lecture notes + docs about electrical design and resistors

docs/Assignments/week_6_electronic_design/electronic_design.md

@@ -0,0 +1,65 @@
+# Electronic design
+
+For this week we are making a start at designing pcb's. Im excited for this week because I can finally make my own circuits instead of using unreliable breadboards. With designing I'm starting out with KiCad.
+
+
+## No symbol table
+When I first tried to start a project for kicad it asked for a symbol table. 
+
+![alt text](image.jpg)
+
+Apparantly KiCad doesn't come with it on Linux systems (I don't know about windows). So I needed to install an extra package called `kicad-library`. After that I could use the standard symbol library. Later on I also found out I needed to install the 3D-models libary. Everything of KiCad on Linux comes separately.
+
+
+## The assignment
+For this weeks assignment henk wanted us to design a pcb with at least a led, a switch and then we had a choice between a speaker and a sensor. I wen't with a speaker because I could use that for my final project.
+
+### KiCad
+I'm going to do this in KiCad because it is the only software I know thanks to the lecture on thursday. I first started out dragging all the parts I needed onto the schematic editor.
+
+![alt text](image-12.jpg)
+Using the `A` key while in this screen you can open the component selector and search for the components needed.
+
+![alt text](image-13.jpg)
+
+After that I needed to think how I wanted to connect everything. I wanted to use the switch as a power switch and the led as some sort of status indicator. wiring up the speaker is going to be the hardest part.
+
+I first started off with the easier parts. So I started with the LED. I accidentally found out when you hover click a part and press `D` you directly go to the data sheet of the part so that's a nice shortcut. 
+
+#### Connecting a LED
+When reading the datasheet I found this graph. With a relation to voltage and mAh of the LED.
+
+![alt text](image-14.jpg)
+
+If I supply the LED with 20 mA it should run at 1.8V. The supply voltage is 3.3V so.
+```math
+R = V / I \\
+
+R = 3.3 / 0.02 \\
+
+R = 165 Ohm
+```
+So I will need a 165 Ohm resistor.
+
+![alt text](image-15.jpg)
+
+This is how I connected my LED. I chose to use the MCU as a ground because Henk once explained how it's better for the MCU and that it could handle more led's or other connections that way.
+
+#### Connecting the speaker
+Now I wanna drive the speaker. But to do that we need some sort of driver because I don't think the mcu's has enough power to drive the speaker.
+
+When searching online and on older fab academy projects I found that people everywhere use IC's to drive them. I wanted to try to make one without an IC because I have seen my friend make one when he was doing electrical engineering. When looking around online all the circuits look super confusing. For example the one on [this forum](https://www.physicsforums.com/threads/amplifier-circuit-driving-an-8-ohm-speaker.967270/) doesn't have any ground symbols.
+
+After searching for a while I found [this](https://www.instructables.com/How-to-Make-Simple-Amplifier-Circuit-Without-IC/) on Instructables
+![alt text](image-16.jpg) 
+
+The only step I needed to figure out is why it work like this and why doesn't the speaker blow up when connected because there is 9 volt on the circuit and the speaker is rated for 1 volt. I still have a lot of trouble wrapping my head around how voltage drops because of a resistor.
+
+Voltage can be seen as the speed of water traveling through a tube. A resistor makes the tube smaller for a small part so the water slows down. So the voltage drops.
+
+Resistors always cause a voltage drop. How big the drop is depends on the amount of current going trough it and the resistance (Ohm)
+
+```math
+V = I * R
+```
+This is Ohms law. So to keep a constant voltage you need to make sure your current is also constant and not changing constantly. In that way you can keep a constant voltage.