I have a SIM800L GSM module like in this link, the GSM module I have.

this is the servo I have.

The problem is when I connect the GSM to my Arduino Uno the GSM turns on for a while and then turns off. I tried to connect it with a 9-volt battery and an LM7805 voltage regulator, but I have the same problem. Attached to the Arduino are an LM35 temperature sensor, two LEDs, a buzzer, an LCD, a GSM module, a gas sensor and a servo.

The other problem is with the servo. I tested the servo and it works fine but when the servo stops moving, it starts to shake. I do not know what the problem is.

  • 3
    9V batteries are useless. They are only any good at powering smoke alarms. Use a proper power supply or better batteries (6xAA or 2S Lithium Ion).
    – Majenko
    Commented Apr 26, 2017 at 22:27
  • But I used LM7805 with battery to drop the voltage down! so you recomnded to me to use one of these,(6xAA or 2S Lithium Ion).?
    – MANSOR
    Commented Apr 27, 2017 at 2:18
  • You "drop the voltage down" by throwing away about half of it as heat. The current remains minuscule since the battery can't provide much (which is where your problem lies). You either need a source that can provide more current (6xAA or 2S Li-Ion) or a switching regulator that can convert the excess voltage into current.
    – Majenko
    Commented Apr 27, 2017 at 9:51
  • Hi Majenko.. i used 6xAA but it is still did not work i donot know why, if u know other way to produce 3.5v and 2A let me know because i think my problem in the current .
    – MANSOR
    Commented May 2, 2017 at 18:35
  • Look for a 5v UBEC from somewhere like hobbyking.
    – Majenko
    Commented May 2, 2017 at 19:36

1 Answer 1


You SIM800 module will pull 2Amps when its transmitting. If your servo is also trying to overcome the inertia at the start of a movement it will pull 4+ times its normal running current.

A 9 volt battery will let you pull a couple of hundred milliamps. So when the GSM transmits you system will shutdown.

You need a proper power supply or a battery pack that can put out these levels of peak current (3+Amps)

  • What did you mean by battery back ? And if i got it how can i connect it and connect it to what? I'm afriade of u because i did not understand it.
    – MANSOR
    Commented May 2, 2017 at 18:42
  • A battery pack, like 4xAA batteries or 2x3.7vLipo, etc. You are going to power source that can deliver a peak current of 3Amps or more at 5V. To start with it will be cheaper to use a plug in power source, once you have verified that your system works you can try and find a "battery pack" that will deliver the current you need. Commented May 3, 2017 at 7:19

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