When the sensor is in water, the led is on and it works with 12 v dc. I will use 12 sensors in the design of the card, and when the sensor does not see water, the led I used on the card will turn on and the relay and buzzer will work even if any of them are lit. I don’t have much experience for design. Can you help me with this?
This forum is for using the Kicad software. You aren’t at that stage yet. You might want to try here.
Good luck with your project. Is it Arduino based? In that case you might try here.
I’m already going to design cards using Kicad. I don’t use Arduino so I asked for help.
The most prevalent moisture sensor in the “hobby circuit” seems to some conductive sensor. These can have a reasonable life expectancy if they’re carefully designed and only use AC signals on the sensor leads. Another thing that may help is to only turn the sensor on for a handful of mili seconds every hour or so (good enough for plants). But DC results in electrolysis and very quick erosioin of the sensor leads.
It’s much better to use capacitive sensing. A quick search:
https://html.duckduckgo.com/html?q=capacitive+water+sensor+schematic
Leads to:
https://www.ti.com/lit/ug/tidu736a/tidu736a.pdf
I did not read that TI application note, but it seems to have some background information, and in general TI writes good application notes.
Your question is how to make the electronics work. Not how to make the software work. This forum is about how to use the software. Not how to design the circuit. As Kicad gets more popular we have had to make the decision to start being more focused on the content. I hope this is a little clearer now.
I understand you even though you weren’t helpful, thank you.
If you are to that stage then you need to be more specific. How much of your circuit is done? Can you at least provide a hand drawing?
I graduated from electronics engineering 2 months ago and got a job in this field. So I don’t have much experience. They asked me to do this drawing. I’m at the idea stage right now.
Trust me on this one. Try the first link. It is a huge leap from school to actual engineer design work. It will get you up to speed on that transition way faster than could happen here. Just be prepared to sink a few hours at a time as you read. Seriously. Good luck. 
Thank you, I’m on that link already and it looks like I’ll be there for long hours.
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I recently designed a Water Sensor for my Hydroponic DWC Buckets.
It’s transistor based (npn) and several different transistors will work. I used BC547.
This approach is nothing more than an Electrolysis configuration. Thus, as @paulvdh inferred, … only turn on for brief time (or the electrodes will transfer metal). I dialed-in the design with 304-Stainless Steel rods mounted on 3D-printed holder (screenshot)… They can remain in H2O/other as long as power is Off.
It works well enough to not be a problem if On for only a few minutes per day. They’ve been on my DWC buckets for 3 months without problem.
[Note: Last week I went back to my old approach of using Straws/Corks as Visual Height indicators because I like seeing the Bouncing Straws under the dynamic movement from H2O agitation from Injected Air)]
The Kicad schematics below…
Thank you for your answer. I have specified the sensor I will use above. I need a pcb for it.
Yes, I read your post and see you’re using a XKC Y25 sensor.
That sensor is NPN transistor based, that’s why I posted my NPN design (schematic) (for commonality and ideas…) and to make it more related to Kicad post/forum
You’re asking for a PCB design but, the XKC Y25 sensor you’re using is already designed so, the only thing you need is a Hook-up/Connections to it (including power).
Thus, the PCB will be very simple: Determine the Connector Mate and place it on PCB (either PCB mounted or via Wires from PCB Pads to mating connector’s wires. Naturally, you’ll need Power into the PCB so, a Barrel Jack Connector is a good choice.
Beyond the Connection Interface, there’s noting to design if using the sensor you identified (unless you want to do something with it’s internal signals, such as to an Arduino/other. But, you didn’t state that). Perhaps I’m missing something in your request
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Thank you for the information you provided was helpful.
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