If I were doing that, I would buy an optocoupled board with 12V relays instead of 5V since you already have a 12V supply. 5V relay coil current is about 75 mA, (8 X 75 = 600 mA), so you will need a 5V supply of at least 1 Amp, 12V coil current is only about 32 mA.
So I'm clear.. the item you link to can be controlled 'DIRECTLY' from an Arduino pin... correct? (just want to make sure I read & understand your comment correctly)
'Wired correctly'....
From a quick glance.. it seems pretty straight forward... (following your image on how to wire it of course)
Thanks.. I'll be ordering it tonight.
update:
If I was looking to purchase from EBAY for example...
Would this be the same model? (as long as wired per your diagram?)
xl97:
So I'm clear.. the item you link to can be controlled 'DIRECTLY' from an Arduino pin... correct?
Indeed. There is the point of the opto-couplers - the connections to the Arduino, running at 5 V, are completely separate from the connections to the relays, running at 12 V.
xl97:
If I was looking to purchase from EBAY for example...
Would this be the same model? (as long as wired per your diagram?)
Link corrected - removed "?" and all the garbage following from eBay link.
If it looks the same, it will be the same, whoever is selling them, they will all be made in the same sweatshop in China.
Interesting question: there are an awful lot of sellers on eBay, though they seem to use the same graphics for the same item and we know that many that look similar are simply in different rooms or "cubes" in the same warehouse and often members of the same family. Just how many different assembly "shops" are there actually assembling the various Arduino and similar electronic modules?
xl97:
Already have some stuff in my checkout/basket/.... (and its a cheaper)
As above, most unlikely to be different quality.
xl97:
I will only have 1 power source... but it is a PSU form an old PC.. that gives 5v & 12v..
5v rail/output will be powering the Arduino..
12V rail/output will be connected to the Relay board...
Will that be a problem then? (noise? risk of blowing Arduino or pin?)
The "risk" is really only of making a wiring mistake. The 5 V line on a PC power supply is likely rated at 30 A or so, so it can easily vaporise a PCB track or component.
Note that the disk drive connectors on a PC supply have two black wires coming separately from the power supply (and the main connector has a number of black wires). They actually connect to the same pads on the PCB of the disk drive but to obtain the full benefit of the opto-isolation you can use one black wire for the Arduino ground (which does not need to connect to the relay board) and the other for the ground to the relay board to match the 12 V.
