Picture of Car Horn Prank Box

A beloved coworker is returning from Canada soon and in his honor I have created the car horn prank box. Basically, when the red button is pressed, and an LED blinks indicating that there is thirty seconds in which to hide the box somewhere dark. Once the thirty seconds expire, the next time that the box sense light, the car horn honks very loudly. Some fun places to hide the car horn is includes drawers, underneath jackets, in closets, buried in a backpack, or simple left in a room in which the lights have been turned off. The amount of potential mischief that this device can produce makes it a perfect welcome back gift.
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Step 1: Materials

Picture of Materials
You will need:

(x1) Car horn
(x1) Enercell 12V/5Ah Sealed Lead-Acid battery (Radioshack #23-945)
(x1) Arduino Uno (Radioshack #276-128)
(x1) LED holder w/LED (Radioshack #276-068)
(x1) LED holder (Radioshack #276-080)
(x1) 7805 voltage regulator (Radioshack #276-1770)
(x1) TIP31 NPN transistor (Radioshack #276-2017)
(x2) 10K ohm resistor (Radioshack #271-1335)
(x1) 1K ohm resistor (Radioshack #271-1321)
(x1) 220 ohm resistor (Radioshack #271-1313)
(x1) 10uF capacitor (Radioshack #272-1025)
(x1) 1uF capacitor (Radioshack #55047773)
(x1) 1N4004 diode (Radioshack #276-1103)
(x1) Small photocell (Radioshack #276-1657)
(x1) Red pushbutton switch (Radioshack #275-646)
(x1) Aluminum heatsink (Radioshack #276-1368)
(x1) Thermal compound(Radioshack #28-1098)
(x1) 12V automotive relay (Radioshack #275-001)
(x1) Dual PC Board (Radioshack #276-159)
(x2) Pack red and blue quick connects (Radioshack #64-3088)

Step 2: Mark and Drill

Picture of Mark and Drill
Measure in 2" from one of the 6" edges of the enclosure's lid and make a centered mark.

Drill through this mark with a 1/4" drill bit.

Step 3: Insert

Picture of Insert
Insert epoxy into the base of the LED holder and then insert a small photocell.

Clean the epoxy of the photocell leads if necessary.

Let the assembly dry.

Step 4: Attach

Picture of Attach
Crimp on 4 red quick connects to 6" red wires, and 4 blue quick connects to 6" black wires.

Step 5: Drill

Picture of Drill
In one of the opposite corners from the last hole drilled in the lid, drill a 1/2" hole, and two 1/4" holes, which are all spaced about 1/4" apart.

must be smaller :D

psychled1 year ago

Where is the template for the L-assembly?

muddog151 year ago
ximeng1 year ago
Very nice work! I want to see the result!
Lindie1 year ago
Do not do this to me!!! :-)
grapenut1 year ago
For how long does the horn honk? and how do you stop it from honking, if it does not stop quickly, on it's own??
randofo (author)  grapenut1 year ago
About 2 seconds is the sweet spot. The horn takes a brief moment to engage.
I had a neat idea some time ago:
Put a battery, a horn, a button and a relay in a box, and wire it so that when the button is pressed the relay activates and feeds the horn and its own coil, so that when the button is released the horn will keep on going as long as the battery lives or someone breaks it open and disconnects the wires.
Just put a huge label on it saying "DO NOT PRESS!", place the box in a frequented area and see who is not able to resist temptation!
This sort would be best done with a klaxon horn.
Anything loud and battery powered does the trick!
Bosun Rick1 year ago
VERY WELL PRESENTED! This is by far one of the very best Instructables I've ever read! Instructions are very clear, concise, and lack the usual 'tech speak' or confusing 'slang' often associated with this site. Congratulations! I'm voting for you!
GarageGuru1 year ago
Your ears and possibly your nerves may thank you if you connect a test light at the horn connection during your testing and debugging phase. Then once you feel you have everything operational, remove the test light and connect the horn. Of course if you enjoy scaring yourself, forget what I mentioned, and carry on!
if you enjoy scaring yourself, lol
I believe if you want that UL certification for use on Canadians, you have to include a TASER circuit for when they grab the box and realize it is not their Christmas gift.