HDTenEightyP/NetNews huggingface dataset:
Newsgroups: sci.electronics

In sci.electronics, pollock@milton.u.washington.edu (Joe Pollock) writes:
> In contrast, a neon sign transformer is typically 6000 - 15000 vac,
> rated to put out 30-60 ma.  Keep in mind that these transformers are
> center-tapped, meaning the mid-point of the secondary is connected to
> the case (and to ground, if you've wired it correctly).  This means
> that THE ONE-HAND IN THE POCKET RULE WILL NOT PROTECT YOU.  Each end
> of the transformer is 7500 vac above ground.  Unless you are very
> well insulated, like on dry wood on glass insulators, you will get
> a shock in at least the "dangerous," if not "lethal," range.

The one hand in the pocket rule is not meant to keep you from getting
zapped.  No matter how the secondary of a neon sign transformer is
wired, and how many hands you keep in your pocket, it is always
possible to get a very serious shock.  What the hand-in-the-pocket
rule is designed to do is to keep you from doing something REALLY
stupid like leaning one hand on the case while touching a hot lead.
This would cause a high voltage path up one arm, through the heart,
and down the other arm -- a much more deadly path than through your
shoes to ground.

--Mike Jassowski (maj@hpesmaj.fc.hp.com)
From: rainer@spot.Colorado.EDU (Rainer Malzbender)
Newsgroups: sci.electronics
Subject: Re: MC68000
Summary: Simple way to do boot time address decoding
Date: 7 Apr 92 18:35:18 GMT
Organization: University of Colorado, Boulder

In article <1992Apr6.033214.15677@resmel.bhp.com.au> jing@resmel.bhp.com.au (Jian Feng) writes:
>
>Easy. MC68000 reads in the Stack Pointer (SP, the system stack pointer)
>and the Program Counter (PC) from address $0. It takes 4 read cycles on
>the 16b bus. Just use a simple 2 bit binary counter which is reset on power-up
>and on counter-overflow it can switch the address.

Although this will certainly work, it requires more circuitry. Here's an
alternative which I used on my last project:

Basically what you need is a signal that says "I'm booting". If you're
building a system with a UART, a good choice is the 2681. In addition
to two uarts, it also has several I/O pins which can be used for any
purpose whatever. I used one of these as my "boot" flag - it gets set to
some state (I forget which - high, I think) on power up, and my software
resets it to the other state after we're on the air.

This boot signal goes into the address decode PAL, which generates device
selects based on the address and a few other signals. The PAL maps ROM
into low memory if the boot flag is on, high memory otherwise.

The eprom then has the restart stack pointer and PC as its first entries.
One of the first instructions executed then resets the boot flag causing
the pal to map ram low, eprom high as desired.

Since I always use a pal in the address decode anyway (for simplicity as
well as future expansion or changes), this requires absolutely no
additional circuitry. Of course, if you can't find an unused I/O pin
around somewhere this won't work.

I hate to admit it, but back in 1981 when I hacked my first 68k system
($140 for the 68000, about the same for 64K dram!) I actually put in
some '244s with jumpers to set the PC and SP at boot time, along with
a cycle counter to set things back to normal. This is better.

--
-- 
Rainer Malzbender                   No quote due to insufficient coffee today.
Post-doc, Physics
U. of Colorado, Boulder (303)492-1366              rainer@shelley.colorado.edu
From: hbg6@phx.mcd.mot.com (John Schuch)
Newsgroups: sci.electronics
Subject: Re: RS-232 Ambient temprature sensor
Keywords: hardware project
Date: 9 Apr 92 01:50:32 GMT
Organization: Motorola Computer Group, Tempe, Az.

In article <1992Apr8.090004.19143@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes:
>In article <1992Apr5.013215.11028@ttank.ttank.com> karl@ttank.com writes:
>>What I would like to build is a Thermometer that can communicate
>>ambient temprature to a computer via RS-232.  I would like to tie
>
>Well, I wouldn't bother with RS232, but you could do it to a parallel
>port quite easily like this:
>

I don't know, how about connecting a temperature sensitive oscilator
to the DTR (DSR? ) pin of the serial port. The period of the signal,
or the number of ticks within a given time would indicate the temperature.

John

------------------------------------------------------------------------
John Schuch           hbg6@citek.mcdphx.mot.com            (602)438-3008
------------------------------------------------------------------------
      One wonders if there would be such a pursuit of artificial
      intelligence if there were more of the natural kind around.
------------------------------------------------------------------------
Newsgroups: sci.electronics
From: sasbge@ant.unx.sas.com (Gantt Edmiston)
Subject: Re: Cable TV Descrambler
Reply-To: sasbge@ant.unx.sas.com
Organization: SAS Institute Inc.
Date: Mon, 13 Apr 1992 19:01:27 GMT
Originator: sasbge@ant.unx.sas.com
X-Bytes: 2131

In article <1992Apr12.>, 2frlclover@kuhub.cc.ukans.edu writes:
>Hi all,
>
>I am thinking of building a CABLE TV descramble Kit but I am not sure whether
>it will worth my money. I am also interested in knowing the quality of the
>picture. Lastly, is it legal in Kansas.
>
>Thanks in advance.
>
>Mike
>

Mike, 

Is it worth your money?  This is a personal question which only you
can answer.  First, you didn't say how much of your money was involved =-)
Secondly, if you learn something about RF, IF and AF circuits during
the process, then try to equate your money to paying tuition for an
electronics course in your local community college.  Not to mention the
personal satisfaction of gaining that additional knowledge.  How much
is you personal time worth?

Is it legal in Kansas?  Don't know but in general:  If you descramble and
receive a "premium" channel (like HBO, etc...), YES that's illegal.  If
you descramble an otherwise free channel (some cable services scramble
everything above channel 13) then it's probably OK.

Legally, you can build, attach and descramble any signal as long as you
advise the local cable company that you are doing so, pay for the services
you receive and don't add any interference into the system that might
degrade the signal out to other customers.  The intent here is to allow
the public to not be required to pay the sometimes outrageous "rental"
charges for descrambler/converter boxes offered by cable service companies.



Based on what I have seen in trade magazines (Radio Electronics, etc...)
descramblers are a dime-a-dozen.  RE mag alone has about a dozen vendors
each month.

As for the quality of the picture?  If you build it correctly, it should
be as good as a picture that was not scrambled originally ;-)


-- 
------------------------------------------------------------------------------
Gantt Edmiston                         =  o     |
QA Host Systems, V416 x6091         =  _ /- _   |  "The fewer the facts,
SASnet: <sasbge@ant.unx.sas.com>   =  (_)> (_)  |   the stronger the opinion!"
------------------------------------------------------------------------------
From: hbg6@phx.mcd.mot.com (John Schuch)
Newsgroups: sci.electronics
Subject: Mercury Memory
Date: 14 Apr 92 19:16:24 GMT
Distribution: usa
Organization: Motorola Computer Group, Tempe, Az.

I was watching the PBS program "The Machine That Changed The World"
last night ( the series deals with the history of computers ).
They mentioned some sort of data storage device called a mercury
tank. If I remember correctly it was used in the ENIAC computer
system. Anybody know what it is or how it works?

John

------------------------------------------------------------------------
John Schuch           hbg6@citek.mcdphx.mot.com            (602)438-3008
------------------------------------------------------------------------
      One wonders if there would be such a pursuit of artificial
      intelligence if there were more of the natural kind around.
------------------------------------------------------------------------
From: Scott.Hass@f550.n226.z1.FIDONET.ORG (Scott Hass)
Newsgroups: sci.electronics
Subject: 80C31
Date: Fri, 10 Apr 92 19:08:30 EST
Organization: FidoNet node 1:226/550 - Lilly Pad, Reynoldsburg OH

In a message of < 3 Apr 92 04:43:12>, Ken Bass (1:226/20) writes:

 KB>Does anyone have a ROM MONITOR program for the 80C31 they would share
 KB>with me or direct me. I need to communicate with the 80C31 via RS232 to
 KB>modify and display memory locations.
 KB>
 
Ken

I have two of them on my board, they are mon31-11.zip (10k), and monplus.zip
(24k). They both include asm source code and doc files (no executables) and 
are freq-able from 1:226/550.

                        Scott


--  
Scott Hass via cmhGate - Net 226 fido<=>uucp gateway Col, OH
UUCP: ...!osu-cis!n8emr!cmhgate!550!Scott.Hass
INET: Scott.Hass@f550.n226.z1.FIDONET.ORG
From: bill@hacktic.nl (Bill Squire)
Newsgroups: sci.electronics
Subject: Re: 46/49Mhz Cordless Phone Amp Needed
Date: 12 Apr 92 21:55:58 GMT

els@hpd.unp.ac.za (Leonard Els @ University of Natal (Pietermaritzburg)) once wrote....
>
>Has anyone come across a 50Mhz RF Amp Schematic (about 5-10W Power output).
>I intend amplifying the signal from both my base station and handset of my 
>cordless phone. The handset will be used in a car, so there is no problem 
>for the power input.
>
>I do have the resources to DESIGN one myself, but this involves a lot of 
>work determining the correct values for coils etc.
>
>I someone has a design, could they get in contact with me.

I've found that the diplexer on a cordless phone will not allow much more
than 100mW.  More than that and you just desensitize the receiver, often
more than the increase buys you!  Using the 100mW at each end with a full
quarter wave antenna at the base may get you about a kilometer of range,
but expect no more no matter what you do.

                                                        Bill
Newsgroups: sci.electronics
Newsgroups: sci.electronics

  What is 'oversampling' and 'bitstream conversion' for a CD player ? As the 
latter tends to replace the former on the front panel of a CD player, I 
suppose it has nothing to do with the 44.1 KHz sampling rate.
  Regards. -Nicolas Tripon
Newsgroups: sci.electronics,rec.music.cd,rec.audio
From: sethb@fid.morgan.com (Seth Breidbart)
Subject: Re: requesting CD player advice
Organization: not very
Date: Tue, 14 Apr 1992 23:05:36 GMT

In article <ku9ldkINNh0l@exodus.Eng.Sun.COM> nemeth@helix.Eng.Sun.COM
(Les Nemeth) writes:

>What you are missing here is the fact that distortion is of no relevance
>in this equation. There are going to be better and/or worse players than
>others regardless of price. Sound quality of the CD player has to do with
>how well the player converts the data from digital to analog. Therefore,
>it is in your best interest to buy the player with the most oversampling
>per dollar spent. It has been proven that, the more oversampling a player
                               ^^^^^^
>has, the better it is at reproducing the sound faithfully.

I'd like to see that proof.

It has been proven that, the better the quality of the capacitors used
in a player, the better it is at reproducing the sound faithfully.

Hmmm....

Player A has 64 times oversampling and cheap analog components.
Player B has no (ok, 1 times) oversampling and very high quality
analog components, including an R2R d/a ladder with hand-selected and
hand-matched to 0.001% tolerance resistors, and a 27th order Chebyshev
brick-wall filter.  It has therefore been proven that A is better than
B, and B is better than A.

So much for proofs.

>A CD player can have .0001% distortion, but if it has a tinny sound who the
>heck is gonna buy it.

Any definition I've ever seen of "tinny" (and every sample of it I've
ever heard) involved a lot more than .0001% distortion.

In many cases, .1% distortion won't be audible.  In others, .025%
distortion will make music unlistenable (consider, for example, a box
that caused a 1-millisecond silence every 4 seconds).

> Conversely, if another player has .001%
>distortion but has a muddy sound, who the hecks gonna want it either.

Likewise, you can't get muddy at .001% distortion.

Seth		sethb@fid.morgan.com
From: LEEK@QUCDN.QueensU.CA
Newsgroups: sci.electronics
Subject: Re: How to estimate 9V Alkaline Battery life ?y
Date: 11 Apr 92 16:05:43 GMT
 <1992Apr10.015016.1816@memstvx1.memst.edu>
Distribution: sci
Organization: Queen's University at Kingston

>In article <JON_SREE.92Apr6094821@world.std.com>, jon_sree@world.std.com (Jon
>Sreekanth) writes:
>>
>> I'm using a 9V alkaline (Duracell, or some similar store brand) battery
                                    :  stuff deleted
>> Is there some magic formula for estimating, from your experience, or
>> any  published specs (where do I find them ?) battery life ? Battery

According to The Art of Electronics by Horowitz & Hill....
               Rint  Voc   Cap to 1V/cell                Comment
9V "1604"
Le Clanche      35    9    300mAH @ 1mA   160mAH @ 10mA
Heavy Duty      35    9    400mAH @ 1mA   180mAH @ 10mA
Alkaline         2    9    500mAH @ 1mA   470mAH @ 10mA
Lithium         18    9   1000mAH @ 1mA   950mAH @ 80mA  Kodak Li-MnO2

You can see that Alkaline & Lithium are pretty good with Lithium at
2X capacity and 2X price depending on where you get it.

>> (Right now, I have a 500maH estimate from Panasonic, and I've looked at
>> Horowitz and Hill. I'm hoping I can get more maH because of the low
>> drain, and because the circuit can go down to about 4V at least.)

Do watch out when you try to drain the cell down to 4V.  The cell
internal resistance goes higher near the end.
Also do watch out - cheap batteries rust & leak whatever's left in them
as years goes by.

You can probably use the Discharge curve (fig 14.1) in Horowitz&Hill
to estimate the battery capacity from the 1V/cell to 0.66V/cell.
From the graph, I would say 20 to 25% for Alkaline.

In article <1992Apr10.015016.1816@memstvx1.memst.edu>,
sowellrm@memstvx1.memst.edu says:
>
>Kodac used to sell a 9V lithium battery that would probably last longer than
>the alkaline.  It costs around $5 though.

Yeap.  2x life at 2x price.  Not bad.

K. C. Lee
Elec. Eng. Grad. Student
From: weigand@vanilla.udel.edu (Steve Weigand)
Newsgroups: sci.electronics
Subject: Re: Software request
Date: 14 Apr 92 17:23:12 GMT
Article-I.D.: udel.1992Apr14.172312.13273
Distribution: usa
Organization: University of Delaware, Newark

In article <1992Apr14.162435.12865@uwm.edu> alanchem@csd4.csd.uwm.edu (Alan Scott Olson) writes:
>I'm looking for some public domain software for a PC that will allow me
>to draw a circuit schematic and the print it on an HP LaserJet laser printer.
>
>Does anyone out there have or know where I can get a copy of such a program?
>
>Thanks
>
>- Alan
>
>-- 
> ___________/ Alan S. Olson  UW-Milwaukee Chemistry Department \______________
>/     e-mail to alanchem@csd4.csd.uwm.edu  OR  alan@alchemy.chem.uwm.edu      \
>|          Want some good music?  Check out Milwaukee's own BoDeans           |
>+-----------------------------------------------------------------------------+

 Ok... Here's the poor man's solution to your problem (assuming that if you
were rich, you'd already have a $5000 circuit schematic program and a 
plotter):

  1. Get yourself a copy of a public domain program for the IBM PC that
     allows you to take HPGL (HP plotter) files and output to any printer
     (especially the HP Laserjet). I know this program exists both for the
     IBM PC and the Amiga computers (and probably MAC and Atari and 
     definitely SUN UNIX). If you have a long list of ftp sites in the
     file "ftpsites.txt", maybe you could do:
  
  	cat ftpsites.txt | fgrep 'HPGL' 

     .. that is if you're on a unix machine.  It would show you all the
	ftp sites out there that have that sort of thing.

  2. Get yourself a CAD program of some sort for the IBM. There are 
     numerous public domain CAD programs. All of them are fairly alike.
     You basically create yourself some "parts" such as resistors, 
     capacitors, inductors, diodes, etc. and you can scale them to
     size, connect them, etc.. Then when your circuit is laid out, you
     should print it in HPGL format and dump it to that program I mentioned
     above. 

   I get very good results using MCAD for the Amiga, which already has 
   some electronic parts made up for it... And in the package, they 
   included a program to convert any HPGL output to your printer. And
   my printer happens to be an HP LJ II.
`

 Hope this helps, 
  - Steve Weigand
    (weigand@freezer.cns.udel.edu)
From: bills@inqmind.bison.mb.ca (Bill Shymanski)
Newsgroups: sci.electronics
Subject: PC Parallel Port
Date: 11 Apr 92 18:15:24 GMT
Organization: The Inquiring Mind  1 204 488-1607

Quoting:
>From: pgf@cayman.COM (Paul Fox)
>Newsgroups: sci.electronics
>Subject: parallel port distance limits?
>Date: 10 Apr 92 19:46:47 GMT
>Organization: Cayman Systems Inc., Cambridge Ma
 
>    How far can a typical PC's parallel port be extended?  I haven't
>    looked at the drivers...  I'd love to go about 50 feet...
 
>    paul fox, pgf@cayman.com
End Quote
   
  I have a parallel port driving exactly 50 feet of shielded cable
that *so far* has shown no signs of distress ( its on a report printer 
that for various good reasons shouldn't be in the same room as the 
computer).  Of course, if it doesn't work, the first thing your computer 
or printer vendor will say is " You shouldn't have a cable longer than 6 
feet."  They are of course right in one sense, but the printer port seems
to be non-fussy about connected load.   I used shielded cable for this
particular setup, more worried about coupling AC hum into the system than 
suppressing RFI; if you do this, you may want to snap a couple of those 
RF chokes on the outside just to keep the neighbors happy. 
   Bill


bills@inqmind.bison.mb.ca
The Inquiring Mind BBS, Winnipeg, Manitoba  204 488-1607
From: goodnuff@phoenix.Princeton.EDU (David W. Goodnuff)
Newsgroups: sci.electronics
Subject: TV and radio reception
Date: 13 Apr 92 09:08:46 GMT
Organization: Princeton University
Originator: news@ernie.Princeton.EDU


	Hello, my room-mates and I are currently suffering from poor
radio and TV reception in our college dorm room.  I was wondering if
anyone has any suggestions for improving our reception.  We are mainly
interested in TV but any suggestions for radio are welcome as well.  One
possibility was suggested to me, get a "power antenna" a device that
supposedly uses the electrical system as an antenna.  Do these work very
well?  And where are they available?  Any home made antenna suggestions
are greatly appreciated!  Please e-mail replies.  Thanks.

-=|=- -=|=- -=|=- -=|=- -=|=-
-David Goodnuff-
goodnuff@phoenix.princeton.edu
From: gary@ke4zv.uucp (Gary Coffman)
Newsgroups: sci.electronics
Subject: Re: FM Modulators
Date: 8 Apr 92 09:08:23 GMT
Reply-To: gary@ke4zv.UUCP (Gary Coffman)
Organization: Gannett Technologies Group

In article <1992Apr4.062328.20252@wpi.WPI.EDU> mishaal@wpi.WPI.EDU (Mashal Abdulra Almashan) writes:
>
>	
>	I am trying to modulate a signal at around 106Mhz (FM). I have an FM modulator from my car audio system, but it's switchable between 89.1M and 88.7M. 
>It has trimmer capacitors inside but the range is limited to <.5M. So I tried connecting capacitors in parallel, but that decreased the frequency. When I tried series the signal got very weak when I try to get to reach 90.5M. PLEASE HELP! should I modify this modulator or should I biuld a new one ( I have some circuit background). This modulator uses a chip labeled BA1404(?). 
>	Can anyone suggest a book I can read about FM modulation & construction. Any response would be appreciated(EMAIL/NET/ANYTHING!).

The frequency is determined by the ratio of L to C in the circuit. Try making
the coil have less inductance. You can either stretch the windings or remove
turns.

Gary
From: knuthf@loke.dhhalden.no (KNUT HARALD FINSTAD)
Newsgroups: sci.electronics
Subject: Software
Date: 10 Apr 92 08:29:24 GMT
Organization: Ostfold College


   I think it might be time for producers, to distribute the source-code
   for some of their computer-programs.
From: dino@inqmind.bison.mb.ca (Tony stewart)
Newsgroups: sci.electronics
Subject: Re: question about RC circuits for timing purposes
Date: 6 Apr 92 05:13:56 GMT
Organization: The Inquiring Mind  1 204 488-1607

jmiller@wendy.bowlgreen.oh.us (Jim Miller) writes:

> Hello everyone,
>     I am trying to rig up a 12 volt DC circuit that will introduce a time
> delay.  In general, here's what I want to do:
> 
>                  +--------+                 +--------+
>    + 12V --------| delay  |------ + 12 -----|  12VDC |-----  relay contacts
>                  | circuit|                 |  relay |
>                  |        |                 |        |-----
>    - ------------|        |------ neg ------|        |                     
>                  +--------+                 +--------+
>                  
> 
To get 1 sec delays and drive a relay coil, you will be a current amp (ie 
a transistor) First go into a series resistor (100K) then into the base 
of a darlington NPN base with Emitter grounded. Put your 22 to 47 uF Cap 
across the Base to Gnd. THis will invert your drive signal also. It 
can take the relay coli "kickback" since darlingtons have internal diodes 
on the collector to protect itself, but it is best to put a diode across 
the coils with the anode (| bar side) to the +12V and cathode on other.
The Collector will drive the Coil low with the other sied of the Cl on 
+12V. So when Input goes high to +12V Q1 turns on after .5 to 1 sec delay 
causeing the output C to go low then drive the RElay.
But if YOU ARE USING A TRANSISTOR ALREADY, ARE YOU SURE YOU NEED A RELAY 
(If you need floating contacts then OK, if just to switch on +12V then 
NO.... In this case just use a PNP Transistor pair with high current gain 
and adequate output drive then put you big caps acros the input Base to 
ground to delay the Rseries input signal. The collector of the PNP will 
provide your switched , delayed tput +12 minus .2 foVsaturation.
THere is a trade-off between adequate drive to your device and time 
delay.
'av fun

dino@inqmind.bison.mb.ca
The Inquiring Mind BBS, Winnipeg, Manitoba  204 488-1607
From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: Tying LSTTL inputs to Vcc?
Date: 16 Apr 92 23:52:30 GMT
Organization: University of Washington, Seattle

In article <dfs.703361967@ro> dfs@doe.carleton.ca (David F. Skoll) writes:

	[tying unused TTL inputs high through a resistor to +5]
> ...the Motorola LSTTL databook says it's OK to tie the inputs
>directly to +5v.  Is this typical of all LSTTL input circuitry, or
>peculiar to Motorola's?  Why in most designs I've seen do people use
>either the resistor or spare gate method?  Would power-on transients
>cause problems?

	The original (7400 series) TTL was specified for Vcc to vary
up to 7 volts (non-operating), to allow for power-on transients on
the power supply.  The absolute-maximum input voltage to the gates
was only 5.5V, with the one exception of SOME of the LS gates
(the ones with diode inputs).  That was how TI did it; Fairchild
apparently had ALL their LS gates capable of taking direct
tie to +5V, and were very careful to point out that THEIR chips
would work with direct connection to +5, but that their competitors'
wouldn't.

	The 1k resistor would fix this problem; even when the input
emitter-base junction broke down, the current was kept low (a milliamp
or so wouldn't permanently injure the device).

	With many families of circuitry today (74F, 74C, 74HC, 74HCT,
74AS, 74ALS) all being more-or-less compatible, that 1k resistor
kept on being used (where it wasn't necessary) simply for backward
compatibility.  I think it was only 7400 and part of the 74LS
that EVER had this problem.