Small soil humidity sensors

Projects
1

Hey! I made a slightly shorter (65mm overall/40mm underground sensing vs 100mm/65mm) “clone” of the Pimoroni Soil moisture sensor, to be used with small pots in my watering project.
As the price difference was negligible, I definitely ordered a lot more than I needed, thus if you’re interested in some free pcb let me know.

I’ll confirm all values once the boards arrive, but this should be a mostly final BOM for the sensors:

  1. ICM7555CBAZ soic8, 1
  2. 74HC4060BQ-Q100 DHVQFN-16 (optional), 1
  3. capacitor 100nf 6.3v 0402, 2
  4. capacitor 10nf 6.3v 0402, 1
  5. resistor 47K 0402, 1
  6. resistor 470K 0402, 1
  7. connector SM03B-SRSS-TB(LF)(SN)
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2

Have you any experience of how long these things last? Although there is solder resist on the faces of the PCB, water can still get in at the edge. I put a bit of epoxy resin round the edges of mine, but haven’t used them much so I don’t know if it helps.

3

I have a set of pimoroni ones in use since at least one year. No issues at all. Probably I’ll coat the electronics with some epoxy before using them, just to be sure the last longer