What Is The Common Positive

[AHarris]

I am looking to use a relay for my ROV however when looking at the plans on the "HomebuiltROVs" website it keeps on mentioning the common positive and attaching it to the control box or connecting it in a loop if it can handle the voltage.

What is this common positive and when they say, 'bring it through to your control box', does this mean I need to connect it to anything?
Is it like a ground wire in that, if there is an electrical fault then it has a shortcut to quickly exit?

Please could you help me in understanding what it does and where it needs to go if I bring it through to my control box?
Thank you

[sthone]

The common positive for the Relays Coils (shown as the green wire in my how to) is the Positive feed from the power source (your battery) to all of the Relay coils (one wire feeds all of the relays which is why I call it common)

If your Relays coils can handle 12 volts you can tie the Common Feed (green Wire) into the same pole (or terminal) that your main positive wire to the thrusters connects to (shown as a thick red wire) as shown below



If your relays can not handle 12 volts (or the voltage drop when you run the thrusters is to much and causes the relays coils to turn off as soon as you turn them on) you would have to run a separate Common positive wire up through the tether to another power source (say a nine volt battery) which would connect here (shown below) and then run up through the tether.



If that doesn't make sense just let me know.

-Steve

[AHarris]

Thanks, that makes a lot moe sense.
I am planning on having internal batteries and then run Cat5 cables as my only tether up to a Joystick (as described in your How To).