New Trend of Greeting

I was interested in making a visual image using multiple LEDs. I thought of the word “Hi”, because this is like my Hello World project in electronics.

1st step: research

I found this tutorial on Youtube: From here, I had a vague idea of having LEDs on parallel circuits. Then, I started to think about how much resistor I need, and all the calculation seems confusing. If the LEDs are in the same column because that is the image I want, then it would be series circuit, what do I do? How many LEDs can a 5V circuit support?

2nd step: try something, start somewhere

I started from somewhere I felt most confident about, which is to layout the LED in the visual form I want. It seems like some will be in series because they are in the same column, and some do not have other lights in their columns. It seems like a complicated circuit… By now, I felt I had a slightly clearer idea of the circuit but still not sure how this would work. I felt I needed a resistor, a switch, and then the circuit fans out into many parallel lines.

3rd step: more research, ask someone, find solutions for each problem

I asked an ITP friend, Chengchao Zhu (CC), for help. We realized that we might need many jumpers going everywhere, and the LEDs might even be covered underneath jumpers. To achieve better visual installation, our solution to this problem is to bring in another breadboard. An important thing I learned from CC is utilizing power rails. All LEDs connect directly from the power rails of the other breadboard. I also learned that the four pins of a switch cannot be connected to each other in the same column. Also, to connect a switch, I need to connect its diagonal pins. Why is that?

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After making these LEDs work, I started to realize that I had an impulse to say hi to people using this installation. Although it was difficult to carry around, this could be an alternate to greet people without verbalizing. There is actually one LED that did not light up. I realized that column was not working. Was it about the breadboard? How do I troubleshoot that? This was also the limitation of this circuit: it was not easy to change it around because I would need to move everything.