the sorcery of copper

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The grill bomb is a defusing game.

Once switched on, you have 10 minutes to cut the right cables and defuse the bomb. Four puzzles will indicate the color of the cable you need to cut. If you solved the puzzle correctly and cut the right wire, the timer will indicate “good”, and the corresponding LED will turn on. If you make a mistake and cut an incorrect wire, the timer will indicate “bad”, and the timer will count down twice as fast. When the 4 correct cables are cut, the torch will turn on, grilling the piece of meat, and you are allowed to enjoy the upcoming barbecue. If you fail to defuse the bomb in time, a poison will be injected in the meat, and you will have to starve.


  • blue pill development board with STM32F103 micro-controller to manage all peripherals
  • TM1637 4-digit 7-segment display to show the count down
  • piezo-element to indicate when a second passes
  • CD74HC4067 16-channel multiplexer to read out is the wires are cut
  • 18650 LiPo battery to power it all (3A is needed when driving the motor)
  • 5V voltage booster for the display
  • DRV8833 dual H-bridge motor driver to control the motor (with slidder) with the syringe to inject to “poison” (just non-toxic blue liquid)
  • DRV8825 stepper motor driver to switch on the kitchen torch (the stepper motor and fixture have been salvaged from a random medical device)
  • MT3608 voltage booster for the DRV8825 (min. 8V required)
  • 4 buttons to place the motor in the starting position
  • 1 power switch


The source code is available here (including binaries).

Note: it is not fool proof, and if you think about how it works, there are plenty of ways to cheat. For example, you win as soon as the 4 right cables are cut within the time, but cutting a wrong cable only speeds up the countdown. Thus, if you cut all cables at once, you immediately win :). Luckily the player was put under pressure from the start on, which distracted him from hacking the device (and he wanted to play the game as intended).

grill_bomb.txt · Last modified: 2020/08/16 22:11 by kingkevin