HDTenEightyP/NetNews huggingface dataset:
From: tod@cco.caltech.edu (Tod Edward Kurt)
Newsgroups: sci.electronics
Subject: Voltage to PWM for DC motor control?
Date: 20 Nov 1992 07:31:00 GMT
Organization: California Institute of Technology, Pasadena
NNTP-Posting-Host: sandman.caltech.edu
Keywords: PWM


Hey everyone,

	Here's my dilemma:  I've got a voltage that varies (say from 0-5v) and
I'd like to have this voltage control a DC motor via Pulse-Width Modulation.
I've got the actual high-current motor driver (MOSFETs) done, I just need some
pulses for it.
	It seems like there should be a chip that does all this, has an
adjustable PWM frequency, and provides a way to drive the motor both forward
and reverse (2 seperate outputs, one for forward, one for reverse)
	Any ideas?  Surely this must have been done thousands of times.  All 
help appreciated.  BTW, this is for an Electronic Speed Control (ESC) for an
RC car.
					Thanks,
						Tod

tod@sandman.caltech.edu
tkurt@vlsi.caltech.edu
From: smckinty@sunicnc.France.Sun.COM (Steve McKinty - Sun ICNC)
Newsgroups: sci.electronics
Subject: Re: Big NASTY Brother Radio Shack
Date: 17 Nov 1992 17:59:37 GMT
Organization: SunConnect
Distribution: world
NNTP-Posting-Host: hardy.france.sun.com

In article <1992Nov17.071923.7429@njitgw.njit.edu>, dcg5662@hertz.njit.edu (Dave Grabowski (KxiK)) writes:
> 
>   Well, seeing this blooming thread, I just HAD to put in my two cents.
> I'm sure everyone is SICK of "RS Sucks" stories.. well, TOO BAD, because
> here's another:
> 
>   A few months ago, a visited a RS store that I've frequented since I
> was old enough to crawl in the front door. I needed a 3-amp fuse for my
> car radio. Grabbed a pack off the shelf, and noticed the price: a
> whopping 79 cents. A small price to pay for good tunes in the ol' Honda.
> The salesman scans it, and asks for $1.05 (99 cents plus 6 cents NJ
> sales tax). Being the consciencious (sp) consumer, I mentioned the
> twenty cent discrepancy. He refused to do ANYTHING about it -- said that
> "we're going through price changes." I'm sure that some of you have had
> similar problems, and what they are SUPPOSED to do is merely take off
> the difference as "Customer Satisfaction."

Interesting. In the UK you could have reported them to the trading
standards people. There have been several cases where supermarkets have
had items with one price marked on the shelf, but when they have been
scanned past the barcode reader at the checkout a higher price has been
rung in. Its usually just carelessness on the part of the staff who
have changed the item price on the computer and missed the label, but
the courts won't buy that.

I was talking to a friend who was a manager in one supermarket chain
and he was just on his way to court for such a situation. The trading
standards officers had checked after a complaint and found one store with
half a dozen mistakes like that. All my friend could do was plead guilty, 
apologise, and pay up.


Steve
From: esm40@cd.amdahl.com (Ed McGettigan)
Newsgroups: sci.electronics
Subject: TI micromachine mirror chip
Date: 18 Nov 92 19:58:45 GMT
Organization: Amdahl Corporation, Sunnyvale CA

In this month's Scientific American there is a large article on micromachine
chips and included a mention of a TI chip that had 2 million mirrors on it.
So I have the following questions:

1. Does anyone know if they are making it available as samples/product?
2. Who can I contact to get more information (someone from TI must read this
   group)?
3. Is there anyone else that makes/will make a similiar chip?

-- 
+------------------------+
|Edward McGettigan       |
|esm40@cd.amdahl.com     | 
+------------------------+
From: squish@endor.uucp (Shishin Yamada)
Newsgroups: sci.electronics
Subject: Re: Death of remote controls
Date: 20 Nov 92 06:57:21 GMT
Article-I.D.: das.1992Nov20.065721.688
Organization: Aiken Computation Lab, Harvard University

Is there any way to insure remotes againt static electricity? Recently
I seem to have broken my SHARP tv remote by static electricity when it
arc-ed in my hand to the tv antenna. I think a humidifier would work
(but is there a better or cheaper way).

By the way, I haven't had time (and my DMM is out with a friend's
broken motorcycle battery) to look at much of the remote. I dunno if
the main CMOS chip is blown or about four or five supporting diodes).
Where do you purchase replacement remotes? 

I have been shocked by everything in my dorm room lately... from light
switches to CD player to bed frame to stereo to tv antenna. I was only
slightly annoyed until my remote broke just last night (Is it possible
to ground my carpet somehow?) The shock went through all the remotes
plastic casing through the remote and arc-ed across about 2mm of air
to get to the tv antenna (so we're talking HIGH potentials). I'm
trying to always take off my sneakers when on this damn carpet. Also,
it makes it particularly painful to shake hands or (ooops.... kiss).

ARGH! -squish@endor.harvard.edu
From: bruce@coos.dartmouth.edu (Bruce K. Johnson)
Newsgroups: sci.electronics
Subject: digital clock for circuit
Date: 17 Nov 92 18:02:05 GMT
Organization: Dartmouth College, Hanover, NH

Hello all.

I have a question about making a clock for my circuit.  First, let me give
you a background --- I'm making an A to D data aquisition box for the MAC's
serial port.  I'm using an ADC0831 chip and want to time it as well as provide
an external clock signal for the MAC's handshake line (the MAC can only run its
serial interface at a top speed of 57900 BAUD internally, therfore, if I want
to run say a 22 KHZ sample rate, I need a much faster ext clock...)

Anyway, I originally started off with an oscillator and a decade counter to
get the two clock signals (one that provides chip select line to the a/d at
about 22 KHZ and the other to provide the BAUD clock about 10 or 14 times the
first clock --- 8 bits of conversion plus a start bit plus several stop bits)

This costs too much.  My project is for use by students in a Physics class
and must be relatively inexpensive for them to purchase.  I then turned to
using a 556 timer to get two clock signals with one chip (a .70 cents chip
compared to a 1.70 osc + other stuff).  The 556 is capable of providing
a stable signal for the 22KHZ clock but not for the 220>KHZ clock.

Is there another cheap alternative to making two clock signals or can I make
the 556 (two 555 on one chip) produce a more stable signal at these high speeds?

Any advice would be greatly appreciated.

THANKS

BRUCE
Newsgroups: sci.electronics
From: abond@rvgs.vak12ed.edu (Andrew H. Bond)
Subject: Re: Motorola BBS mirror ftp site?
Organization: Virginia's Public Education Network (Roanoke)
Date: Fri, 20 Nov 92 09:56:35 GMT

rda735z@nella16.cc.monash.edu.au  writes:
> Is there an FTP site around the place which mirrors the Motorola BBS?  My
> reason for asking is that placing a call to the BBS from Melbourne,
> Australia is probably going to stretch my limited budget a little :-)
>
> Thanks,
> Simon.

check out these ftp sites:

bode.ee.ualberta.ca	/pub/dos/motorola/68hc11
calvin.stanford.edu	/motorola/68hc11
ee.utah.edu		/admin

hope this helps--AHB
-- 
Andrew H. Bond, Roanoke Valley Graduate Center
Newsgroups: sci.electronics
From: kolstad@cae.wisc.edu (Joel Kolstad)
Subject: Re: Using big caps as computer power supply filters (?)
Organization: U of Wisconsin-Madison College of Engineering
Date: 17 Nov 92 11:54:12 CST

In article <1992Nov17.165023.29174@julian.uwo.ca> wlsmith@valve.heart.rri.uwo.ca (Wayne Smith) writes:
>I've got some big electrolytic caps (20000 to 60000 uf, 16 to 40 volts),
>and I was thinking of putting them across the 5V and 12V power supplies
>in my pc.  I would think that cap's that big would provide maybe 1
>second of backup power.  

I think that asking for one second would be a little much.  Here's hwy:

Consider: Let's let your 5V line drop by 1V, to 4V.  TTL chips aren't
speced to work that low, but if you're lucky, maybe they will.  Next let's
assume that that 486 DX2/66 number masher of yours draws 5A.  This is
probably conservative, too, but anyway...  We'll also assume that the
current being drawn is constant, since, between 4 and 5V, it probably
won't change that much.  Again, all of this is going to happen in 1s.

Now then... I=C*dv/dt, or V-Vo=1/C*(integral of) I (WRT t).  1=1/C*5 -->
C=5 FARADS.  That's 83 of those 60000uF capactiros in parallel. :-)

						---Joel Kolstad
Newsgroups: sci.electronics
From: gnamasiv@wam.umd.edu (N. Girirajan)
Subject: Re: Radio Transmitter
Organization: University of Maryland, College Park
Date: Mon, 16 Nov 1992 16:22:41 GMT

Thanks to all who replied.  It was very useful and I will look up all 
the sources suggested.  I didn't realize quite how much was involved
in all this. :)  As to legality, I don't think there will be a problem, 
so I'm not worried about that.  What I was really thinking of was something
like a homing beacon (which is how I should have phrased my request in 
the first place), a pulsed single frequency signal with a range of a few
miles for maybe an hour.

--girirajan--
gn1@umail.umd.edu
From: glusk@mechcad3.esd.sgi.com (Mark Glusker)
Newsgroups: sci.electronics
Subject: Question Re: BROKEN TUBE AMP
Date: 17 Nov 92 15:55:24 GMT
Organization: Silicon Graphics, Inc.

In his reply to nasiom@vccnw10.its.rpi.edu (Milton Peter Nasiopoulos),
sehari@iastate.edu (Babak Sehari) writes:

>  Q. How to check specker impedance.
>  A. Use a signal generator, to generate a 1KHz signal put the speaker
and
>   a one ohm resistance in series, and connect the speaker-resistance
>   combinations to the signal generator. Measure, the voltage across the
>   speacker and the one ohm resistor. Now you can calculate the speaker's
>   resistance at 1KHz.  Also check the DC resistance of the speaker with
>   ohm-metar.

My question is; does this procedure work at radio frequencies, provided one
uses an AC voltmeter that responds over those frequencies?  Is this a good
alternative to using devices like RF bridges or Q-meters to measure
reactances at radio frequencies?

Thanks in advance for your help and advice,  

Mark Glusker
Newsgroups: sci.electronics
From: schuch@phx.mcd.mot.com (John Schuch)
Subject: Is Digitalker Dead?
Organization: Motorola Computer Group, Tempe, Az.
Distribution: usa
Date: Wed, 18 Nov 1992 20:05:59 GMT

Some time ago I had a rep tell me that Naional had discontinued the
Digitalker line of speech synthesis chips (DT1050, DT1057). Now
the Jamco catalog I got yesterday has full sets for sale at regular
list price. Does anyone know if their still being made or is Jamco
just sitting on a large stock-pile?


John

BTW: The component section in the latest Jameco catalog (autumn) is
     pretty darn impressive. Check it out.


-- 
| ONE LINE NOVEL: She backed away from the corpse slowly, not so much out  |
| of fear, but simply unsure of what the crowd expected her to do with it. |
+--------------------------------------------------------------------------+
| John R. Schuch  -  Motorola Computer Group  -  Manufacturing Engineering |
From: root@cibbs.UUCP
Newsgroups: sci.electronics
Subject: Ring Detector IC
Date: Sat, 21 Nov 92 22:28:37 EST
Reply-To: uunorth!cibbs!root
Organization: DataSoft Consulting (Toronto, Ont. Canada)

I am building a project that will detect the ring of the telephone and then do
some processing (which is not important). What I need to know is if anyone
knoews of a ring detect IC? Radio Scrap used to sell one years ago. I know it
can be done with an optocoupler and a few other parts; however, I would like
to make it more simplict than that. It would be nice if this IC took the phone
line as a input and produced either a TTL level or CMOS compatible output.

Any ideas? If you know of such a circuit, please email me as I don't often get
a change to run through all the messages on the net.

Send email to: uunorth!cibbs!root
Thanx
Mark

----
Club InSaNiTy BBS   |   BBS:+1 416 691 0679 |   root@cibbs.UUCP
DataSoft Consulting | Voice:+1 416 691 5529 |   uunorth!cibbs!root
Mark Buckaway       | Toronto, Ont. CANADA  |   1@4653 (WWIVnet)
Newsgroups: sci.electronics
From: cerulean@access.digex.com (Bill Christens-Barry)
Subject: Nickel Metal Hydride batteries
Summary: questions about buying, using, charging NiHM batteries
Organization: Express Access Online Communications, Greenbelt, Maryland USA
Date: Fri, 20 Nov 1992 01:26:08 GMT

I'd like to get some C size nickel metal hydride batteries for an r/c car
and some AA size batteries for other purposes.  Can anyone suggest where
I can get these and what they should cost?

I'd like to get the C size cells preassembled into battery packs of 7 cells
(=8.4v).  If they're not available this way I thought I'd solder them together.
Are there any special problems in doing this?

Also, I'd like a fast ac, dc, or ac/dc charger, so anything you've got on
that would be helpful.

Thanks in advance....
From: whitten@kuhub.cc.ukans.edu
Newsgroups: sci.electronics
Subject: SCA Reciever Design
Date: 19 Nov 92 22:55:46 CST
Organization: University of Kansas Academic Computing Services


Once again, in a quest to keep net readers on their toes, I've got
a couple of somewhat quirky questions I'd like to get some input on.

First, I'm designing an SCA reciever, and while the PLL section to
do the demodulation is easy, I'd like to get recommendations on
an IF.  Great would be some single chip solution from a company that's
really into giving out samples.  This thing will be for one
specific frequency so hopefully there's some clean solution for this.

Thanks,
Chris

==============================================================================
 WHITTEN@KUHUB.CC.UKANS.EDU                  Chris Whittenburg, N0TWA
 WHITTEN@UKANVAX.bitnet              Univ. of Kansas - Electrical Engineering
==============================================================================
From: whit@carson.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: digital clock for circuit
Date: 18 Nov 92 07:12:54 GMT
Article-I.D.: u.1992Nov18.071254.29582
Organization: University of Washington, Seattle

In article <1992Nov17.180205.19383@dartvax.dartmouth.edu> bruce@coos.dartmouth.edu (Bruce K. Johnson) writes:
>Hello all.
>
>I have a question about making a clock for my circuit.  First, let me give
>you a background --- I'm making an A to D data aquisition box for the MAC's
>serial port.  I'm using an ADC0831 chip and want to time it as well as provide
>an external clock signal for the MAC's handshake line (the MAC can only run its
>serial interface at a top speed of 57900 BAUD internally, therfore, if I want
>to run say a 22 KHZ sample rate, I need a much faster ext clock...)

	The upper limit on the Mac serial port is 239 kbaud, NOT 57.9k.
You are perhaps speaking of the upper limit of some particular
piece of software?
	In fact, with external clocking the Mac can take up to 4 Mbaud
in synchronous-input mode.  Depending on the model, it might not
always keep up with the input data at that rate, of course.

>Anyway, I originally started off with an oscillator and a decade counter to
>get the two clock signals ...

>This costs too much.  My project is for use by students in a Physics class
>and must be relatively inexpensive for them to purchase.  I then turned to
>using a 556 timer to get two clock signals with one chip (a .70 cents chip
>compared to a 1.70 osc + other stuff).  The 556 is capable of providing
>a stable signal for the 22KHZ clock but not for the 220>KHZ clock.
>
>Is there another cheap alternative to making two clock signals or can I make
>the 556 (two 555 on one chip) produce a more stable signal at these high speeds?

	A variety of '555-equivalents are available.  What you
want is an ICM7556 or similar CMOS timer chip, if the straight
NE556 is too slow for your preferred clock rate.

	In fact, you can make astable or gated clock generators from 
CMOS Schmitt triggers (74HC14 or 74HC132), for even less money.

	John Whitmore
Xref: sparky sci.electronics:19201 misc.consumers:19268
From: kz08+@andrew.cmu.edu (Ken Zuroski)
Newsgroups: sci.electronics,misc.consumers
Subject: Charger for Sony Camcorder Batteries
Date: 19 Nov 92 15:38:22 GMT
Organization: Doctoral student, English, Carnegie Mellon, Pittsburgh, PA

Hi:

I have an 8 mm Sony camcorder, with 2-hour rechargeable 6.0 V battery
pack, the charger of which also doubles as a plug-in power cord. Well,
long story short, I lost the charger/power cord. Looked for it;
couldn't find it. Called Sony to see how much a replacement would
cost--$169! Holy boinkers. That's almost a third of what I paid for
the camera.

So, do you have any suggestions how I could replace this power
supply/charger for less money? Any offbrand names that would work just
as well? Would it be difficult to build one of these things? Any place
I should advertise for second-hand replacements? 

Thanks for any info--

Ken


---
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ken Zuroski
Department of English
Carnegie Mellon University
Pittsburgh, PA 15213 USA
kz08@cmu.edu
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Newsgroups: sci.electronics
From: hcooper@javelin.sim.es.com (Harrison Cooper)
Subject: PD compilers for Intel/Moto
Summary: Looking for PD compilers for microcontrollers
Keywords: compilers
Organization: Evans & Sutherland Computer Corp.
Date: Mon, 23 Nov 1992 13:50:43 GMT

Is anyone aware of public domian/shareware C compilers that target
either Intel 8051 uControllers or the Motorola 68xx (6800,6805, etc)
family.

Please email to hcooper@orca.es.com

-- 
--------------------------------------------------------------------------
| Harrison Cooper                    | Methods of locating me :           |
|                                    | email : hcooper@javelin.sim.es.com |
| SP Hardware Design                 | Phone : 801-582-5847 ext 3578      |
From: tbruseha@hollywood.ems.cdc.com (Tom Brusehaver)
Newsgroups: sci.electronics
Subject: Re: telephone interface to many speakers
Date: 17 Nov 92 20:52:30 GMT
Organization: Empros Systems International, a division of Control Data

In article <laird.721967281@stable.ecn.purdue.edu> laird@stable.ecn.purdue.edu (Kyler Laird) writes:
>I'm working on a paging module which "answers" a phone call as
>soon as it arrives (before a "ring" in generated for the calling
>party - quite confusing for some) and broadcasts the audio of the
>caller on speakers around the building for a preset time (LS7210
>digital delay - way cool).  The intent is that it can be used as
>a pager, outgoing line, and incoming line in response to the page.

This sounds pretty cool, maybe post block diagram.
>
>So far, it works beautifully feeding a Radio Shack amp/speaker
>module.  (and if you call 317-463-3447 while I'm working on it,
>you too will be a part of the testing...)

Al right, this is always fun to see results.
>
>I haven't ever tried distributing a signal like this.  I've read
>that I need to match my load (speakers) to my source (amp), but
>I'd like to use a cheap standard audio amp (8 ohm) and cheap
>little speakers (4 or 8 ohm).  I've seen speaker selectors with
>matching circuits built in, and would like to make something
>similar.  I'd like to keep it simple - resistors and transformers -
>if I can.  I'd also like to be able to add more speakers and vary
>the volume of each speaker (at the speaker  - parallel bus)
>without redesigning much.

Go back to the olden days (alright, maybe just comercial systems)
where everyone used 70 volt systems.  All the speakers are driven from
a high voltage/low current line.  (Works great for home stereo stuff
too, no more fat cable arguments).

Basically you need a step up transformer on output from the amplifier,
and step down transformers on all the speakers.


|-------|	  	  						speaker bus
|       |---|=|------------------------------------------------------------
|  amp  |	   	  		 |                    |              |
|       |  xformer       |      	     	  |	             |
|-------|	       xfmr |=|     	     	 |=|			|=|
				         |    /	   	   	      |    /		 | 	  /
				         |--||		  		  |--||			 |--||
				              \		  			   \			  \

					      4ohm speaker

The bad news, you have to be an electrician to install this system in
comercial buildings.  There is a practical limit to the number of
speakers you can hang off this bus, but if your amp has enough watts
you can drive a bunch of speakers.

give it a shot.

Tommy B.
Newsgroups: sci.electronics
From: caffrey@spot.Colorado.EDU (Mark A. Caffrey)
Subject: Soundblaster voicemail help needed
Keywords: Voice mail
Organization: University of Colorado, Boulder
Date: Thu, 19 Nov 1992 02:54:40 GMT

I would like to Hook mySoundblaster to the phone line without getting in trouble
with the phone co. The idea is to be able to speak into my microphone have the
pc do something and put the sound out over the phone line. I also want to be able to receive from the preson at the other end of the line who also has a 
soundblaster. 
I do not know much electronics but can soulder a few wires if needed and buy a few
parts.
I can be reached at ted.duncan@boardwatch.com
.
From: chris.guli@factory.com (Chris Guli) 
Newsgroups: sci.electronics
Subject: PCB FABRICATION
Date: 22 Nov 92 11:49:00 GMT
Distribution: world
Organization: Invention Factory's BBS - New York City, NY - 212-274-8298v.32bis
Reply-To: chris.guli@factory.com (Chris Guli) 

TO: ALL

I've seen several messages posted here concerning printed circuit board
fabrication, and am interested in hearing other opinions and experiences
from people who have tried one or more of the various methods.

I am particulary interested in the direct toner and reversal film
methods (Datak), but I will entertain any other methods.

So far, I have tried two of the direct toner methods. One is called
press-and-peel (P-n-P) sold by Techniks. It is supposed to be an
improvement over the original TEC-200 film, but I can't say that for
myself since I haven't tried TEC-200. The P-n-P film has a special blue
coating which acts as a release agent and toner strenthener. I've had
mediocre success with this film, but if the time, temperature and
pressure factors are optimized, I suspect I can achieve a much higher
success rate. I've been using a clothes iron to make the transfers, but
I am considering purchasing a heat press. They are hard to come by and
are expensive in my area (NYC). Problems I have encountered: not all of
the toner transfering (too little heat/ time/ pressure ?), smudges or
hourglass pads/ traces (too much heat/ time/ pressure ?). I think
optimizing these factors will be easier with a press.

Another method is the new Toner Transfer System that is advertized
in Nuts and Volts and also sold by DC Electronics. I've purchased 5
sheets and tried several already. This is a paper rather than a film. It
has a sugar coating on one side. You iron the pattern on as with the
other films. The toner adheres to the water soluble sugar base as
well as the board and, you guessed it, bathing it in a warm bath
releases the paper and leaves a nearly perfect pattern on the board
ready for etching. Minor problems with this method: traces and lines
spread out and toner is very brittle after transfering. Both problems
are related to heat/ time/ pressure factors. I prefer the former
method, however, since the transferred pattern is more rugged and can
be repaired if a trace is missing, eg. Also, the P-n-P film is less
expensive (10 sheets for $5 vs. $10 for 5 sheets of the sugar paper.)
The press will solve most of these problems.

Another method I'm going to try is the Datak pos-neg process. This is
more involved and time consuming (far less than sending it out), but it
can produce more precise patterns on the board.

I am planning to build projects using SMT devices and will use the
pos-neg process for SMT, and P-n-P film for TTH designs, unless I can
achieve accurrate transfers (SMT fine pitch) with the P-n-P film.

Anyone else have PCB fabrication experiences they would like to share ?

Chris