Thanks so very much for all the help. My first problem, assessing feasibility, is solved in the affirmative. Next if possible I’ll just try to keep from making a fundamental mistake in choosing the hardware components.
The DHT22 as I understand it is a digital output sensor, so I don’t think I need an analog multiplexer.
I’ve read some about the limitations of these sensors, but for my application they are more than adequate. I am building a tool to help me design a micro climate. It would be generous to call my project a greenhouse. It is better described as an orchidarium, where a pretty bad habit growing green and white paphiopedilum plays itself out. I only have about 25 square feet of bench space, but must do a very good job of keeping it controlled. Circulation, light, humidity, temp., to say nothing of the care and feeding… As I close the envelope around the plants, I want to know how the placement of vents and how location of heat sources, etc., etc., is impacting conditions.
I aim to model with 3d graphing software the volume of my display case, so I can find warm spots or cold spots - dry spots or wet ones. I want to study how changes in the display case and its components impact the climate. I can’t just leave a circulation fan on high in there, and figure everything will equalize, because it’s crowded in there and the plants can’t tolerate that kind of wind. I’m a hobbyist. Some people do crosswords.
Back to the electronics, I’ve noticed that the Mega 2560R3 has 50-something digital input/output pins. That’d be more than enough. I have read on one of the replies how the Uno with 20 pins would be sufficient. I don’t truthfully see myself automating control of the ‘greenhouse equipment’. Maybe, but it’s hard to imagine. The only other output I can think of at present is the SD card writer. I have seen a $20 shield from Adafruit that would work with either the Uno or the Mega, I think. The question is whether the Uno has enough input/output pins for the 16 sensors and the SD card writer.
It seems a waste to use something as capable as the Mega for what I’m up to. Unless I did start remote controlling it all.
If the Uno would work with the card writer and 16 DHT 22’s, then I need to quit talking about it and start buying some parts. And again, many thanks for the experience you’ve shared in reply to my initial post. I will no doubt be back again, after doing my best to figure out the programming from the may published helps.
This is why its most encouraging to learn that I can use arduino boards for my project - because I can think about what my next problem is, search that specific problem, and read the experiences of people who have posted their projects on line.