Wire and distance for sparkfun soil moisture probe

1

I am new to this. My first project is to develop a tank monitor and automated irrigation system. I would like to attach a sparksfun soil moisture sensor to a particle relay board. The moisture sensor is to be placed approximately 18 meters from the board. I was wondering what type of wire would be best to use (and where to get it) and if voltage drop is likely to be a problem.

Thanks
John

2

Hi John,

I would use a twisted pair wire to try to avoid signal loss on a long run, but be aware that you will only get a reliable signal up to 5m away from the sensor. You could get the wire at a hardware store, go for about 22AWG. Why does the sensor need to be so far away from the board? Sounds like you need to go wireless!

3

Thanks for your reply Stephen. I was planning to use the moisture sensor in the garden. The garden bed is about 15 m long. Electricity at one end. I was going to place a sensor at each end. If I were to go wireless what hardware would you recommend?
Thanks

4

John,

First I would recommend giving it a shot and see how it works out. I had assumed you were using a digital signal, but most moisture sensors are analog. If you find you have too much voltage drop for the analog signal to be usable you can use an amplifier. You only need to boost the signal enough to reach the board though, be careful that you don’t supply greater than 3.3V to the Particle or it will cook.

Another option is to use a 5V moisture sensor with no amplifier, perhaps the max output when fully when will drop to a safe 3.3V over that run and be safe for the Particle. If not, add a resistor.

Let me know what you try out!

5

Thank you Stephen. I am using the sparkfun soil moisture sensor. I will trial different lengths and see how it goes and let you know. Got it connected and working on short leads at the moment. Working on learning how to code to have it read and turn on a relay when dry. Having fun!
Thanks

John

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