OT: Where to get local weather data including humidity?

Gents,

Anyone know where to obtain local weather data that has 20-30min interval readings with humidity in there? This was perfect but last Wednesday they quit updating this station:

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In the past I've used this to gauge whether to run the evaporative cooler with or without water circulation overnight. Cold+humid meant it had to run sans water pump or you'd have a damp house. On dry nights it's better to run with the pump or the house is still hot in the morning.

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Regards, Joerg

http://www.analogconsultants.com/
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Joerg
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Buy a few of these?

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tm

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tm

You guys didn't vote for Obama, so you lost your NOAA station ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson

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Ain't going to help. I know the current humidity and that would be all these meters show. What I need is to find the trend. That plus the shape of the "waveform" from the previous night is a fairly good indicator for the coming night.

Ok, I could put an MSP430 in there, hook up a laptop that has RS232, have it massage the data, send it onto the LAN, into this here PC ... but that would get old :-)

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Regards, Joerg

http://www.analogconsultants.com/
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Joerg

Or build your own humidistat ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson

Mirror, LED, TEC, find OUTLET dew point in real time, cycle water pump accordingly. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson

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:-)

This is not a joke, one of the California dems seriously said that and might pay the political price for it some day: He said that if the folks in more conservative districts don't want to support tax increases then they might face "selective cuts", meaning only in those districts. Of course they'd still have to pay the same as anyone else. Whoever runs against this guy, if he or she is smart, they'll probably dig that out of the ground.

Well, I do have some uC that could do this but I don't have a TEC and I really don't want another project on top of the bazillion projects that are already on the honey-do list.

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Regards, Joerg

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Joerg

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How about this one?

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tm

DIY it with

Or a COTS unit like

Oregon Scientific has lots of models; the under $50 variety with remote sensors work okay. Available at the usual on-line vendors. I've had an older model, now discontinued, for years and it's still working fine. Had to replace the outdoor sensor last spring, as the humidity element finally lost sensitivity (possibly due to the spiders nesting around it). The new one is within a few percent of the official RH, probably as well as can be expected given that I'm closer to the water than the official stations are.

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Rich Webb     Norfolk, VA
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Rich Webb

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I think you can get what you need from inlet and outlet temperature.

Get a psychrometric chart and study it...

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I studied evap coolers quite extensively around 35 years ago. You can do quite well if you're willing to add a lot of control systems around them. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson

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Yikes, those cost well over $600. I didn't quite want to go that far :-)

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Other than that, the manual doesn't say but if the graph field can be configured to graph humidity it'll work. 24 points isn't that great but sufficient.

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Regards, Joerg

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Joerg

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That's a good idea. Not that I wanted another project on the list but this would boil down to the sensor, a bandgap and a relay. Still hoping I find a source on the web though :-)

AFAIK those can't graph.

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Regards, Joerg

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Joerg

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I have that next to the cooler, in table form. The inlet and outlet temperatures will tell you almost exactly what the moisture is. But now you have to build two temp sense locations, plus a uC or some analog stuff, plus ...

Those coolers are great. Right now it's 90F outside, 69F comes out of the cooler, and the house is 78F. It has a really hard time cooling the house down but if you let it run full bore in the morning it does a fairly good job of not letting the indoor temps get up too high. I'll probably need an outlet for the air somewhere in a ceiling so it works a bit better.

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Regards, Joerg

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Joerg

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Make a miniature evap cooler and run it outdoors simply as a sensor. Measure T_Inlet and T_Outlet. It is left as an exercise for the student how to calculate humidity (the psychrometric chart can be reduced to an equation... I've done it ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson

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Oh yeah, yet another project ...

Or just look it up and whistle innocently :-)

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Regards, Joerg

http://www.analogconsultants.com/
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Joerg

Once-per-hour projections are the best my page does. Here's Sacramento's.

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(Set you interval.)

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JeffM

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Thanks, Jeff, Sacramento is a bit far off though and the humidity out there is often very different, mostly higher than here. We are at around

1450ft elevation, they are at 16ft with a big wide river going through there :-)
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Regards, Joerg

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Joerg

I log that outside data at my house for my furnace, using a HIH4000 sensor and a 1wire battery monitor chip. I use it to decide if I'm going to run the air conditioner, or just wait for someone to open a window.

Of course, my furnace already has a bunch of small MCUs in it that talk

1wire for indoor sensors too, so it was part of the larger project.

I got specs and software if you want it...

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has some of it.

Reply to
DJ Delorie

Joerg wrote:

Did you enter *your* town into the dialog on the page? Did you edit the URL, putting in *your* latitude/longitude? (Enter as many decimal places as you like and it will find the best match it has.)

Reply to
JeffM

Have you checked how often the local airport updates the METAR report, which contains the devpoint ? From temperature and devpoint, you can calculate the relative humidity.

If you fail to find that information on the internet, try to check if this METAR information is broadcasted on some VHF aviation channel in the 118-137 MHz band (AM). Perhaps the airport has a telephone number with a similar recording.

Reply to
upsidedown

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