I came across a Soil Moisture Sensor schematic online. I have being trying to figure out how they did the Sensor probe section i.e connecting a global label to a footprint and where to even get the sensor probe footprint. for ways to get the footprint Sensor Probe in Kicad like it was done online. Below is the part of the schematic and the pcb. Any ideas ?
This doesn’t need a footprint - you can simply place two filled zones, and set their nets to GND and PROBE2.
Will it be possible to make this part of in gold plating or how to specify that so it could be something like this after:
You’ll need to also draw a graphical shape on the F.mask and / or B.mask layers to show the soldermask should be removed over this area. You’ll need to speak to your manufacturer about plating.
If you wish to create the probes as pads:
Use the Create Graphic Polygon icon (green arrow) to form the shape.
Place a pad on that polygon (see LH spear)
RM Button > Edit pad as graphic shape (hotkey CTRL E)
CTRL E a second time
Footprint complete (see RH spear).
This may be an easier way to create what you want, as it appears you need identical pads on both the front and back of your board, bound with vias.
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From what I know, these sensors generally have a very short life, because of electrolysis. It just removes the copper from one electrode. Using an AC signal will prevent this. You can for example use a microcontroller pin in PWM mode with a series capacitor, and a charge pump on the receiving side.
Or at the very least, you can limit the duty cycle. When sensing for a few micro seconds every 4 hours you will reduce electrolysis by about 9 orders of magnitude compared with continuous sampling.
Also, What do dissolved copper compounds do in your soil? As far as I know this stuff is quite poisonous, but I also believe it is a trace element that plants need to grow (But those may be other copper compounds. I never looked into the details.