(SOLVED) Servo and External Power Supply

Hello,

I'm trying to power a Servo by external power source because I've read (and checked) that by feeding it with the BEC of an ESC can cause problems for power down.

I followed several intructables to reduce power 8v (2S LiPo) to 5-6V requiring servo (NS-05 Walkera).

I used the built LM371T power loss and effectively get the ~ 5V. And also try with with 4x1.5v AA with the same result.

The problem is that when I connect it and make a simple sketch the servo does not stop turning, it is not positioned as indicated by the signal cable.

However, connect the servo to the VCC and GND pin Arduino and at the same signal and does work correctly. What's wrong?

I checked with a multimeter 5v both the Arduino and external power I did and give the same voltage and amperage (~ 3mAh)

Sketch:

#include <Servo.h>

Servo a;
void setup() 
{
  Serial.begin(57600);
  Serial.flush();
  Serial.println("OK");
  a.attach(6);
}

void loop() 
{
  a.write(90);
  delay(500);
  a.write(180);
  delay(500);
  a.write(0);
  delay(3000);
}

Can you post your actual circuit diagram?

I just forgot put the Arduino GND pin to the extenal power source.