I am interested in making a DIY PCB soil sensor based on 555 timer IC. The circuit works well but I have problems with regard to manufacturing a durable PCB. As I keep the PCB based soil sensor immersed in soil for longer than a month, the PCB starts to discolor and rust. This does not happen for the commercial sensor shown below. Note: even if there is a laminated layer around the copper to protect it, the sensor detects soil moisture fine. However, this lamination is not durable.

This sensor is still in the prototype phase. I would appreciate advice on how I can ensure the durability of the PCB.

I heard that a process called "Conformal coating" can be done. But I do not know what type of manufactures I should refer to have such a PCB manufactured. The generic PCB manufactures seems not to do Conformal coating.

Image of DIY soil sensor on top and a commercial sensor on bottom

  • \$\begingroup\$ Even conformal coating may not last in soil. I think you will need to pot the entire board in, for example, epoxy. Not sure if the sensor will work after potting. You can conformal coat or pot prototypes yourself. I am sure you can find information online. \$\endgroup\$
    – user57037
    Commented Nov 2, 2017 at 6:26
  • \$\begingroup\$ But the one I have shown below lasted quite a long time with no bad effects on its PCB. I'm wondering what coating they did. \$\endgroup\$
    – Denis
    Commented Nov 2, 2017 at 10:19
  • \$\begingroup\$ How is the upper part (with the exposed components) protected from moisture? \$\endgroup\$
    – τεκ
    Commented Nov 2, 2017 at 21:32

1 Answer 1


Is this sensor measuring the moisture all the time, or do you only apply voltage to the circuit when it is needed? I have heard that a lot of soil sensors start to rust very fast if they are under voltage all the time. Have you tried reducing the time of measurement to a minimum? In most cases a couple of milliseconds per hour is enough to get the data that is needed.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.