Cyberscann54

if you are going to use this with a raspberry pi you will use the 3v circuit without the LED and 47ohm resistor or you can keep it as is with the LED and resistor. if the pi is powering the circuit you can attach a wire between the collector of the transistor and the LED and put it on one of the input pins and you can put a resistor in the input wire to ensure the maximum current going to the IO pin don't exceed 16mA

so is the button to be activated when a liquid product gets low if so this sensor circuit won't work. what is the dash button doing ordering a product or some modified use i will create a circuit to fit your needs to work with the button

To better help you what does the button do. What does it turn on or off. Is it in series(a switch wired in line with the + or -) with a pump is it a button of a control board(circuit board). Depending on this it could be as simple as an other transistor or a Mosfet transistor (can handle more power) or a relay switch (a lot more power)?