Thank you so much for the explanation! I am quite new to the electronic modules and sensors for the RPI. I do have some basic experience with GPIO, pull-up/down, DAC, resistance and all that. I will definitely give it a try and let you know. You have been very helpful and I appreciate your input on this.

Yes, I am aware of the varying resistance if I were to increase cable distance for the sensors. I read some people have tried low resistance CAT5 computer network cables, soldering them directly with much success but requires a bit of tweaking in the sensor values. they are cheap to obtain, has an appropriate gauge copper wire..so I will try that too. Will update you on this.

Many thanks again. Keep up the good work, your system is by far the best I've seen with thorough documentation and friendly support :)

Hi, that is a nice garden there!

Back to the points: The connection between the sensor and the MCP3008 should be quite simple, you can just connect the analog output of the sensor (AOUT) to one of the input pin of the MCP3008. The inputs are marked as CH0 to CH7.

The other pins on the sensor (GND,VCC) are the power and the ground and can be directly connected to the +5v and Ground of the raspberry or better to the power supply.

For reference, here I also include the connection of the MCP3008 to the raspberry:

Regarding the length of the wires, there should be an impact on the sensor reading especially if the wires section is quite small, anyway it is hard to quantify it.

Please ensure stable connection between the analog pin and wires as the sensor reading is quite sensitive to variation of resistance.

In case you require additional info, just let me know.

hi thanks for your reply. No worries, I'm welcomed to your valuable feedback based on your many experiences with the moisture sensors. :)

Noted on the AP2192 i will avoid using it. So i guess I will need to obtain the MCP3008 for ADC conversion, direct to the capacitive sensors. I'm not sure if it will work with the capacitive sensors, i have not found any documentation for it. I normally see these capacitive sensors beings used with a ADS1015 12 bit via I2C. Is it possible if you can provide a simple schematic on how to connect 4 sensors to the MCP3008 if I were to use the capacitive sensors instead?

And another question, how do you extend the length of the sensor cables to reach different garden beds (around 5m apart), will the current readings be affected significantly? I have 4 sprinklers to cover different zones of my garden. Some might not have enough water coverage, so the sensors need to be moved around accordingly.

Hi,

Regarding the capacitive moisture sensor in the link, I see no problem using it. It is important to configure the Hydrosys4 hardware table properly, but should be quite easy and I can give you indications.

For the ADC, the system works only with the MCP3008, I have used this chip for long time and I think it is the best compromise between price and performances, especially because the Moisture reading does not require precision.

Regarding the AP2192, for capacitive sensors you can avoid to use it. The AP2192 is required for resistive sensors to reduce the corrosion on the sensor plates, but as far as I understood with capacitive sensors this is not necessary, on the contrary it might create a problem due to reading stabilization time in capacitive sensors.

For last I'd like to give some advice as I have gained experience with the Moisture Sensors and real life usage (most of the review of the moisture sensors you can find on internet are made from “Electronics Guys” perspective with little experience on real plant grow). There are many factors affecting the moisture sensor reading and one of the most important is the position. Humidity does not diffuse in the soil as well as we might think, relative position between sprinklers and sensor is very important as well as the position relative to the plant roots. In most cases the moisture sensor was very useful to save my plants due to sprinkler clogging or other problems with irrigation system, which is very valuable. Anyway I found that the best way to use moisture sensors is as complement to the irrigation scheduling and not as replacement. In fact the automatic irrigation algorithm option that I end up using most is the “Under Min over Max”, with this option the algorithm uses a watering scheduling that has been set for the selected irrigation line and uses also the soil moisture reading to either provide more water in case the reading is below Minimum threshold or stop the scheduled irrigation in case the reading is above the max threshold.

Hope I didn’t get too much off topic ;).