Hyy actually i have 5 pieces of sg90 9g microservo and i want to control it through external power source without powering it directly through arduino uno..
So pls suggest any power supply source that can supply power to servo for full torque
Its pretty simple, actually.
Online datasheets refer it needs around 550 miliamps, so 550*5=2750miliamps or 2.75A at 5 volt. You need atleast a 5v 3 amp supply. You could do with 2.5A, even 2A depending on how much torque is needed. But if you want the full potential power, then a 5 volt 3 amp supply does the job.
You cant, and shouldnt ever power a servo directly from arduino. Servos are pretty much sophisticated, just couple the grounds of the circuit and thats all you need.
Another option is, you can use a buck converter (heatsink maybe required). To stepdown the voltage from a more common source
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The relevant servo parameter is the stall current, which the servo draws every time it starts up (as well as when stalled). The manufacturer states the SG90 stall current to be 650 +/- 80 mA, so call it 750 mA for a safety margin.
Your power supply needs to be capable of providing at least 750 mA times the number of servos that will be moving at once.
theRoBobuilder:
Hyy actually i have 5 pieces of sg90 9g microservo and i want to control it through external power source without powering it directly through arduino uno..
Just as well because you simply cannot possibly "power it directly through Arduino UNO". In no way whatsoever is an Arduino a power source for anything over 50 mA - if that.
750 mA by five is 3.75 A. A little more that a typical high-end "phone charger" block. Best to use a 5 A "brick":
Maybe first you should explain just what it is you want to do overall. 
Sorry, eBay link now expired! Aliexpress search (shockingly bad search engine though) may be more productive. They don't last forever! 
Thanks for helping,
Actually i'm making a robotic hand,where its all fingers are controlled by servo(sg90) with pushbutton controll movement system..
There is also a problem with my arduino its light is so dim and when i connect a single servo with arduino is running very very slow i think my arduino board is damages, Do you know what happen with the board..
https://drive.google.com/file/d/1k4ichaaxq7d9q_T8GhGGZnINag2qj67c/view?usp=sharing
OK, so another matter is that you should not be powering the Arduino through the "barrel jack" because that is only suitable for powering the board itself with essentially nothing attached. Once you start to connect other things and attempt to use any power from the "5V" pin, you rapidly get into trouble.
You need to make a point of powering it from a regulated 5 V supply - a "Phone charger" with a USB connector powering via the USB connector is generally most suitable, or some other regulated 5 V supply connected to the "5V" pin and ground.
As to the "L" LED being "dim", I have to ask why you think it should be otherwise? This is the pin 13 indicator, it is telling you that pin 13 is not being used by your code. It (pin 13) is actually picking up general interference and the LED is actually rapidly flashing in concert with whatever it is picking up. As you see, the power indicator is perfectly bright.
The Arduino is digital. It either works at the right speed, or not at all. If it is slow, that means your code is slow. If you wish to discuss that, then that is another matter and you will have to after reading the instructions on how to do so, post your actual code.
Why dont you just measure the current (with a multimeter) under a typical load ?
Because that is not the stall current, so it doesn't help much.
Paul__B:
As to the "L" LED being "dim", I have to ask why you think it should be otherwise? This is the pin 13 indicator, it is telling you that pin 13 is not being used by your code. It (pin 13) is actually picking up general interference and the LED is actually rapidly flashing in concert with whatever it is picking up. As you see, the power indicator is perfectly bright.
Thanks sir yes pin 13 was used by my code so i changed it and now the "L" light is bright
When you apply power to a motor, it is at rest, not moving.
So, it needs extra current (power) to overcome inertia. This
surge current is the same as the stall current for the motor.
I hope this helps.
Herb
herbschwarz:
So, it needs extra current (power) to overcome inertia. This
surge current is the same as the stall current for the motor.
Stall current draw at startup has NOTHING to do with inertia. It has EVERYTHING to do with the magnetic fields inside the motor - and how they increase the impedance of the coils as the motor spins up. For the same reason the current increases with increasing load (and the decrease of motor speed).
Paul__B:
As to the "L" LED being "dim", I have to ask why you think it should be otherwise? This is the pin 13 indicator, it is telling you that pin 13 is not being used by your code. It (pin 13) is actually picking up general interference and the LED is actually rapidly flashing in concert with whatever it is picking up.
The built-in LED is powered by pin 13, so as long as pin 13 is an INPUT it won't shine. If interference makes it shine, that interference is probably strong enough to make the rest of the Arduino shine in the same colour.
Pin 13 used as servo output will make it shine dim, as a servo signal is like a very low duty cycle PWM signal.
ok so can i use this 5v 2.4amp dc mobile charger as external power source for powering 5 servo motor,
as by above discussion and suggestion by member sg90 uses 700mA stall current for full torque so for using 5 servo i need 5*700= 3.5A at 5 volt right???
So pls see the image attached of my phone charger can i directly connects its -ve & +ve with all 5 servo's -ve & +ve pins??
ok so can i use this 5v 2.4amp dc mobile charger as external power source for powering 5 servo motor
Not if all the servos are moving at once. See reply #2.
If you want maximum torque you have to increase the voltage to the maximum allowed 6V. Stall current will increase accordingly of course.
Don't load your servos too much; if they have to draw near stall current for long time (e.g. because the arm is being pushed hard away from the setpoint) they'll overheat. In that case, get a stronger servo.
wvmarle:
The built-in LED is powered by pin 13, so as long as pin 13 is an INPUT it won't shine. If interference makes it shine, that interference is probably strong enough to make the rest of the Arduino shine in the same colour.
If you refer to the Google drive links given, you will see that he is in fact using a (genuine!) UNO. Pin 13 set as an INPUT and not connected to anything will result in the LED shining or flickering at random.
wvmarle:
Pin 13 used as servo output will make it shine dim, as a servo signal is like a very low duty cycle PWM signal.
Correct. It will vary in intensity slightly according to the servo position.