Arduino + 12v signal electronics

Other Hardware General Electronics
1

Hello

A lot of industrial communication is done using 12v instead of 5v, not sure why but it is that way.
From what i have heard very little amps but 12v, as a power for signal only .

I was thinking i need to interface a machine that uses 12v; in its bus it also provides +12v and ground, if i connect other pins to this 12v it performs some actions.
One way of doing this would be using relays, i think their safe to use and prevent wrong currents into the arduino.

Might it also be possible to connect the ground of the bus to the arduino ground; and use transistor ( or mosfet? ) so that an arduino pin out triggers the fet with 5v (well perhaps put a resistor for less there) and then the transistor would connect my device bus ? (perhaps put in a diode too, to prevent against wrong currents. (what kind of transistor / mosfet should i use?)

2

With so many unknown things, you better use relays.
If they are signal wires, perhaps you could use reed relays. They are small and some are 5V 10mA. You could use an Arduino output to drive such an relay without transistor, but you still need a protection diode over the relay.

3

Or for low current take a look at optocouplers (or optoisolators as they are sometimes called).

-Matt

4

Relays are ok, though they look a bit of an overkill if you just need to signal a condition from the Arduino to the PLC. Relays, however, won't allow you to send messages (such as sensor readings) to the PLC; for this you need serial communication.