We can race against the clock when assembling jigsaw puzzles online but what about competing against each other in the real world? [HomeMadeGarbage] came up with the simplest of solutions with his jigsaw puzzle timer that stops only when the puzzle’s completely assembled.
His simple solution was to attach copper foil tape to the back of the pieces, with overlap. He did this in a serpentine pattern to ensure that all pieces had a strip of the tape. The puzzle he used comes with a special container to assemble it in. At two corners of that container, he put two more pieces of copper foil, to which he soldered wires. Those two act as a switch. Only when the puzzle is completed will those two pieces be connected through the serpentine strip on the back of the puzzle.
Next, he needed a timer. The two wires from the puzzle container go to an Arduino UNO which uses an ILI9325 touch panel TFT display for both the start, stop, and reset buttons, and to show the time elapsed. Press the touch screen when it says START and begin assembling the puzzle. When the last piece is inserted, the serpentine strip of copper tape completes the circuit and only then does the Arduino program stop the timer. As you can see from the video below, the result makes doing the puzzle lots of fun.
Naturally, it takes some work to apply the copper tape and you wouldn’t likely do this for puzzles with a thousand pieces but most online puzzles don’t have many pieces either. It’s the fun of the race that matters, and with people taking turns, you want it to be quick anyway.
If you have a printed photo that you want to turn into a puzzle with suitably sized pieces, then you can use this online program that produces an SVG file to tell your laser cutter how to cut out the puzzle. Or maybe you’d prefer to make a robot to make the puzzle for you? In that case, you can start with [thomasgruwez]’s pick and place jigsaw puzzle aid.