HDTenEightyP/NetNews huggingface dataset:
From: massoud@chemteca.sdsu.edu (Massoud Ajami)
Newsgroups: sci.electronics
Subject: Re: Minimum speed on processors
Date: 27 Aug 92 20:17:12 GMT
Organization: San Diego State University

In article <1992Aug27.135703.26001@zip.eecs.umich.edu> johnwitt@cdrom.engin.umich.edu (John P Wittkoski ) writes:



>For a 33MHz 68030, there is a minimum clock speed listed for it in
>the databooks. I think it's somewhere around 25Mhz for a 33MHz version, but I
>don't have my databook handy.

>My question is: why is there a minimum?
>One possibility I have heard is that the on-chip registers and/or cache
>are dynamic in nature, and since the chip is geared for 33MHz, it divides
>this down to whatever rate is needed for the refresh circuitry. Therefore,
>if you go below the minimum, the refresh rate slows to below the minimum
>needed for the refresh.

>Now, is there someone out there who knows about this? I'm interested
>specifically in the 68xxx CPUs, but any general info would be helpful.
>For example:
>1. Is the guess I made above accurate, or is there some other reason?
>2. If the reason above is correct, does it apply to the registers, the
>   cache, or both (or neither?)
>3. If it's just a testing parameter, how far could I crank the clock speed
>   down? 20Mhz? 16,8,2,1???

>Just curious.
>Reply by newsgroup or email, whichever is easiest for you.

>        --John Wittkoski
>          University of Michigan
>          johnwitt@engin.umich.edu



Yes, all registers (memory locations) on the processor are dynamic, and they 
get refreshed by cycle stealing mode (transparent to the system).

1- Your guess is correct.
2- It apply to all memory locations. Notice that static RAMs consume a lot 
   of real estate.
3- It is not testing parameter, but you can change the frequency down until 
   the system crashes; That is the minimum.



Peace and Prosperity!
  ---==< 110 >==---
Newsgroups: sci.electronics
From: frank@rover.uchicago.edu (Frank - Hardware Hacker - Borger)
Subject: Re: Weird Science?
News-Software: VAX/VMS VNEWS 1.41    
Reply-To: frank@rover.uchicago.edu
Organization: Joint Center for Radiation Therapy
Date: Mon, 31 Aug 1992 22:59:00 GMT

In article <17u3gbINNfuv@darkstar.UCSC.EDU>, haynes@cats.ucsc.edu (Jim Haynes) writes...
> 
>I've got this circuit which consists of
>   8:1000 ohm input transformer feeding
>   DIP bridge rectifier feeding
>   base-emitter junction of a transistor.
>The idea is to connect the 8-ohm input to the output of a radio or
>tape recorder and turn on the transistor when there is some signal.
> 
>It works fine, at first.  After it sits for a while, turned off, it
>won't work.  Then I disconnect one of the secondary leads from the
>transformer, observe with an AC voltmeter that there is voltage there,

	Ah yes, but there is also probably DC voltage there.

	When you put ac on top of dc into a transformer, the resultant
	E-H curve keeps jacking up the magnetic field until it saturates.

	Try putting a large cap in series with the transformer primary to
	block the dc component.
	

   Frank R. Borger - Physicist    __       Internet:  Frank@rover.uchicago.edu
Michael Reese - Univ. of Chicago |___      Phone : 312-791-8075 fax : 567-7455
  Center for Radiation Therapy   | |_) _   
    2929 South Ellis Avenue        | \|_)  Dr. Livingstone I Presume
    Chicago, Illinois 60616           |_)  The full name of Dr Presume
Newsgroups: sci.electronics
From: riepe@ifwm11.ifw.uni-hannover.de (Michael Riepe)
Subject: Re: How hot can the 486-50 cpu run ?
Organization: University of Hannover, Germany - IFW
Date: Fri, 28 Aug 1992 03:54:45 GMT

I'm sorry but you're talking nonsense.
Silicon semiconductors have max. chip temperatures of about 75 to 125 deg C.
I may be wrong, but I think the maximum for the 486-33 is 85 deg C. The case
temperature depends on the case type (ceramics or plastics) but will always
be lower, approximately 40 to 60 deg C.

Anyway, in PC-486's sold today, the max. temperature will be exceeded in most
cases unless you are using an additional cooling fan *near* the CPU and/or
an ICECAP or s/t like that.

-- 
 Michael Riepe                         <riepe@ifwm11.ifw.uni-hannover.de>

     IIII  FFFFFFFF  WWWW           WWWW             Univerit"at Hannover
    IIII  FFFF       WWWW   WWW   WWWW    Institut f"ur Fertigungstechnik
   IIII  FFFFFFF     WWWW WWWWW WWWW       und spanende Werkzeugmaschinen
  IIII  FFFF         WWWWWW WWWWWW                   Schlosswender Str. 5
 IIII  FFFF          WWWW   WWWW              W-3000 Hannover 1 (Germany)
--
Newsgroups: sci.electronics
From: FREYER@hauk.hsr.no (Stle Freyer)
Subject: Re: Mac to Phone connections...
Organization: Rogaland University Centre
Date: Mon, 31 Aug 1992 08:51:52 GMT

In article <1992Aug31.043725.13428@u.washington.edu> wiml@milton.u.washington.edu (William Lewis) writes:
>From: wiml@milton.u.washington.edu (William Lewis)
>Subject: Re: Mac to Phone connections...
>Date: 31 Aug 92 04:37:25 GMT
>In article <1992Aug27.160630.615@fwi.uva.nl> aroest@fwi.uva.nl (Axello de Roestello) writes:
>>rubin@cis.ohio-state.edu (Daniel Rubin) writes:
>>
>>>Hi all... I want to connect my Mac to my phone.  I am going to connect the
>>>speaker of the Mac to the mic of the phone and the speaker from the phone to
>>>the Mac's mic...
>>
>>>I know that the levels do not match.    ...
>>
>>Don't do it!!!
>>Not only do the levels not match, the phone line can have 60 volts across its 
>>wires and will fry your Mac when it is ringing. 
>
>  To me it looks like Daniel wants to connect his Mac speaker to the
>*phone handset* mike input, not directly to the line. In this case
>the phone probably provides all the isolation he needs, as well as the
>FCC-approved interface and hook switch and all thet cruft. 
>  The problem in this case is that the solution probably depends on
>the phone you're patching into and what kind of mike it uses.
>I don't know enough about current brands of phones to say if there's
>one overwhelmingly common circuit design (somehow I doubt carbon 
>mikes are still in style) or if there's a way to connect to the phone
>circuit after the first stage of amplification, or whatever...
>
>
>-- 
>email: wiml@u.washington.edu             |  Home:  Seattle, Washington   |
>     (William Lewis)                     |  47 41' 15" N   122 42' 58" W | 
>NeXTmail: wiml@ingalls.cs.washington.edu `-------------------------------'
>        --*-- Member, Coalition to Preserve Semantic Vacuity --*--

Why not try a well known principle, known as 'acoustic coupling'. Putting a 
speaker in front of the phone's microphone (you may isolate it from acoustic 
noise with som styrofoam) will give you a relative easy way to ensure 
correct impedance (volume control), does not violate any rules or laws (FCC 
or otherwise), does not alter the phone, gives you galvanic isolation (no 
risk of frying your Mac) and probably will it give you more than adequate 
sound quality.

Give it a shot.


* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
| Staale Freyer               | E-Mail: freyer@hsr.no                       |
| Rogaland University Centre  | Tel: +47-4-874100(exchange)                 |
| Ullandhaug,N-4004 Stavanger | Tel: +47-4-874419(direct), Fax: +47-4-874300|
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
From: alex@fermat.uucp (Alex Gerbessiotis)
Newsgroups: sci.electronics
Subject: Re: multi-standard VCR`S  (Re: NTSC to PAL  Did anyone try?  )
Date: 2 Sep 92 20:50:06 GMT
Article-I.D.: das.1992Sep2.205006.19553
Organization: Aiken Computation Lab, Harvard University

In article <1992Sep2.103956.14680@lmpsbbs.comm.mot.com> michaelr@ecs.comm.mot.com (Michael Roetzer) writes:
>In article <1992Sep2.023848.10324@iitmax.iit.edu> technews@iitmax.iit.edu (Kevin Kadow) writes:
>>In article <31AUG199217470293@robin.rp.csiro.au> awhichel@robin.rp.csiro.au (Adrian Whichello) writes:
>>)In article <28AUG199216305565@judy.uh.edu>, cscc13@judy.uh.edu (NAVEED IQBAL) writes...
>>)>Did anyone try converting NTSC to PAL system? 
>>
>
>Where can you buy or mail order multi-standard VCR`s ?  And how much are they?
>Last year I asked in several electronics and video shops in Tucson, AZ about those VCR`s but they
>     Michael
	Check the Sunday edition of New York Times. A company whose name
	escapes me at the moment advertises such VCRs and TVs (among other
	things). Its ad occupies  the whole last page of a section of NYT).

	Once upon a time (at least a year ago) I got a catalog from
	42st Photo (name?) (it also has ads on NYT) that also
	advertised multiple system VCR and TVs (from Philips,
	Sony, JVC).  Prices were in the range of high $300's to $600 (for VCRs).

	BTW, I've never purchased any such system from
	either of these companies.

	Hope this helps,
	alex
From: u9dmlb@ohm.york.ac.uk (Duncan McL Barclay)
Newsgroups: sci.electronics
Subject: Re: Filtering TV Commercials
Date: 3 Sep 92 14:27:48 GMT
Organization: Electronics Department, University of York, UK

In <1992Sep03.042045.5095@ecst.csuchico.edu> rmintz@ecst.csuchico.edu (Rich Mintz) writes:

>I'm interested in building a device (or making my 386sx 
>act like one) that will be able to distinguish television 
>commercials from television programs. I've talked to a 
>few people and have heard of a couple of ways it is said 
>that this can be done.
> 
>First, I was told that the audio during commercial 
>announcements on tv is boosted higher than that used for 
>normal programs (for obvious reasons). However, I've 
>tried all kinds of analysis with volume levels, averages 
>over specific periods of time, etc, using my computer's 
>sound card (with stereo capability), with no luck at 
>finding any dependable pattern to distinguish    ads from 
>shows.
> 
This idea has been around for some time, unfortuantely as you have
discovered the levels arent really changed. However from having the
TV on in the background adverts do sound louder. I can only imagine that
they are compressed (an audio technique which compresses dymanic range)
more heavily to make you notice them (drums etc seem to be higher in the
sound mix). IF this is so it may be possible to try and discrimate on this
basis, although I havent got a clue how.

>Someone else told me they had heard that what I'm wanting 
>can be acomplished by analyzing the video transmission 
>for the presence of computer-encoded information that 
>accompanies programs, but not commercials. I assume he 
>was referring to Closed-Captioned (CC) text sent along 
>with many shows for the benefit of the deaf who have 
>special receivers for these signals.
> 
In the UK Tv signals are sent with quite a bit of information. Firstly there
is Teletext, a viewdata system (which includes the CC text); timing markers
for opt-out stations to que to (these are in other spare lines but I dont
know where) and most importantly the little funny square. On our commerical
stations two queue markers are sent at the right hand edge of the screen in
the top 20 or so lines, these look to be some sort of tone which masks the
signal underneath. The tv companies use these to que in local adverts in
networked programmes. I think the first marker appears 30seconds before the
adverts. So you could build a box to look for this and once its found it
wait 30secs and kill the audio. However I dont know if this is present
in US systems.

>Any suggestions? Thanks.
> 
>   Rich -> rmintz@cscihp.ecst.csuchico.edu

Raggy

-- 
Raggy                 | God smiles upon the little children, the alcoholics, and
u9dmlb@ohm.york.ac.uk | the permanantly stoned. S.King.
From: CSMSMAS@MVS.OAC.UCLA.EDU (CSMSMAS)
Newsgroups: sci.electronics
Subject: Re: Humidity Sensor Needed (Cheap!!!)
Date: 26 Aug 92 06:33:23 GMT

In article <BtKDF8.4G8@cmptrc.lonestar.org>, on 26 Aug 1992 00:01:56 GMT,
neal@cmptrc.lonestar.org (Neal Howard) writes:
>Can anyone out there help me with my search for something to use as an
>electronic relative humidity sensor. So far my search has revealed the following
>methods for building a sensor device for use in constructing an electronic
>hygrometer I wish to interface to my PC:

Probably not what you are looking for, but you left out:

4).  Dew point measurment?
     Some temperature sensors, one solid state cooling device,
     an optical sensor, and some control circuitry...
     Wouldn't this be "self calibrating" (or only depend
     on the temperature sensor's accuracy)?
     I haven't tried this, just thought about it,
     (probably read about it somewhere...)
From: michael@vk2bea.UUCP (Michael G. Katzmann)
Newsgroups: sci.electronics
Subject: Re: Stripping NTSC Color Burst
Date: 28 Aug 92 13:20:11 GMT
Reply-To: michael@vk2bea.UUCP (Michael G. Katzmann)
Organization: Broadcast Sports Technology, Crofton. Maryland.

In article <1992Aug26.125832.1@vax.sonoma.edu> butler@vax.sonoma.edu writes:
 >I have an NTSC video signal that I would like strip the color burst 
 >out of.  I'd also like to invert the video.  Can anyone think of a 
 >clever circuit to do this or of a device that might work?  I thought
 >about filtering out the 3.58 mhz, but I might lose some video 
 >information.  I'd appreciate any info or ideas.
 >

If you have a sharp enough filter you could remove the colour burst without
problems but you'd remove the colour as well (I suppose you realized that).
3.58 crystals are dirt cheap, so a crystal filter is probably a good
road to take. 
You could try using an LM1881 to derive the burst gate
and clamp the back porch, which would remove the burst. A simple
one transistor amp would invert the whole signal. To invert just the
video, use the horizontal blanking as a switch signal.

-- 
Michael Katzmann	  >	Broadcast Sports Technology Inc.
~~~~~~~~~~~~~~~~	 <	Crofton, Maryland. U.S.A
Amateur Radio Stations:   >
NV3Z / VK2BEA / G4NYV	 <	opel!vk2bea!michael@uunet.uu.net
Newsgroups: sci.electronics
From: heuring@riker.cs.colorado.edu (Vincent Heuring)
Subject: PD Logic Simulator Needed
Organization: University of Colorado, Boulder
Date: Wed, 2 Sep 1992 23:43:47 GMT


Does anyone know of a public domain digital logic simulator
that is available at any of the ftp sites?

Tnxxx

-- 
---
 Vincent Heuring   Dep't of Electrical & Computer Engineering
 University of Colorado at Boulder      Boulder CO 80309-0425
 heuring@cs.Colorado.EDU   o) 303-492-8751    h) 303-449-8868
From: laird@stable.ecn.purdue.edu (Kyler Laird)
Newsgroups: sci.electronics
Subject: Running computer from vehicle's electrical system.
Date: 31 Aug 92 15:34:48 GMT
Organization: Purdue University Engineering Computer Network

I was just reading the thread about running a computer from a
car battery, and I realized that I need help doing the same, but
this time, the battery is in the vehicle (a tractor).

How simple is it to filter out spikes and sags?  I was thinking
of limiting the power supply to a 15V Zener diode, 12V regulator,
"large" capacitor, and switching diode (to keep capacitor from
draining back into the tractor's electrical system).

My background is primarily in digital electronics, so I need help.
Is a more complex circuit needed?  I'm not too interested in
efficiency; most of the circuit will be shut down with the engine,
and draining the battery a bit will not be a big problem.

The circuit I'm powering is a 68HC11EVB and Zenith laptop.  The
EVB needs +12V only, and the Zenith takes +16.5V, but I suspect
that it will run on +12V.

Thanks for the help!

--kyler
From: henry@zoo.toronto.edu (Henry Spencer)
Newsgroups: sci.electronics
Subject: Re: Rigging up a sound card so that it will do voice mail
Date: 28 Aug 92 20:45:30 GMT
Organization: U of Toronto Zoology

In article <1992Aug27.010101.13945@u.washington.edu> gunthar@milton.u.washington.edu (John Jacobson) writes:
>I am thinking about rigging up my computer so that it will :
>    - Determine whether an incoming call is voice or modem

This is kind of difficult, since both an incoming modem and an incoming
human typically will wait for your end to say something.  The modem won't
say anything until it gets a tone it recognizes as a suitable form of
carrier.  The human will probably eventually say "hello?" :-).
-- 
There is nothing wrong with making      | Henry Spencer @ U of Toronto Zoology
mistakes, but... make *new* ones. -D.Sim|  henry@zoo.toronto.edu  utzoo!henry
From: derekn@vw.ece.cmu.edu (Derek B. Noonburg)
Newsgroups: sci.electronics
Subject: where to get DSPs?
Date: 28 Aug 92 18:24:38 GMT
Distribution: sci
Organization: ECE Department, Carnegie Mellon University

The recent issues of Circuit Cellar Ink, Radio Electronics, and QST
have included a total of four DSP projects.  So now that they've
convinced me that I want to build a DSP board :-) does anyone know
where I can get DSP chips in small quantities?  None of the articles
mentioned any suppliers (unless you want to buy entire kits).

The articles used the Analog Devices ADSP-2101 and -2105, and the TI
TMS320C10.  I've also heard good things about the Motorola 56k series
(the 56156 apparently has an onboard CODEC).  I'm not picky :-)

The usual places (Digi-Key, Jameco, JDR) do not carry exotic parts
like these (of course), so I'm looking for somewhere else to buy
onesies.  I suppose I could try to get samples, but this doesn't seem
quite ethical (since it's for a personal project), and besides, if I
ever want to get another one or two, I'd probably be out of luck.

- Derek

--
Derek Noonburg                                derekn@vw.ece.cmu.edu
Electrical & Computer Engineering Dept., Carnegie Mellon University
From: kirk@sdd.hp.com (Kirk Norton)
Newsgroups: sci.electronics
Subject: Re: Ion generator skematic wanted
Date: 3 Sep 1992 20:05:06 GMT
Organization: Hewlett-Packard, San Diego Division
Distribution: world
NNTP-Posting-Host: hpsdl225.sdd.hp.com

In article <BtytnC.KFA@hsi.com>, kanakis@hsi.com (Tony Kanakis) writes:
|> Does anyone have a skematic or diagram describing how to build an ion
|> generator similar to ones used in homes to clean the room air?

A design for one appeared in RE a few months back.
As I recall, it was just a simple voltage multiplier circuit.
Anybody remember which RE issue it was?

-- 
 Kirk Norton (kirk@sdd.hp.com) --  Hewlett-Packard, San Diego Printer Division
Newsgroups: sci.electronics
From: arm@helix.nih.gov (Andrew Mitz)
Subject: coating materials for antennas
Followup-To: sci.electronics
Keywords: antennas materials
Organization: National Institutes of Health, Bethesda
Date: Fri, 28 Aug 1992 20:51:11 GMT

I am building an outdoor antenna for radio telemetry.  It will
receive signals at about 100 MHz.  It will be made of aluminum
tubing.  Because of environmental constraints, the antenna will
be cleaned regularly with high temperature, high pressure water.

Question:
What paint or other coating material can I use to avoid oxidation
of the aluminum?  I am assuming that aluminum oxide is not a very
good conductor and will decrease the radiation efficiency due to
the skin effect.  Certainly many paints will be as inefficient
as the oxide, so the choice of coating material is probably important.
Mosely (a now-defunct antenna company) once made a clear coating
solution for antennas, but I do not know what material they used.

Please offer suggestions.  Practical ones would be more valuable than
theoretical ones, but both are welcome. 



-------------------------------------------------
Andrew Mitz          |    NIH Animal Center
Biomedical Engineer  |    Poolesville, MD
-------------------------------------------------

All opinions expressed are my own.


Newsgroups: sci.electronics
From: wtm@uhura.neoucom.edu (Bill Mayhew)
Subject: Re: Power supply regulation
Organization: Northeastern Ohio Universities College of Medicine
Distribution: sci
Date: Wed, 26 Aug 1992 01:25:04 GMT

Using 3-terminal regulators for high voltage regulating circuits by
referencing the "ground" leg to something other than zero volts is
tricky.  The problem is making sure that none of the voltages
appearing between the leads of the 3-terminal regulator at
power-up or power-down exceed the manufacturers' recommended
ratings.

3-terminal regulators a la 78xx series get very angry if the load
side voltage exceeds the input side voltage by much (relative to
the ground pin).  The first line of defense is to put a reverse
biased rectifier diode across the input and output.  This prevents
blowing the regulator at power-down if you have a lot of
capacitance on the output side.  It is a good idea to use a
protection diode even if you aren't lifting the ground terminal.

If you are trying to regulate a 60 volt supply, the outboard
components to protect the 3-terminal regulator are going to begin
to become complex.  It would probably be just as easy to use
discrete components for the pass elements.


-- 
Bill Mayhew      NEOUCOM Computer Services Department
Rootstown, OH  44272-9995  USA    phone: 216-325-2511
wtm@uhura.neoucom.edu   (140.220.1.1)
Newsgroups: sci.electronics
From: dont@klic.rain.com (Don taylor)
Subject: semiconductor life = f(temp), was How Hot
Organization: KLIC
Distribution: na
Date: Thu, 3 Sep 1992 02:49:08 GMT

I am not really interested in socket or solder failure.

About a decade ago I read the Motorola MECL Design Guide that described how
the life of mecl went down 100 or 1000 fold (I don't remember anymore) for
EACH 30 degree c temperature rise.

Does anyone have current data for parts like the 486?

The issue is whether it is heavily dependent on the cleanliness of the process
or really inherent in the silicon itself.

I would really like a documented source for this info.

Please reply by email if at all possible

Thanks
Don Taylor
503-235-6853
dont@klic.rain.com
qiclab!loop!dont

Newsgroups: sci.electronics
From: whit@milton.u.washington.edu (John Whitmore)
Subject: Re: Success! Resist Pen Works in HP Plotter!
Keywords: resist pens, pcb, etching
Organization: University of Washington, Seattle
Date: Fri, 4 Sep 1992 01:40:44 GMT

In article <18219@acorn.co.uk> agodwin@acorn.co.uk (Adrian Godwin) writes:

<about making PC boards>
>I'd like to go one further than David and avoid the need for chemicals 
>altogether : machining the copper surface directly. The cutter would have
>to be extremely small to do a useful job, but perhaps some sort of spark
>erosion system might do it.

	Spark cutters (electrical-discharge machining tools, EDM)
are probably not the best way to do this.  In principle, one makes a
fast spark and blasts out material with a combination of heat and
ionization (the + ions that result from metal eroding are usually
repelled from the workpiece, which is a positive electrode), with a 
bit of acoustic 'blast' effect.  EDM works well on brittle or
nonrefractory metals, or on materials with a low thermal conductivity.
There is a minimum of electrical conductivity, below which 
EDM is ineffective.

	Removing a thin layer of copper runs into two problems: first,
the EDM machine will have to follow the plane of the copper board very
well (a few thousandths of an inch is enough to change the spark).
Second, the EDM has to be well-connected (electrically) to the parts it is
cutting out.  You'd have a hard time making it work with a 
plotter-style 'cut list', because a section of the copper could 
become electrically isolated during cutting.  Better would be to 
raster-scan the PC board, which requires some conversion software
(and a bit-map picture of the board to be created, with fine detail...).

	You could just sandblast, of course.  It might be possible to
do the drilling at the same time as the etching (saving those pesky
little extra steps...).


	John Whitmore