Battery holder: card powered battery for the real time clock chip so the board can continue counting down; Buzzer: 5V DC buzzer do alarm clock key tone; Photoresistor: Induction of ambient light intensity; Thermistor: detect ambient temperature; K1~K3: chip can be scanned directly touch of a button; U5: TM1636 ie four 8-segment common anode LED Driver IC; U3: DS1307 namely real-time clock chip; D1 ~ D4: blue green red red 3mm plug-in LED. Digital tube: four 8-segment common anode LED with clock points while the decimal point is not displayed only for orientation recognition purposes. Occupy the Arduino pin resources: total occupied 10 digital pins two analog input pins an I2C interface D2: control blue LED1 D3: Control the green LED2 D4: Control the red LED3 D5: Control the red LED4 D6: control the buzzer; D7: Connect TM1636 clock pin SCLK; D8: Connect TM1636 data pins DIO; D9: control keys K1; D10: control keys K2; D11: control buttons K3; A0: Connect thermistor; A1: Connect photosensitive resistance; A4: Connect the DS1307 I2C data pin SDA; A5: Connect the DS1307 I2C clock pin SCL. Voltage 4.5~5.5V Current: 80mA A product for Arduino that works with official Arduino boards.