Soil moisture probe (conductance probe) after approximately 3 months in operation. The probe is only powered for 0.5 second every 6 hours. Metal layers in good shape, still as shiny as when they were put in service.
As you do to feed 0.5 seconds every 6 hours with a esp?
with a relay?
@Paco_Garcia I use a GPIO pin to power the probe. A relay would also work, but the current is so low, a gpio pin is plenty. When I take a reading, I set the GPIO output high to power on, sample the ADC, then set the output low to power off.
This greatly extends the probe life, as DC is not constantly feeding through the metal, eating it away.
Thank you. It’s fantastic. I did not know vcc could be connected to a digital pin.
Yes when testing conductance, one side of the probe is a digital pin, the other side is the ESP’s analog pin.
The probes I’m using actually have an analog daughter board that handles the conductance sensing, and uses an op-amp to buffer the output. So my connection to the probe is probe Vcc to esp digital pin, probe analog Out to esp analog pin, probe Gnd to esp gnd.
See here for schematic of my multi-channel hygrometer board, it connects to ESP using i2c connection. https://drive.google.com/open?id=0B8I8gtvTqCqrRnRzUjg3Ynp0dUU
Here’s a little write up and picture of the entire solution: https://plus.google.com/+GordonMcLellan/posts/XKftengSDXt
Thank you very much. I will study your explanations.
Excellent suggestion. Thanks for sharing