Hello! I'm fairly new to Arduinos and engineering. I'm trying to create a circuit that powers one of my sensors and also a solenoid valve. Basically the idea is that if certain variables in the sensor are hit, open the valve.
I realized that I'm going to be placing me project outside and would ideally prefer to limit myself to using a single power source. I wanted to know if it was possible to power the entire board with a single power source. The solenoid valve requires 12 volts and the sensor can do with 3 volts. Basically I'm trying to reduce the amount of clutter as best as I can. I think I'm going to need a diode between the negative and positive ends of the valve, but not sure about that either. I also have a 4 way relay board that would connect the valve to the arduino board.
EDIT: Forgot to mention that the valve requires 12-Volt DC / 450 mA power
get a buck converter to drop the 12 v to 5 v for the arduino. don't even say "I thought..." size of a postage stamp, and chump change.
Which Arduino? Which sensor? Post a link to the relay board.
Thats pretty much it and just throwing in a bunch of jumper cables to connect everything, but I'm not sure if anything is going to get fried or overloaded. If I absolutely have to, I'll use two power sources to power the board and valve, but it would be ideal to keep things as singular as possible.
4 relay coils at 75mA each = 300mA, Arduino and moisture probe = 100mA. 5V load = 400mA, too much for the Arduino's onboard 5V regulator, you will need a 12V to 5V buck converter rated at least 1 Amp and 12V power supply rated 2 Amps (being conservative). Since you would have a 12V supply, I would use a board with 12V relays switchable by 5V logic signals, (30mA per coil) and power the UNO with the 12V into the barrel jack.
EDIT: And don't forget a 1N4004 diode across the valve coil, cathode (end with band) toward V+ to suppress contact arcing and EMI.
12V Relay
Here's a project I did last Christmas. It has a 12V PSU, one 5V buck converter (the black box on the left) and two Wemos D1 Mini boards. All to control sixteen LED strings.
