Arduino-to-Arduino Psychic Communication
When you need to pass messages from one Arduino board to another, there are a wide variety of options, from WiFi or simpler RF modules, to infrared, or even hard wiring the two together. Hari Wiguna’s Arduino Psychic device, however, is able to guess a number generated by second board, with nothing linking both.
As seen in the first video below, he’s using a single Arduino Nano on a breadboard to produce random numbers with the press of a button. When it pops up with a two-digit number that he likes on its seven-segment display, this is stored with the press of a second button, and written down on a pad of paper.
Subsequent presses of the first button generate new random numbers, and when it hits on the selected digits, it blinks after another button press to show it’s hit on the right one.
Where things get interesting is that these random guesses – not the first number chosen – are input into a second Arduino via a keypad. It says "no" if it's not the right number, and blinks when the correct number is chosen.
There is no link between the two, and of course this inexpensive Nano unit doesn’t have eyes to see the original number chosen, but it is still able to recognize when the correct entry.
The schematic in Wiguna's build write-up doesn’t give much more clarity as to how this is done, though perhaps the included code for each unit does. If you’re stumped, or would rather just see an explanation, all is revealed in the second clip!