This Coin Acceptor works by compare the coin that already inserted in this sensor (blue color at sensor) with the coin that inserted at the front hole. If the coin is the same, the coin will accepted, but if coin is different, the coin will be rejected.
View More Coin Acceptor or Coin Sensor Tutorial with Arduino
There are some heartbeat sensor in market with cheap price. I’ve used three of them. In my opinion, the most stable is easy pulse plugin.
View More Easy Pulse Plugin Heartbeat Sensor with arduino Tutorial
MLX90614 can measure an object temperature without touch the object. It is also can measure high temperature. And it is easy to use with an arduino.
View More Non Contact Temperature Sensor MLX90614 With Arduino Tutorial