Servo only working with Arduino(Nano) Onboard 5v supply


I am trying to power my towerpro MG995 servo using an external regulated 5v supply. The external supply is regulated with 7805 regulator.

The problem I am facing is that the servo responds when i power it with the arduino on-board 5v supply, but dosen't work using the external supply.

I checked that the output voltage of the regulator as 4.88vdc. I connected the GND terminals as well with the GND of the external supply. I have tried the same using a 6v battery as well. Same results. It just dosen't respond to it.

Please help.

Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.,148850.0.html then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Can you post a picture of your project so we can see your component layout?

Thanks… Tom… :slight_smile:


I have attached a hand drawn circuit diagram which i used. Sorry couldn’t give you an actual picture of the setup this time. I will try to upload once i redo the circuit.

Thank you.

Image from Reply #2so we don't have to download it. See this Simple Image Guide


Your diagram is great - much better than a photo of the hardware.

You don't have any capacitors either side of the 7805 - see the datasheet. I always use them but I don't know if they are essential.

Are you getting 5v from the 7805?

Assuming you have all the GNDs connected I don't see anything else that might explain why the servo won't work.



I did have 10μF capacitors either side of the regulator. Also I am not getting exact 5v as you ask. The exact voltage was 4.88vdc.

I checked the spec sheet for the servo and it mentioned 4.8-7.2vdc. I am not sure if that little voltage difference is the root cause.

Also I am not getting exact 5v as you ask.

I only meant approximately 5v.

4.88v seems to be within the spec for a 7805 and should easily power the servo. The ones I have work with 3 x AA cells (4.5v).

Maybe try a battery just in case the 7805 is faulty.


You need at least 1000uF across the output of the rectifier to smooth the pulsed DC.

Put your DMM in AC volts mode and measure the input volts and output volts of the 5V regulator.

Tell us what it reads.

Thanks.. Tom... :slight_smile:

Just to make sure: do you have the Arduino ground connected to the servo ground?