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Weather station sensors?

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HarveyH42

Banned
Found an interesting bit on Atmel's website. There was an appnote about thermally correcting the ADC. Seems some AVR chips have a built in temperature sensor (diode), which can be read, and used with the ADC. Didn't see a list of chips in the PDF, but will look for it when I looking through the data sheets.

We had some thunderstorms yesterday, was kind of thinking about a lightning strike indicator. Probably a little too much for this project, something to add on later after this is built.

Have had some thoughts on the temperature reading though. Measuring indoor temperature probably wouldn't be the most useful, since most people use heating/AC to maintain a certain range of comfort. Also will need some method of adjusting min/max range for each sensor, and set the scale according to what is most useful. Maybe I can make it self learning in software, just store the lowest/highest readings in EEPROM. Wonder if all this will fit in 2k, or if I'll need to move up to a bigger chip.
 

mrmonteith

New Member
Lightning strike indicator is a good idea. I hadn't thought about that for mine. Should be very easy. A small antena from radio or even a piece of wire, feed that to a simple diode detector and maybe and op-amp. Should be able to pick those babies up easy enough.

Michael
 

HarveyH42

Banned
blueroomelectronics said:
How are you going to run the data from the sensors? I2C is not terribly fond of long cable lengths.
I wasn't going to run them any place, just stuff everything in a box under the lamp. Air pressure should be the same indoors or out. Humidity will be a little lower indoors, but not a big enough difference to have any effect here. The temperature part... will likely stick with the indoor temperature for this first one. I don't run the heat or AC unless dressing accordingly is of little help. It's really more about changing conditions, not measuring how much of a change.

The lamp should stay in the same basic color range for the various weather conditions. A radical color change, would indicate storms coming...
 

3v0

Coop Build Coordinator
Forum Supporter
Human hair hygrometer

Harvey would not want to use this but others may find the hair hygrometer of interest.

Hair changes length depending on humidity. On more humid days, hair will lengthen.

The diagram below shows a simple hair hygrometer. It takes about a foot of hair to create a sensor but it could be wound around a pulley or two to decrease the length. The pointer could be used to block light between a LED and a photo transistor for sensing.

Image about.com.

EDIT: Horse hair can also be used and may be more durable.
 

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mrmonteith

New Member
HarveyH42 said:
......Humidity will be a little lower indoors, but not a big enough difference to have any effect here. ...
I have to disagree. Might want to actually do a test of that assumption. I have a guage set of meters for all the above. I can take it from the house to outside and the humidity can vary a LOT.

Think about it. Unless you're fanning doors or have windows open the inside is isolated from the outside. Plus if you're running either A/C or heat it's going to change even more depending on the type of heat.

It will try to even out but it usually takes quite a long time based on how much air flows in and out of the house. If you're dead set on it being inside you could set it on a window sill with a window cracked open to get as close as possible.

Michael
 

HarveyH42

Banned
mrmonteith said:
I have to disagree. Might want to actually do a test of that assumption. I have a guage set of meters for all the above. I can take it from the house to outside and the humidity can vary a LOT.

Think about it. Unless you're fanning doors or have windows open the inside is isolated from the outside. Plus if you're running either A/C or heat it's going to change even more depending on the type of heat.

It will try to even out but it usually takes quite a long time based on how much air flows in and out of the house. If you're dead set on it being inside you could set it on a window sill with a window cracked open to get as close as possible.

Michael
Yeah, I get what yo mean. This isn't going to be something I figure on moving around much or carrying in my pocket. The actually readings for indoor and outdoor humidity will be different, but there should be similar changes. Like right now, it's cold and dry air. Humidity might be a little higher indoors (shower, coffee maker, people/pets), but different than yesterday, which was warmer but wet.

The readings I take, will be crunched down to an 8 bit value, to set the pulse width for each color of an RGB Led. Hopefully, I'll notice which colors and intensities indicate what sort of weather to expect. Could turn out to be as useless as the local TV news, or might make for a pretty neat gadget. Wonder if some Chinese company will have something like this on the market, before I get my parts from Futurlec?
 

HarveyH42

Banned
3v0 said:
Harvey would not want to use this but others may find the hair hygrometer of interest.

Hair changes length depending on humidity. On more humid days, hair will lengthen.

The diagram below shows a simple hair hygrometer. It takes about a foot of hair to create a sensor but it could be wound around a pulley or two to decrease the length. The pointer could be used to block light between a LED and a photo transistor for sensing.

Image about.com.

EDIT: Horse hair can also be used and may be more durable.
I saw something like that when I search for weather related science fair projects. Figured it wouldn't last more then a few days or weeks. My hair is llong enough, fairly strong. My thought was to hook the hair to a light spring, and use the spring for the coil in an oscillator. Stretching the coil should change the frequency. Figured It would be very subtle, an kind of involved getting into a microcontroller. Would be nice to find a cheaper humidity sensor for this project. The one I ordered is $9.90, about twice any other part in the project, so still keeping my eyes open for alternate sensors. Mostly, I want to get something thrown together, just to see if this idea was any good, then work on making it simpler and cheaper. I don't think I get away with just making one or two if it works out.
 

HarveyH42

Banned
Just got this from Futurlec:

Date: Fri 02/29/08 05:13 AM


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Dear Harvey

Your order is complete, except for HP01D and IDCC10, we are currently following up on these 2 parts with our warehouse. We will fulfill them to your order and keep you updated as soon as they become available.


Should you have any further enquiry, please feel free to contact us.

Best Regards
Amp
Futurlec
The HP01D is the barometric pressure sensor. So looks like I'll need to find another source. Mr. Amp's english isn't too clear on whether or not I'll be getting those two parts, figure it might be a while.

Finding the serial comunications is a huge mess. Kind of wondering what sort of nighmare I walked into here. TWI and I2C seem to be the same thing, or very similar. Some AVR impliment in hardware, or sort of... but, it can be done in software. SPI is different, and may or may not be hardware, but again several software solutions. Seems like a lot of problems and questions using this stuff. Been looking for an AVR tutorial for this stuff, but looks like I'll be learning AVR stuff from a PIC site again. Wonder if Nigel's PIC tutorials has something. Haven't visited in a while....
 

Shax

Member
HarveyH42 said:
Just got this from Futurlec:

The HP01D is the barometric pressure sensor. So looks like I'll need to find another source. Mr. Amp's english isn't too clear on whether or not I'll be getting those two parts, figure it might be a while.
Do what I do... Register with Freescale, and blag some freebies.. Plenty of pressure sensors to choose from..
Shipping time from placing my sample order was 3 days! Not bad eh?
I now have a barometric altimeter using the local QNH from Heathrow that cost me less than £10 to build..

Hope this helps..
 

HarveyH42

Banned
Got my Futurlec order yesterday, so have a lot of work ahead of me on this project. I'm going to try and post everything here as I progress, and hopefully keep it complete. Wish it wasn't summertime so soon, hours at work are already picking up, and a couple of minor repair jobs (hopefully), that got dump on me after Mother's Day dinner Sunday. Good news though, have a week vacation end of the month, should work out well.

Shouldn't take too long to throw this together once I figure out how to read the sensors. I want to store the min. and max. values on chip, and find what percentage of that range is the current reading. That percentage will be sent out to an LED as its brightness level. The actual numbers, precision, and calibration aren't going to be a concern, since I'm not looking to display them, just RGB levels for Temp, humidity, and pressure. Will probably use an LCD to watch numbers in the beginning, mostly to see that I'm actually getting a reading, and they change throughout the day. Eventually, I'll need to go wireless, and put the sensors outside, or just run a cable for the LED.
 
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