Have you ever had someone cut you off in traffic but honking your horn isn't enough?
I'm a passive driver; it takes a lot to get me mad but I got to thinking of a fun way to let people know they cut me off using an unexpected means.
Therefore, I made a motorized squirt gun for my car.

Step 1: Shopping List

For this project you'll need:

an Arduino a liquid pump I used this one here

button of some sort

Cigarette power adapter here

a diode - the motor runs at 12v and 14.5w - you'll need one rated for at least 1.2A.

Radioshack near me only had a couple diodes so mine is overkill

About 10ft of hose. I used 1/4 air hose (easier to install different nozzles) but you can also use the one recommended on the site here . The 1/4 line is slightly large for the inlet/outlet of the motor so that will need to be addressed.

1/4" hose clamps

a container to hold water

Depending on which route you want to go you can use either a relay or an N-Channel MOSFET transistor

MOSFET method

RFP30N06LE MOSFET can be bought at sparkfun.com

150 OHM resistor

Relay method

Relay board on amazon.com

Optional

1Sheeld here

it's a bit pricy just for this project but I love using it while I'm prototyping projects. You can simulate button presses (and a ton of other stuff) from your android phone without needing the hardware. Also, if you're familiar with Tasker, you can create a widget that toggles pins high or low.

Step 2: Wiring

The first photo is a basic view of how I started out wiring this project with the MOSFET method.

I ended up ditching it because I have more ideas for my car and the relay made more sense.

The seeedstudio relay shield I'm using is now discontinued but you might still be able to find it at radio shack. It uses pins 4-7 as well as 5v and ground. Connect your 12v supply to comm and your motor's load to NO (normally open). If you don't have a shield, connect 5v from your arduino to the vcc on relay module and pin 7 to IN1. Make sure to wire in the diode in the proper direction.

You can use the button debounce sketch found in the Arduino IDE. Just make sure you switch the pin from 13 to 7. Also, if you're using a button make sure you wire it up to pin 2. There are plenty of tutorials which show you how to wire one up so I won't get into it here.

With the 1Sheeld you can use the button sketch and set the button pin to 2 in the app. Then tap your screen to control the flow of water

Step 3: Motor

Since the 1/4" line is too big for the inlet/outlet of the motor, I used a small piece of duct tape and wrapped it around the hole once. I was then able to squeeze the hose on and tighten it down with the hose clamps. Currently I have a nozzle on that's used for inflating sports equipment.

Step 4: Testing It Out

I don't have it fully installed yet cause the weather is still dropping below freezing at night. The video is more of a proof of concept. I plan on hiding it a bit better and maybe adding a servo to control the direction.