Identifying Part

Hi there,

I am looking at buying an Motor Driver Stepper Shield (link below for reference)

I was wondering if anyone knows what the yellow PWR part is, I've looked around but don't know what it is.

Any help would be appreciated

Removable link, to disconnect (separate) motor power (screw terminal) from V-in (external power for the Arduino).

Note that this is the old v1 motor shield.
Inefficient, and only good for small toy motors.
It certainly is NOT a stepper driver shield, and shouldn't provide power for servos either.
Leo..

Tell us what you are trying to accomplish.

The part you linked is a clone of the DK Electronics Motor Shield
DK Electronics Motor Shield

The above link contains a board schematic link but I have attached a screenshot of it.
In the upper left corner, the "PWR" part (as you called it) is simply a configuration jumper.
If you can read a schematic, it will be clear to you that the jumper connects the external +12V power
supply to the Vin pin. If you know anything about the Arduino R3 board, this should ring a bell.
This is a shield. So what do you do with shields ? You plug them into arduino R3s. So what is the
Vin pin for on an arduino R3 ?
(anyone ? anyone ? ....)
It is the external power input pin of the R3 (input to the 5V regulator).
Consequently, IF you leave that jumper on, then the R3 will be powered by the +12V power supply
and will not require any other power source to run it.
Is this a good thing ? Well, maybe, and maybe not. If you have no other way to power the arduino
besides you 12V power supply then this is probably good. Is it the preferred way to do it ?
That depends on who you ask. At least 50% or more of the people you ask will say running an arduino
off 12V is going to heat up the 5V regulator. The specs say it can tolerate it but the regulator will run
hot. This may not be an issue if there is any airflow or ventilaition. If you put it in a sealed box with no
airflow there is a chance the 5V regulator will get so hot it will shutdown.
Choose wisely, Grasshopper...