So why hook the bat up to the spears in the first place? And why is there only one colour wire on the spears instead of three? Don't they all just fire at the same time?
Let me clarify with some numbers. Suppose the bat activates the top row of spear traps at time 0, and the next row at time 0.1 seconds. Then the bat sends the NPC into the activation chamber and the NPC activates the spear traps 30 times a second. However, the spears have a cooldown on 1.5 seconds each. Therefore, the top row of spears will activate at the 1.5 second mark, then at the 3 second mark, then at the 4.5 second mark etc. The next row of spears will activate at the 1.6 second mark, then at the 3.1 second mark, then at the 4.6 second mark etc.
In other words, you need to activate the rows of traps in staggered fashion first, and only then send the NPC into the activation chamber. If you send the NPC into the activation chamber without using the bat to stagger the activations, then the spear traps will all fire in unison at the 1.5 second mark, then at the 3 second mark etc.