# How to use Arduino to control the switch on a 4.5v circuit

I've been building a wall mounted lightsaber using the below board.

At the moment the switch is turning it on and off, however I want to automate this with an Arduino.

Can I use a digital output pin to act as the switch and connect the Arduino ground to the ground on my board?

My power source is a 2amp 4.5v DC. The Arduino would plug into the USB on the same AC/DC adapter as this board.

Thanks!

• Use a logic level FET with heatsink or rated for >15A – Sunnyskyguy EE75 Jul 14 '18 at 22:03
• what does the existing switch look like. how much voltage do you measure across it, how much current through it when activated? – Jasen Jul 14 '18 at 23:20
• Use an optocoupler , it will be nice , easy and safe. – seccpur Jul 17 '18 at 14:53

Spectra V2 seems to be a microcontroller based LED light-show controller with a soft power button.

As such the button input only uses a very small current, if you connect a 5V arduino you should be able to use a digital IO directly,

set the arduino port output low and set the direction to input, when you want to trigger the button input change the direction to output

|You can probably use the the same 4.5V supply to run both the arduino and the Spectra. 4.5 is an acceptable VCC voltage for arduino.

• This is what I am trying, however there is a large current running through the Spectra, around 2-3amps. Will the Arduino be okay with this? – LVLYXL Jul 15 '18 at 10:18

Just use a 3.3v or a 5v microrelay and replace the switch with it. These types of relays can directly be controlled (and powered) with arduino itself as they don't draw much current.

The relay would ensure that the connection is external and it can easily handle upto 10-12A of current with 20-30V.

If required connect the relay through an amplifying circuit such as transistor or opam.