We started out second session with a recap of resistors and why we use them when building circuits. Check out this video by Collin’s Lab for a succinct review of the topic. There is an awesome part at 3:30 where Collin shows how to draw your own resistor!
We also talked about Ohm’s law which states that Voltage = Current * Resistance. The following online tool can be used to draw circuits and measure the voltage, current and resistance at a particular point in the wiring. This is useful to get your head around Ohm’s law. To get started, choose Circuits -> Basics -> ‘Ohm’s Law’. You can experiment with adding different components and seeing how the voltage, current and resistance changes at different parts of the circuit.
http://www.falstad.com/circuit/circuitjs.html
We worked together on Project 4 from the Arduino starter kit, ‘Color Mixing Lamp’, which was a bit fiddley. It introduced the phototransistor, which is a component that generates a current proportional to the quantity of light it absorbed. It has a long leg (collector) which connects to the positive and short leg (emitter) that connects to the negative. We also looked at how Pulse Width Modulation (PWM) can be used to fade an RGB LED by producing a rapid On Off sequence of 5 V pulses known as a duty cycle. The circuit we created detected levels red, green and blue light in the environment using the phototransistors and lit up the RGB LED with the same colour.