Somewhat Interactive Time Bomb

by jinzhouliu4 in Circuits > Arduino

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Somewhat Interactive Time Bomb

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VID 20230515 2031471

This here is a time bomb with the added feature that it beeps the defusing code in morse using 2 LED's and a active buzzer.

Supplies

Electronics:

16x2 LCD Display with I2C module x 1

3x4 Membrane Keypad x 1

Active buzzer x 1

Arduino (Uno in this case) x 1

PCB x 1

Wires

LED x 2

9V battery holder x 1


Case materials:

4mm MDF

M4 bolts and nut set x 5

Wood Glue

Nail x 1

Laser cutter x 1

Circuit

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The circuit is nothing too complicated. Since I have an LCD display with an I2C module it allows me to operate the LCD display with only the SDA & SCL pins.

I have 3 wires in Digital pins 11 through 13 that are only connected to the ground. They will be used as switches to detect if the respective wire has been cut/disconnected.

In the circuit drawing I have an Piezo buzzer but in the actual project I use a active buzzer. It will come with 3 pins. but I ignored the middle pin so you can safely(?) follow the drawing.

In the project I also use an 3x4 Matrix Keypad. The drawing shows a 4x4 Keypad. You can still follow the drawing. Just make sure that you leave 1 pin unused on both sides.

Connected 2 LEDs that will be used for various functionality.

Programming

For the file to work you will need to install the following libraries;

  • I2C_LCD
  • Keypad

The code itself simply reads the input of the keypad and checks if a boolean is true. Depending on the keypad input it will check a boolean and in turn will go into a "Mode". This way you can enter the arming code or set the timer.

I used the String type to store the set time and arming code. It has come to my attention though that using the String type should be avoided on systems with limited memory. So you should use an array of the char type.


Downloads

Case

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I made the case design in Inkscape. Its just a simple box with a few additions to it. Including a locking mechanism for the back panel using tabs so you can access the insides after assembling everything.

Putting It Together

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If you have all the parts from the supplied .svg file construction will be quite straightforward.

  1. Attach Keypad to front panel. Insert the pins through the rectangular cutout.
  2. Attach LCD's & LEDs to front panel.
  3. Attach Battery holder and Arduino to a plate.

Note: you can tape all of it. :)

for the case:

  1. Glue the side panels and bottom panel to the front panel with glue.
  2. insert the tabs with holes into the back panel.
  3. insert the long tabs in the side panels.

Now all you have to do is wire it all up to the Arduino. It is quite finicky honestly. At the time I drew the design for the case I thought I was clever and it would be easy to take it apart and assemble everything...

I was wrong. But it shouldn't be impossible to wire everything up.

Last thing to do is hookup the battery!