How to send measured data from a remote soil moisture sensor to an arduino-uno?

Hello! Could you please help me?

I have one Arduino-Uno card and 3 soil-moisture sensors. One sensor is directly connected to the card. The measured data from this sensor are stored via USB port in a database in the laptop. The other two sensors are designed to measure soil moisture in other ends of the field and store it in the same database. My question is:

What is still missing? (I mean, which hardware do I need), so that the measured data of the other two sensors are sent to the laptop and stored in the same database?

Thanks in advance.

define: field

You can use meters or feet, but the unit ‘field’ is too vague.

Thanks Koepel for your answer. You're right the term Field is too vague. In this case the field measures 16 square meters.

Thanks in advance

4x4 or 1x16 or 16x1, then the distance is about 10 to 20 meters.

When you want to transfer the data wireless, then you need an Arduino board for every sensor. That means a total of 4 Arduino boards. A commercial manufacturer could make a simple remote sensor with a single AA battery. But that is sadly not possible with the Arduino.

There are many 315/433 MHz modules, or even wifi is possible (with a WeMos for example).

If you measure in meters, then probably 433 MHz is used in your country instead of 315 MHz.

You could use the cheapest 433 MHz ASK transmitters with a single receiver. Those transmitters don't use power when they are not used. The RadioHead library can be used with the RH_ASK option. It can transfer only very little data. Temperature, soil moisture and a few other things every minute is no problem. They cost less than 1 euro or 1 dollar on Ebay/AliExpress. The timing for the transmitted signal and for the receiver is done with an interrupt. That means that other interrupts might influence it, and the interrupts may not be turned off. Always use a receiver that uses a X-tal for the frequency, not the receivers that uses a tuned coil.

A transceiver does not have those problems with interrupts. A big list is on the RadioHead page for the supported hardware.

Adafruit has the Feather series with the RFM69.

SparkFun says that their nRF24L01+ can do 100 meters. It can transfer a lot of data. I don't know if a cheap module with a fake nRF24L01+ from Amazon/Ebay/AliExpress can do 100 meters.

Conclusion: The cheapest 433 MHz ASK modules is a poor man's solution. If you have no problems with software and the Arduino has nothing else to do, you can use that. Otherwise the nRF24L01+ is a good option, because it is used a lot. If you want something reliable out of the box, the Adafruit Feather with RFM69 is a good choice. These are only three out of 20 good options.

At these distance (4-16 meters, depending on the shape of the field) a wired connection would be feasible as well. Makes at least powering them a lot easier. It depends on the type of sensor whether it can handle such long wires.

Thank you very much Koepel and wvmarle for the detailed, fast and very helpful answers. Could you please suggest a few websites of original electronic products.

Thanks in advance

Define "original".

Options include E-bay, Amazon, Element14, Aliexpress, Digikey, Taobao, RS-online, Adafruit, Sparkfun.