switching different circuit on/off using arduino

Projects General Guidance
1

Hi there,

I'm working on a project for which I'm using servo motors, temperature, pressure sensors and an accelerometer. One of the requirement is to have an automatic shutoff function where I need to power down the systems and illuminate an LED (without disconnecting anything physically) whenever a sensor value reaches threshold etc. I would appreciate if anyone could guide me on how to go about this in most simplest way.

Thank you

2

Presumably, in the event of a threshold being reached, you want to power down only part of your system (say the motors). If you power down the Arduino, you will not (easily) be able to display a LED.
What action will you take when the LED is lit ?