stooby
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Joined: Sun Jun 16, 2019 7:35 pm

Soil sensor (2 nails) ads1115

Sun Jun 16, 2019 7:39 pm

Hi,
Just a bit of a sanity check ... because I somehow cried a couple of Pies messing about 🤦🏻‍♂️

Does this circuit look ok?

Thanks
S
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mahjongg
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Re: Soil sensor (2 nails) ads1115

Sun Jun 16, 2019 8:58 pm

NO!
use the logic power supply of an RPI, which is 3V3, NOT 5V!

otherwise you risk pulling the I2C lines to 5V (the board has pullups to the logic power of the board) which might damage the RPI.
remember the first rule of the RPI, never allow any voltage more than 4V to reach a GPIO pin!!!!


The RPI is NOT 5V tolerant!

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Burngate
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Re: Soil sensor (2 nails) ads1115

Mon Jun 17, 2019 9:29 am

Why are you using a GPIO to feed the nail sensor? Wouldn't a constant 3v3 be better?

You could perhaps use two GPIOs, one to each nail via its own resistor, and one output low with the other output high, and use the A-D in differential mode.
Then regularly swapping the low and high around could reduce electolysis problems.

And, as mahjongg says, DON'T use 5v Anywhere!

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