Power up transient time

[kebor]

Hello I am using the soilwatch sensor to a Gsm soil moisture monitoring station located in Greece.It is arduino based and solar powered also, which means it is using an battery. For power save I have connected the power(+) line of the Soilwatch to an arduino pin and the code is powering it,just before system needs to take a measurement  of soil humidity. How long has the code to wait before it takes an accurate measurement?

[pinolec]

Hi,

The sensor is ready to take stable reading within 100ms. We don't recommend using Arduino pin to power SoilWatch 10 sensor. It may work but there are few things to consider before. First is what the maximum current Arduino pin can provide. For Arduino Nano, it is 40mA as far as I remember but for Arduino MKR 1200 it is only 7mA. You may think you are ok with 40mA but it may get you. The 40mA is true but nobody mentions voltage drop above 20mA. If you power it from 5V you will not see the difference as even 1V drop will still provide enough voltage to the sensor. Now consider what will happen when you power the sensor via Arduino @ 3.3V. We recommend using suitable n-MOSFET to turn the sensor on.

Regards,
Piotr