I built a simple setup according to this tutorial using a 9v battery (in the meantime replaced it with a 120A battery): https://www.bc-robotics.com/tutorials/controlling-a-solenoid-valve-with-arduino/

Also i attached a humiditiy sensor to measure the soil-humidity. My plan is: 2 times a day (evening and morning before sunrise) wake up arduino and check humidity, if it is below a certain %, open the 12v-valve, wich i operate at 9v (like the one in the tutorial).

I read a lot about how to reduce power on the arduino and found this tutorial for the pro mini, wich seems a LOT easier than to modify the standard arduino uno: https://www.whizzy.org/2015/06/howto-very-low-power-usage-on-pro-mini-v2-arduino-clone/

Now, my question is: would a pro mini v2 work as well for controlling the valve? On the uno, i have the vin-pin wich provides the 9v for the valve, on the pro mini instead, as far as i understood, i need to use that pin (named RAW pin there) as power supply for the arduino... but how would i get out the 9v from the arduino like i did on the uno? Is there any possibility at all?

Thanks in advance!

  • there is nothing about a battery in the tutorial. how did you connect the battery to Uno if you connected the solenoid to Vin, where I would connect the battery too?
    – Juraj
    Apr 4, 2018 at 10:32
  • Hi, thanks for your resonse! I connected the battery to the standard jack.. (wich obviously is not present on the pro mini)
    – pixx
    Apr 4, 2018 at 10:48
  • Because you are using a 9V battery, do not remove the power regulator as per the instructions in your second link. You need that regulator to lower the voltage down to the 3.3V or 5V (depending on the version chosen).
    – sa_leinad
    Apr 4, 2018 at 13:29
  • You can connect more than one wire to a single Arduino pin.
    – Gerben
    Apr 5, 2018 at 9:09
  • @sa_leinad: Thanks, that was one major doubt, even if it sucks a lot of energy.. (i would choose the 3.3, since i do not need a lot of processing power, it does not need to be fast or super-precise timing). In another tutorial (on the uno however) they talk about replacing the linear regulator with another one by soldering out the default one and putting in a dc-dc regulator... do you think that that would work to save power on the mini too?
    – pixx
    Apr 5, 2018 at 14:22

1 Answer 1


Vin and the barrel jack are the same power input on Uno.

RAW is the label for Vin on Mini Pro.

You can connect the + of the battery to power rail of the breadboard and from there to Vin/RAW pin of Arduino and to the solenoid powering contact.

  • Thanks! That sounds great! I connect the + from the battery to lane 1 for instance and from there one pin goes to the arduino and another pin to the solenoid if i understand the solution?
    – pixx
    Apr 4, 2018 at 12:22

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