Driver to drive?

[Daniel Haude]

On 2 Nov 2004 04:19:51 -0800,
Winfield Hill <Winfield_member@newsguy.com> wrote
in Msg. <cm7u170gkc@drn.newsguy.com>

What, that tickets are dirt cheap, or that we don't fly much anymore?

Massive air traffic is the principal source of high-altitude
pollution, a main ingredient for the greenhouse effect. Much more
effective than burning oil on the ground. So ... less flying, less
pollution. Good news, no?

--Daniel

--
"With me is nothing wrong! And with you?" (from r.a.m.p)

 

[Reg Edwards]

But I'm talking about RF *design* which I assume as a
child, was beyond you, as it was me (and I *still* have a lot to learn
x decades on).
--
========================================

Once having learned the relatively few basic electrical principles, and how
to do arithmetic, with practice on the bench you know it all. Then all
that's needed as an aid to thought are the manufacturers' components and
chip catalogues.

But those unfortunates who were too lazy to learn arithmetic, or were
frightened away from it by ill-educated, unimaginative primary school
teachers, will remain seriously handicapped for the remainder of their
working lives.
----
Reg

 

[Robert Baer]

Andrew Holme wrote:

I'm playing with an old hard disk drive (WD Caviar 280). I've got it
spinning with a crude 3-phase unipolar driver - no Hall sensors - no back
EMF sensing. It just needs a little push to get it started! I might try
something fancier later on - six stepping perhaps.

What I really wanted to do was mount an audio cassette deck read/write head
close to the surface. Can I expect to record and detect a signal this way?
My application is digital not analogue: it's a replica of a magnetic drum
storage device as used in early computers. The required storage capacity
would be very low indeed.

The Caviar 280 pre-dates GMR. The heads are centre-tapped coils. I was
planning to rip the actuator assembly out but then I wondered if I could use
it instead of the audio head. What is the signal level at the read
amplifier input? Micro-volts? Milli-volts? I can't see anything across
the coil on my 'scope.

I tried connecting an almost flat 9V battery across the coil while the disk
was spinning in the hope of recording a large magnetic disturbance but I
still couldn't see anything on the 'scope. I made and broke the circuit
while the disk was spinning and there was a lot of contact bounce. Perhaps
I need a polarity reversal?

I know the normal HDD recording level is necessarily low to facilitate high
data density, I would like to record low density data at a high level to
simplify the read amplifier. Is this possible?

Thanks,
Andrew.

I would think that the electronics for a floppy drive would work, and
if you do not have a head for the HD, use one from a floppy drive.
The signal from a floppy drive is amplified using a uA733, so i would
guess the signal to be in the 3-30mV (peak) range.
The gain taps are used with a capacitor, giving a high frequency AC
gain of 400 with a 40MHz bandwidth, but a low frequency gain of 10.
Now for the signal mod/demod, get an old FDC controller for a
286/386/486.
....or, using only the cable length given for any computer, use the
computer as the I/O and the electronics + head in a floppy drive to
interface to the HD.
**
What may be bothersome, is the nasty question: what about controlling
the flying head height, and all of those *huge* (in comparison) dust
particles????????????
In short, haven't you scratched the sh*t out of the platter surface,
making it useless?

 

[legg]

On 30 Oct 2004 19:24:18 GMT, chrisgibbogibson@aol.com
(ChrisGibboGibson) wrote:

legg wrote:

[snip]

Your circuit construction and
isolation methods should comply with those of BF type patient-applied
parts.

The only time this is not the case, is when you are dealing with
inanimate or dead matter.


Well....

OP did say that.....

When the differential amplifier blows, some sort of leakage current
back-feeds from the amp, through the leads, and into the heart
(causing fibrillation).


Which quite often can lead to death.

He describes the damage to the monitor as being correlated to the
simultaneous application of either electrosurgery or defibrillator
equipment.

Monitors of suitable isolation class intentionally do not exibit
excess LF leakage under external influence, nor is this permitted
under single-fault abnormal conditions (ie failure).

I believe inaxx isolation amplifiers data carries a disclaimer
indicating that they are not inherently safe in this application. I do
not doubt that they could possibly be so configured, if the
application requirement is understood and the resulting circuitry and
power supply interface is designed and tested for the application.

RL

 

[Keith Williams]

In article <bstao0hkgpbq2fdqes105afks8sovp6b3l@4ax.com>,
jjlarkin@highlandSNIPtechTHISnologyPLEASE.com says...

On 31 Oct 2004 14:38:44 -0800, Winfield Hill
Winfield_member@newsguy.com> wrote:

Frank Bemelman wrote...

I would mind. But I know you are not very 'professional', whining
about some lost diodes in *public*, and other things, ...

Now, now Frank, John wasn't whining about lost diodes, he was
reminiscing about some precious little gems he sent me, showing
his generous and sharing nature. Of course that doesn't mean
that I approve of his attitude wrt Bush and Kerry!

And I still give a copy of AoE to all of my interns, even of it was
co-authored by a New England Whatever.

(Hey, we were up at Cornell last week, visiting The Brat. It was peak
leaf-peeping season, the ducks were ducking, the waterfalls were
waterfalling, and it was beautiful. The number of Bush signs and Kerry
signs in the neighborhood were pretty near equal.)

What a difference a few miles makes (fall fell at least three weeks ago
in Vermont). All that's left is brown (ground) and gray (sky), or is
waiting for the rake. :-(

--
Keith

 

[Frank Bemelman]

"John Larkin" <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> schreef in
bericht news:sndao0tvq4kfr6t4g2ada3ipdce38r6096@4ax.com...

Hey, Win, would you mind if I snipped chapters from AoE and published
them here?

I would mind. But I know you are not very 'professional', whining about
some lost diodes in *public*, and other things, but then again, I am
not like you. Anyway, 'publish' it, if you must. You are ear marked
already.

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

 

[Clarence]

"xray" <notreally@hotmail.invalid> wrote in message
news:n5hao0lll19tprgurj27p00ufa2jcrr7nh@4ax.com...

On Sun, 31 Oct 2004 19:46:54 GMT, "Clarence" <no@No.com> wrote:

I know that all that name calling happened, and we commonly referred to
people
who used those names as "Childish, and Immature" So we all know where you
fit
in.


Stick and stones may break my bones,
but Clarence will never have anything useful to say.

Validation!

 

[Paul Burke]

Winfield Hill wrote:

Paul Burke wrote...

... or the attoBoldon.


Yes?


http://news.bbc.co.uk/hi/english/sport/commonwealth_games/newsid_173000/173310.stm

 

[Fred Bloggs]

Julie wrote:

That very well may be the case. But, I do not flaunt my minuscule amount of
intelligence over those that have none.

None pretty much describes the subset of the human race you could hope
to lord over on the basis of superior intelligence.

 

[Fred Bloggs]

Tom Seim wrote:

... (murderinging
civilians, for instance).

"murderinging"?! Complete brain death is just a few more hours away for
you. You can't even hack three syllable words anymore, but you think you
can hack the long haul of global war- typical insubstantial little arm
chair warmonger.

 

[Paul Burridge]

On Tue, 02 Nov 2004 14:35:26 +0000, Paul Burke <paul@scazon.com>
wrote:

Winfield Hill wrote:
Paul Burke wrote...

... or the attoBoldon.


Yes?


http://news.bbc.co.uk/hi/english/sport/commonwealth_games/newsid_173000/173310.stm

Wrong spelling.

--

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

 

[Paul Burridge]

On Tue, 2 Nov 2004 13:52:48 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

Once having learned the relatively few basic electrical principles, and how
to do arithmetic, with practice on the bench you know it all. Then all
that's needed as an aid to thought are the manufacturers' components and
chip catalogues.

<boggle!>
It's a bit more involved than *that* Reg!
--

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

 

[Rich Grise]

On Tue, 02 Nov 2004 04:08:53 +0000, John S. Dyson wrote:

Also there has been other similar more official testimony that only
helps to strengthen the position that Kerry is incredibly ethically
corrupt.

Well, I guess today we'll find out if America decides to sell her
soul to Evil.

Thanks,
Rich

 

[Ken Smith]

In article <418700BB.5BFA@armory.com>,
R. Steve Walz <rstevew@armory.com> wrote:
[...]

He regarded the entire Vietnam WAR as an atrocity, but only in
retrospect,

The subject he was refering to was a little more specific. He was
refering to the "free fire zones". That is what this is all about. Kerry
opposed the war, but I don't think you can find a reference where he said
that the who thing was an atrocity. He was refering to more specific
items than this.


--
--
kensmith@rahul.net forging knowledge

 

[Rich Grise]

On Tue, 02 Nov 2004 13:19:40 +0000, Jim Yanik wrote:

That seems to be the media's goal(old media,at least).
Evidence is now emerging about the old meida's bias towards Kerry.

Well, in case you'd care to check it, back when America had a soul,
bias against mass murder was a _good_ thing.

Thanks,
Rich

 

[Anders F]

"Yzordderex" <yzordderrex@verizon.net> wrote in message
news:a69e22f6.0411020704.4920d6a1@posting.google.com...

I am trying to develop a current sensor that will detect ground fault
currents. These currents are to protect a 50amp IGBT. Not to protect
a human being.

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Anybody know of a manufacturer who produces small discs?

Sorry - but if you can handle the cost, Allegro has readily available
integrated 50/100A current probes...

/A

 

[Rich Grise]

On Tue, 02 Nov 2004 07:04:32 -0800, Yzordderex wrote:

I am trying to develop a current sensor that will detect ground fault
currents. These currents are to protect a 50amp IGBT. Not to protect
a human being.

I am using a smd hall effect sensor which is mounted very close to the
current carrying tracks. The sensitivity is marginal and I would like
to concentrate the flux by gluing a small ferrite disc on the opposite
side of the board.

So I am looking for a small disc. Diameter should be about 1/8" to
1/4".

Anybody know of a manufacturer who produces small discs?

I've done a quick search, and so far just come up with ferrite
rod cores, which you _could_ slice with a diamond saw. Call some
ferrite dealers, maybe.

Good Luck!
Rich

 

[Spehro Pefhany]

On 2 Nov 2004 07:57:34 -0800, the renowned mdeblis@hotmail.com (Mike
Deblis) wrote:

Hi,

I have a project that I want to have made commercially - maybe a
maximum of 1000 units, but only 50 to start with. I am not a
practicing engineer.

There are about 40 components - I want most to be SMD... no BGA, but a
few uSOP and mostly 0805 Rs & Cs (a couple of larger tant Cs). Some
non-standard, e.g. power connector & SMD inductor etc. I want SMD
because I want the unit to be compact... 2-layer PCB, 10mil traces,
FR4 with solder mask on both sides & silk screen one side (i.e. a very
standard board).

Okay. Why 0805s? I'd suggest 0603 or even 0402 where there's a choice.

So, is PTH cheaper to make than SMD ?

The board probably can be smaller, so that much could be cheaper.
Assembly may not be much different in small quantities. I think most
assembly houses will use hand assembly in 100 piece lots. The mask for
solder paste screening (and associated setup) is a bit of overhead.

For a small board like this
(maybe 10cm x 10cm) what might I expect to pay for assembly?

Really varies a lot. From a few dollars in a few hundred lots to maybe
$15-$20 US in small lots, I'd guess. Plus shipping etc. If you have a
local supplier you can drop off parts and pick up assembled boards,
which saves a lot of hassles. You can also inspect their facilities to
make sure they are careful, get an idea of their clientele (toys or
aerospace?) and make sure they have ESD and quality control
procedures. The best results are tiny companies with few formal
controls and very qualified workers and bigger companies with lots of
controls and well trained workers. The worst results come from the
middle ground with poorly paid workers that don't stay long. IME.

Is it
worth going to the Far East for quotes - what quality issues might
that entail?

Unless you want multiple lots of 1K minimum each I don't think it's
worth the overhead, communication issues, time and risks. If you're
willing to make multiple 1K-5K lots, it might well fit. In some cases,
the parts may be cheaper in Asia. Fancy analog and industrial parts
don't tend to be. Jellybean parts often are.

If there are one or two PTH devices on the board, does
this really complicate matters or is it incidental?

I don't find it matters much in smaller lots.

I really would apprecate a few pointers about where to get started,
and experiences of using local vs. remote far East etc.)
fabricators...

It's usually worth it to pay for 100% electrical testing on the bare
boards.

many thanks

Mike

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

 

[Joel Kolstad]

"Pedro" <pedroenglish@hotmail.com> wrote in message
news:10e8a33b.0411020022.36800f06@posting.google.com...

Could a common Fluorescent ballast from a domestic light fitting be
used as a LF or audio or smoothing choke?

That I couldn't tell you.

I believe the core has an
air gap to prevent saturation, any idea of the typical inductance?

I believe the running voltage of many fluorecent lamps (in the U.S.) is in
the ballpark of ~90V. For, say, a 30W fixture, then, you need ~330mA. With
30V across it, the inductor to get ~330mA at 60Hz is ~240mH.

---Joel Kolstad

 

[CFoley1064]

Subject: School project resolution
From: BZ not@available.now
Date: 10/31/2004 4:38 PM Central Standard Time
Message-id: <6Qdhd.47486$186.4001@fe1.texas.rr.com

Hi everyone,

Thanks for the kind and helpful answers to my questions last week.

Congratulations, Super Dad. IMO, helping the kid with the science fair project
is one of the most satisfying parts of being a parent.

Remember, this is only part of the grade. Spend the time and effort to do a
good writeup, and you'll be in good shape. If there's a judge interview, try
quizzing her with practice questions. Judges always like contestants with
knowledge and poise, and that comes with practice.

Do us a favor, and let us know if she wins a prize.

Good luck (which is the residue of hard work, so I'm sure you'll have it)
Chris