I'm building automatic garden watering system using
- Arduino Uno
- 5V relay module - this one https://www.amazon.co.uk/2-channel-trigger-module-JQC-3FF-S-Z-RBTMKR/dp/B01NAJ67ML, here are technical details https://www.generationrobots.com/media/JQC-3FF-v1.pdf
- Solenoid valve, I bought this one https://www.banggood.com/12-inch-DC-12V-250mA-Electric-Solenoid-Valve-Flow-Switch-p-91741.html?rmmds=myorder&cur_warehouse=CN
First of all, relay module contains in itself transistor and kick back diode included, so no need for those.
I'm concerned about the current passed to valve (I'm afraid of burning it :)), so I have a few questions:
On a page I posted above for valve, it said current is 250 mA. However, on a valve I got its written 12V 4.8 W. How come that current is 250 mA? We know that I = P / u = 3.8 /12 = ~ 400 mA
Now, I know that valve and relay should have resistance, but I could not find it. In a page I posted above for relay module it says coil resistance if 70 ohm at 5 A. Does this mean that current that comes to my valve will be 12V / 70ohm = ~180 mA ?
Which consumer you recommend to measure a current with multimeter, maybe 12 V doide? I wanted to check which is the current that will flow to valve before linking it.
Any info on this topic is welcome. Thanks in advance