Quantity   Component name
1 × ESP-07/ESP-12 or Olimex ESP-Dev board ESP8266 dev board with multiple IOs
1 × 16" x 1" ID schedule 40 PVC tubing for the sensor tube
1 × 16" x 1" OD cardboard tube for the inside of the sensor tube
2 × IR Emmiter/Detector pair IR LED and photodiode available commonly online
1 × 16x2 I2C LCD Display
1 × 5V Power Supply 5V Supply with barrel connector for Olimex
2 × 470 Ohm 1/4 W resistors current limiting resistors for IR emitters
2 × 10K or 20K Linear Potentiometer to adjust sensitivity of triggers (value depends upon light sensors and tube design)
2 × 3.3K 1/8W resistors provide load resistance to SCR trigger
2 × 2N2222 transistors amplify the IR sensor output
2 × MCR100 SCRs Silicon controlled rectifiers are triggers for our circuit
1 × green LED Gate 1 detect indicator LED
1 × yellow LED Gate 2 detect indicator LED
2 × 220 Ohm* resistors current limiting resistors for indicator LEDs
2 × 470 Ohm resistors load resistors between GATE and GATE_ENABLE pins