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Topic: Moisture and NTC Temperature Sensor with Pulse output (Read 63 times) previous topic - next topic


Based on a 555 like (ICM7555 CMOS) timer, it has an open drain the output needs to be pulled up to the MCU voltage. A HS1101LF capacitive moisture sensor is used as the timing capacitor, and a thermistor B=4500 is used for one of the timing ramps. I think it can be used with the AVR input capture (ICP) hardware to measure very slight changes. I have found the wiring between the sensor and MCU can be a fairly long (.e.g. over 70m or 200ft).

Project Board Page: http://epccs.org/indexes/Board/MSPM01/

Electrical Schematic:

Board Design:

This is a prototype, I need to work on the ICP firmware example and find some plastic dip and contact gel to allow it to last in condensing moisture. I've researched a few options and the HS1101LF has survived and provided what looks like reasonable measurements more so than anything else anyway.

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