Here is the wiring diagram... Notice that there is a single power supply.

https://synthiam.com/uploads/motor-634669130571562500.jpg

I need to know how to wire it with dual power supplies, one for the ez-b and the other for my motors

Don't quote me on this as I haven't seen the schematic for it but I would assume that VCC & Ground which come from the battery would be taken from Supply #2 (Supply #1 being that for supplying the EZ-B). AFAIK that is how they generally work.

Let me put this a different way...

Is it possible to use two separate power sources with an h-bridge?

Specifically, I want my motors to be driven by a 7.2V power source while my ez-b is controlled by a 12V power source.

If I wire them using below diagram, I would be feeding 12V into the h-bridge. The problem is, I'm not sure the little motors in my OWI-535 robot arm can handle 12V but I'm pretty sure 7.2V will be okay.

https://synthiam.com/uploads/motor-634669130571562500.jpg

Does my question even make sense?

Okay...

So where is the ground connection for the EZ-B?

Connect the GND from the EZ-B Battery to the ground from the L298N Battery

I guess I need to brush up on my electronics.

I was afraid current might flow the wrong direction if I did that because there would be potential between the EZ-B ground and the 7.2V battery ground.

I guess I need to break out my multi-tester

Please keep one thread per topic.

Again, the answer is connect the GND of the two batteries together. That is the answer to your question

Also, the EZ-B does not require 12v. You can simply connect the EZ-B to the same power source as the motor and not need two power sources

Cool thanks a lot!