audio recording on IC -help wanted

[john jardine]

"michael nikolaou" <michaelnikolaou_remove_me_@yahoo.com> wrote in message
news:fq1is0$2i0f$1@ulysses.noc.ntua.gr...

Thank guys for your replies .Some of them i have to study first

Let me make some things clear about the circuit and values chosen

1. I've measured turn-on , turn-off delay at 3.3 ms for the driver
relay.All
results are
after calculating this delay .So what is see on the scope is at the moment
i'm explaining
2. the arc is across the driver relay .The power board is inside a control
unit box so
i have to leave with small distances and cpu disturbances.Its actually
a
microcontroller
having the problem .Driver relay contact current rating is 5A at 220V
.Power relay coil is rated is 6
watts consumption at 220V.
[ ... ]

From your info', my guesstimate says the big relay has a 8kohm, 4H coil (I'm
working from a UK 50Hz). This means the current running through it will be
nearly in phase with the voltage across it.
Let's say the current is running about 1mS late, then add on the 3.3mS delay
for the relay to pull in and it seems not unreasonable that you need to be
switching ON about 4-5 mS from the sensed 0V Xover to give minimum
transients. This -coincidentally- just happens to be at the peak AC voltage
point.
A different relay may well have bigger inductance and lower resistance,
these would need measuring and the Arrctan thing doing to get a new phase
angle/delay for the current.

If you put say a 10k ohm 2Watt resistor in // with the power relay coil this
will be effective in quickly quenching the relay coil energy. Or better
still, fitting a Varistor will simply clip the transient to whatever it's
rated voltage is.

 

[clicliclic@freenet.de]

Hamid.V.Ans...@gmail.com schrieb:

On Jul 20, 2:44?am, John Fields <jfie...@austininstruments.com> wrote:
On Sat, 19 Jul 2008 03:56:11 -0700 (PDT), Hamid.V.Ans...@gmail.com
wrote:

Only visit:
http://hvansari.googlepages.com? ?or
http://www.geocities.com/hamid_vasigh

---
Your premise seems to be that if the dielectric constant of material
interposed between parallel conductors is greater than that of the
vacuum, then the energy storage in that system should decrease. ?

The opposite, in real life, seems to be true.

Dielectric attracts more charge onto the plates of the capacitor,
so it plays the role of an emf supply. On the other hand it is
shown in the paper that capacitance of a capacitor depends
only on the configuration of its plats not also on the existence
of any dielectric.

In any case, you should try to verify this revolutionary theory before
you publish it!

You might for example take one of those old AM radio tuning capacitors
with air dielectric, connect it to a capacitance meter, and observe
what happens to the reading when you immerse the capacitor in
destillated water, or in turpentine, etc. You will then discover that
your theory is contradicted by experiment, so there must be something
very wrong with it.

Calculating the capacitance of an actual ceramic capacitor according
to your theory, and comparing the result with the specification or a
meter reading might also help you see the problem. I suggest you check
the capacitance of an old single-layer disk capacitor first, and break
it open then. (For modern multilayer models you would need to study
the cross-section under a microscope.)

Martin.

 

[Chris]

On Feb 26, 7:14 am, "sycochkn" <sycoc...@earthlink.net> wrote:

"michael nikolaou" <michaelnikolaou_remove_...@yahoo.com> wrote in message

news:fq0kg4$1n3d$1@ulysses.noc.ntua.gr...





Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the
contact of the driver relay i placed one RC snubber circut (27NF with 100
R resisitor in series) to help with some spikes that were influencing the
low voltage driver circuits.
The driver circuit is able to detect  mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point  to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV  at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform  to
0 volt after 5 periods of    500 HZ  but no overshoot. The relay presents
no arcing.  If i remove the snubber and make the experiment the best place
to switch is zero crossing but i also see large SHARP spikes up to 500
Volts Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large  spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael

Use a solid state releay and dont worry about it.

Bob- Hide quoted text -

- Show quoted text -

Right. If you have a resistive load for the final 220VAC load, a
plain old solid state relay will work fine (be sure to heat-sink the
SSR at about 1.5 watts per amp load). If you have an inductive load,
you may want to spec a SSR made to switch these loads, which have back-
to-back SCRs to eliminate the possibility of not being able to turn
off the SSR).

If this is a class project, you won't lose any points by going for the
simple solution, as long as it also happens to be the best one.

Good luck
Chris

 

[Don Klipstein]

In article <4f00b9ac69dave@davenoise.co.uk>, Dave Plowman (News) wrote:

Have you never wondered why most prefer the colour temperature of tungsten
for domestic lighting?

Personally, I like more like 3500K at most brighter indoor lighting
levels, closer to 3,000 for dimmer indoor lighting.

Higher color temperature often appears "dreary" unless illumination
level is very high.

People often find it "dreary" outdoors under overcast conditions with
color temperature around 6000 K, especially when illumination level gets
under several thousand lux.

Things can look dreary at dusk and dawn, though people can be in a less
dreary mood outdoors then. At dawn things are brightening, and at dusk
people are likely to be on their way home from work or towards
entertaining activities.

As for why higher color temperature can make things "drearier" at lower
illumination levels:

1. The spectrum is richer in wavelengths favorable to scotopic vision,
which lacks ability to see color. Higher color temperature favors things
looking grayish when illumination level is down to several lux or less.

2. More light of wavelengths favorable to scotopic vision can make your
eye's pupil smaller than otherwise for a given illumination level. 100
lux at 5000 K can make your pupil smaller than 100 lux at 3000 K. (The
lux and other photometric units are defined in terms of photopic vision
and not scotopic vision.) That can make things appear dimmer. This can
also have an effect on color vision if illumination level is down to a few
lux or less, by depriving the color-sensing cones of light.

3. Reds look darker at higher color temperature, and can "drop out to
black" when color temperature is high and illumination level is low enough
to start making photopic vision marginal.

- Don Klipstein (don@misty.com)

 

[Tom Gugger]

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[Mr.T]

"James Sweet" <jamessweet@hotmail.com> wrote in message
news:t5Ihi.2134$DM4.1499@trndny06...

The only difference between 120V and 240V CFLs is the configuration of the
rectifier and filter capacitor(s) on the input.

Which do fail.

Some are crap and fail quickly, others last years.

Never had one that lasted "years", and I've used dozens.
12-18 months is the best I've had, zero being the worst.

Start cycles seems to
have a large effect on life,

Of course, and turning off lights when not in use saves more power than
leaving CFL's on.

the ones that are in dusk till dawn lights
outdoors have lasted me to or beyond their rated life, save for one that
failed in the first couple weeks.

Wow, and how much power can you save by turning them off?
My outdoor lights are solar powered.

Full size fluorescent tubes do last a long time, though the ballast is the
reason for most of this. CFL ballasts are just not robust, they're built
to
be disposable.

Not all. I did buy a two part CFL once, and when the tube failed, no
replacements are available.
Back to standard tubes for me!

MrT.

 

[Joerg]

Mark Zenier wrote:

In article <9FB3l.3539$jZ1.590@flpi144.ffdc.sbc.com>,
Joerg <notthisjoergsch@removethispacbell.net> wrote:
It's been really long ago that I had to make custom GPIB/HPIB bus
connections. Are those the regular 24-pin Centronics like this one?

http://media.digikey.com/pdf/Data%20Sheets/Norcomp%20PDFs/111-yyy-103-001.pdf

Digging out my copy of IEEE Std 488-1978, the answer appears to be yes.
As a footnote, it calls out Amphenol (or Cinch) "Series 57 Microribbon"
or AMP "CHAMP". (An Allied or Newark catalog would give a good overview
of that old stuff).

I have a 1991 AMP catalog 2ft from my eyes. Hardcover no less. But it
functions as a stand for a really heavy CAD monitor because its color
blends in nicely ;-)

So I'll just get a few of those 24-pin Centronix connectors. But solder
cup, I do not like ribbon cables, they spew out too much EMI.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Paul Luggar]

Got some from Icom UK, really helpfull people.

--



Paul Luggar

M0SCI

Website WWW.M0SCI.CO.UK

Amsat-UK Member 6484

www.m0sci.co.uk/forum Devon and Cornwalls Amateur Radio Message Board

m0sci@gb7cow.#44.gbr.eu
"Paul Luggar" <luggsey@hotmail.com> wrote in message
news:f5jieo$em6$1$8300dec7@news.demon.co.uk...

Still looking!!

--



Paul Luggar

M0SCI

Website WWW.M0SCI.CO.UK

Amsat-UK Member 6484

www.m0sci.co.uk/forum Devon and Cornwalls Amateur Radio Message Board

m0sci@gb7cow.#44.gbr.eu
"Paul Luggar" <luggsey@hotmail.com> wrote in message
news:f58ukv$dv0$1$8302bc10@news.demon.co.uk...
Still looking!

--



Paul Luggar

M0SCI

Website WWW.M0SCI.CO.UK

Amsat-UK Member 6484

www.m0sci.co.uk/forum Devon and Cornwalls Amateur Radio Message Board

m0sci@gb7cow.#44.gbr.eu
"Paul Luggar" <luggsey@hotmail.com> wrote in message
news:f4n65s$lbo$1$8300dec7@news.demon.co.uk...
I need one to repair my preamp, I can't get one anywhere unless I have
3000!
NEC3SK299 is a drop in replacement I think.
Anybody help?
I will pay all costs to obtain one or possible 2 or three!
Cheers.


--



Paul Luggar

M0SCI

Website WWW.M0SCI.CO.UK

Amsat-UK Member 6484

www.m0sci.co.uk/forum Devon and Cornwalls Amateur Radio Message Board

 

[HarryD]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:n1qe84pvvg5bfomsm6uvu2e8a42mf35ouk@4ax.com...

On Wed, 23 Jul 2008 09:59:26 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Hello All,

Got a circuit where in hindsight the client decided they need >10 times
the juice than initially spec'd. This was truly unforeseen for them and
we have to make it work at least for a proto series. Of course, now all
those 0805 resistors in the power path would exceed their usual 1/8W
spec. Found these at 1/3W:

http://www.susumu.co.jp/english/pdf/products-j01-07.pdf

I plan to run them around 200-250mW. Was expecting those to be really
tall to vent off some heat but they are surprisingly flat, only 0.4mm
high. Will this become a heat problem on FR-4 for stuff that can run
24/7? Any experience?

Sounds OK to me. We push regular 0805's harder than that. Zero fails
so far.

We experimented with various resistors, 0603 through 1206, with a
thermal imager that has plenty of resolution to find the hot-spot temp
on all the parts.

Turns out that the actual part thetas are astronomical, and what cools
resistors is the copper pads and traces, more than the bodies
themselves. An 0603 soldered to big copper pours can dissipate as much
as a 1206 ditto; the hot spot temps are the same. That makes sense
physically, as theta is determined by the L/W ratio and the substrate
thickness, and all the resistors we checked were all 20 mil thick
alumina.

A better substrate, BeO or AlN, would help a bit, at great expense.

If there's a ground plane close, that helps a lot.

The easiest thing to do is fire up the board and scope it with a Flir,
and see how hot stuff gets. You can borrow mine, or come here and use
it.

ftp://66.117.156.8/IR_0026.jpg

ftp://66.117.156.8/IR_0032.jpg

John


Thermal vias are your friend. Vias in pads are now standard procedure for

most PCB houses. Put a thermal via in each pad and one under the center of
the part. Tie TVs to heat spreader on another plane.
JL, tell us more of your FLIR, type, cost and performance.
Cheers,
Harry

 

[Eeyore]

"Mr.T" wrote:

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:46831734.E187EF8F@hotmail.com...
It would be crazy to eliminate halogens.

Why???
The QH downlights used in large multiples because of their narrow light
spread, are the very WORST offenders!
Each one draws as much as a standard globe (including the power wasted in
the transformer)

Ban them FIRST I say.

They're not the only kind of halogen lamp.

GE and Philips are working on getting halogen efficiency up to the level of
CFLs.

Graham

 

[Phil Allison]

<faceman28208@yahoo.com>

I am looking for a small laser that I can mount in a sci-fi model for
visual effect. No, I am not trying to get a star wars style solid blue
line. Just something that one to give some kind of effect.

** You dopey Q was answered yesterday on " sci.electronics.basics".

Go learn something about laser light

- you dumb twat



..... Phil

 

[pbanny]

Hi

Has anyone else had problems using Dagnall or Clairtronic (same company) PCB
mount transformers.

I am getting very frustrated replacing burnt out transformers. Firstly the
transformers bulge and the plastic case darkens and run noticeably hot.
Then, I would assume windings start to short and any fuse supplying the
transformer blow. The rate of failure is currently running at around 12 -
15% out of the 500 or so after 18months in use.

The transformers we use are the 14VA types which are split primary and
secondary, we are running the transformer at around a 50% load factor with
occasional peaks for about 10 secs to about 80% rating. When there is a
'burn-out' the blackening only appears in one of the four bobbin segments,
sometimes one of the primary and sometimes one of the secondary windings.
This seems to point that it is not overload problem as I would expect to see
both the primary or secondary windings 'burn' together but so far this has
never been the case.

We have approached MGC Electronics who make these transformers in Malta who
were of little help and are still holding about 100 of our transformers for
'testing'. We have heard nothing from them for 6 months or more now. We have
also approached the original suppliers, Farnell, who say they have had no
other complaints and can only follow the findings of the manufacturer.

Our solution has been to swap to a similar unit made by Block from Germany,
of exactly the same VA rating, and so far have swapped around 100 over the
last year with absolutely no failures whatsoever.

One of my biggest ever mistakes, the day I chose to use Dagnall for our
design.

BE WARNED!!!!

Paul Bannister
Data Solutions

 

[Fred Bloggs]

Thank guys for your replies .Some of them i have to study first

Let me make some things clear about the circuit and values chosen

1. I've measured turn-on , turn-off delay at 3.3 ms for the driver relay.All
results are
after calculating this delay .So what is see on the scope is at the moment
i'm explaining
2. the arc is across the driver relay .The power board is inside a control
unit box so
i have to leave with small distances and cpu disturbances.Its actually a
microcontroller
having the problem .Driver relay contact current rating is 5A at 220V
.Power relay coil is rated is 6
watts consumption at 220V.
3. Using large value capacitors over 33 nf was causing sometimes latch of
the power relay so i have
value limitation here
4. The capacitors i've chosen are X2 self healing 275VAC. With no ZC control
they are blown
to 0 nf value (some of them) after 10-12 months of operation.
5. I don't have the space or budget to use large sized capacitors rated at
higher voltages or SSR .
The idea was to use ZC to avoid using expensive and large size protection
snubber
So the question is .

Does the relay On/OFF time differs with time .If it's 10% it's not a
problem since again
the arc will not be so high .Since its the current break that causes the
arc i must switch off at Peak of the
ac voltage .This is what my reading confirmed .In this case switching a
resistive load must i change the driver
algorithm ???

Any helpful comments will be apreciated

See section 15.2.12.5 and in particular Circuit B of figure 15.6 in the
link below. You will want 450WVDC electrolytics and 600PIV rated diodes
along with possibly a small inrush limiting resistor in series with the
whole lot. The idea is to dynamically form a peak clamp circuit and this
has been used in many high end line surge protection devices for many
years with good success. The zero crossing helps a bit but is largely a
waste of time.
http://www.leachintl2.com/english/english2/vol6/properties/00053.html

 

[Stuart]

In article <495EA761.BE86871E@hotmail.com>,
Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

High-fidelity Microphone

" Common uses include matching the relatively low 2K ohm output
impedance of a microphone to an amplifier’s much higher line input
impedance of 10K ohms. Studios commonly use the three terminal “XLR”
type of connector which is a balanced connection method with a terminal
for a center tap. A separate ground terminal, tied to the XLR
connector’s case is almost always present. The center tap may be used to
phantom-feed a small amount of current for powering a pre-amp or active
“condenser” microphone."

LMAO !

You mean you didn't know that either?

Ok, a typical dynamic microphone is often nearer 150-300 ohms output
impedence and Ribbons can be as low as 50 Ohm but otherwise......

--
Stuart Winsor

For Barn dances and folk evenings in the Coventry and Warwickshire area
See: http://www.barndance.org.uk

 

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[Jamie]

michaelnikolaou@yahoo.com wrote:

On 27 Öĺâ, 03:24, Jamie
jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

michael nikolaou wrote:

Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the contact
of the driver relay i placed one RC snubber circut (27NF with 100 R
resisitor in series) to help with some spikes that were influencing the low
voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform to 0
volt after 5 periods of 500 HZ but no overshoot. The relay presents no
arcing. If i remove the snubber and make the experiment the best place to
switch is zero crossing but i also see large SHARP spikes up to 500 Volts
Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael

WHen you say relay, I assume you mean a mechanical contact?

if so, It takes time for the contacts the release. If you turn it
off at what you detect as the zero crossing point, the contacts most
likely will not actually release until some where in some mid point .
Many contactors are fast but not fast enough to open before current
can get a charge going.
That's just my evaluation of what you're doing.

By you signaling to turn off the relay at a peak, the contactor will
most likely not open until it gets near the zero crossing point.

--- Áđüęńőřç ęĺéěÝíďő óĺ đáńÜčĺóç -

- ĹěöÜíéóç ęĺéěÝíďő óĺ đáńÜčĺóç -


I observe all signals with a scope . I see actually the "driver relay"
signal .So all my observations
about timing are correct . My notion was different though .I expected
to turn off at zero crossing
voltage and have no arc .Actualy when the transition happents at the
peak of voltage then i see only a
decaying waveform ,no overshoot, for which i suspect since i know the
capacitor and measure the
frequency one could calculate the total inductance value (cables+relay
coil). Since its clear that V(emf)=-L*di/Dt
as pointed out by your emails also then the correct point to switch
off the driver relay is at peak voltage
since current lags voltage by 90 deg in any inductor.
Now i only have to find out how much can a relay type deviate from the
measurements i have made.
Thank's for all you help guys
if you're trying to save the contact life you can assist it with a SSR

across the terminals.
The SSR will conduct just prior before the contacts close, this will
create a shunt on the contacts. when the contacts finally make, they
will remove the load from the SSR.
When opening the contacts, the SSR will switch to save the day and
unlatch at the base line. If you decide to employ this, you need to have
a snubber tide across the SSR because of slight delays of the SSR, you
could damage it when the contacts open on a high peak.
Just select a SSR with the same turn on voltage as the contactor and
tie them to the same control voltage.


--
"I'd rather have a bottle in front of me than a frontal lobotomy"

http://webpages.charter.net/jamie_5"

 

[Jamie]

Joerg wrote:

Eeyore wrote:


Joerg wrote:

Hello Folks,

What would be a really low noise FET? Should be well under 10nV/rtHz at
the lower end of the audio band, say at 20Hz. Ideally 5nv/rtHz. Looked
at former Matsushita parts, now Panasonic:


2SK369 Toshiba. The nV/sqrtHz isn't stated but the NF at 1kHz with 100
ohms
source is a mere 1 dB typical.


Yes, Phil had already mentioned that one iand it's an excellent JFET.
Toshiba doesn't seem to be a big believer in SMT though. But we can
probably cram one in there, the others don't have to be that good.


Is your favourite BF862 noisy at audio freqs ?


It ain't my favorite because it's single-sourced. Usually RF FETs aren't
that great at audio.

with some of the modern day rap music I hear blasting out of these cars

going by while they attempt to knock out my windows with that distorted
base, I would thing that noise factor in the audio spectrum would be
attractive!


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

 

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[Caspian]

Some domestic appliances come with rechargeable cells that need charging
for many hours before their first use.

For example, I have a Panasonic DECT phone with two AAA NiMH cells which
needs charging for 7 hours.

But maybe you can't wait that long for some reason and you simply
"must" use the appliance!

How much would cell life be reduced if such an appliance is used after,
say, only 30 to 60 minutes of charging instead of the 7 hours?

 

[David L. Jones]

"Paul" <energymover@gmail.com> wrote in message
news:e522f235-fe26-4a21-b838-8341fe53f4ff@41g2000yqf.googlegroups.com...
On Jan 15, 3:12 pm, "David L. Jones" <altz...@gmail.com> wrote:

"Paul" <energymo...@gmail.com> wrote in message

news:7f239414-f99c-48ad-90e2-c9b0d0db2424@l39g2000yqn.googlegroups.com...
On Jan 15, 2:19 pm, "David L. Jones" <altz...@gmail.com> wrote:

The Agilent U1253A also has it. Spec is ">1Gohm".
There are quite a few meters I've seen over the years that have it too.
I think I even saw it on one of those $10 disposable meters too.

Dave.

I think the Agilent U1253A typically lists for $450. That's a bit more
expensive then the $40 AM240.

Hardly comparing apples and oranges!
If you are purely after "the cheapest meter that has a high impedance mV
range" then that's a different ball game.

Do you have model # for the $10 one?

No, sorry. These things come and go like the wind.

Dave.