As far as I can tell, the correct way to use traps for defense in my settlements is to place a trigger (plate or tripwire) where an enemy is likely to walk over it, place a trap nearby the trigger, and wire them to a generator in series. This works, in as far as my Defense rating goes up when I do it.
But, I frequently find that my own settlers, in their random wanderings, are setting the traps off. This seems especially true if I try to place both traps and guard posts at chokepoints — the guards on patrol walk over the traps. It also makes it impossible to trap high-value areas like the crops, generators, etc.
I assume that I could set the traps, then fence them in so no one could trigger them, and my Defense rating would go up, but it also breaks the immersion a bit, and makes traps useless in a real fight. I may as well just drop nothing but turrets.
Is there some trick to setting the traps so that the bad guys might still fall into them, but the good guys won't?
Best Answer
The way I set up traps so that they are only activated during an attack is to use a Siren.
The Siren wont allow power to pass through it unless it is turned on. Conveniently, in the event of enemies attacking, it is turned on automatically, and allows power to pass through it.
Simply route all your power from your generators through a Siren, then to the traps. The traps wont activate until there is an attack.
I like to combine it with a gate that automatically closes during an attack (again using a Siren and Logic Gates) so that enemies are outside with the traps and my settlers are inside.
Automatically closing gate instructions. This requires the Contraptions DLC:
Attach a power line to one input of a NAND gate, and a line from a Siren attached to a power source on the other. Attach the NAND gate's output to the node on the gate.
The gate will be powered and open until an attack happens, when the Siren is turned on allowing power through. This causes the NAND gate to turn off, stopping power to the gate and causing it to close. When the attack ends, the siren turns off, stopping the power from it. This turns the NAND gate back on, opening the gate.