Information

ManualsBrandsCatnip Electronics ManualsRobot PartsI2C Soil Moisture Sensor

Table Of Contents

I2C soil moisture sensor

The sensor can be read via I2C protocol and provides these features:

 Soil moisture sensing

 Light sensing

 Temperature sensing

 Reset chip

 I2C address change

 Deep sleep

Please checkout FAQ below before asking questions, if you still need help, please don't

hesitate to contact me.

Technical data

 Version 2.7.5

 Supply voltage 3.3V - 5V

 Current consumption: 1.1mA @ 5V, 0.7mA @ 3.3V when idle, 14mA @ 5V,

7.8mA @ 3.3V when taking a measurement. When constantly polling sensor at

full speed, current consumption averages to 4.5mA @ 5V, 2.8mA @ 3.3V

 Operating temperature 0°C - 85°C

 Moisture reading drift with temperature - <10% over full temp range

 Don't forget to provide pullups for SCL and SDA lines

 Default I2C address is 0x20 (hex)

 To read soil moisture, read 2 bytes from register 0

 To read light level, start measurement by writing 3 to the device I2C address,

wait for 3 seconds, read 2 bytes from register 4

 To read temperature, read 2 bytes from register 5

 To change the I2C address of the sensor, write a new address (one byte [1..127])

to register 1; the new address will take effect after reset

 To reset the sensor, write 6 to the device I2C address.

 Do not hotplug the sensor into the active I2C bus - address change command

has no protection and this might result in a random number set as an address of

the sensor. Use I2C scan sketch to find out the address if the sensor stops

responding with proper values.

More documentation and example code is available on github page. Also check out

the FAQ

The easiest way to get the sensor working on Arduino compatible environment is to use

the library by Ingo Fischer it is available thru Arduino environment, make sure to use

version 1.1.4 or later as it contains some fixes for address change and bus hang bugs

fixed in the firmware version 2.6.

Summary of content (5 pages)

PAGE 1
I2C soil moisture sensor The sensor can be read via I2C protocol and provides these features:       Soil moisture sensing Light sensing Temperature sensing Reset chip I2C address change Deep sleep Please checkout FAQ below before asking questions, if you still need help, please don't hesitate to contact me. Technical data              Version 2.7.5 Supply voltage 3.3V - 5V Current consumption: 1.1mA @ 5V, 0.7mA @ 3.3V when idle, 14mA @ 5V, 7.8mA @ 3.3V when taking a measurement.
PAGE 2
How to interpret the readings Both light and moisture sensors give relative values. Meaning, more moisture will give you higher reading, more light, lower reading. Moisture is somewhat linear. I test all sensors before shipping and they give about 290 310 in free air at 5V supply. I didn't measure linearity of the light sensor, it gives 65535 in a dark room away form desk lamp.
PAGE 3
The sensor comes coated with PRF202 - a moisture resistant varnish for electronics. It's ok for play around in a flower pot but not enough for outdoor use. You must add an additional protection to the whole sensor after soldering cable to it! Some suggestions on making the sensor more robust after attaching the cable:    Polyester or epoxy resin - this method is the most bullet proof as the resin is totally resistant to the water.
PAGE 4
Frequently asked questions Do you have the exact dimensions, or even better a CAD drawing of the sensor in 3D? Sensors are 18mm x 149mm. Zipped step file is available in github repository. How to set up multiple sensors connected to one Arduino Uno? You can connect several sensors to a single I2C bus. Exact maximum amount depends on many factors, mostly on the wiring length. To have several sensors working on a bus, you have to assing an individual address to each sensor.
PAGE 5
In depth technical analysis is available here. Add this call after you initialize I2C bus: Wire.setClockStretchLimit(4000); How durable are non-rugged sensors? Standard solder mask seems to last about 3 months before flaking off. It really depends on the type of your soil and how often do you remove and insert the sensor as scratches will damage the surface and shorten the lifespan. I have had sensors working flawlessly for over a year in the flower pot at home when not disturbed.