Hey!
I shorted out my spare receiver while probing around and haven't had the nerve to poke into my remaining one. I've been busy traveling around the country and haven't done much with Arduino lately. I'm certainly interested to see anything you come up with.

I played around with connecting more than one SHT75 to a single Arduino. I tried powering them individually from a digital output but I think I got some kind of conflict from them being alternately powered from feedback from their clk or data line so I didn't follow up on that. You can operate them with a common data line and a separate clk to each device. When you hold the clk low, they are effectively asleep. You have to pull the data line up with a 10K resistor. I didn't try using the internal pull-up.

Is it possible that your door strike has a delay built in so that it won't activate again until some time passes?

Sorry for replying so late, private life kept me away from my Arduino last week.

Thank you so much, it works like a charm now!

Yeah, life gets in my way too.  I'm glad you got it working.

After getting the headers and some boards to try them with, I'm going with your suggestion that they are probing pads. They have the right pitch but a header would have to be unusually slim to fit.

I know the area. I have hiked the West Elk Wilderness area not too far from there.
I think you're talking about the doctor in the clinic on the mountain. I saw him for an injury or two. Yeah, summer was that period between the end of mud season and winter.

How many people do you know that have driven from Marble to Gothic via Schofield pass? 

Not many. The "roads" are just jeep trails up there.

Then you might recognize my user name.  Were you in C.B. when Larry T. was the doctor there?

That is the first thing that came to my mind when I saw your user name. A run off the East River chair or if you're coming off the North Face. I remember the lonnnnng lines at that chair near the end of the day. And the VW size moguls on Resurrection.

I remember a "happy" doctor I believe by that name. Is that the one?

If you decide to use Hall sensors you could take a look at this post
http://arduino.cc/forum/index.php/topic,71362.msg548748.html#msg548748
My system has 8 Hall sensors and displays 16 wind directions. With 4 sensors if your magnet is wide enough to trigger two sensors when it is between them you could get 8 directions.

Thank you, I'll check that out.

I'll have to write my own delay(). I intend to repurpose the other timer/counters anyway, it's just a pity that AAG didn't use a different pin.

I can just do it and see what happens but I was hoping someone knew if it was going to break anything else.

The AAG weather station that I'm reprogramming has the Hall effect for wind speed connected to T0. Reconnecting it to a different input would be a major pita so i'd rather not.

Since Timer0 is used by the system, I can't just commandeer it for my own purpose without disabling the Timer0 ISR. What is the best way to do that?

I've considered commenting out it's initialization routine in wiring.h void init() and then redefining SIGNAL(TIMER0_OVF_vect). Is there more to it than that? I realize I'll lose millis() and some PWM but that doesn't concern me.

Also, there are some rectangular pads near the chip area that appear to be for installing 0.050 pitch surface mount connectors or headers. Any ideas about that?

Hmm - maybe surface mount headers? Probe points?

They remind me of what these Samtec headers are designed for. I've ordered some Schmartboards and I'm about to hit Samtec up for some "sudden samples". I'll report back what I find.

That looks good! I don't think the 3K3 resistor makes any difference. I'd have to study the datasheet a little more about the filter to give any kind of relevant answer. I'd try a simple low pass filter first and note the results.

I have a question about Schmartboards.  It looks like the through holes on their QFP adapters are on a staggered 0.050" grid but there are no dimensions on their drawings. Is that true? Also, there are some rectangular pads near the chip area that appear to be for installing 0.050 pitch surface mount connectors or headers. Any ideas about that?