Hacking a Water Gun
Step 0: Obtaining the water gun
A classic water gun will be really hard to control with electronics. You’d need a way to pull the trigger with a motor, which is complicated and prone to failure.
The kind of water gun that you really want is an electronic one.
Here are some examples for searches for them:
Though you can use any search engine you want
Here is the model water gun we used:
These water guns use the trigger as a switch instead of as the energy to propel the water. The energy comes from some batteries onboard. You can bypass the switch to use a microcontroller to control the water flow.
Enough of the theory—let’s get to taking the thing apart
Step 1: Disassembly
First, take out the water clip.
Turning the water gun on one side, you’ll see a lot of screw heads. Grab yourself a matching screwdriver and unscrew them all.
Make sure you don’t lose any screws. If you lose one or two you’ll probably be fine, but don’t lose too many. A suggestion would be to put them all together in a box.
Once the screws are out, the two halves of the water gun should be loose from each other. Just pull them apart.
Inside you’ll see a bunch of things.
Step 2: Observation
Here’s a picture of the inside of the water gun we used:
Let’s take a look at the components inside. Near the muzzle (shooting end) of the water gun, you’ll see a tube connected to a nozzle. Following the tube back, you’ll come to a water pump. Out of the pump, you’ll see two wires.
Following those wires will bring you to a switch. In our water gun, the switch was on top of the battery pack and the trigger pushed it closed.
Now you have two options. You can use the on board batteries or decide to power it on your own. Powering it on your own is easier to set up but make sure you don’t use too much power or you risk burning out the pump in the water gun making it not be able to shoot anymore.
Step 3a: Controlling the water gun with external power
Take the wires connected to the pump and clip them as far away from the pump as you can. Strip them, and solder them to longer wires (seal with electrical tape or shrink wrap). Cut a hole in the water gun and thread the wires out. Now you can screw the water gun back together.
That’s all. To shoot the water gun, apply voltage between the two wires. No voltage and the gun doesn’t shoot.
Just be careful not to destroy the pump’s motor with too much voltage.
Here’s what the wiring looks like:
Step 3b: Controlling the water gun with internal power
Take the wires from the pump and follow them to the battery pack. You’re on your own a bit here, but here is the object:
– Make a hole in the water gun
– Thread one wire through that hole
– Make sure that one wire is still connected to the battery pack
– Connect a wire to the other terminal of the battery pack
– Thread that wire through the hole in the water gun
If you succeed in doing that, you’ll have two wires leading from the water gun. If they are connected together (be more specific), the water gun will shoot. If not, the water gun will not.
A good way to control this setup is by using a relay (refer to relay section of etoolbox if you have a question). Connect the wires to the COM and NO pins. Now, you can use an Arduino to turn the water gun on and off through the relay without worrying about supplying the correct amount of power.
Hacking into a water gun is pretty easy and you shouldn’t feel scared to incorporate them into your project.