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measure temp with diodes
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ebiz_59
Mon, 23 Nov 09 03:33:04 +0000
I am a farm kid who has cylindrical steel bins that have temperature cables hanging in them. The system I use is Opi One, and the company says the cables contain temp sensitive diodes. These cables then come out of each bin, and I travel to each bin to hook up a display that reads each sensor (up to 7 sensors in a cable - all come out to a DB9 connector, calculates and displays temperature. I'm working on a farm-wide 802.11 network and am thinking that I'd like to read the temps in these bins remotely. The company says I need to buy all new cables with digital sensors and cable reader that is wireless, etc. So the question is, how hard would it be to create a device that would obtain a reading from a sensor and convert that to some sort of data that I could ship back to my office through my 802.11 network? thanks, Chuck


17 replies folowing
Sheldon Dedek
Mon, 23 Nov 09 13:51:00 +0000

I wouldn't think that it would be too difficult. It appears that all
that is happening is that a known current is being passed through each
sense element. Depending on temperature (humidity?), a variable voltage
drop is measured that corresponds with a temperature.

Perhaps through the use of self-aware controllers (Hobo, Zigbee, others)
you will be able to measure remotely, feed to old laptop at each grain
bin. There are devices that have wifi capability built in, but they
typically are low power. They may not have the ability to send a signal
back to your office computer, especially when there may be farm
machinery / transportation equipment moving around in between.

Another possibility is to provide your own precision current, obtain
your voltage, buffer that voltage, and send it to another location over
shielded ethernet or similar. You would need to come up with a voltage
/ temp calibration curve, but it shouldn't be that difficult.

In any case, you will likely have to put your data into the computer
manually, since your "reader" won't like interfacing to your creation.

Sheldon

-----------
Posted by: "ebiz_59" chuckm@3rivers.net ebiz_59
Sun Nov 22, 2009 7:33 pm (PST)


I am a farm kid who has cylindrical steel bins that have temperature
cables hanging in them. The system I use is Opi One, and the company
says the cables contain temp sensitive diodes. These cables then come
out of each bin, and I travel to each bin to hook up a display that
reads each sensor (up to 7 sensors in a cable - all come out to a DB9
connector, calculates and displays temperature. I'm working on a
farm-wide 802.11 network and am thinking that I'd like to read the temps
in these bins remotely. The company says I need to buy all new cables
with digital sensors and cable reader that is wireless, etc. So the
question is, how hard would it be to create a device that would obtain a
reading from a sensor and convert that to some sort of data that I could
ship back to my office through my 802.11 network? thanks, Chuck
-----------
dicsEE
Mon, 23 Nov 09 14:09:40 +0000
 
jong kung
Mon, 23 Nov 09 14:09:40 +0000
ebiz_59 (or is it ChuckM),


> So the


> question is, how hard would it be to create a device that would obtain a


> reading from a sensor and convert that to some sort of data that I could


> ship back to my office through my 802.11 network?


The temp reading (using a diode, transistor, or even dedicated temp sensor) is trivial.  Converting it to digital is part of analog to digital conversion process (also trivial).

It is the 802.11 part that gets slightly trickly (anything that has to do with wireless comm gets a little tricky).  One way is to get a 802.11 transceiver and communicate to that external circuit via serial communication (which becomes a trivial serial comm).

The problem would be finding the 802.11 transmitter / receiver that you can easily wire into (or designed for hobbyist).

====

There's another solution to wireless comm problem.  You can try ZigBee wireless comm.

http://en.wikipedia.org/wiki/ZigBee

They have ZigBee transmitter /receiver packages that you can easily wire into serially.


Jong
















[Non-text portions of this message have been removed]

Howard Hansen
Mon, 23 Nov 09 16:31:05 +0000
It would be easy to build a system to collect temperature data from your
grain bins and transmit the data to your office if you were willing to
purchase off the shelf components. See:
http://www.dataq.com/applicat/articles/wireless.htm
The 150 ft distance shown in the figure could be extended if you use
directional antennas. However, the DI-730 shown in the block diagram
costs over US$3,000.00. DataQ has a lower cost version a DI-710-EL that
costs US$600.00. Then you say you have up to 7 sensors per cable
therefor you may need one DI-710-EL per grain bin.

At the other end of the cost spectrum if you built your own data
acquisition and wireless transmission modules you could probably do it
for a cost of less than US$100.00 per grain bin. But considering the
amount of experience you have with electronics and programming it most
likely will take you over a year working 4 hours a days on the project
to build a working model.

Hence it will be a trade off between dollars and time as to which
approach meets your requirements.

Howard

ebiz_59 wrote:

>
> I am a farm kid who has cylindrical steel bins that have temperature
> cables hanging in them. The system I use is Opi One, and the company
> says the cables contain temp sensitive diodes. These cables then come
> out of each bin, and I travel to each bin to hook up a display that
> reads each sensor (up to 7 sensors in a cable - all come out to a DB9
> connector, calculates and displays temperature. I'm working on a
> farm-wide 802.11 network and am thinking that I'd like to read the
> temps in these bins remotely. The company says I need to buy all new
> cables with digital sensors and cable reader that is wireless, etc. So
> the question is, how hard would it be to create a device that would
> obtain a reading from a sensor and convert that to some sort of data
> that I could ship back to my office through my 802.11 network? thanks,
> Chuck
>
>




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rtstofer
Mon, 23 Nov 09 17:02:07 +0000


--- In Electronics_101@yahoogroups.com, Howard Hansen wrote:

>
> It would be easy to build a system to collect temperature data from your
> grain bins and transmit the data to your office if you were willing to
> purchase off the shelf components. See:
> http://www.dataq.com/applicat/articles/wireless.htm
> The 150 ft distance shown in the figure could be extended if you use
> directional antennas. However, the DI-730 shown in the block diagram
> costs over US$3,000.00. DataQ has a lower cost version a DI-710-EL that
> costs US$600.00. Then you say you have up to 7 sensors per cable
> therefor you may need one DI-710-EL per grain bin.
>
> At the other end of the cost spectrum if you built your own data
> acquisition and wireless transmission modules you could probably do it
> for a cost of less than US$100.00 per grain bin. But considering the
> amount of experience you have with electronics and programming it most
> likely will take you over a year working 4 hours a days on the project
> to build a working model.
>
> Hence it will be a trade off between dollars and time as to which
> approach meets your requirements.
>
> Howard
>
> ebiz_59 wrote:
> >
> > I am a farm kid who has cylindrical steel bins that have temperature
> > cables hanging in them. The system I use is Opi One, and the company
> > says the cables contain temp sensitive diodes. These cables then come
> > out of each bin, and I travel to each bin to hook up a display that
> > reads each sensor (up to 7 sensors in a cable - all come out to a DB9
> > connector, calculates and displays temperature. I'm working on a
> > farm-wide 802.11 network and am thinking that I'd like to read the
> > temps in these bins remotely. The company says I need to buy all new
> > cables with digital sensors and cable reader that is wireless, etc. So
> > the question is, how hard would it be to create a device that would
> > obtain a reading from a sensor and convert that to some sort of data
> > that I could ship back to my office through my 802.11 network? thanks,
> > Chuck
> >
> >
>



Over at Sparkfun, they have a selection of microcontroller based web servers. The intent of these devices is to be able to remotely monitor (via a web browser) the status of a digital signal and to also be able to change a digital signal.

It wouldn't be a stretch to change the code to read analog values and pass them out the web server. In fact, it would be pretty easy.

Of course, you first have to GET the analog values but most every uC has analog inputs. You just need a suitable sensor. Or you can just buy a sensor board that will interface with the web uC.

Search their site for 'web'. Something like
http://www.sparkfun.com/commerce/product_info.php?products_id=7830
might do the job.

Richard


rtstofer
Mon, 23 Nov 09 19:52:06 +0000
Here is an EDN article that is right on point:
http://www.edn.com/article/CA6619020.html

Basically, you measure the temperature by watching a capacitor discharge through a reverse biased diode.

There are other articles out there. Google for 'measuring temperature with a diode'.

One thing you didn't mention is the range of temperatures you expect to measure and the required resolution of the measurement.

Analog devices makes some nice temperature sensors www.analog.com
http://www.analog.com/en/analog-to-digital-converters/temperature-to-digital-converters/products/index.html

I might try the TMP03 or TMP04 devices because the signal ISN'T analog. It is a ratio of 'on' to 'off' time and that can be easy to measure. Almost every uC has a timer gadget.

How many sense points per tank? How many tanks?

It would be simple to use a digital multiplexer chip to select one pulse train from many. A 74LS151 will select 1 of 8 inputs
http://nitc.ac.in/nitc/dept/ece/public_html/student/digital/74LS151.pdf
A 74LS150 will select 1 of 16 inputs.

So, the uC outputs a selection value, initializes a timer and arranges for interrupts on the rising and falling edge of the selected input. The ratio of the resulting timer values times a constant gives the temperature.

The same uC could also be the web server.

Pretty straightforward.

Richard


Howard Hansen
Mon, 23 Nov 09 20:50:46 +0000
Richard, the OPi one system uses a long cable with the sensor attached
to one end. When the grain bin is empty the sensor is lowered into the
grain bin through a hole in the center of the roof. The sensor is
lowered to within 2 to 3 feet of the bottom of the grain bin and secured
to the bottom of the grain bin with a short piece of wire to keep the
sensor from migrating when filling the grain bin. The other end of the
cable is drop over the out side of the grain bin. for measurement
access. One temperature sensor is used with grain bins up to 20 feet in
diameter. Larger diameter grain bins require more temperature sensors
placed about 20 ft apart. The temperature sensors are used o detect the
temperature increases that take place when the grain starts to spoil.

Hence because of the cost of the cable and sensor our first priority
when making recommendations should be to use the existing cable and
sensor. I suspect an accuracy of plus and minus 2 degrees Fahrenheit
over a -30 to 100 degrees Fahrenheit range is reasonable for this
application.

Howard


rtstofer wrote:

>
> Here is an EDN article that is right on point:
> http://www.edn.com/article/CA6619020.html
>
>
> Basically, you measure the temperature by watching a capacitor
> discharge through a reverse biased diode.
>
> There are other articles out there. Google for 'measuring temperature
> with a diode'.
>
> One thing you didn't mention is the range of temperatures you expect
> to measure and the required resolution of the measurement.
>
> Analog devices makes some nice temperature sensors www.analog.com
> http://www.analog.com/en/analog-to-digital-converters/temperature-to-digital-converters/products/index.html
>
>
> I might try the TMP03 or TMP04 devices because the signal ISN'T
> analog. It is a ratio of 'on' to 'off' time and that can be easy to
> measure. Almost every uC has a timer gadget.
>
> How many sense points per tank? How many tanks?
>
> It would be simple to use a digital multiplexer chip to select one
> pulse train from many. A 74LS151 will select 1 of 8 inputs
> http://nitc.ac.in/nitc/dept/ece/public_html/student/digital/74LS151.pdf
>
> A 74LS150 will select 1 of 16 inputs.
>
> So, the uC outputs a selection value, initializes a timer and arranges
> for interrupts on the rising and falling edge of the selected input.
> The ratio of the resulting timer values times a constant gives the
> temperature.
>
> The same uC could also be the web server.
>
> Pretty straightforward.
>
> Richard
>
>




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rtstofer
Mon, 23 Nov 09 22:52:23 +0000


--- In Electronics_101@yahoogroups.com, Howard Hansen wrote:

> Hence because of the cost of the cable and sensor our first priority
> when making recommendations should be to use the existing cable and
> sensor. I suspect an accuracy of plus and minus 2 degrees Fahrenheit
> over a -30 to 100 degrees Fahrenheit range is reasonable for this
> application.
>
> Howard


I did post a link to an EDN article that shows how to use diodes for temperature measurement using reverse current leakage.

There is some merit to using what is already in place. But that would never be a primary driver for one of my projects.

Still, there are a bunch of articles on Google for doing just this type of thing.

Richard


Herbert E. Plett
Tue, 24 Nov 09 07:45:35 +0000
I would suggest using Dallas 1wire system (DS18S20). directly digital.
any small uC will manage dozens of sensors, all you need is have the uC send the data to the main comp, wireless are several alternatives.



--- On Sun, 11/22/09, ebiz_59 wrote:

> From: ebiz_59
> Subject: [Electronics_101] measure temp with diodes
> To: Electronics_101@yahoogroups.com
> Date: Sunday, November 22, 2009, 11:33 PM
> I am a farm kid who has cylindrical
> steel bins that have temperature cables hanging in
> them.  The system I use is Opi One, and the company
> says the cables contain temp sensitive diodes. These cables
> then come out of each bin, and I travel to each bin to hook
> up a display that reads each sensor (up to 7 sensors in a
> cable - all come out to a DB9 connector, calculates and
> displays temperature.  I'm working on a farm-wide
> 802.11 network and am thinking that I'd like to read the
> temps in these bins remotely.  The company says I need
> to buy all new cables with digital sensors and cable reader
> that is wireless, etc.  So the question is, how hard
> would it be to create a device that would obtain a reading
> from a sensor and convert that to some sort of data that I
> could ship back to my office through my 802.11 network?
> thanks, Chuck





Chuck Merja
Tue, 24 Nov 09 12:53:49 +0000
Thank you gentlemen. I wasn't really looking to redesign the cables, rather
understand why OPI did so, and I had two main areas of interest in asking
the question.
1 - I was hoping to avoid the cost of replacing all the cables, since they
work well, if I'm willing to drive to the bin locations with the cable
reader. Not replacing the cables was actually a primary design criteria -
unless they are found to be totally wanting, but I've had some of them in
bins for over 25 years, and they are still working fine.
2 - What does OPI know that I don't know about electronics (which could be a
lot) that would make me want to change away from working analog cables to
new digital cables. Or put another way, why didn't they just redesign the
cable reader to make it useable with existing cables and a mini-network that
could be connected to a farm-wide network through a webserver? And if it is
"easy" to do, why don't I make a cable reader that I could access via my
network.
BTW, when I talked to OPI, they were surprised to know that I had a
farm-wide network, so I'm wondering if it is really something I want to
purchase.
Thanks, Chuck

> >Hence because of the cost of the cable and sensor our first priority
> when making recommendations should be to use the existing cable and
> sensor. I suspect an accuracy of plus and minus 2 degrees Fahrenheit
> over a -30 to 100 degrees Fahrenheit range is reasonable for this
> application.
>
>> Howard


>I did post a link to an EDN article that shows how to use diodes for

temperature measurement using reverse current leakage.

There is some merit to using what is already in place. But that would never
be a primary driver for one of my projects.

Still, there are a bunch of articles on Google for doing just this type of
thing.

>Richard




[Non-text portions of this message have been removed]

rtstofer
Tue, 24 Nov 09 13:57:08 +0000


--- In Electronics_101@yahoogroups.com, "Chuck Merja" wrote:

> 2 - What does OPI know that I don't know about electronics (which could be a
> lot) that would make me want to change away from working analog cables to
> new digital cables. Or put another way, why didn't they just redesign the
> cable reader to make it useable with existing cables and a mini-network that
> could be connected to a farm-wide network through a webserver? And if it is
> "easy" to do, why don't I make a cable reader that I could access via my
> network.


Although there will be contrary views, accurate measurements (if accuracy is even a requirement) are difficult with analog circuitry. Take that simple 'discharge the capacitor through a reverse biased diode' circuit. The huge problem is the change in capacitance over temperature. Same with whatever is being used to provide the reference voltage for the analog conversion.

That TMP03 device is ratiometric and digital. The digital portion implies that we are interested in 'when' the signal changes state, not by how many volts it changes (subject to meeting logic thresholds). The ratiometric portion means that the measurement is the 'ratio' of 'on' time to 'off' time. Hence, the actual frequency of the uC clock, which may be temperature sensitive, is not important.

The more I think about the diode circuit, however, the more I like the idea that I could limit energy. In other words, I could limit the potential for creating a spark. I'd have to think about that when I ran the +5V and Gnd levels down the signal cable. Hm...

If you had a schematic or access to the internals of the cable reader and some basic skills in circuit design/analysis, you might be able to reverse engineer the reader. Once you know how the manufacturer designed the circuit, all you would have to do is build a similar circuit and feed the output to a uC. Of course, you might have to manipulate the output a little (change the range and offset with an OP amp) to make maximum use of the uC A/D input.

The web server and network are the easy part. It's all this electronic stuff that gets in the way of just having fun with C code.

Richard


jong kung
Tue, 24 Nov 09 14:24:29 +0000
Chuck,


> Or put another way, why didn't they just redesign the
> cable reader to make it useable with existing cables


You are assuming that they (OPI people) are interested in OLD clients / old installations.  Most of the factory are only interested in new / next sales.  This is the source of income.  The more you replace, the more you buy, the more income for them.
===
Also, many companies / factories have new wave of engineers, that have NO IDEA what is out there (especially installations that's 25 years old).  So these NEW engineers design new products with new material (or the only materials they know of).

Or even worse, these days, they often FARM OUT the engineering to off-shore (translation: india or china). The off shore engineers knows absolutely nothing of current installations. One day they are designing farm sensors.  The next day they are designing paper warehouse sensors.

====

There are some difference in old analog cables and digital cables.  Analog cables are often thicker because they carry voltage signals (or try to prevent voltage drop).  The newer digital cables are usually designed for high freq signals (like Ethernet cables). 

But that is NOT to say old analog cables can't be made to carry digital signal - look at POTS (play old telephone service / AKA house telephone) wires.  DSL cables are often POTS analog line - just reused.  But the Ma Bell and Baby Bells (telephone companies) had a vested interest in re-using their huge installation of wires.

====

> And if it is "easy" to do, why don't I make a cable
> reader that I could access via my network.


That's more engineering dollars out of their pockets with very little sales dollars in return.  In fact it can be argued that they are spending more engineering dollars that will ultimately lower their sales dollars (less parts / wires / cables to sell).


Jong







[Non-text portions of this message have been removed]

Capt Wright
Tue, 24 Nov 09 15:19:02 +0000
There are cheap temp sensors on the market. They often come in a 3 pin TO92 package and put out a current/deg (1ma/deg). They are very easy to use.

The problem is getting this analog data back and then concerting it and then putting it on your internet or remote system. It will require some design. Another problem is getting the temp sensor info back to a central location. This may require some sort of buffer at the sensor. Another design.

You might be able to build a scanning device in front of the reader you have so it can scan between the sensors. However, I am sure you want to ID remotely what sensor is doing what. This info would be in the scanner, but getting it out and sending it to remote location would require design.

The company you are working with has done this and of course sells as a product. Just depends on how much you wish to do. However, it is a trivial task technology wise with most all buy off the shelf components.

73, ron, n9ee/r



--- In Electronics_101@yahoogroups.com, "Herbert E. Plett" wrote:

>
> I would suggest using Dallas 1wire system (DS18S20). directly digital.
> any small uC will manage dozens of sensors, all you need is have the uC send the data to the main comp, wireless are several alternatives.
>
>
>
> --- On Sun, 11/22/09, ebiz_59 wrote:
>
> > From: ebiz_59
> > Subject: [Electronics_101] measure temp with diodes
> > To: Electronics_101@yahoogroups.com
> > Date: Sunday, November 22, 2009, 11:33 PM
> > I am a farm kid who has cylindrical
> > steel bins that have temperature cables hanging in
> > them.  The system I use is Opi One, and the company
> > says the cables contain temp sensitive diodes. These cables
> > then come out of each bin, and I travel to each bin to hook
> > up a display that reads each sensor (up to 7 sensors in a
> > cable - all come out to a DB9 connector, calculates and
> > displays temperature.  I'm working on a farm-wide
> > 802.11 network and am thinking that I'd like to read the
> > temps in these bins remotely.  The company says I need
> > to buy all new cables with digital sensors and cable reader
> > that is wireless, etc.  So the question is, how hard
> > would it be to create a device that would obtain a reading
> > from a sensor and convert that to some sort of data that I
> > could ship back to my office through my 802.11 network?
> > thanks, Chuck
>



jong kung
Tue, 24 Nov 09 15:42:48 +0000
ChuckM,

Capt Wright wrote:
... However, it is a
trivial task technology wise with
... most all buy off the shelf components.


I agree with Capt Wright.  This isn't a problem that requires new technology (like GPS technology that required massive satellite network and ground based maintenance system).  Much of this type of problem (remote temp sensing) is already done.  It can be easily done with off the shelf components.  And temp being slow changing variable, it can be done using relatively low tech.

Even re-using your old wires can be figured out (ex: even on LONG wires, CURRENT is always equal everywhere in the circuit).  Just make sure it doesn't pick up inductive current.

So if you really want to you can make this work (not even too much electronics either).  Or search your local engineering college for students who wants to make some extra side $$.  My only reservation with EE students are that they seems to know how to pass exams and not really make (design) working circuits.

We had our share of EE students asking newbie questions (at their senior year).


Jong
















[Non-text portions of this message have been removed]

Howard Hansen
Tue, 24 Nov 09 16:54:40 +0000
The information provided at the following four web pages supplies some
hints as to why OPi changed the types of cables and sensors they use to
monitor grain temperature.
http://www.grainbins.com/HowOpiOneWorks.htm
http://www.grainbins.com/HowStorMaxWorks.htm
http://www.grainbins.com/HowStorMaxProWorks.htm
http://www.opistormax.com/customer_support/installation.html

Two significant differences between the old style and the new style
cables are the old style cables used a 9 pin connector and had no built
in identification information. whereas the new style cables use a 2 pin
connector and have built in identification information.

When using diodes for temperature sensors you need 1 lead and a common
for each diode hence with a 9 pin connector you could have up to 8
temperature sensors in a cable. My hypothesis is because Opi is using a
2 pin connector Opi is using One Wire temperature sensors. The neat
thing about One wire temperature sensors is each sensors has a
unique.ID. Hence when reading the temperatures a StorMax can
sequentially poll each sensor in a cable. With one wire technology it is
also possible to build into the cable, a cable ID. Furthermore the new
cables can be connected in a daisy chain thereby permitting the sensors
in every grain bin to be read from one location.

This is my best guess based on the information supplied in the web pages
listed above. Other interpretations are welcomed. My conclusion is being
able to provide cables that had built in identification information with
temperature sensors with built in identification information justifies
OPi decision to add new style cables to their product list.

For more information on one wire see:
http://www.maxim-ic.com/products/1-wire/

Howard


Chuck Merja wrote:

>
> Thank you gentlemen. I wasn't really looking to redesign the cables,
> rather
> understand why OPI did so, and I had two main areas of interest in asking
> the question.
> 1 - I was hoping to avoid the cost of replacing all the cables, since they
> work well, if I'm willing to drive to the bin locations with the cable
> reader. Not replacing the cables was actually a primary design criteria -
> unless they are found to be totally wanting, but I've had some of them in
> bins for over 25 years, and they are still working fine.
> 2 - What does OPI know that I don't know about electronics (which
> could be a
> lot) that would make me want to change away from working analog cables to
> new digital cables. Or put another way, why didn't they just redesign the
> cable reader to make it useable with existing cables and a
> mini-network that
> could be connected to a farm-wide network through a webserver? And if
> it is
> "easy" to do, why don't I make a cable reader that I could access via my
> network.
> BTW, when I talked to OPI, they were surprised to know that I had a
> farm-wide network, so I'm wondering if it is really something I want to
> purchase.
> Thanks, Chuck
>
> > >Hence because of the cost of the cable and sensor our first priority
> > when making recommendations should be to use the existing cable and
> > sensor. I suspect an accuracy of plus and minus 2 degrees Fahrenheit
> > over a -30 to 100 degrees Fahrenheit range is reasonable for this
> > application.
> >
> >> Howard
>
> >I did post a link to an EDN article that shows how to use diodes for
> temperature measurement using reverse current leakage.
>
> There is some merit to using what is already in place. But that would
> never
> be a primary driver for one of my projects.
>
> Still, there are a bunch of articles on Google for doing just this type of
> thing.
>
> >Richard
>
> [Non-text portions of this message have been removed]
>
>




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lists
Thu, 03 Dec 09 22:14:30 +0000
In article <4B0AB8C9.2000505@att.net>,
Howard Hansen wrote:

> At the other end of the cost spectrum if you built your own data
> acquisition and wireless transmission modules


Wont there be issues with the latter because they need to be proved that
they comply with the relavant standards.

Stuart
http://www.torrens.org.uk/ZFC/gallery/winsor.html
Howard Hansen
Fri, 04 Dec 09 00:38:58 +0000
Good point Stuart I should have said with wireless transmission modules
like Zigbee modules which have been certified to meet relevant standards
by the manufacture of the module. See the following for an example of a
Zigbee module and noticed on the bottom of the page the standards the
modules meet.
http://www.digi.com/pdf/ds_xbeemultipointmodules.pdf

Howard


lists wrote:

>
> In article <4B0AB8C9.2000505@att.net >,
> Howard Hansen > wrote:
> > At the other end of the cost spectrum if you built your own data
> > acquisition and wireless transmission modules
>
> Wont there be issues with the latter because they need to be proved that
> they comply with the relavant standards.
>
> --
> Stuart
> http://www.torrens.org.uk/ZFC/gallery/winsor.html
>
>
>




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James Bishop
Fri, 04 Dec 09 00:48:30 +0000
If you have the time to tinker, then an interesting and probably fairly
cheap option would be to re-purpose a Linksys wireless router, like the
famous WRT54G. These things can be 'hacked' to run an open source linux
operating system. There are also heaps of modifications posted on the net,
such as interfacing to 1-wire temperature sensors.

Here's a few links, or just google 'linksys temperature sensor':
http://www.the-mesh.org/tiki-index.php?page=TempSensorLinksys

http://www.lecad.uni-lj.si/~leon/other/wlan/wrt54ow/

http://www.digitemp.com/

Also here is a wifi development board which is pretty cheap at $99, but I
dont know anything about it. It would be a more ground-up DIY solution:
http://www.rabbit.com/products/rcm5600w/


On Mon, Nov 23, 2009 at 2:33 PM, ebiz_59 wrote:

>
>
> I am a farm kid who has cylindrical steel bins that have temperature cables
> hanging in them. The system I use is Opi One, and the company says the
> cables contain temp sensitive diodes. These cables then come out of each
> bin, and I travel to each bin to hook up a display that reads each sensor
> (up to 7 sensors in a cable - all come out to a DB9 connector, calculates
> and displays temperature. I'm working on a farm-wide 802.11 network and am
> thinking that I'd like to read the temps in these bins remotely. The company
> says I need to buy all new cables with digital sensors and cable reader that
> is wireless, etc. So the question is, how hard would it be to create a
> device that would obtain a reading from a sensor and convert that to some
> sort of data that I could ship back to my office through my 802.11 network?
> thanks, Chuck
>
>
>



[Non-text portions of this message have been removed]



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