Command:/enchant @? ID 0

Usually when I use a sword,the command block with the command:
/enchant @a 16(sharpness id) 0
the command block should turn on some redstone power and,
when I use the sword the power should went out.
But the command block isn't giving any power all the time.
I made sure that everything was fine.
command block is updating,
comparator,
everything.
Please fix this,I really enjoy this command