Wawa:
An Uno/Mega has a reverse protection diode with an absolute max rating of 1Amp between the DC socket and V-in, so forget about powering anything that draws more than 1Amp THROUGH the Arduino.
Power for a motor driver has to go to the motor driver, and then (split) to the Arduino.An Uno/Mega on 12volt is borderline.
It could already overheat and shut down with the current of an LCD backlight.
12volt to power a small Arduino, Nano/ProMicro/etc. is a big NO.
You must drop this to a lower voltage, or power it with e.g. a 5volt cellphone charger on the USB socket.
Leo..
Great thanks for explaining that out for me.
So what would be my best option for powering the driver and the arduino via just one 12v (6-10amp?) power supply?
I'm assuming there is many ways to accomplish this, but what would be the simplest:
1. a sort of power distribution board if that exists?
2. physically splitting the power supply wires and powering the motor driver, and a step down convertor?
3. L298N H Bridge motor driver... this provides a 5v output for powering an Arduino...but only does 2A continuous output and I need at least 5amps for the linear actuator
4. Connect power supply to arduino 12v barrel jack, and split power supply somehow to also connect to motor driver?
5. Pololu 12A, 5.5-24V Single Motor Controller (https://www.robotshop.com/media/files/pdf/datasheet-1451.pdf) can this send a 5v power out to power the arduino??
5. other options?...
Thanks again for the responses, I thought it would be relatively simple to power the uno and the motor driver with one 12v power supply. But its quickly getting beyond my capabilities as I don't know what is available and I want to obviously keep this safe.