Connect four

Soldering the SMD components was too difficult for me to be done manually and so recently i have contacted the company Gravitech Thailand that has PCB assembly equipment (pick and place machines) to help me put the project in production. This company is also the organizer of a local maker fare in Bangkok called "mini maker faire" and the upcoming "maker land" currently postponed due to COVID-19.  They suggested to add sound effects to the toy and also put the project on Kickstarter to have some funds to start the production.

CLEAR 4: Connection Board Game With See-Through Design, via @Kickstarter https://www.kickstarter.com/projects/463050344/clear-4-connection-board-game-with-see-through-design?ref=android_project_share

At first i tried to connect the IR sensors directly to the Arduino inputs. Like this it may happen that a disc is detected twice as the signal may oscillate nearby the thresold level. The signal oscillates because the disc may move sideways while dropping. To solve this problem I added a smith trigger for each sensor that have an isteresys of 1/3 of the supply voltage. I choose to use Opamps because i can set the isteresys i want while if i used a cmos IC with 6 inverting Schmitt triggers the isteresys would be fixed at 0.9 Volts.