Instructables Electronics Project: Prank BoxAssembly Time: 5-8 hours
The Prank Box is basically a sealed wooden box with an electric bell inside that is activated by a key switch. Once it is turned on, a relay inside the box is latched and it cannot be turned off without knowing the secret trick (spoiler alert: magnets). Quite understandably, a completely sealed box with a ringing bell inside that doesn't seem to stop can quickly become maddening. It is very funny to watch people ponder the implications of the device, reluctantly turn it on, and then stress out when they cannot turn it off. It is even funnier to get panicked emails from your friend in Canada after you mail it to him without any explanation, and he decides to ignore the directions on the box and turn it on.
Required tools and components:
|9V Battery||ALK 9V 522|
|D-Cell Battery||ALK D EN-95|
|Heat Shrink Tubing||FIT-221B-3/16-BK100|
|SPDT Reed Switch||35-756-BU|
|9V Battery Clip||GBH-1009-R|
|Cable Ties||KSS 0301CV-200 CLEAR-R|
|4-D Battery Holder||BH-142-A-R|
Wood glue & woodworking tools
Drill and 1/8" drill bit
Red and black wire
Step 1 - Review Parts and Download TemplatesTake a moment to be sure you have all the required parts. You can download the two template files titled "DoNotBox.cdr" and "DoNotBox.eps" here
Step 2 - Insert LockInsert the lock into the hole in the front panel from front to back and then epoxy it firmly in place.
Step 3: Mark Mounting Holes for ComponentsPlace the wooden mounting bracket atop the bottom side of the box and place all of the components atop their designated spots on the bracket. The reed switch does not have a designated spot, but it should line up flush with the edge of the bracket on the side nearest the 9V battery holder.
Step 4: Glue the Inner-Side of the Box BottomThe bracket should be placed on top and line up to the edge of the box, so when the box is put together the reed switch is flush against the wall of the box. Clamp in place and wait for it to dry.
Step 5: Drill Mounting HolesDrill the mounting holes with a 1/8" drill bit. It should go deep into the wood, but not pass all the way through.
Step 6: Mount ComponentsLay two zip ties vertically across the battery holder's footprint and another two horizontally and mount all of the major components to the bracket with screws.
Step 7: Wire It UpAttach the red wire to the common connections for the reed switch and the key switch. Then attach another red wire to the normally open (NO) connections on both switches. Connect these two wires to the red wire from the 9V battery clip. Attach black wires to the two normally closed (NC) connections on both switches. Connect these two wires to the black wire from the 9V battery clip.
What you have just done is create a situation in which ground is always connected in the circuit. By engaging one of the switches, you are introducing a positive voltage. This flips the polarity one way or another and latches the relay open or closed. Now when you turn the key, it latches it closed and keeps the bell ringing. When you engage the reed switch, it flips the polarity and latches it open and turns off the bell.
You will need to wire the bell to the D battery holder and the relay. First, wire together the black wire from the battery holder to the frame of the bell. Then connect the red wire from the battery holder to the center pin on the relay. Last, connect the red wire from the battery holder to the coil connection on the bell. This is the mounting terminal not connected to the frame. Cover all the exposed electrical connections with shrink tubing.