Arduino 5v to 12v driver switch

Arduino 12v interface

Last Updated on March 11, 2022

Arduino 12v interface – 5v to 12v switch

If you tinker with Arduinos, then chances are you need an interface to convert the low voltage outputs to 12v to drive a device. This circuit describes a Darlington pair that switches a nominal 12v VCC. The choice of the final switching or output transistor determines the current (Ic) that is supplied to the downstream device.


I first used this circuit in the VK3RST beacon. It was used to switch the GALI-84 driver which only drew a few milliamps. It’s quite a robust circuit and can easily be adapted for higher current applications. An Arduino 12v interface like this will become a commonplace in your projects.

Arduino 5v to 12v switch
Arduino 12v interface

Bits Required

Parts list

2 x 4K7 .25w resistors
1 x 22K .25w resistor
1 x 680R .25w resistor
1 x 293904 – Jaycar
1 x 2N3905
1 x LED
1 x Breadboard – Jaycar

Benefits or advantages of Darlington transistor

A Darlington transistor or simply Darlington pair is mainly used to offer a very high current gain even with a low base current.

Darlington pair has several advantages as compared with a standard single transistor. Some of them are

  • It produces a very high current gain than a standard single transistor
  • It offers a very high input impedance or good impedance transformation that can alter a high impedance input or source to low impedance load.
  • These can be made by two separate transistors or come as a single package.
  • Easy and convenient circuit configuration as few components are used.