Hello internet friends, this week was my sixth working in Columbia University’s Plasma Physics Laboratory, and the project is definitely nearing completion. On Monday, I was able to get my frequency-to-voltage chip working the way I need it to, which means that for all the frequencies of the rotating plasma, a different voltage will be fed to the microcontroller, which will then tell a digital potentiometer what value to assume. This was a good start to the week, but on Tuesday I ran into a snag.

Somehow, I had missed a potentially harmful flaw in my previous design of the 90 degree shifter, which is essential for this circuit to work correctly and is the focal point of pretty much everything I’m doing this summer. The problem is that at higher frequencies, the signal drops off for some reason, meaning that rather than a pure cosine wave, the function starts to look like a constant is subtracted from the value of the normal function. Obviously, this would be a problem, but on Tuesday and Wednesday I was able to devise a solution through using another one of my frequency-to-voltage converters to compensate for the unexplained decrease in voltage. I also mapped out the resistances I need for a flat shift across the entire band of interest, and fitted that data to a curve.

Then it was back to the relatively unfamiliar territory of coding, where due to some help from one of Professor Volpe’s colleagues, I was able to write my own code for the microcontroller. The problem I then had to deal with was the minutia of getting the code to a point where it would be palatable to the microcontroller, but on Friday morning, the program that I wrote compiled successfully, which stunned me initially, because I foresaw this being much more of a drag than it ended up being. I am now ready to move forward with programming the microcontroller, which I will attempt to do once another part gets to the lab.

Tomorrow Professor Volpe returns from vacation, and I’m hoping to show him the prototype I made during the fifth week as well as show him my sketch of what the final circuit design may look like. Hopefully the part I need to program the microcontroller will come in soon, and I can be well on my way to completing the circuit on schedule. By the end of this week, I hope that I will be well on my way to testing the microcontroller with the frequency-to-voltage converter and the digital potentiometer, but a lot of that depends on the part I need getting here, so we’ll see. Hopefully tomorrow I’ll be able to show off my prototype, which in my opinion is a solid proof of concept, and the week will take shape from there.

That’s all for now,

Lucas

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