Dispenser tower defense

I'm making a Minecraft server with a tower defense on it and I need to know how to make dispensers fire automatically without showing any redstone. I also want the dispenser to MOVE UP and have a block to be placed under it. I want to use only commands and redstone. I'm playing MC version 1.9.2

Solution 1:

You can use commandblock clock, placing redstone block adjacent to dispenser, then second commandblock in chain will revert that block to another solid block - for example stone. Use some kind of fast clock for that and you are done.

For players there will be always stone visible, because redstone block will change so fast. But dispenser will fire.

If it is not fast enough for you, you can mask it with something around it. Also be aware that a lot of those will have performance hit to the server.