Topic: Building a Weather Station

[iic1tls]

Does anyone know of any websites that discuss the technical aspects of designing and building weather hardware?  I have been searching around the web for such resources, but have found almost nothing on the subject.  I might be using the wrong key words on Google...   

Anyway, I am an electronics hobbyist, and I am working on a digital temperature sensor and software for Windows Vista.  Next stop is a Barometric pressure sensor.  I have obtained the parts, but have not yet figured out a procedure to calibrate it.   

Web pages detailing how to build some of this stuff are coming, probably later this year...

Please let me know if anyone else has tried this yet - I really would be interested in reading their notes.

THANK YOU!

[wmiler]

Does anyone know of any websites that discuss the technical aspects of designing and building weather hardware?  I have been searching around the web for such resources, but have found almost nothing on the subject.  I might be using the wrong key words on Google...   

Anyway, I am an electronics hobbyist, and I am working on a digital temperature sensor and software for Windows Vista.  Next stop is a Barometric pressure sensor.  I have obtained the parts, but have not yet figured out a procedure to calibrate it.   

Web pages detailing how to build some of this stuff are coming, probably later this year...

Please let me know if anyone else has tried this yet - I really would be interested in reading their notes.

THANK YOU!

Calibration for most sensors are fairly straight forward. You'll need a standard to compare your designs against, calibrated standards aren't cheap however. If you are just doing this for your joys, you can probably use a few things around you to get close. For temp/dewpoint, you can use a good ol' regular thermometer, for dewpoint, just stick a piece of lightly damp cloth around the bulb of the thermometer. For the barometer, you'll need your local airport's station pressure, and convert it for your elevation.

Also, your sensors should have arrived with some performance specs that you will need to account for in your software (Davis and friends do that sort of stuff in their firmware). Not all sensors work in a perfectly linear manner unfortunately, no matter what the engineer said!

[iic1tls]

Thank you for the reply. 

I thought of the same idea for the Barometric pressure sensor (going over to the airport), and as for the thermometer, I could come up with some ideas around the house.   

When I mention building sensors, I mean that I actually search around, find the electronic pieces, and then design schematics to wire together the sensor, microprocessor, and associated communications devices to get the sensor data to the computer.  I also write the software to interprete what the sensor is indicating.  I dont buy any pre-fabricated sensor systems from the various manufacturers.  To the contrary - I am discovering that the parts for building weather sensors are far cheaper than the store bought stuff, and there is some fun to building, calibrating, and writing software for this stuff.  It is difficult, but not impossible.

If anybody knows of any such sites, or you have any other ideas of different ways to calibrate sensors (and what standards might be used from ordinary household items), I would sure appreciate it!

THANK YOU!

[wmiler]

When I mention building sensors, I mean that I actually search around, find the electronic pieces, and then design schematics to wire together the sensor, microprocessor, and associated communications devices to get the sensor data to the computer.  I also write the software to interprete what the sensor is indicating.  I dont buy any pre-fabricated sensor systems from the various manufacturers.  To the contrary - I am discovering that the parts for building weather sensors are far cheaper than the store bought stuff, and there is some fun to building, calibrating, and writing software for this stuff.  It is difficult, but not impossible.

Oh I realized that, I meant the 'actual' sensor itself, ie the tranducer (endless you really want to go to all the trouble to completely build this from scratch

On a related note, any interest in writing (for free) some GPL'd software to read/write to some aftermarket commercial sensors?

[wuhu_software]

When I mention building sensors, I mean that I actually search around, find the electronic pieces, and then design schematics to wire together the sensor, microprocessor, and associated communications devices to get the sensor data to the computer.  I also write the software to interprete what the sensor is indicating.  I dont buy any pre-fabricated sensor systems from the various manufacturers.  To the contrary - I am discovering that the parts for building weather sensors are far cheaper than the store bought stuff, and there is some fun to building, calibrating, and writing software for this stuff.  It is difficult, but not impossible.

Oh I realized that, I meant the 'actual' sensor itself, ie the tranducer (endless you really want to go to all the trouble to completely build this from scratch

On a related note, any interest in writing (for free) some GPL'd software to read/write to some aftermarket commercial sensors?

What kind of sensors?

Thanks.

[iic1tls]

Hey Guys!

Again - thank you for your replies.  I am glad to see that someone actually has noticed some things that I have written.

***

Lets take a barometric pressure sensor as an example for this discussion.

From www.mouser.com, you can obtain a temperature compensated, absolute pressure sensor, manufactured by Freescale Semi (part number MPXM2102AS).  This part, when interfaced with a MicroChip Corp 12-bit analog to digital converter (ADC) (part number TC7109CPL), provides me with barometric pressure, at 12bits of precision (13 if you count the sign bit).   

I have finished the first stage of a design, which takes the ADC output and then displays the results as 3 hex digits.  This design simply proves to me that I have the Sensor interfaced with the ADC correctly.  As the atmospheric pressure changes, the digits change, thereby indicating that the ADC part of the design is converting a signal from the pressure sensor.   

The second stage of the design will couple the ADC with a microprocessor.  Dont laugh, but I have chosen to use an old Intel 8086 that a local hardware supplier has lying around in large quantities.  I have already built a couple of projects using the 8086, so figuring out an interface with the ADC wont be impossible - timing maybe, but not the operation.  ROM Burners are available for *cheap* on eBay now, and ROM chips are still fairly plentiful.  Finding the software though (ie masm) for the 8086 has been a challenge, but again - entirely doable on the internet...

After I interface the ADC with the Microprocessor and am able to read intelligible results, I need to know how to calibrate the sensor.  Specifically, I will already have an idea of how to calibrate the upper and lower bounds of the sensor (between 28 and 31 inches of Hg), but what standard do I use for calibration?

I found an old boy scout manual from the 1950's that shows how to build a home made mercury barometer, but the problem is that today, you can not just go down to the corner drug store and purchase a bucket full of mercury - people dont do that anymore.  Too, I am not going to put my hand into a bucket filled with Mercury...   

So, assuming that someone does not have access to a radio to listen to an AFIS broadcast at their local airport, how could someone calibrate this device?  I cant build a Mercury barometer, and I dont have a radio tuned to airport radio frequencies...

THANK YOU for any ideas you might have...

[ncpilot]

So, assuming that someone does not have access to a radio to listen to an AFIS broadcast at their local airport, how could someone calibrate this device?  I cant build a Mercury barometer, and I dont have a radio tuned to airport radio frequencies...

THANK YOU for any ideas you might have...

Just go to the NWS--they'll have barometric pressure at the airport... or any other weather service will have it... You might also be able to go directly to the airport's website, and they might provide pilot weather information...

Check out: http://adds.aviationweather.gov/ -- besides having a ton of info... admittedly I haven't been on the page in a while... I recall the ability to get ATIS/METARS from any airport...

[wmiler]

On a related note, any interest in writing (for free) some GPL'd software to read/write to some aftermarket commercial sensors?

What kind of sensors?

Well, I have my decommissioned Vaisala ceilometer, and also a visibility sensor as well. I'm currently using the ceilometer to learn how to program in python I do have it talking to the ceil now (2-way even!), and I've started on getting the output messages into some reasonably intelligent form. I still need to implement the 20-min averaging cycle stuffs, and get the output stuffs working as well to feed a db and my web page, and possibly generating some strip chart graphics.

The cool thing is on the Vaisala, once I have code working for the ceilometer, almost the exact same code can be used for the VIS (averaging routine would have to be changed mainly).

[wmiler]

The second stage of the design will couple the ADC with a microprocessor.  Dont laugh, but I have chosen to use an old Intel 8086 that a local hardware supplier has lying around in large quantities.  I have already built a couple of projects using the 8086, so figuring out an interface with the ADC wont be impossible - timing maybe, but not the operation.  ROM Burners are available for *cheap* on eBay now, and ROM chips are still fairly plentiful.  Finding the software though (ie masm) for the 8086 has been a challenge, but again - entirely doable on the internet...

After I interface the ADC with the Microprocessor and am able to read intelligible results, I need to know how to calibrate the sensor.  Specifically, I will already have an idea of how to calibrate the upper and lower bounds of the sensor (between 28 and 31 inches of Hg), but what standard do I use for calibration?

So, assuming that someone does not have access to a radio to listen to an AFIS broadcast at their local airport, how could someone calibrate this device?  I cant build a Mercury barometer, and I dont have a radio tuned to airport radio frequencies...

Nothing wrong with the 8086 as an embedded processor, it's not like you need the speed As I recall, the Space Shuttle still uses 80586 machines in their flight controls...

Almost all AWOS/ASOS stations have dial-up voice capability, if it's an ASOS facility you can prolly get it through ncpilot's ADDS link, otherwise just call your airport's FBO/manager's office, and they can give you the dial-up number.

NOTE: All numbers presented will be AVERAGED indications.

[wuhu_software]

On a related note, any interest in writing (for free) some GPL'd software to read/write to some aftermarket commercial sensors?

What kind of sensors?

Well, I have my decommissioned Vaisala ceilometer, and also a visibility sensor as well. I'm currently using the ceilometer to learn how to program in python I do have it talking to the ceil now (2-way even!), and I've started on getting the output messages into some reasonably intelligent form. I still need to implement the 20-min averaging cycle stuffs, and get the output stuffs working as well to feed a db and my web page, and possibly generating some strip chart graphics.

The cool thing is on the Vaisala, once I have code working for the ceilometer, almost the exact same code can be used for the VIS (averaging routine would have to be changed mainly).

That sounds like a cool project. I would implement it in my code however I doubt there would a be a 2nd user for it (unless you find me a nice decommisioned set )