor.

When designing resonant circuits, you pick the capacitance and
inductance. Ideally, you will operate at frequencies that are far away
from the self-resonant frequency of the individual components. Of
course, there are special circumstances where you might do a design
that involves utilizing components near their self-resonant frequency,
but it isn't that common.
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Phil Allison
electronics forum Guru


Joined: 20 May 2005
Posts: 1368

PostPosted: Tue Aug 22, 2006 1:28 am    Post subject: Re: 240V relay contact suppression Reply with quote

"Stanislaw Flatto"
Quote:
John Fields The diode provides a path to Vcc for the high-voltage spike
generated when the relay driver turns off, in order to protect the
driver. The price, though, is that the current won't only flow
through the diode, it'll also flow through the coil (since that's
where it comes from) until it's dissipated to the point where it can
no longer hold the armature closed. That means that the relay will
stay closed longer than if the diode wasn't there, but the driver
won't be destroyed.



Too modern for me. What "driver"?


** General term for whatever solid state device switches the coil current on
and off.


Quote:
~1960 AD working on telephone exchanges, relay technology, diodes(?),
were called rectifiers then, selenium plates, and were used (rarely!)
to improve responses by allowing faster collapse of the magnetic field.
Anything changed since?


** The laws of magnetics must have been suspended in that clunky old
exchange.





...... Phil
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John Larkin
electronics forum Guru


Joined: 29 Apr 2005
Posts: 4320

PostPosted: Tue Aug 22, 2006 1:53 am    Post subject: Re: Zero Ohms = Mathematically Incorrect Reply with quote

On Mon, 21 Aug 2006 04:31:49 GMT, "Homer J Simpson"
<nobody@nowhere.com> wrote:

Quote:

"G. Schindler" <milt1954@yahoo.com> wrote in message
news:JXTFg.11296$9T3.10623@newssvr25.news.prodigy.net...

First things first ..... dividing by zero is not in itself wrong! The
correct terminology, by the way, is 'undefined' not 'incorrect' and not
'error'.

No, it is wrong and the correct answer is error, not undefined.



"Error" is what a $4 calculator will tell you that 0/0 is.
"Indeterminate" is what an engineer will call it. "Undefined" is what
a mathematician might say.

The reason is that you can spell ErrOr on a 8-digit, 7-segment
display, but you can't spell UNDEFINED or INDETERMINATE.

John
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JeffM
electronics forum Guru


Joined: 02 May 2005
Posts: 1007

PostPosted: Tue Aug 22, 2006 2:31 am    Post subject: Re: transistor help Reply with quote

Quote:
I have a home irrigation controller
Imran Khan

Yes, I seem to have read that before:
http://groups.google.com/groups/search?filter=0&q=insubject:transistor&enc_author=hSmEcR4AAAAJBV5fu91W81q55jVVANXFAG1snRRmtkc2-Zuq7Zp-kA&scoring=d

Here's how you should have done it:
http://groups.google.com/group/sci.electronics.basics/browse_frm/thread/7b7c0624331012bb/3958f18673b5f374?q=EVERY-group-*-*-*-*-*-*-*-*-appear+*-proper-answer-*-*-*-given+much-easier-*-*-*-*-what's-going-on+*-frowned-on+*-correcting+*-polite-*-mention-*-*-*-*-*-*-*+*-*-_perfect_-*-*-*-*+*-Followup-To-*+*-*-*-too-lazy-*-*-*-*-*-appropriate-*+Just-because-*-*-*-*-*-*-*-*-does-not-mean-*-*-*-*-*-*+*-*-*-*-two-groups-*-*-aren't-*-different
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ehsjr
electronics forum Guru


Joined: 03 May 2005
Posts: 863

PostPosted: Tue Aug 22, 2006 3:20 am    Post subject: Re: Will a Gas Operated Generator Work? Reply with quote

mea305 wrote:
Quote:
Concerning the use of the macerator, would a gas-powered generator
work? There is a receptacle for 12 VDC, and on the bottom of the
outlet, it appears that the outlet produces 8Amps (designated with 8A).
If this unit works, will it be safer than using the DC power supply
with an automotive battery?

Thanks,

Mark


Not the best choice. The generator is underrated for
the load, but even if it wasn't - are you going to
run out and start the generator every time you need
to flush the toilet?

Use the battery!

Ed
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