Author: Brett Stoddard
Hello Everyone!
For the past few weeks, I’ve been further examining the RFID Dogbone Tags. This time I’m testing their capability as capacitive humidity sensors. This article describes the system I built to test them out.
Abstract and Objectives
This blog post describes a system to log data from multiple Smartrac Dogbone RFID moisture sensing tags in the air over the course of the day. The goal of this system is to log the Dogbone’s moisture sensor levels vs a DHT11 Humidity and Temperature sensor. After logging data for multiple day cycles, enough data should be present to tell if there is a relationship strong enough between the Dogbone’s measurements and the DHT11. Further testing would be warranted if such a relationship exists.
To measure multiple tags at once, this system incorporates a HyperRail prototype. The HyperRail’s details can be found distributed throughout this blog page on the OPEnS site.
Materials
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1 Constructed HyperRail
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1 Arduino Uno
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Sparkfun GPS SD logger shield (any SD card logger could work, I just had this handy)
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DHT11 (any temp/moisture sensor would work, I just had this one handy)
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Breadboard, prototyping wires
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2 GB μSD card
Libraries
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SoftwareSerial [default]
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SPI [default] (for SD card)
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Bill Greiman’s SdFat Lightweight SD card library
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Adafruit Sensor Library (dependency of DHT Sensor Lib)
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Description
Results
Over the weekend the system was run. It gathered some data, but not enough to make a sure prediction of whether the Dogbone tags can be used as humidity sensors. However, this is an example of what the code output should look like.
What data should look like when opened in Excel
Known Issues
As of now, the SD card will only log data when the Arduino is plugged into both USB. This shouldn’t be necessary because it is already powered by Vin. This issue is probably a power supply limitation of my specific setup, however, I thought it was worth noting here.