Arduino connected to both USB and a device that also provides(low) power??

Hello everyone, first-time arduino user here.

I have this little project where I want an arduino to control an automatic burette that I use in the chemistry lab.

This burette is able to take inputs and send outputs through a d-sub cable.

The burette itself is powered, and does provide power(0-5VDC) to the outputs to send its data.

For this project I want to connect the arduino to the burette, as well as to the computer to save the results. (see diagram: |500x310 (Burette isn't analog but digital, oopsie))

Problem is, both the burette and the usb cable provide power to the arduino.

How do I wire this without screwing up my computer, arduino or burette?

On a related note, the burette's manual mentions that the outputs are 'open collector' outputs. It may be of help, I have no idea how that works.

Edit: Here is some information on the burette's I/O port.


You do not need to connect the Burette 5v to the Arduino.

Simply connect the Gnds together.

Open collector simply means it will take the pin to Gnd when it is active. This means you need to tie the input pin of your Arduino to 5v with 10k resistor and look for a low in your program.