Here we are mid September, and already we can see Autumn on the horizon. The leaves are starting to fall from the trees, the evenings are getting colder and the suns rays begin to deteriorate earlier and earlier; all the signs that summer is drawing to a close. But in hindsight, its been a very productive and successful summer at the lab.
I have completed a large number of projects, more in such a short space of time than I have ever before. And most importantly, I have managed to finish those projects I started years ago that had only been collecting dust on a shelf, discarded until I had the time and funding to complete them.
And even though I have not completed everything I set out to achieve this summer, I am happy with what I have done and am actually looking forward to a bit of a break from hands on work for a short while.
Unfortunately I have not managed to document every project I have worked on this summer, but the vast majority have been captured on film and uploaded to my Halfcorp YouTube channel in the form of showcase videos which you can find and watch at your own discretion here:
Alas, I have to go back to university now so further documentation cannot continue until I return. But rest assured, when I do return, the projects will continue, they will be bigger and better, they always are!
Until then, spread the word and the video links to anyone who might be interested in my shenanigans. Catch you all in a few months time.
Tuesday 11 September 2018
Advanced Power Monitoring System
For as long as the lab had been an idea in my head, a power monitoring system was also. The premise for this project is simple: a system that monitors the power entering the lab and displays it on a screen on the power cabinet. And since I have finally had a load of time in the lab, I have designed and built that very power monitoring system and its more advanced than any other on youtube.
Simply put, my power monitoring system is the most advanced there is, not because I'm egocentric, but because it measures every possible piece of data you could want to measure on the power flowing into the lab. It measures:
Voltage
Current
Power Factor
Phase Angle
Apparent Power
Real Power
Voltage and current are a given, but I have also decided to make the system measure power factor. The reason for this is because, voltage times current does not tell the full picture of power.
For a detailed explanation of power factor and phase angle, see a proper video but here is the basic principle. Power in a DC circuit is calculated by multiplying voltage and current, in AC its more complicated. When reactive loads are placed in an AC circuit, the voltage and current sine waves become out of phase as current either leads or lags voltage. This means simply doing RMS voltage times RMS current does not give the correct value for power. Proper measurements can be derived using the power factor.
The cosine of the phase shift between the two wave forms gives the power factor. Current times voltage results in a measurement called the apparent power; apparent power multiplied by the power factor gives the real power. The difference is known as the reactive power.
My system is more than just a simple voltage current monitoring system since it records the power factor by measuring the time difference between the zero crossing of each wave form enabling the system to measure and calculate all of the different power values.
Despite this, current is arguably the most important and useful parameter to measure as it allows me to see the current a project or a particular set of systems draws. The other parameters will not be used much but it is still handy to have them recorded.
The main purpose of the project was not just to present the power consumption of the lab on a screen but also as a learning experience to expand my Arduino and programming skills. This project was actually very multifaceted as it involved electrics, electronics, programming and mathematics/data processing. And at the end of the day, it was fun to do and an achievement.
The hardware required for this project is quite extensive. Current transformers were used for current monitoring, a step down transformer was used for voltage and multiple IC chips, diodes and potential dividers were needed for all the rest. Not to mention the the OLED screen for presenting the data, numerous wires/cabling as well as the Arduino Nano that sat at the heart of it. All of this took up a lot of room, luckily there was a lot of room left in the power cabinet to facilitate this.
Here is a view of the cabinet before the instillation of the power monitoring system. The empty space is ample to contain the power monitoring and backup power systems that would soon be added.
Testing and refining of the circuits happened outside of the cabinet. Once I had the system working as I intended it was mounted inside and wired up to the labs power supply. My new mini oscilloscope was instrumental in the completion of this project and has convinced me to get a much bigger and better one in the future.
The components were mounted inside the cabinet and a long USB cable was used to program it.
Finally, I programmed the system to display all of the relevant information on the small yet versatile OLED screen.
Observant viewers will notice information pertaining to a backup battery, this is for the backup power system which will be explained in the next post.
Mistakes were made in the construction of the project, it took me three attempts at making the primary circuit board as parts kept breaking!
The system had to be carefully calibrated in order for it to turn the recorded value into meaningful voltage and current values. This was done by placing a dummy load on the system and measuring values at incremental power consumption. Graphing and regression analysis could then take place to determine the constant of proportionality needed to obtain the true values. It should be noted the system isn't perfectly accurate but functions well enough for anything I need and can be improved further if needs be.
Once the server is set up in the lab, the data will be recorded and logged. This data will then be able to be viewed in a graph of power consumption. Finally, the price per kilowatt will be factored in and the electricity usage of the lab annually or daily can be calculated!
For much more information, circuit diagrams and a much closer look at the system whilst running, check out the video overview I have made on the project here:
