AVR-Chat

Hi, I'm new to the group and have just received my STK-500 and I'm ready to
start my first application (one-off) which is data logging, control and
monitoring of the irrigation pump & filter supplying our small orange grove in
Tampa, Florida.

Background:  I'm a retired software developer (Financial Electronic Funds
Transfer, Automated Teller Machine systems as well as communications).
Electrical Engineer by training.  I'll be programming AVRs mostly in C as that
is the language I'm most familiar with but I'm not afraid of ASM in situations
that require it.

Clock: For data logging timestamp purposes do folks use an external xtal and
onboard timer channel (assume Atmega16) or should one use an external RTC?
Tradeoffs?  I'd like accuracy on the order of 10 seconds per month.

Backup Power: 110 VAC power is normally available but I'd like to provide backup
power to maintain the RTC clock function mentioned above.  What's the
easiest/cheapest way to do this?  One thought was to just purchase the smallest
battery UPS I can find.  Another thought was a 12v battery supplying the
processor, etc. with a 'float' charger attached to it.  Tradeoffs?

Field Connections: There are currently two pressure transducers (located outside
the weatherproof cabinet) feeding the microcontroller as well as a 24VAC signal
from the irrigation controller (pump start request, in the same cabinet) and a
24VAC signal to the pump start relay (outside the cabinet).  Considering the
field connections to the pressure transducers in particular what precautions
should be used to protect the microcontroller from lightning, etc. (this is
located in Florida, lightning capital of the world!) - except, of course, a
direct strike where all bets are off :-)  The transducer signals are 0-5vdc.
Varistor?  Some kind of fast acting clamp?

Communications:  I would eventually like to connect this site to a phone line
via a modem for status reporting and non-time critical command functions.  I've
seen several chips/modules that provide this to 10-BaseT/100-BaseT nets but not
for dialup.  Can you point me to available libraries supporting the
sending/receiving of email via dialup?  I have a dialup ISP.  I assume I'd need
dialer functions (easy to for me to do but why reinvent the wheel), TCP/IP
stack, SMTP/POP3 functions, etc.

Cheers,

Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck

> Backup Power: 110 VAC power is normally available but I'd like to 
provide backup
> power to maintain the RTC clock function mentioned above.  What's 
the
> easiest/cheapest way to do this?  One thought was to just purchase 
the smallest
> battery UPS I can find.  Another thought was a 12v battery 
supplying the
> processor, etc. with a 'float' charger attached to it.  Tradeoffs?

Most RTC's can be powered from two sources.  one is about 1/2 volt 
higher (or less).  the lower voltge one is often a button battery.  
when the high voltage, if you call 5 volts high, is lost, the button 
battery kicks in at 3. something volts and then kicks out when the 
power is restored.

The button will have a realtivly short life of 5-10 years in moderate 
use, 2-3 in continuous use and about 25 years in reserve.

Not too bad for a 50 cent battery and a $1.50 for a holder.

I use the 12.5mm solder leg verson for my RTC's, or the 22mm for 
larger projects like data loggers that are only powered briefly and 
are unplugged 99% of the time.

For the sunny climate, a solar charger will be of great use to re-
charge your battery packs.

also, read the data sheet for the RTC.  Some have the ability to 
trickle charge the back-up battery.

Dave

On Thursday 21 October 2004 05:42, Chuck Hackett wrote:

> Clock: For data logging timestamp purposes do folks use an
> external xtal and onboard timer channel (assume Atmega16) or
> should one use an external RTC? Tradeoffs?  I'd like accuracy on
> the order of 10 seconds per month.

Independent RTC... mainly because of it makes the programming much
easier ans well as ...

> Backup Power: 110 VAC power is normally available but I'd like to provide
> backup power to maintain the RTC clock function mentioned above.  What's
> the easiest/cheapest way to do this?  One thought was to just purchase

Independent RTC with its own battery. Monitor battery voltage with
the AVR when the controller is active. The controller could go into
a low-power mode and be woken up once a second (or so) by the RTC
driving an interupt.

When mains power is available, provide a "float charge" to supplant
the battery supply. A series resistor between the battery and the
rest of the circuit is usually enough to prevent the battery from
actually charging at a dangerous rate, while only increasing the
power consumption during a power failure by a small amount. Resistor
selection will depend on the current drawn by the RTC. Some RTC's
probably have the integrated ability to draw from two power sources
(i.e. main PSU and battery) making circuit design a lot simpler.

You won't need any special circuitry if you use alkaline cells for
battery backup; just keep your possible "charge" current below a
milliamp or thereabouts (you could possibly "drive" it using an AVR
pin as output; if the pin supports ADC, then you can periodically
test the battery state by switching it "off" and after a decent
interval, measuring a voltage indicative). Alkaline cells have a
shelf life of about 7 years which you should be able to approach.

> the smallest battery UPS I can find.  Another thought was a 12v battery
> supplying the processor, etc. with a 'float' charger attached to it. 
> Tradeoffs?

Maintenance and battery life. This all adds to cost.

> Field Connections: There are currently two pressure transducers
> (located outside the weatherproof cabinet) feeding the
> microcontroller as well as a 24VAC signal from the irrigation
> controller (pump start request, in the same cabinet) and a 24VAC
> signal to the pump start relay (outside the cabinet).  Considering
> the field connections to the pressure transducers in particular
> what precautions should be used to protect the microcontroller
> from lightning, etc. (this is located in Florida, lightning
> capital of the world!) - except, of course, a direct strike where
> all bets are off :-)  The transducer signals are 0-5vdc. Varistor?
> Some kind of fast acting clamp?

Transorbs on power and "local" wiring. Optical isolation on signal
inputs with long wires.

> Communications:  I would eventually like to connect this site to a
> phone line via a modem for status reporting and non-time critical
> command functions.  I've seen several chips/modules that provide
> this to 10-BaseT/100-BaseT nets but not for dialup.  Can you point
> me to available libraries supporting the sending/receiving of
> email via dialup?  I have a dialup ISP.  I assume I'd need dialer
> functions (easy to for me to do but why reinvent the wheel),
> TCP/IP stack, SMTP/POP3 functions, etc.

SMTP is amazingly simple, but the underlying TCP/IP stack is quite a
lot of baggage. If you have a dialer, then why not simply call a
pre-determined number, have that answer and log the status? Thsi is
how many "monitored" alarm systems operate. If you're anywhere near
a GSM (or similar) network, then you can send status using SMS; and
also receive messages to re-program as necessary.

GSM phone modules aren't very expensive; unfashionable mobile phones
are a cheap resource. Some will accept a serial connection and talk
an AT-like protocol to allow the sending of messages without a
landline.

-- 
/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
\ /  ASCII ribbon campaign | I'm a .signature virus!
 X   against HTML mail     | Copy me into your ~/.signature
/ \  and postings          | to help me spread!

Thanks to all for you comments on my remote site question.  Thanks to Dingo in
particular for providing part numbers.  See more comments interspersed below:


> From: Dave Mucha
> 
> ....
> I use the 12.5mm solder leg verson for my RTC's, or the 22mm 
> for larger projects like data loggers that are only powered 
> briefly and are unplugged 99% of the time.
> 
> For the sunny climate, a solar charger will be of great use 
> to re- charge your battery packs.
> 
> also, read the data sheet for the RTC.  Some have the ability 
> to trickle charge the back-up battery.

The site has 110VAC power 99% of the time so I think a button cell would easily
cary it through the power outage cycles.


> From: Bernd Felsche
> 
> ....
> Independent RTC... mainly because of it makes the programming 
> much easier ans well as ...

The DS1307 that Dingo recommended looks good to me.  Now I have another thing to
learn, SPI, :-)

> ....
> Independent RTC with its own battery. Monitor battery voltage 
> with the AVR when the controller is active. The controller 
> could go into a low-power mode and be woken up once a second 
> (or so) by the RTC driving an interupt.

The DS1307 auto switches to a button cell and the AVR has brown-out detection so
I think I'm covered there.

> ....
> Transorbs on power and "local" wiring. Optical isolation on 
> signal inputs with long wires.

While searching the net for info on Transorbs I found this on Lightning
protection that may be of interest to others:
http://www.telebyteusa.com/catalog/refinfo/appnote1.htm

I searched Digikey (and International Rectifier) for "Transorbs" but didn't come
up with anything.  Having seen the above web page I searched for "avalanche
diode" and came up with 69 items on Digikey ...

Am I searching for the wrong thing?

Would I be looking for Schottky or "Standard Recovery" avalanche diodes.  Also,
I saw none with voltage ratings below 100V.  For the analog data lines I assume
I'd be looking for something in the 10v range.

Since I'm protecting an analog signal line here I assume optos are inappropriate
(at least I've only seen ones suitable for digital, as opposed to analog,
links).  I assume that the Transorb does not effect the signal line until the
voltage exceeds it's rating?  I also assume they conduct in the forward
direction like a normal diode if the surge takes the data line in the reverse
direction (i.e.: forward polarity with respect to the Transorb)?

> ....
> SMTP is amazingly simple, but the underlying TCP/IP stack is 
> quite a lot of baggage. If you have a dialer, then why not 
> simply call a pre-determined number, have that answer and log 
> the status? Thsi is how many "monitored" alarm systems 
> operate. 

If I had a predetermined phone number it would have to be dedicated to this
function with a system to answer it.  Seems like overkill when the Internet is
everywhere.

I just realized that I do have high-speed Internet available but it's about 400
feet from the device and there is a Telco grade twisted-pair cable between the
site and the location of the cable modem.  Does anyone know of a 10-BaseT line
driver/converter that can drive 10mbit over 400 feet of twisted pair?  If so I
could use one of the 10-BaseT Internet devices.

----------------------------------------------------

Further thoughts on the clock:  Since the 110VAC power is up 90% of the time
and, as I understand it, powerline frequency is very accurate over long periods
(e.g.: 24 hours) but not necessarily over short periods.  Are there any RTCs
that have a 'reference' input that can be derived from the power line to keep it
accurate when the 110VAC power is present?

Communications:  No one has a URL for libraries that support SMTP/POP3/TCP/IP
functions over Async?  (I haven't searched AVR freaks yet but it's on my list).

Thanks again to all, sorry for the long message :-)

Cheers,

Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck

At 01:09 PM 10/21/04 -0500, you wrote:
> > ....
> > Transorbs on power and "local" wiring. Optical isolation on
> > signal inputs with long wires.
>
>While searching the net for info on Transorbs I found this on Lightning
>protection that may be of interest to others:
>http://www.telebyteusa.com/catalog/refinfo/appnote1.htm
>
>I searched Digikey (and International Rectifier) for "Transorbs" but 
>didn't come
>up with anything.  Having seen the above web page I searched for "avalanche
>diode" and came up with 69 items on Digikey ...
>
>Am I searching for the wrong thing?

Transorb (Tranzorb?) is essentially a brandname for a particular type of 
TVS (Transient Voltage Suppressor), rather like Hexfet vs Mosfet.  Digikey 
has many.

>Would I be looking for Schottky or "Standard Recovery" avalanche 
>diodes.  Also,
>I saw none with voltage ratings below 100V.  For the analog data lines I 
>assume
>I'd be looking for something in the 10v range.

Maybe higher.  Series protection is not uncommon, TVS devices don't usually 
have a very sharp breakover so having something like a TVS to catch high 
spikes followed by a zener in parallel with the sense input / resistor in 
series for dropping the voltage to provide a more precise cutout point is 
sometimes used.  Another thing to watch out for is TVS devices are meant to 
be used in a transient mode only. That's how they get such high power 
ratings in such a small package size.


>Since I'm protecting an analog signal line here I assume optos are 
>inappropriate
>(at least I've only seen ones suitable for digital, as opposed to analog,
>links).  I assume that the Transorb does not effect the signal line until the
>voltage exceeds it's rating?  I also assume they conduct in the forward
>direction like a normal diode if the surge takes the data line in the reverse
>direction (i.e.: forward polarity with respect to the Transorb)?

There are analog opto-isolation devices but they are more expensive.  TVS 
devices are often bidirectional.  The other thing to be aware of is that 
they do provide additional capacitance on the line they protect.  I suspect 
that is not an issue for you but if you need high speed it's something to 
watch out for.

Another way to approach isolation is to put the A/D convertor on the 
isolated side and use a serial protocol to get the info back.  Probably too 
complex and pricey for your setup though.


> > ....
> > SMTP is amazingly simple, but the underlying TCP/IP stack is
> > quite a lot of baggage. If you have a dialer, then why not
> > simply call a pre-determined number, have that answer and log
> > the status? Thsi is how many "monitored" alarm systems
> > operate.
>
>If I had a predetermined phone number it would have to be dedicated to this
>function with a system to answer it.  Seems like overkill when the Internet is
>everywhere.

I seem to remember seeing (in the back of one of those product magazines) a 
device that provided a modem with a built-in tcp/ip stack.

Robert


" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III

At 02:49 PM 10/21/04 -0400, you wrote:

>At 01:09 PM 10/21/04 -0500, you wrote:
> >Since I'm protecting an analog signal line here I assume optos are
> >inappropriate
> >(at least I've only seen ones suitable for digital, as opposed to analog,
> >links).  I assume that the Transorb does not effect the signal line 
> until the
> >voltage exceeds it's rating?  I also assume they conduct in the forward
> >direction like a normal diode if the surge takes the data line in the 
> reverse
> >direction (i.e.: forward polarity with respect to the Transorb)?
>
>There are analog opto-isolation devices but they are more expensive.


And there are also industrial isolation devices for analog (see for example 
http://www.dataforth.com/catalog/doc_generator.asp?doc_id=266 ).  For some 
applications these make more sense than rolling your own (already fully 
tested, Burr-Brown's analog quality, rapid assembly, available with a wide 
range of input to output scaling) but they are pricey $200-$300 US 
AFAIR.  Analog devices also makes plug compatible modules.

I've used them for test benches.  Made any questions about isolation and 
accurracy a lot easier to deal with.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III

If you only need to send data 400 feet you could look to 433MHz radio modules. (They are similar to Garage door remotes, but designed for serial data).

I'm thinking a microcontroller at each end of the 400 feet. One to the device and the other into the serial or ethernet port.

They are really cheap - starting at US$5. I would caution though, the slighly more expensive ones do seem to provide people with a better experience.

Lightning cannot strike the wireless part of a wireless link :)

To give you an idea see this site http://www.futurlec.com/Radio.shtml . These are just the SAW-locked cheapies though. I personally have used the TRX433 on this Australian site http://oatleyelectronics.com/remote.html to great effect. The added advantage of these is they have very useful circuitry for serial data. They also configure really easily.

In the US, www.sparkfun.com also have some easy to use wireless modules. They claim you can just feed serial in one and data comes out the other. I've never used them so I can't vouch for that personally.

If for some reason you need to convert the received data to analogue (but I don't think you will), you can just use an DAC (digital-to-analogue convertor). The speed at which you need to convert the digital signal will be a big factor in the price of such a chip. Some basic ones are here: http://www.futurlec.com/ICDAC.shtml

As for range on SAW wireless modules, some claim over a kilometre. To get this though would require a proper antenna I'd imagine. For 400 feet you could probably get away with just a nice small antenna. This really isn't my area though :)

Ethernet with microcontrollers has always been a bit expensive for my tastes :)

But see the "Ethernut board" at avrfreaks. There are also quite a few around. As for 400 feet from a microcontrolled board I don't know. Plus the added problem of communicating with a router and all the protocols that need to be implemented might be beyond a simple microcontroller.

This is why my designs usually have two micros at each end of the wireless link with one talking to a PC via a serial port - no TCP/IP overhead :)

----- Original Message -----

From: Chuck Hackett

To: AVR-Chat@yahoogroups.com

Sent: Friday, October 22, 2004 4:09 AM

Subject: RE: [AVR-Chat] Re: Remote site questions

Thanks to all for you comments on my remote site question. Thanks to Dingo in
particular for providing part numbers. See more comments interspersed below:


> From: Dave Mucha
>
> ....
> I use the 12.5mm solder leg verson for my RTC's, or the 22mm
> for larger projects like data loggers that are only powered
> briefly and are unplugged 99% of the time.
>
> For the sunny climate, a solar charger will be of great use
> to re- charge your battery packs.
>
> also, read the data sheet for the RTC. Some have the ability
> to trickle charge the back-up battery.

The site has 110VAC power 99% of the time so I think a button cell would easily
cary it through the power outage cycles.


> From: Bernd Felsche
>
> ...
> Independent RTC... mainly because of it makes the programming
> much easier ans well as ...

The DS1307 that Dingo recommended looks good to me. Now I have another thing to
learn, SPI, :-)

> ....
> Independent RTC with its own battery. Monitor battery voltage
> with the AVR when the controller is active. The controller
> could go into a low-power mode and be woken up once a second
> (or so) by the RTC driving an interupt.

The DS1307 auto switches to a button cell and the AVR has brown-out detection so
I think I'm covered there.

> ....
> Transorbs on power and "local" wiring. Optical isolation on
> signal inputs with long wires.

While searching the net for info on Transorbs I found this on Lightning
protection that may be of interest to others:
http://www.telebyteusa.com/catalog/refinfo/appnote1.htm

I searched Digikey (and International Rectifier) for "Transorbs" but didn't come
up with anything. Having seen the above web page I searched for "avalanche
diode" and came up with 69 items on Digikey ..

Am I searching for the wrong thing?

Would I be looking for Schottky or "Standard Recovery" avalanche diodes. Also,
I saw none with voltage ratings below 100V. For the analog data lines I assume
I'd be looking for something in the 10v range.

Since I'm protecting an analog signal line here I assume optos are inappropriate
(at least I've only seen ones suitable for digital, as opposed to analog,
links). I assume that the Transorb does not effect the signal line until the
voltage exceeds it's rating? I also assume they conduct in the forward
direction like a normal diode if the surge takes the data line in the reverse
direction (i.e.: forward polarity with respect to the Transorb)?

> ....
> SMTP is amazingly simple, but the underlying TCP/IP stack is
> quite a lot of baggage. If you have a dialer, then why not
> simply call a pre-determined number, have that answer and log
> the status? Thsi is how many "monitored" alarm systems
> operate.

If I had a predetermined phone number it would have to be dedicated to this
function with a system to answer it. Seems like overkill when the Internet is
everywhere.

I just realized that I do have high-speed Internet available but it's about 400
feet from the device and there is a Telco grade twisted-pair cable between the
site and the location of the cable modem. Does anyone know of a 10-BaseT line
driver/converter that can drive 10mbit over 400 feet of twisted pair? If so I
could use one of the 10-BaseT Internet devices.

----------------------------------------------------

Further thoughts on the clock: Since the 110VAC power is up 90% of the time
and, as I understand it, powerline frequency is very accurate over long periods
(e.g.: 24 hours) but not necessarily over short periods. Are there any RTCs
that have a 'reference' input that can be derived from the power line to keep it
accurate when the 110VAC power is present?

Communications: No one has a URL for libraries that support SMTP/POP3/TCP/IP
functions over Async? (I haven't searched AVR freaks yet but it's on my list).

Thanks again to all, sorry for the long message :-)

Cheers,

Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck

On Friday 22 October 2004 06:51, Dingo wrote:
> If you only need to send data 400 feet you could look to 433MHz
> radio modules. (They are similar to Garage door remotes, but
> designed for serial data).
>
> I'm thinking a microcontroller at each end of the 400 feet. One to
> the device and the other into the serial or ethernet port.

Good idea. I've used (not built) a similar radio link for telemetry
from a solar car to a support vehicle. [The uC at both ends is an
AVR.] Initial experience was quite disappointing, with an effective
range of less than 30 metres.

> As for range on SAW wireless modules, some claim over a kilometre.
> To get this though would require a proper antenna I'd imagine. For
> 400 feet you could probably get away with just a nice small
> antenna. This really isn't my area though :)

With the solar car, we kept the original antenna (that was properly
tuned anyway) but increased the ground plane size from the original
sheet metal size of about 20 cm diameter, to one using two strips of
aluminium foil glued onto the exterior of the supporting fibreglass
panel; for an area of about a metre square. That was sufficient to
increase the reliable range to well over 50 metres which made the
experience rather more safe. At one time we were able to get
intermittent telemetry from over 100 metres; with the solar car
enclosed in a sheet-metal trailer!

A fixed installation shouldn't have too many ground-plane problems.

-- 
/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
\ /  ASCII ribbon campaign | I'm a .signature virus!
 X   against HTML mail     | Copy me into your ~/.signature
/ \  and postings          | to help me spread!

At 08:02 AM 22/10/04 +0800, you wrote:
>
>On Friday 22 October 2004 06:51, Dingo wrote:
>> If you only need to send data 400 feet you could look to 433MHz
>> radio modules. (They are similar to Garage door remotes, but
>> designed for serial data).
>

I have just ordered 2 TX/RX modules from Oatley electronics to hook
up our electronic signs to a computer. Will report on findings once I get
them (~1 week).

Regards

John Samperi

******************************************************
                        Ampertronics Pty. Ltd.
  11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
         Tel. (02) 9674-6495       Fax (02) 9674-8745
               Email: samperi@ampertronics.com.au
                 Website  http://www.ampertronics.com.au
* Electronic Design   * Custom Products   * Contract Assembly
******************************************************

> 
> Since I'm protecting an analog signal line here I assume optos are 
inappropriate
> (at least I've only seen ones suitable for digital, as opposed to 
analog,
> links).  


If you are protecting an analogue line, why not make it into a 
digital signal and then use an opto  or even fiber optic ?

I am working intermitantly  on a sensor for a plasma cutter machine 
and that pulse is in the 300 volt range.  it varies from about 20 to 
220 for it's actual work and when working it should hold very close 
to some setting the operator chooses.   ie: if set for 90 volts, it 
should operate around 90 volts unless things start to change like 
holes in the metal or the gas pressure or the part warps.

converting the raw signal into a digital and then over a fiber optic 
line is the goal.

Dave

At 02:53 PM 22/10/04 +1000, you wrote:
>     Which ones? I love the $33 ones - worth the price  IMO    -----

I think they are the ones, based on the Nordic chip (NRF401?)

Regards

John Samperi

******************************************************
                        Ampertronics Pty. Ltd.
  11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
         Tel. (02) 9674-6495       Fax (02) 9674-8745
               Email: samperi@ampertronics.com.au
                 Website  http://www.ampertronics.com.au
* Electronic Design   * Custom Products   * Contract Assembly
******************************************************

> From: Dave Mucha
> > 
> > Since I'm protecting an analog signal line here I assume optos are
inappropriate
> > (at least I've only seen ones suitable for digital, as opposed to analog,
> > links).  
> 
> 
> If you are protecting an analogue line, why not make it into 
> a digital signal and then use an opto  or even fiber optic ?

In this particular case I think it would be overkill but I grant you that it's
one approach.

Cheers,

Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck

--- In AVR-Chat@yahoogroups.com, "Chuck Hackett" <egroupscdh@W...> 
wrote:
> > From: Dave Mucha
> > > 
> > > Since I'm protecting an analog signal line here I assume optos 
are
> inappropriate
> > > (at least I've only seen ones suitable for digital, as opposed 
to analog,
> > > links).  
> > 
> > 
> > If you are protecting an analogue line, why not make it into 
> > a digital signal and then use an opto  or even fiber optic ?
> 
> In this particular case I think it would be overkill but I grant 
you that it's
> one approach.
> 
> Cheers,
> 
> Chuck Hackett


It may be, but the unit is monitoring the voltage of a plasma 
cutter.  the noise will effect any unprotected anything electronical 
in the area.

The fiber optic was just to eleminate any potential problems.  And, I 
have a friend who works for the phone company and can get me a couple 
feet now and again.

I'm still looking for network installers who trash the end of a roll 
with only 20 or so feet left.  

Dave






> "Good judgment comes from experience, experience comes from bad 
judgment"
> 7.5" gauge Union Pacific Northern (4-8-4) 844
> http://www.whitetrout.net/Chuck

Dave Mucha wrote:

> 
> --- In AVR-Chat@yahoogroups.com, "Chuck Hackett" <egroupscdh@W...> 
> wrote:
> 
>>>From: Dave Mucha
>>>
>>>>Since I'm protecting an analog signal line here I assume optos 
> 
> are
> 
>>inappropriate
>>
>>>>(at least I've only seen ones suitable for digital, as opposed 
> 
> to analog,
> 
>>>>links).  
>>>
>>>
>>>If you are protecting an analogue line, why not make it into 
>>>a digital signal and then use an opto  or even fiber optic ?
>>
>>In this particular case I think it would be overkill but I grant 
> 
> you that it's
> 
>>one approach.
>>
>>Cheers,
>>
>>Chuck Hackett
> 
> 
> 
> It may be, but the unit is monitoring the voltage of a plasma 
> cutter.  the noise will effect any unprotected anything electronical 
> in the area.
> 
> The fiber optic was just to eleminate any potential problems.  And, I 
> have a friend who works for the phone company and can get me a couple 
> feet now and again.
> 
> I'm still looking for network installers who trash the end of a roll 
> with only 20 or so feet left.  
> 
> Dave
> 
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> 
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> 
> 
>>"Good judgment comes from experience, experience comes from bad 
> 
> judgment"
> 
>>7.5" gauge Union Pacific Northern (4-8-4) 844
>>http://www.whitetrout.net/Chuck
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> 
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>  
> Yahoo! Groups Links
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>  
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> 
Where are you dave ?

What size do you want ?

Regards,

Kat.

-- 
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> From: Dave Mucha
> 
> ....
> > > If you are protecting an analogue line, why not make it into a 
> > > digital signal and then use an opto  or even fiber optic ?
> > 
> > In this particular case I think it would be overkill but I grant you that
it's
> > one approach.
> > 
> > Cheers,
> > 
> > Chuck Hackett
> 
> 
> It may be, but the unit is monitoring the voltage of a plasma 
> cutter.  the noise will effect any unprotected anything 
> electronical in the area.
> ....
> Dave

Sorry Dave, miscommunication here.  I was saying that it was overkill for MY
pump monitor application.  Sounds like a GOOD idea for your plasma cutter
application.  Sorry for the confusion.

Cheers,

Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck