Step 2: So How Does it Work?

Picture of So How Does it Work?
The remote is made up of the (surprise surprise!) a remote (transmitter) and a receiver.  The remote is powered by a small 12v battery and works from a distance of supposedly 100 meters, although I’d be wary of this!  The wireless signal can pass through walls, floors and doors.  Once the button on the remote has been pressed, it activates the receiver which turns on a relay and allows power to flow to whatever you want to turn on. 

The remote control receiver needs to have 12v to enable it to trigger the relay.  I used 2 X 9v batteries to do the job and it works fine but you could potentially use a small, 12v battery; the same used in the remote. 

As the rocket launcher uses 18V to activate the sprinkler valve, I was able to wire up the receiver so when the relay was closed (activated by the remote) it used the power from the 2, 9V batteries to trigger the sprinkler valve.   
If your device that you want to power uses a different voltage then the receiver, then you can also rig it up so it uses a different power source.