Driver to drive?

Rich The Newsgropup Wacko · Jan 7, 2005

On Fri, 07 Jan 2005 16:26:13 -0600, John Fields wrote:

On Fri, 07 Jan 2005 21:49:42 GMT, Richard the Dreaded Liberal
eatmyshorts@doubleclick.net> wrote:

On Tue, 04 Jan 2005 09:24:11 +0100, Frank Bemelman wrote:

Q: What is the title of the thinnest book on Earth?
A: 200 years of German humor.

"Italian War Heroes"
"Jewish Business Ethics"
"Niggers I've Met While Yachting"

---
"The Wit and Wisdom of Rich Grise"?

http://www.google.com/search?&q=%22rich+grise%22
http://groups.google.com.au/groups?q=%22rich+grise%22

Sorry. ;-p

Cheers!
Rich

Winfield Hill · Jan 8, 2005

Richard the Dreaded Liberal wrote...

Q: What is the title of the thinnest book on Earth?
A: 200 years of German humor.

Subtlety and dry humor may not be Rich Grise's forte.

"Italian War Heroes"

Another stupid time-worn prejudice. It's a well-documented
fact that Italy had more than their fair share of war heros.

"Jewish Business Ethics"

ALL my Jewish business friends have exemplary business ethics,
a claim I wish I could make about all the rest of my friends.

"Niggers I've Met While Yachting"

And just how much yachting have you done? I thought so.

--
Thanks,
- Win

Don A. Gilmore · Jan 4, 2005

<dmartin@newarts.com> wrote in message
news:1104778786.321726.203130@z14g2000cwz.googlegroups.com...

Don,
Your previous comment (Jan 3, 8:32 am) implies you are interested in
current flow that is due to electrical boundary conditions on opposite
sides of the sheet. Is that correct?

Your original post said.."Here are the corresponding
resistivities for some nominal inch thicknesses:

.031 in ---> 300 ohm-m
.062 in ---> 150 ohm-m
.125 in ---> 75 ohm-m
.188 in ---> 50 ohm-m"

I may have mis-interpreted this as meaning you are interested in
current flow between electrode areas separated in the plane of the
sheet. The resistance one would measure perpendicular to such a sheet
will depend on the size and lateral displacement of the electrodes
relative to the thickness of the sheet.

Perhaps your question was much simpler: if I had a material with a
bulk resistivity of 75 ohm-m and gave you a piece in the shape of a
.125" thick sheet is that all you want?
If so, how large a sheet? Flexible or rigid? Durable?

Yes, that's all I want. I would prefer sheets as large as possible...in
roll form would be great. It doesn't have to be super-flexible, but I don't
want it brittle like glass either. It will be applied to a slightly
irregular surface, but generally planar...maybe sort of like a large
airplane wing. It will not be subjected to much abuse, but it might be
exposed to normal outdoor temperatures.

So far I'm leaning toward some conductive plastic sheet material that
McMaster-Carr carries. But only because it's all I've found yet (and it
only comes in 12" x 12" sample sheets". That's why I was wondering if one
of you clever guys might have heard of something else that I missed.

Don
Kansas City

John Woodgate · Jan 4, 2005

I read in sci.electronics.design that Jim Thompson
<thegreatone@example.com> wrote (in <4holt0pci2qed5neu0sldpm4rod8rrl3kj@
4ax.com&gt

about '40M for Bush Inauguration and 15M for Tsunami Disaster
WAS Re: Bush accused of undermining the UN with aid coalition', on Tue,
4 Jan 2005:

On Tue, 4 Jan 2005 18:04:58 +0000, John Woodgate <jmw@jmwa.demon.contras
pam.yuk> wrote:

I read in sci.electronics.design that Martin Frey
martinfrey@snipclara.co.uk> wrote (in <bojlt0de0bk5rrcfds0cd580sri07tur
qf@4ax.com&gt about '40M for Bush Inauguration and 15M for Tsunami
Disaster WAS Re: Bush accused of undermining the UN with aid coalition',
on Tue, 4 Jan 2005:

Snails must have more sense than I credited them with.

You may confirm this by a study of their reproductive behaviour. (;-)

Sno-o-o-o-ort! ROTFLMAO!

You win some, you lose some. Clearly, snail sex is more reliable than
German ladder logic. (;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Jim Thompson · Jan 4, 2005

On 4 Jan 2005 12:38:25 -0800, jondoeengineer@hotmail.com wrote:

1) Hide it from whom?
Hide it from plain view... It's not the most attracive piece or
furniture.

2) Do you even know what a "subwoofer" is?" If so,
The ominidirectional base speaker.

3) Why would you want to relocate it in the first place?
I want to hide it behind an end-table or the couch. (See question 1.)

4) As needed by whom? For what?
As needed by ME. Maybe I won't like the way it sounds or looks where
it is.

Now, what is a "plain ol'...."? I apologize for my ignorance on this.

Personally I would look for pre-made transmitter-receiver pairs.

Keep us posted as to what you find... I'm interested also.

Nevermind some of the replies... some folk don't have a clue about
aesthetics ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice

480)460-2350 | |
| E-mail Address at Website Fax

Jim Thompson · Jan 4, 2005

On Tue, 4 Jan 2005 20:19:23 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

[snip]

Rhetorical Question - How did USA gas-guzzling automobile gasoline supplies
manage to find their way beneath the sands of occupied Iraq and Saudi
Arabia?

Or in Central Asia. Or West and North Africa.

480)460-2350 | |
| E-mail Address at Website Fax

Jim Thompson · Jan 5, 2005

On Wed, 5 Jan 2005 01:19:14 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

Reg, I just *love* your reply... shows TOTAL IGNORANCE as to where we
get a great portion of our oil.

===================================

Dear Jim, I think you've missed the rather obvious point.

Your World geography and geology need brushing up.

It is not where the oil comes from at present which matters.

What matters is from where the USA intends to obtain its oil when the
present supplies run out. There's not a lot left. There's not a lot of time
left either.

And how could you say such a naughty cruel thing to an old man like me?

Have you no respect for your elders? Boo-hoo!
----
Reg

480)460-2350 | |
| E-mail Address at Website Fax

Reg Edwards · Jan 5, 2005

Reg, I just *love* your reply... shows TOTAL IGNORANCE as to where we
get a great portion of our oil.

===================================

Dear Jim, I think you've missed the rather obvious point.

Your World geography and geology need brushing up.

It is not where the oil comes from at present which matters.

What matters is from where the USA intends to obtain its oil when the
present supplies run out. There's not a lot left. There's not a lot of time
left either.

And how could you say such a naughty cruel thing to an old man like me?

Have you no respect for your elders? Boo-hoo!
----
Reg

John Popelish · Jan 5, 2005

Rich Grise wrote:

On Tue, 04 Jan 2005 17:43:06 +0000, Rolavine wrote:
From: "Frithiof Andreas Jensen"
"Peter Kiproff" <peter@microtrendrobotics.ca> wrote
What would be your recommendation?
...
I prefer to put the voltage limiter across the *driver*,
contacts/transistor, not the coil, because it is the *driver* and not *the
coil* that needs overvoltage protection (and some site techies might forget
it if it is not soldered in ;-)!!

Good points. How is a 1N4004 as a flyback eater diode? Is it fast enough? When
I look up the specs they are not very specific about speed, since they are
intended to be rectifiers, however when I test them they seem fast enough, my
100 meg scope shows no transient. If not a 1N4148, what is the stronger
cheapest option? How about a BAW78? Do you think a coil driver really benefits
from a faster clamping device?

Personally, I'd use a 1N4007, but only because the 4004 is only a 100V
diode.

Make that a 400 volt diode.
http://www.fairchildsemi.com/ds/1N/1N4004.pdf

From what I recall from the OP, the duty cycle was in seconds, so I
don't think speed is a consideration here - all you're doing is dumping
some charge, after all.

I agree that the coil would very likely have an L/R time constant well
under a second, since it sounds like a fast response hydraulic valve.

Whoever recommended a 1N4148 as a solenoid diode needs to read the book
again. ;-)

For a 100 volt 1 ampere coil, I agree. For a 50 volt or less 250 ma
or less coil, they work fine.

--
John Popelish

Rodney Josey · Jan 5, 2005

On Tue, 21 Dec 2004 17:41:51 +0000, Danny T <danny@nospam.oops> wrote:

Hi All,

I'm trying to control hundreds of LEDs from my parallel port (8 data
pins - will soon be replaced with the output of a programmed PIC, also 8
pins).

I'm not an electronics guy (I'm a software developer), so trying to
control x00's of LEDs from 8 pins looks a bit tricky...

snip

What are my options? And what components would I need to achieve
something like this (I imagine right down at the end, I'll need a number
of registers for the LEDs. If these come in chips with 8 output legs, I
guess I'll need 38 for 300 LEDs. The bit between my 8 data pins and the
computer isn't my area though, so I'm stuck!

Oh, and this is just a hobby thing, so the cheaper the better. I'm sure
I can already buy scrolling screens, but I don't have the money, and I
want the fun of building one!

------------------
Hi Danny,

Came across your initial post a few days ago - & have followed the threads avidly. Most
interesting!!! The majority of the replies have been suggesting you use the 'serial-to-parallel'
data transfer method and that you also use either a PIC or an AVR micro - well I agree with the
later (in principle) BUT (there's always a but, isn't there ...). you need to be aware that most of
the PIC's and the AVR micro's have a "limited" amount of memory available - especially when you most
probably need to store the message or graphic before you output it to the LED display - now in most
of these micro's your control program takes up a fair chunk of the memory thus leaving a small (in
some micro's - VERY samll) amount of free memory space to store the other things like 'variables',
'tables', as well as your 'message/graphic' data.

I agree with the many suggestions regarding 'multiplexing' of the LED array BUT driving the array by
using the venerable 74LS595 (or 74HC595) serial-to-parallel shift register method is OK if you have
plenty of speed and time to do the data setup & transfer in - with most of the micro's in question
you may find this method a bit tight on time &/or speed - AND - the other thing to keep in mind is
that your chip count CAN BE fairly large (38 or so 595's plus several control chips - already over
45 chips) which also means a larger PCB for your system, more costs, etc.

After a few days twiddling with the concept I came up with the following - you might want to
consider another method which could save you in costs as well as lower chip count and more
FLEXIBILITY in what & how the LED MATRIX can be utilised.

The proposed method uses around 18 or so IC's; 72 FETS for row & column drivers; 1 x power FET - for
PWM control of the LED supply; approx 90 resistors; a handful of small value capacitors; 384 LEDs -
in a 8 x 48 matrix; plus either 1 or 2 PCBs.

As can be seen from the circuit diagram below - the 2 main IC's are the 62256 SRAM (32K x 8 bits
static ram) & the microprocessor - an PICAXE 28X. The LED MATRIX uses 6 x 74LS574s for column drive
& 1 x 74LS574 for row drive (these are 8 bit parallel tri-state registers).
The "flexibility" spoken about above is - each LED in the matrix can be turned on or off
individually - e.g. ALL on, 1 on, combination on, many on (in any position), PLUS a 'moving' display
- right / left / up / down, etc, are all possible display options.

The row & column drive FETs are 2N7000 N-Channel fets - 60 VDC (max), 400mA current (continuous) or
2A (pulsed), Rds(on) = 1.2 ohms, gate drive 2.4V, in a TO92 package. With each LED drawing 20mA
'on' current - column FETs drive 8 x LEDs = 160mA (total - all on); row FETs drive 16 x LEDs (@ 3 x
FETs per row) = 320mA (total - all on). 2N7000 @ $0.35 in qty's 25+

1 x MTP3055V N-Channel Power MOSFET is used to PWM the LED positive supply to the LED MATRIX - freq
= 250 Hz, pulse width varies for brightness / dimness. With ALL leds on the max current drawn from
the LED supply is approx 7.8A - the MTP3055V can handle 12A @ 60V DC.

The 62256 SRAM is used for storing the data to be displayed on the LED MATRIX - 32K x 8 bits
provides for up to 4600 different graphics displays - the matrix is setup as 8 x characters @ 8 bits
high x 6 bits wide (= 384 LEDs). A full (384 LEDs) graphic/character display takes up only 7 x data
bytes in the SRAM - 6 bytes for column drive; 1 byte for row drive.

The PICAXE 28X micro controls the LED display functions as well as the updating of graphics data to
the SRAM. PWM output 2 (pin 13) of the PICAXE 28X is used to drive the MTP3055V MOSFET.

The 74LS138 IC's provide gating & control signals to the rest of the circuit as directed by the
relevant PICAXE 28X Output portC pins.

I also suggest that the i2c pins (pins 14 & 15) of the PICAXE 28X be utilised to provide
communication with an external PC via an PICAXE 18X chip (i2c pins 7 & 10) and a few extra IC's -
all configured as a PC Parallel port - to - i2c converter.

I hope this gives you some more useful insights into how 'multiplexing' displays can be designed!!

The Circuit Diagram:
----------------------------------------------------------------------------------------

Ic9 LED MATRIX
.--. (8 x 48 = 384)
| | Col Col
PICAXE o--o +--------------------+ 1 48
28X | | | | o|-/-------------------------------/-- Rw1
.------. | '--' 62256 | Ic7 o|-/-------------------------------/--
| | | .-------. | .--.o|-/-------------------------------/--
| | | .--.Ic10 | | | | |o|-/-------------------------------/--
| o----o | | |A0 D0| | | |o|-/-------------------------------/--
| | o--o +------+ +-----|----+ |o|-/-------------------------------/--
| | | | | |A7 D7| | | |o|-/-------------------------------/--
| | | | | |A8 | | '--'o|-/-------------------------------/-- Rw8
| o--o | '--' +---+ | | | |
| | | | .--. | |A14 | | ######## ######## ########
| Ic14 | | | | | | | | | .-------. .------. .------.
'------' | o--o +--+ | | | | Ic1 | | Ic2 | -------- | Ic6 |
| | | | | | '---+---' '---+--' + + + '---+--'
| | |Ic11 | Ic8 | | | | | | | |
| '--' '-------' +---\--------+---------+-----+-+-+-------+
| 8
| .--.Ic12 Data Bus
| | |
o----o | ----------------------------------------------------------------
| | | | LED MATRIX Set-Up:
| '--' | Col X
| .--. | +Vled +
| | | | o--o-o-+^+-+------+ Rw1a |
o----o | | o = | ||| # = +
| | | | === FET 1 ||-+
'--'Ic13 | | | ||<- FET X
| +--------+ o---o-||-+
Ic1-7,10,11 = 74LS574 | | | Rw X |
| | o--o+^++-------+ Rw1b |
Ic8 = 62256 SRAM | | | ||| ===
| | | === FET 2 GND
Ic9 = 74LS244 | | | | Col X
| +----------+ Rw X +
Ic12,13 = 74LS138 | o/p | | / = o-|-----------|---o
| 1 | o--o+^++-------+ Rw1c +-->|---+ |
Ic14 = PICAXE 28X | | ||| Led X | |
| | === FET 3 ___ | |
FETs = 2N7000 | | | +-|___|+ |
| +--------+ +----------+
| Res X +
|
(created by AACircuit v1.28.4 beta 13/12/04 www.tech-chat.de)

Oz-Rod

The Ghost In The Machine · Jan 5, 2005

In sci.math, John Woodgate
<jmw@jmwa.demon.contraspam.yuk>
wrote
on Tue, 4 Jan 2005 18:50:38 +0000
<DfMlxAN+Vu2BFwP7@jmwa.demon.co.uk>:

I read in sci.electronics.design that Jim Thompson
thegreatone@example.com> wrote (in <4holt0pci2qed5neu0sldpm4rod8rrl3kj@
4ax.com&gt about '40M for Bush Inauguration and 15M for Tsunami Disaster
WAS Re: Bush accused of undermining the UN with aid coalition', on Tue,
4 Jan 2005:
On Tue, 4 Jan 2005 18:04:58 +0000, John Woodgate <jmw@jmwa.demon.contras
pam.yuk> wrote:

I read in sci.electronics.design that Martin Frey
martinfrey@snipclara.co.uk> wrote (in <bojlt0de0bk5rrcfds0cd580sri07tur
qf@4ax.com&gt about '40M for Bush Inauguration and 15M for Tsunami
Disaster WAS Re: Bush accused of undermining the UN with aid coalition',
on Tue, 4 Jan 2005:

Snails must have more sense than I credited them with.

You may confirm this by a study of their reproductive behaviour. (;-)

Sno-o-o-o-ort! ROTFLMAO!

You win some, you lose some. Clearly, snail sex is more reliable than
German ladder logic. (;-)

Now waitaminnit -- does this mean that snails can't have sex on
German ladders?

--
#191, ewill3@earthlink.net
It's still legal to go .sigless.

John Woodgate · Jan 5, 2005

I read in sci.electronics.design that The Ghost In The Machine
<ewill@sirius.athghost7038suus.net> wrote (in <1h5sa2-511.ln1@sirius.ath
ghost7038suus.net&gt

about '40M for Bush Inauguration and 15M for Tsunami
Disaster WAS Re: Bush accused of undermining the UN with aid coalition',
on Wed, 5 Jan 2005:

Now waitaminnit -- does this mean that snails can't have sex on German
ladders?

Strecklisch verboten!
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Fred Bloggs · Jan 5, 2005

If power fails at the remote site, so does the control circuitry and its
power. So a traditional delay relay won't work.

The relay, powered by mains, simply opens the wireless sensor's sense circuit
when power goes away. I just want it to do so after waiting a few minutes to
see if power comes back on.

The wireless "sensor's sense" ciruit is most likely something with a
weak pull-up of say 100uA, so that shunting the relay input terminals
with C=100uA/(3V/300secs)=10,000uF 10WVDC should get you close:
View in a fixed-width font such as Courier.

+--------[100]--+------->
| |
o | +
/ === to sensor
o | 10,000u
| |
+---------------+------->

Winfield Hill · Jan 5, 2005

Stephan Goldstein wrote...

Tim Shoppa wrote:

The data sheets for analog 4-quadrant multiplier-on-a-chip chips are
remarkably vague as to what goes on inside the chip. I'm thinking
specifically of the Analog Devices AD633 and the Burr-Brown MPY634,

I looked around in my files yesterday and couldn't find anything
specific to the innards of the AD633. But the basic principles of
a 4-quadrant multiplier are in ADI's _Nonlinear Circuits Handbook_
-- basically, make two 2-quadrant multipliers and tie them together.
It's a little more than this, of course, but that's the general idea.

These multipliers are translinear circuits, not logarithmic ones, so
the thermal issues that always arise with loggers are not a problem.

There's lots of good detail in Barrie Gilbert's patents, including
his very effective linearizer secrets, with schematics and full math.

4,156,283 - Multiplier Circuit
4,586,155 - High-Accuracy Four-Quadrant Multiplier Which is
Capable of Four-Quadrant Division
6,074,082 - Single-Supply Analog Multiplier

Another good info source is Barrie's two lengthy chapters in the book,
"Analogue IC Design: The Current-Mode Approach," edited by C. Toumazou.

--
Thanks,
- Win

Nico Coesel · Jan 5, 2005

et472@FreeNet.Carleton.CA (Michael Black) wrote:

"Tam/WB2TT" (t-tammaru@c0mca$t.net) writes:
"Tim Wescott" <tim@wescottnospamdesign.com> wrote in message
news:10tlsi3kk9sok87@corp.supernews.com...
Dave Garnett wrote:

Toko used to provide a lot of data, but it's difficult to find in
English. I had Japanese help about 10 years ago. If you care to email me
with what you want, I'll see if I can help. No guarantee.
--

http://217.34.228.137/MAIN/main.htm is an online TOKO catalog - near
identical to the printed catalogue I have. Finding a source in reasonable
quantities is another problem entirely.

However, you may find that toroids are a better bet for multi winding
inductors - see the ARRL handbook for details
Digi-Key carries a large selection of TOKO coils.

Toroids will give you better coils, but they're more expensive in
production.

I think he is looking for something that can be tuned.

Then you use a variable capacitor, or maybe more specificall a trimmer
capacitor.

I haven't priced new coil variable coil forms lately, but I suspect they
may be getting expensive. Toroids are still relatively cheap, and the
cost of trimcaps likely will be cheaper than buying new variable coil
forms.

My idea exactly. Even better: if you replace the trimcap with a
varicap diode, you can make a digitally tuned filter. Very handy for
automated post production calibration.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

Spehro Pefhany · Jan 5, 2005

On Wed, 5 Jan 2005 15:57:55 +0000 (UTC), the renowned
kensmith@green.rahul.net (Ken Smith) wrote:

In article <6ermt0936qbqih5m76at2hpv2lukdgfk1g@4ax.com>,
Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:
On Wed, 5 Jan 2005 02:22:05 +0000 (UTC), the renowned
kensmith@green.rahul.net (Ken Smith) wrote:

[...]
Take a slice of quartz and drill a hole this big:

-----------------------------
H H ^
\ / Diameter of the hole
O V
-----------------------------

The water vapor can go through but bigger stuff can't.

Kind of like RO, eh?

Very like RO. In RO, you drill little holes in some plastic so that only
liquid water can get through. Drilling the plastic is harder because the
little bitty drill bit get stuck more easily.

<VBG>

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

Guy Macon · Jan 5, 2005

(Reposted from another thread...)

| From: Charles Jean <alchemcj@earthlink.net>
| Message-ID: <iu1nt09bddmt7revemhv8kvl8a28mkv5nf@4ax.com>
|
| "WayneL" <nospam-mail@wlawson.com> wrote:
|
| >Can anyone advise where I can get Quartz triple distilled
| >water from (I'm in the UK) and what is it the best
| >conductivity you could expect from the most >purest water
| >
| >Also what is the best way of 1/ storing ultra pure water
| >and 2/ dispensing it so that the rest of the water does
| >not get contaminated. Should I >dispense it in to several
| >small bottles with pipette lids?
|
| Highest resistivity you can get is about 18.3 megohm-cm at
| 25 deg C. Self-ionization of water limits it to any higher
| value. This type of water can be produced by triple
| distillation in quartz apparatus or by mixed-bed
| deionization(much easier). Keeping it this way is tough,
| because it will have a tendency to dissolve the countainer
| it is in and absorb atomspheric gasses, especially carbon
| dioxide. I've seen a demineralizer setup that produced 18.3
| megohm-cm water(as measured by an in-line probe) that would
| measure around 5 after falling through about a foot of air!
| Purging the container with an inert gas, like argon would
| help with this, but then you'd have to he concerned about
| contaminants in the argon, etc. Some argon would dissolve
| in the water, but couldn't be measured by conductivity.
| Also there my be organic compounds present that can't be
| measured by conductivity. What is your application for this
| water?

GMAN · Jan 5, 2005

In article <1104787856.310883.276250@z14g2000cwz.googlegroups.com>, nooneinparticular314159@yahoo.com wrote:

Ok. I should probably point out some design constraints to go with my
original question :

I live in a high rise apt building. I can not mount anything on the
exterior of my building, nor do I have line of sight to a satellite
(especially since the 15 story building was put up in front of me).
This includes roof antennae

I can not modify the building in front of me. That building is still
under construction, and I do not own it, nor do I have access to it.

I am not looking to subscribe to any sort of pay service, such as cable
or satellite. It's too expensive. Likewise, I am not looking for a
replacement for my TV right now.

In other words, anything I do needs to be inside my own apt, and should
not be very expensive.

Thanks,
michael

You live in a high rise appartment and find $42 a month too expensive for

DirecTV?

CWatters wrote:
nooneinparticular314159@yahoo.com> wrote in message
news:1104719289.791502.171590@f14g2000cwb.googlegroups.com...
I am currently using a
Radio Shack amplified antenna with two telescoping antennae,

Get a proper roof mounted aerial. It should look something like
this....

http://www.abcaz.com/5_1160279/aerials-boosters-and-splitters/masterplug-gold-5
2-element-tv-aerial.html

Don A. Gilmore · Jan 5, 2005

"John Fields" <jfields@austininstruments.com> wrote in message
news:n3llt0924ghrj7i8gl770s51npspg9tsnj@4ax.com...

On Tue, 04 Jan 2005 02:25:38 GMT, "Don A. Gilmore"
Yes, that's all I want. I would prefer sheets as large as possible...in
roll form would be great. It doesn't have to be super-flexible, but I
don't
want it brittle like glass either. It will be applied to a slightly
irregular surface, but generally planar...maybe sort of like a large
airplane wing. It will not be subjected to much abuse, but it might be
exposed to normal outdoor temperatures.

So far I'm leaning toward some conductive plastic sheet material that
McMaster-Carr carries. But only because it's all I've found yet (and it
only comes in 12" x 12" sample sheets". That's why I was wondering if
one
of you clever guys might have heard of something else that I missed.

---
You might want to try:

http://www.advsys.com.au/downloads/cuming%20catalogue.pdf

In particular, Technical Bulletin 320-8 on page 67.

Also, Series Number 26200 at:

http://www.right-tape.com/html/prod_silicone_rubber.html#photo6

Also there are a lot of hits you might want to check out at:

http://www.google.com/search?q=electrically+conductive+rubber+sheet&hl=en&lr=&start=20&sa=N

Great. Thanks John. The silicone is particularly intriguing.

Don

WayneL · Jan 5, 2005

see
The difference between a "galvanic cell" and "electrolyte cell"

Wayne

"Guy Macon" <http://www.guymacon.com/> wrote in message
news:10toe4mh7oaglbd@corp.supernews.com...

WayneL wrote:

According to the Electrochemistry Dictionary
http://electrochem.cwru.edu/ed/dict.htm#o08

overpotential
The difference in the electrode potential of an electrode between its
equilibrium potential and its operating potential when a current is
flowing.
The overpotential represents the extra energy needed (an energy loss that
appears as heat) to force the electrode reaction to proceed at a required
rate (or its equivalent current density). Consequently, the operating
potential of an anode is always more positive than its equilibrium
potential, while the operating potential of a cathode is always more
negative than its equilibrium potential. The overpotential increases with
increasing current density, see Tafel equation. The value of the
overpotential also depends on the "inherent speed" of the electrode
reaction: a slow reaction (with small exchange current density) will
require
a larger overpotential for a given current density than a fast reaction
(with large exchange current density). Also referred to as "polarization"
of
the electrode. See also overvoltage.
An electrode reaction always occurs in more than one elementary step, and
there is an overpotential associated with each step. Even for the simplest
case, the overpotential is the sum of the concentration overpotential and
the activation overpotential.

overvoltage
The difference between the cell voltage (with a current flowing) and the
open-circuit voltage (ocv). The overvoltage represents the extra energy
needed (an energy loss that appears as heat) to force the cell reaction to
proceed at a required rate. Consequently, the cell voltage of a galvanic
cell (e.g., a rechargeable battery during discharging) is always less than
its ocv, while the cell voltage of an electrolytic cell (e.g., a
rechargeable battery during charging) is always more than its ocv.
Occasionally also referred to as "polarization" of the cell.
The overvoltage is the sum of the overpotentials of the two electrodes of
the cell and the ohmic loss of the cell. Unfortunately, the terms
"overvoltage" and "overpotential" are sometimes used interchangeably.

Does any of this apply if the systtem is not a cell (often incorrectly
called a "battery") but is instead a conductivity meter?

Driver to drive?

Rich The Newsgropup Wacko

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