Hi guys,
I am trying to power up my Arduino, 3 Relays and 3 Solenoids with the same 12V power supply.
I have made a quick schematic (yes, I know it looks awful and I do apologize) below:
Is this ok or am I doing something very wrong?
Thanks! 
It's hard to say...
The relay terminals are not labeled and we don't know the relay specs or the solenoid specs.
What's relay coil voltage & current rating? Most relays can't be directly driven by the Arduino because they require more voltage & current than the Arduino can supply. So usually, you need a relay driver circuit or you can get a relay board that has a driver built-in. You can get 5V & 12V relays (coil voltage). Since you have a 12V supply you'd want relays that operate from 12V.
The 12V power supply needs to supply the solenoid current requirement (Amps).
To extend the life of the relay contacts, [u]add a reverse diode[/u] across the solenoid coil... When the solenoid is switched-off, you get a high-voltage Back-EMF spike that will arc (spark) the relay contacts, and the diode will "kill" the voltage and prevent arcing. (Your relay driver circuit should have a similar diode across the relay coil.)
DVDdoug:
It's hard to say...The relay terminals are not labeled and we don't know the relay specs or the solenoid specs.
What's relay coil voltage & current rating? Most relays can't be directly driven by the Arduino because they require more voltage & current than the Arduino can supply. So usually, you need a relay driver circuit or you can get a relay board that has a driver built-in. You can get 5V & 12V relays (coil voltage). Since you have a 12V supply you'd want relays that operate from 12V.
The 12V power supply needs to supply the solenoid current requirement (Amps).
To extend the life of the relay contacts, [u]add a reverse diode[/u] across the solenoid coil... When the solenoid is switched-off, you get a high-voltage Back-EMF spike that will arc (spark) the relay contacts, and the diode will "kill" the voltage and prevent arcing. (Your relay driver circuit should have a similar diode across the relay coil.)
Yes, I should have labeled the relay terminals, but lets assume they are connected in the 'correct way'.
The relays are 12VDC and, indeed, they can't be driven by the Arduino itself, that's why their DC+ connection is connected on the 12V from the Power Supply, and its Signal connection is connected on the 5V from the Arduino.
About the solenoid, I don't know how many Amps it requires. It only says 'Power 4 8W Voltage 12VDC', while my Power Supply can give 500mA 12VDC.
I'll be adding those diodes, indeed. But overall, I was just worried if the 'basics' of this circuit is correct.
Thanks for the reply!
About the solenoid, I don't know how many Amps it requires. It only says 'Power 4 8W Voltage 12VDC', while my Power Supply can give 500mA 12VDC.
You already answered your own question, and the answer is a resounding no.
Whether that space between the 4 and 8 was intentional or a typo, one would require 4A ea, and the other 667mW ea. Regardless, either is more than the 500mA supply you have.
Are you using a relay or a relay module? Straight relays don't have signal connections, and relay modules can use mixed voltages to control/energize the relay, which depends on the actuating voltage of the relay coil itself.
500 mA at 12V is 6 Watts, what does 4 8W mean?
edgemoron:
500 mA at 12V is 6 Watts, what does 4 8W mean?
I am not sure, it is literally written 'Power 4 8W Voltage 12VDC' on the solenoid.
tinman13kup:
You already answered your own question, and the answer is a resounding no.
Whether that space between the 4 and 8 was intentional or a typo, one would require 4A ea, and the other 667mW ea. Regardless, either is more than the 500mA supply you have.
I see.. Well, I can confirm that the solenoids do work with such 500mA 12V Power Supply (alone). But anyway, that's not a problem, I can find another Power Supply.
tinman13kup:
Are you using a relay or a relay module? Straight relays don't have signal connections, and relay modules can use mixed voltages to control/energize the relay, which depends on the actuating voltage of the relay coil itself.
I am using a relay module, and you just answered an old questioning I had about using different voltages as a signal to control the relay.