Makerdoit 4pcs Micro Servo Motor SG90, for Robot Arm/Hand/Walking/Servo Door Lock;

What is SG 90 servo?
It is tiny and lightweight with high output power. This servo can rotate approximately 180 degrees (90 in each direction) and
works just like the standard kinds but smaller. You can use any servo code, hardware or library to control these servos.
It comes with 3 horns (arms) and hardware. A Servo can be positioned to specific angular positions by sending the servo a coded signal.
Servos, in general, require a lot of currents to operate since they have a motor inside. If you only need to control one small servo
like this one you can connect it directly to Arduino.
If you need to control two or more servos you need an external power supply or battery pack.

Specifications
Operating voltage: 4.8 V ~6V
Operating speed: 0.1 s/60 degree
Stall torque: 1.8 kgf·cm
Dead bandwidth: 10 µs
Temperature range: 0 ºC - 55 ºC
Weight: 9g

How to connect SG90 micro servo motor to Arduino Uno?
The connection with Arduino is extremely easy. The servo has three leads. The brown one is the Ground so connect to it Arduino Ground.
The red one is VCC which usually requires a voltage between four points eight to seven point two volts. So connect it to Arduino 5V.
The last lead, the orange one is the control signal which needs to be a PWM signal with a periodic time of twenty milliseconds aka 50 Hertz
and a duty cycle of one to two milliseconds so five to ten percent.

While an on time of one millisecond represents the -90° position of the motor shafts, one point five milliseconds represent 0° position and
two milliseconds the plus 90° position. That means you can rotate the shaft a total of 180°.
The SG90 servo has 3 wire interfaces in which the connections should be made as follows:
Red wire-5V
Brown wire-Ground
Yellow wire-digital pin 9