Intro to Physical Computing

Basic Things.

This is how a breadboard looks like inside.

Abbreviations

V : Volts
A : Amperes
W : Watts
mA : miliAmperes
VA : Volt Amperes
VAC : Volts AC
VDC : Volts DC
DC : Direct Current
AC : Alternating Current

Components

Conductors are materials through which electrical current moves freely.

Insulators are materials which prevent the flow of electricity.

Resistors resist, but do not totally block, the flow of electricity. They are used to control the flow of current. Current can move either way through a resistor, so it doesn’t matter which way they’re connected in a circuit. They are symbolized like this:

Capacitors store up electricity while current is flowing into them, then release the energy when the incoming current is removed. Sometimes they are polarized, meaning current can only flow through them in a specific direction, and sometimes they are not. If a capacitor is polarized, it will be marked as such on the diagram. Don’t wire a polarized capacitor backwards; it might explode.

Capacitors are symbolized like this:

Diodes permit the flow of electricity in one direction, and block it in the other direction. Because of this, they can only be placed in a circuit in one direction. They are symbolized like this:

Light-Emitting Diodes (LED’s) are special types of diodes which emit light when current flows through them. They are symbolized like this:

There are many other types of components which you’ll come across:

switches control the flow of current through a junction in a circuit:

transistors and relays are switching devices:

thermistors change resistance in reaction to varying temperature;
photoresistors change resistance in reaction to varying light;
flex sensors change resistance in reaction to being bent or flexed;
piezoelectric devices create a varying voltage in reaction to slight changes in pressure.

Lab: Electronics and using a Multimeter
Sep 1, 2025

I accidentally miswired the 5-volt voltage regulator. I connected the power supply’s positive lead to the Output pin instead of the Input. The LED still lit up, but the regulator quickly became very hot. Using a multimeter, I traced the mistake and confirmed the problem. It was a good reminder to always double-check pinouts before powering the circuit.

This is time I wired correctly.

Lab: Switches
Sep 1, 2025

This went very well.

Lab: Digital Input and Output
Sep 8, 2025

Lab: Tone output
Sep 20, 2025

In this lab, I learned how to create Notes in Arduino which I didn’t experienced before.
At first, I use soldering machine to connect wires with my speaker. Then, I use 3.3v for the power-in, but the number on multimeter was not my expectations. Somehow, I got the expect number, near 5V on multimeter, when I use the VIN pin for power-in.

Lab: Servo motor control
Sep 20, 2025

In this Lab, I learned how to use Force Sensitive Resistor (FSR) to trigger the servo.
Based on last week class, it’s necessary to make sure the original map range is same as the range from serial monitor.

On the first video, I test the output of FSR on serial monitor, then I got the data from the range of near 0-980. Then I applied this range to the map in my code, and the result went well. But here is one question: When I press slightly and keep hold this FSR, the servo would spin back and forth, WHY?

Still figuring out the creative part...

Lab: Sensor Change Detection

Sep 28, 2025

Midterm experiments

Sep 29, 2025

This week I processed my first naive idea for midterm.
I want to build a hand that do the “🖖” & “🖐️” when people are paying attention to it. There’s a camera to detact people’s face.

After the day of my first prototype came out, I talked to Tom about my idea, and the feedback is: You can’t tell a person is paying attention if there’s an actual action. Means: If the person is looking at it or staring at it, you don’t know if they’re actually paying attentions on it.

Which makes me to reconsider my midterm idea.

Lab: Transistor and relay lab

Oct 5, 2025

Learnt about DC.

DC means Direct Current: electricity that flows in one constant direction.

What’s the difference between DC motors, RC servomotors, and stepper motors?
-Key differences in practice:

DC motors: simplest; you vary voltage to change speed and reverse polarity to change direction. Need a driver (H‑bridge) and protection diodes for back voltage.
RC Servomotors: you command a target angle with pulsewidth; they include gearing and position feedback, so they “go to” and “hold” positions without external sensors.
Stepper Motor: you move in exact steps by driving coil sequences; excellent for repeatable positioning, usually open‑loop (no internal feedback), and require dedicated stepper drivers.

Lab: Controlling a DC Motor with an H-Bridge

Oct 5. 2025

My proudest part of the week:

My process of soldering the motor driver went very well at first, but I don’t know why the angle of the pins changes when I take the driver off the breadboard. I tried to melt the solder and imagined gravity could do the work, but unfortunately I failed. I thought I would probably need to buy a new one. Then I thought maybe the solder sucker could work. Ceren doubted me at first, but I insisted. I added more solder on the top and used the sucker to extract from the bottom—and it worked!

(I’ve been there before)

Week5 Reading:
Just like riding a bike

Oct 5, 2025

“Intuitive interfaces draw heavily on earlier learned behavior, while unintuitive ones require distinct new skills or metaphorical connections.”⁠

The essay argues “intuitive” interfaces are learned, not innate; design for teachability.

The author challenges the myth of “natural” or “intuitive” interfaces using the metaphor of learning to ride a bike: what feels effortless is actually the result of prior practice. Interfaces exist to abstract complex systems, but they still demand users learn what can be manipulated and how actions map to outcomes. Even celebrated gestures like Apple’s pinch‑to‑zoom felt “intuitive” largely because launch ads acted as micro‑tutorials; many first‑time users still struggled.

Labeling interfaces as “natural” can erode empathy, blaming users when they simply haven’t learned yet. A better lens is ease‑of‑learning on a sliding scale, shaped by the user’s past experience and the interface’s reliance on familiar metaphors (cut & paste, file folders, stars). In short: “intuitive” means it draws on already learned behavior; “unintuitive” asks for new skills or mappings. Designers should embrace the teaching responsibility—build discoverability, clear affordances, feedback, and safe trial—because the learning curve can be flattened, never erased.

Understand Electricity

Oct 6, 2025

Theremin experiment

Oct 6, 2025

Tried to make a theremin and referred to this doc, but it uses an Arduino Uno, which is different from my Nano 33 IoT.

Built the circuit:
I was not familiar with LM358, but I still tried to understant it.

Coding:
I copied the code in the doc but two of the libraries (NewPing, NewTone) cannot being used by Nano. So I asked ChatGPT to change the library to one that works for the Nano. I uploaded successfully and got the number from my ultrasonic sensor in Serial Monitor. But the problem is I couldn’t hear anything from my speaker. I tried to troubleshoot by changing a speaker and adding a transistor to make the sound louder?, but I failed at both :(

What is a theremin?
A theremin is an electronic musical instrument controlled without physical contact by the thereminist (performer). It was patented by Leon Theremin in 1928. The instrument's controlling section usually consists of two metal antennas that sense the relative position of the thereminist's hands and control oscillators for frequency with one hand, and amplitude (volume) with the other.

click to play the video.

I tried to do it without the LM358 op-amp and lowered the resistor to 47 ohms.

it finally worked!!!

credit to Gabriel, and also Justin & Arjun who told me to try this :)