Corrective Action

Well, I did not disappoint! As of last Friday (3/12) I was about 95% done. All I had left was to adjust timing a little for my buzzer and put the code onto my board. But, today I went to lab with the intent of only being there for a few hours... I was sadly mistaken. As intended, I was able to finish developing my C code that runs on the Nios CPU that I have developed. I was also able to program my hardware code such that, when the device is powered on, the FPGA will be automatically configured.

When I began running my project without a USB cable connected, the board would power down (slowly) after only 30 seconds of being on, not an intended feature! This slow and consistent death of my project pointed to only one culprit, the power regulation board. Before anyone begins to worry, all of my hardware is still fully functioning, including the power regulator. In fact, the the well being of my hardware is thanks to a built-in feature of the regulator, where it will shutoff if it becomes too warm. This excessive heat can be caused by a small number of things, and in my case it was simply due to a lack of cooling.

As it turns out, I made a small error in calculations. Instead of dissipating only about 0.3 Watts of heat (which is not much to worry about), the regulator was producing 3 Watts (definitely something to worry about)! A simple recalculation shows this:

12.5 V in - 7.5 V out = 5 V dissipated by the regulator
The system draws about 600mA's from the regulator
5 V * 600mA = 3 Watts

In order to fix this, I had to add a heat sink and a couple fans, not really a big deal by the sound of it. Unfortunately, to do this required moving the power supply to a new location where a fan could directly point at it. Also, I now need to make not one hole, but two, to accommodate the fans and create airflow.

This ordeal has set me back a day, and my project is currently in pieces due to the remodeling of the package. I now plan to spend a significant amount of time tomorrow finishing the remodel and completing the project. I have to have it all done by Thursday of this week (3/18) as I have made plans to go to the range and test it out.