Synchronize a counter between two arduinos

Hey there
i'm trying to synchronize a counter of one master arduino to an slave one in order to create a stopwatch that can be installed on the two borders of a swimming pool, the fact is that i've already done the master counter but till now i'm unable to syncrhonize the counter to the slave arduino. the objetive of this project is to provide to the swimmers a device that alowthem to measure their trainning in seconds and minutes. Can anyone in this forum helpme with this issue?

It might be simpler to have the slave merely repeat the display from the master - no synchronisation required

Do you have any wiring between the two? Or are you going to do it wireless?

If it is just seconds resolution you can indeed just send the new time to the slave every second, and have the slave display this. Even a slow wireless link is probably so fast you can't see the delay.

Competition pools are 25m long. Available Infrared transmitters/receivers can cover that distance. You could syncronise using light pulses.

Competition pools are 50metres long in my hemisphere.

Competition pools are 50metres long in my hemisphere.

You must be rich :slight_smile: Olympic pools are 50m but competition pools can be 25m. IR could still work at 50m but low cost components might be struggling.