Can anybody suggest or recommend if this would work or a better approach?
The relay used would be a 12V relay and not a 5V as listed on the attached image.
The aim is to use one power supply. I have a motor which is 12V, with three wires. Common is ground, and the other two are for moving the motor in either direction. (It's actually a Ball motorised valve (CR02 - wiring)) - I would of ideally used a MOSFET but ideally the extra relays will come in handy going forward. I don't really want to have two or three separate PSU's but I would love to hear anybody's opinion.
The aim is that the 12V would supply the Relay, Arduino & Motor while the Relay is setup with "Optical Isolation" to reduce the current per pin (then maybe could use a shift register going forward)
Sounds OK. You can run an Arduino off 12V as long as you don't need much current at 5V. Your relays have 12V coils, so they will run directly off the 12V supply. The transistors on the relay board won't need much current at 5V.
Isolation is the complete separation of two electrical system. It is used, for example, when you can not be sure that the grounds of two systems will be at the same potential with respect to ground. It can also be used when one system is at a much higher voltage than another, like when trying to interface mains to a low voltage system.
I would suggest that in your application it is not an issue.
Be careful not to use arduino boards that come with bad regulators. Plenty of problems with thermal breakdown on the bad arduino regulators if you supply 12V. So check your board. If it says arduino.org, you're likely to have problems.
liudr:
Be careful not to use arduino boards that come with bad regulators. Plenty of problems with thermal breakdown on the bad arduino regulators if you supply 12V. So check your board. If it says arduino.org, you're likely to have problems.
Oh dear.. I've just had a MEGA 2560 delivered, and it says arduino.org
xerof:
Oh dear.. I've just had a MEGA 2560 delivered, and it says arduino.org
Does it have a regulator, a small black rectangle wit metal tabs along its long sides near power barrel, that says )|| on it? It will likely not want 12V. Write a short program to print increasing numbers to an LCD in an infinite loop, say increasing once a second. Upload and watch the LCD. If it overheats and shuts down, the the number restarts. I discovered the problem about 2 years ago and the last time I heard of this issue was a couple of weeks ago. It was a 3.3V regulator on a shield.
