Soil Moisture Probe

Hi everyone,

I've done quite a bit of research but I am still definitely a noob.

That being said I am trying to build a soil moisture probe that has 3 capacitive sensors at varying depths that will hopefully be powered by a solar panel and battery bank, or perhaps just solar panel if I could make that work...

My current idea is to have the 3 sensors on a probe wired to an arduino which then transmits data wirelessly using RF to a receiver such as a raspberry pi which would then somehow post the data to a website that I can view wherever. The maximum wireless transmit distance would be around 200ft. The readings could be taken once or twice a day, or perhaps every hour if there is plenty of power.

Would this work? Can one arduino accept three sensors and transmit them all wirelessly? If not, does anyone have a better suggestion on how to go about this? Any suggestions on the best way and transceiver to transmit this data?

whattheheld:
Hi everyone,

I've done quite a bit of research but I am still definitely a noob.

Would this work? Can one arduino accept three sensors and transmit them all wirelessly? If not, does anyone have a better suggestion on how to go about this? Any suggestions on the best way and transceiver to transmit this data?

for your project to be successful, you need to understand the problems.

  1. do you have a 'sensor' that will create 'readings' that are valuable? (accurate, repeatable)
  2. how much power is available? (solar, battery)
    this controls how your project will communicate, If the design relies on Solar for all of it's power generation, then a 'scheduled' transmission is not possible. A simple Solar configuration would send the readings whenever there is power. A more complex Solar + battery would allow for scheduled reading. With a battery now you must minimize idle currents, Currently the Arduino platforms do not have a powerdown feature. They run full blast as long as they have power. You would need to either construct a dedicated 'compatible' board with lowpower features to be successful. And with a battery you need a charge controller.
  3. The radio comms decision needs more info.
    a. Is it line of site between receiver and transmitter? or are there walls and metal between?
    b. Is 2-way communications required?
    c. will there be multiple transmitters
    d. how much money will you spend?
  4. What are you skills
    a. electronics
    b. software

Anything is possible with enough cash.

Chuck.


Check out my Kickstarter Project Memory Panes an expansion RAM Shield for Mega2560's. It adds 1MB of RAM for those projects where 8KB is not enough.

When you can make one sensor work, adding further sensors should be easy.

chucktodd:
for your project to be successful, you need to understand the problems.

  1. do you have a 'sensor' that will create 'readings' that are valuable? (accurate, repeatable)
  2. how much power is available? (solar, battery)
    this controls how your project will communicate, If the design relies on Solar for all of it's power generation, then a 'scheduled' transmission is not possible. A simple Solar configuration would send the readings whenever there is power. A more complex Solar + battery would allow for scheduled reading. With a battery now you must minimize idle currents, Currently the Arduino platforms do not have a powerdown feature. They run full blast as long as they have power. You would need to either construct a dedicated 'compatible' board with lowpower features to be successful. And with a battery you need a charge controller.
  3. The radio comms decision needs more info.
    a. Is it line of site between receiver and transmitter? or are there walls and metal between?
    b. Is 2-way communications required?
    c. will there be multiple transmitters
    d. how much money will you spend?
  4. What are you skills
    a. electronics
    b. software

Anything is possible with enough cash.

Chuck.


Check out my Kickstarter Project Memory Panes an expansion RAM Shield for Mega2560's. It adds 1MB of RAM for those projects where 8KB is not enough.

  1. I've ordered three capacitors that this guy used in his project. http://jenfoxbot.blogspot.com/2014/09/diy-soil-moisture-sensor.html. I will need to do some testing to get the calibration right, but I'm hoping I can work that out. Capacitive sensors seemed to be more sensitive as well longer lasting than other sensors, which is my reason for choosing them.

  2. I'm not sure of the power requirements at the moment... I would imagine 5V for the arduino, but I'm not sure if the sensors or wireless transmitter would require additional power. I wouldn't think they would. If there weren't any tremendous downsides to just having the arduino and sensors transmit continuously, then it would be nice to just have it run off a solar panel for simplicity.

  3. a) Max distance would be 200ft. One wall and 2 trees would be a very realistic expectation for the obstacles that would be in the line of site.
    b) 2 way communication not required
    c) Thats what I am trying to determine. I believe it would be economical and simpler to have 3 sensors with one arduino transmitter if that were possible.
    d) I'd like to keep the project under $100. I have one arduino uno that I got for free to start with

  4. I've taken a computer controls class and an electronics class, however they were introductory so I'm fairly new. I completed a simple automated watering project in the past that closed a solenoid valve when a resistive soil moisture sensor became wet and opened the valve when the sensor was dry. Programming experience is weak, but something I'd like to improve.

DrDiettrich:
When you can make one sensor work, adding further sensors should be easy.

Very true, I will probably start out that way. I'd still like to know how to expand it however

Also thank you both for your replies, I appreciate your time

Let's postpone multiple sensors until you could make one sensor work. Then we'll know more...

whattheheld:
2) I'm not sure of the power requirements at the moment... I would imagine 5V for the arduino, but I'm not sure if the sensors or wireless transmitter would require additional power. I wouldn't think they would. If there weren't any tremendous downsides to just having the arduino and sensors transmit continuously, then it would be nice to just have it run off a solar panel for simplicity.

power = voltage * amperage. I agree that 5v would be your most common voltage, to calculate your power total (watt/hr) (solar panel voltage * solar panel Amperage * hours of Sun light) = XX
Power Usage ( voltage * amperage * 24 hrs) == YY
if (XX>YY) then possibly enough to charge a battery to last all night.

if(YY>XX) then power usage reduction necessary.

whattheheld:
3) a) Max distance would be 200ft. One wall and 2 trees would be a very realistic expectation for the obstacles that would be in the line of site.
b) 2 way communication not required
c) Thats what I am trying to determine. I believe it would be economical and simpler to have 3 sensors with one arduino transmitter if that were possible.
d) I'd like to keep the project under $100. I have one arduino uno that I got for free to start with

The NRF24L01a might be usable, the modules with an external antenna and PowerAmp.

whattheheld:
4) I've taken a computer controls class and an electronics class, however they were introductory so I'm fairly new. I completed a simple automated watering project in the past that closed a solenoid valve when a resistive soil moisture sensor became wet and opened the valve when the sensor was dry. Programming experience is weak, but something I'd like to improve.

Learning is why this forum exists.

Chuck.


Check out my Kickstarter Project Memory Panes an expansion RAM Shield for Mega2560's. It adds 1MB of RAM for those projects where 8KB is not enough.

another way to skin the cat