Ultrasonic ranging module HC - SR04 provides 2cm - 400cm non-contactmeasurement function, the ranging accuracy can reach to 3mm. The modulesincludes ultrasonic transmitters, receiver and control circuit. The basic principleof work:(1) Using IO trigger for at least 10us high level signal,(2) The Module automatically sends eight 40 kHz and detect whether there is apulse signal back.(3) IF the signal back, through high level, time of high output IO duration isthe time from sending ultrasonic to returning.Test distance = (high level time×velocity of sound (340M/S) / 2,
Connect the Vcc pin to the positive rail on your breadboard.
Connect the GND pin to the negative rail on your breadboard.
Connect the Trig pin to any digital pin on the arduino.
Connect the Echo pin to any digital pin on the arduino.
Finally, connect the positive rail of the breadboard to 5V pin on the arduino and the negative rail of the breadboard to the Gnd pin on the arduino.SG90 Servo Motor
Tiny and lightweight with high output power. Servo can rotate approximately 180 degrees (90 in each direction), and works just like the standard kindsbut smaller. You can use any servo code, hardware or library to control these servos. Good for beginners who want to make stuff move without building amotor controller with feedback and gear box, especially since it will fit in small places. It comes with a 3 horns (arms) and hardware.