Using PCB platines as capacitor

Thread Starter

AT11

Joined Dec 26, 2020
2
Hello to all,

For our project, I am trying to design a very easy PCB with a NE555 Timer to measure the soil humidity.
My first idea was to use a circuit board (attached as a photo) as my capacitive sensor. There is epoxy between the copper layers. I soldered one cable to each side to measure the capacity at different conditions like in the air, in a glass of water, in soil, etc. In the end, I connected this "sensor" to my circuit and it worked really well. I measured the frequency of around 250 kHz in the soil.
Now I want to bring this circuit and the sensor on one PCB, something like in the attached file. For the purpose of this project, I can't just order it from amazon.
I designed the circuit in EAGLE but I don't know exactly how I should be designing the rest of the board. You can see the screenshot of my circuit attached. There is a capacitor called SENSOR. One leg of it needs to be one side of the board and the other leg other side of the board.

I hope you could help me with your ideas :)
I wish you a Merry Christmas and a healthy new year :)
 

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jpanhalt

Joined Jan 18, 2008
10,933
Welcome to AAC.

Is your question about converting the schematic to a board? If so, when in the schematic part of the program, there is a button that will go the the board. Place component and route there. This is what it looks like in my version of Eagle:

1608994374107.png

Yours probably looks different, but it will be in the top bar. It toggles between schematic and board.

If you need help with learning Eagle, it is important to know which version you are using.
 

Thread Starter

AT11

Joined Dec 26, 2020
2
Welcome to AAC.

Is your question about converting the schematic to a board? If so, when in the schematic part of the program, there is a button that will go the the board. Place component and route there. This is what it looks like in my version of Eagle:

View attachment 225889

Yours probably looks different, but it will be in the top bar. It toggles between schematic and board.

If you need help with learning Eagle, it is important to know which version you are using.
Thank you for your answer.

Sorry I couldn't be more clear. I don't have a problem with converting schematic to a board. My problem is with the capacitor. I want to use one side of the pcb as one leg of capacitor and other side of the pcb as other leg of capacitor. I want to use the pcb as my capacitor.
 

jpanhalt

Joined Jan 18, 2008
10,933
I don't understand. Several years ago, I used Eagle to design a capacitor made from a PCB. I don't have a picture of it. Imagine two intermeshed combs. I was playing with different configurations for a capaciflector (proximity detector). Here's something I did photograph, also done with Eagle:

1609005406174.png

1) You don't need a schematic to make a board.
2) You do not need a schematic to make a device.

However, the simplest way to incorporate your sensor in the schematic is probably to make a device with a corresponding symbol.
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