The ELL-i Hackathon was my first experience with the ELL-i platform, and my second experience with an Arduino-based system. I come from a software development background, so in the morning, when the Hackathon started, I had no idea about what the icons of the diagram shown below tried to tell me or how that could be represented in a protoboard. Building this and making it work was my goal for this Hackathon.
The circuit diagram
I first walked around the tables and found a team that was speaking in English, so I joined them. They had different levels of experience in electronics and software, so that was good as we could support each other. I started by collecting the parts for the LED driver we wanted to build, and got an ELL-i board for me. I opened the development environment that I installed and tested beforehand and wrote my first program that I found around the internet to turn on a LED. Basically, a digital output of 3.3 Volts on one pin. I remember from my previous studies that someone told me that you should not connect a LED directly to the board because the LED has almost no resistance and can burn. So you should also have a resistor, and that was pretty much all I remembered about electronics.
I also knew that something like PWM existed and it was used to turn on and off the 3.3 Volts of the pin very fast to drive servos, motors or to dim LEDs. This was important to know for the LED driver, as it basically takes the voltage down by turning on and off a transistor very fast, that is like a light switch.
I found among the parts available for the participants a small LED light that was already wired to a resistor, so I guessed that was what I needed. I connected the LED to the corresponding pin, the other side to ground and loaded my program….. And nothing happened… Then I remembered another thing about LEDs: They have a direction, so the long leg must go on the side of the board pin. I wired it the other way around now, turned it on and finally I had a small LED on! I was very happy of this achievement and looked at my table companions that were already building complex circuits, so after loading a new program to blink the LED on and off and seeing that it also worked, I started building the circuit.
We had a tutorial in the morning that explained the icons of the diagrams and how the whole circuit worked, so I already had identified the pieces I needed and in what part of the diagram they had to go and what the whole idea and objective of it was. I started following the instructions to build the circuit part by part and test it, so I built the first part and it seemed to work. You should have checked it with an oscilloscope, but I never understood how to really use it, especially the portable one we had on our table, so I just checked with a voltmeter and using the small LED to see if I was getting the desired behaviour.
It was all working as expected, so now was the time for the truth. The ELL-i boards gets about 50 Volts from the ethernet port using power-over-ethernet. I was using only the power from USB of 5 volts to test that all was working, so now it was time to wire the 50 volts to my circuit and see if something burnt. While I was doing this, one of the protoboards that someone was using on my table started smoking, a resistor was blown. I was hoping that this would not happen to my circuit as I would have to start again. So, I plugged it in and… no smoke! that was good! And I put my voltmeter on the other side of the circuit and I was getting around 13 Volts, so the whole power switching thing was working! My 48 volts were down to almost 12V, that I needed to turn on the Power LED!
Now we were all hungry, so together we walked to have lunch and spoke of several things including ELL-i, Finland, other electronics projects and what each one had as a background. This was a nice break to reload energy and get to know better the people I was working with.