Motor Shield not giving full power, LED DIMS

Question

I have an Adafruit Motor Shield, the V1. I have been using this thing with my OPSEPP Uno and a stepper motor with no issues. (Powered by 12v DC wall wart [CASIO]).

My question, or issue, not sure yet, is this:

Why when I connect my motor directly to the 12v power supply it operates efficiently (for my purposes) and when I run it through my Arduino with the Adafruit Motor.h library does it not power the same.

Basically on direct connection it works fine, but I want to be able to regulate the connection and reverse it, change the speed, etc.

It is possible I am utilizing the library or the board wrong.

Can someone indicate why the power or, torque seems to drop when through the board. I have tried all KHZ all speeds etc, no way to get the same 12v power directly and modulate it?

Answer 1

According to the Adafruit page the V1 version of the shield is not as powerful as their V2 version.

Where is the 12V coming from to get to the shield? There isn't really 12V broken out on the Uno anywhere. If it comes from V_in then there is a 0.7V drop through the reverse polarity protection diode. Plus, the tracks on the Arduino board may not be thick enough to provide enough current.

It looks like the shield may take an external power source (it is hard to tell because they discontinued it). You could try using that.