Debugging the Arduino Motor Shield

Our L293 based motor shield has some problems! How do we diagnose what the problem is and create a better design? Our first article in this series described how we designed our prototype UNO motor shield (Figure 1).

Designing your own Arduino UNO Motor Shield

The second article explained how we wrote an Arduino library to use the shield.

How to create your own Arduino Library

This final tutorial (hopefully), will explain how we went about troubleshooting the issues and creating a better circuit to be used in version 2 of our design.

Figure 1. The Reefwing UNO Motor Shield (version 1.0)

The Problem

The issue we have with the current design, is that with the battery and motors connected, the Arduino 5V regulator switches off and the UNO has no power. The shield and UNO work correctly when both the battery and USB is connected simultaneously.