Control 2Amper Load with arduino pin 3.3V

Hello guys, hope you'r doing great,
Im looking to control a load that can work up to 2 ampr with a pin arduino 3,3V

The idea is to cut OFF/ON the voltage from the load
so It's connected to a battery 3,7V nominal,
i found this schematic and i am searching for right transistor and the diode reference,
any advice,
i will apreaciate your help
thank you

Sans titre

Diode goes across the load, only needed if the load is inductive (in which case its essential). Where did you get that schematic, Instructables perhaps? (in joke).

For 2A you'll need a darlington or MOSFET to get enough current without overloading the Arduino pin. With a Darlington you can just use a 560 ohm base resistor or so, with a MOSFET 220 ohms gate resistor, and 10k on the gate to ground to stop it conducting during reset/power cycling.

hey Mark :D, first thank you for the reply
Can you tell me how to choose the right Darlington transisotor that can support 2amp emetter collector...

It's worth going for higher current. E.g. search for "darlington transistor 5A". There are loads including the old favourite TIP120. But I'd use a MOSFET.


Don't omit the base resistor. You need to limit the current from the Arduino output pin.

Yes thank you

TIP120 is good one 5A it will be controlled with 3,3V ?

Yes, 3.3V will turn it on. Again, use a base resistor that saturates the transistor, but doesn't blow out the Arduino output. Your diagram shows no base resistor.

A Darlington does not fully saturate, so at 2 amps some heat will be generated. A mosfet shouldn't have that problem to the same degree. I agree with slipstick that a mosfet is the better choice.

Hi, @mimito
Welcome to the forum.

What is the 2A load?

Thanks.. Tom... :grinning: :+1: :coffee: :australia:

So as everyone points out, the "right Darlington" is a logic-level FET.

For controlling a 3.3 V circuit, a Darlington is a really bad idea! (I think most people missed the actual supply voltage you mentioned in saying the FET is merely the "better" choice". :roll_eyes:)

:smiley: 2Amper load mean that he load work up to 2Amper

Mosfet is a good choice too , i found that ao3400 is good one

But what is it;

  1. Motor
  2. Lamp
  3. LED
  4. Relay Coil
  5. Solenoid

The type of load can make a big difference to switching devices.
Tom... :grinning: :+1: :coffee: :australia:

Oh the load is a module GSM GPS

So you want to low-side switch a GSM module powered from 3.7V? You realize it then has all its input and output pins held at 3.7V, which could be bad news for whatever its connected to.

Its much more usual to high-side switch subcircuits like this so there's a common ground.

Also doesn't the module have a power-down mode anyway? It might be as simple as controlling that.

This is why we ask people to explain the complete problem right at the beginning.

Yes it have a powerkey pin but it still a software on/off pin , so iam trying to make a sure hardware cut off of power,

This is a nice advice, cuz i only need to cut of the power when the module is no more responding
I think i need a p mosfet

Do you know how to control a GSM module?????
Just applying power will not make it send a message.
Before worrying about powering the GSM, PLEASE get the hardware together and at least write code to prove you can communicate with it and how to get it to send something.

That circuit in post #20 will short the battery out if you activate to Arduino pinout, can you see that?

In fact the 3.7V Lipo will probably blow the BJT off the PCB?

Can you please tell us your electronics, programming, arduino, hardware experience?

Tom... :grinning: :+1: :coffee: :australia: