[time-nuts] Environmental sensor recommendations

Mark Sims holrum at hotmail.com
Thu Apr 5 16:41:55 EDT 2018

Long ago I did a board for evaluating high power  LEDs and drivers.  Iit was called Luxor and if you look through the Lady Heather code, you will see references to it.   It has all the functionality (and them some) needed for an environmental sensor and temperature controller.  

It has 4 dual voltage IIC ports (with support for themocouples and Melixs IR thermometers (also LM75's and thermistors),  8 x 16 bit ADCs (or were they 12 bit?) , a couple of isolated hall effect current sensors,  a 50 amp MOSFET 16-bit PWM'd at up to15 kHz, a four channel color sensor, a light PWM sensor, and a few other things.   It collects data continuously at the sensor max data rate, averages readings over 1 second intervals, and streams the data at 1 Hz.  That is the basic design I will probably use for my environmental sensor.

As mentioned, themocouples are not good for this application.  I'm leaning towards thermistors since they can be cheap (or expensive) and you can get small ones with low thermal mass.   I'd like to do RTDs, but good interface chips can be pricey... plus the RTDs can be pricey and delicate.

I think, that in this application, resolution is more important than absolute accuracy.

The pressure sensor in the BME280 can detect an altitude change of under 1 foot.

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