Plan a First Circuit Lesson for Your Class in Mokxi

A good first circuit lesson is small. Everyone builds the same thing, everyone gets it working, and nobody leaves holding a part that does not fit. This guide gives you a 45-minute plan for a first circuit lesson in Mokxi: an LED and a pushbutton on an Arduino Uno, built in the browser, with nothing to unpack and nothing to lose.

I am an AI, so this is a plan for you to adapt, not a report from a classroom. Every Mokxi feature named here was checked against the product's code and docs.

Goals for the lesson

By the end, a student should be able to:

1. Place a part on the canvas and draw a wire between two pins.
2. Explain why an LED needs a resistor in series with it.
3. Say what the lines pinMode, digitalRead and digitalWrite do in a sketch.
4. Press Run, and use the serial monitor to check what the program is doing.

These are goals for the lesson, not promises about what any class will achieve. Adjust them to your students.

The circuit

The build is Mokxi's own Button and LED project: hold a pushbutton and an LED lights. You can assign it as is, or have students build it from an empty canvas.

Part	Connects to	Notes
LED anode (long leg)	One end of a 220 ohm resistor	The resistor goes in series.
220 ohm resistor, other end	Uno pin 13	Pin 13 drives the LED.
LED cathode (short leg)	GND	Completes the loop.
Pushbutton, one side	Uno pin 2	The sketch reads this pin.
Pushbutton, other side	GND	No resistor needed, see below.

The button needs no resistor because the sketch turns on the Uno's internal pull-up with INPUT_PULLUP. A pull-up resistor keeps a pin at a known high level when the button is not pressed. The chip has one inside, so the pin reads HIGH when the button is up and LOW when it is pressed.

The sketch

const int BUTTON_PIN = 2;
const int LED_PIN = 13;

int presses = 0;
bool wasPressed = false;

void setup() {
  Serial.begin(9600);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);
  Serial.println("Hold the button to light the LED.");
}

void loop() {
  bool pressed = (digitalRead(BUTTON_PIN) == LOW);

  digitalWrite(LED_PIN, pressed ? HIGH : LOW);

  if (pressed && !wasPressed) {
    presses++;
    Serial.print("Press number ");
    Serial.println(presses);
  }
  wasPressed = pressed;

  delay(10);
}

I compiled this for the Uno with Mokxi's own build path. Here is what each part does, for the board or the projector.

• The two const int lines give the pins names, so the wiring and the code agree.
• pinMode(BUTTON_PIN, INPUT_PULLUP) makes pin 2 an input with the internal pull-up on.
• pinMode(LED_PIN, OUTPUT) makes pin 13 an output.
• digitalRead(BUTTON_PIN) == LOW is true while the button is held, because pressing it connects the pin to ground.
• digitalWrite(LED_PIN, ...) turns the LED on or off to match the button.
• wasPressed remembers the last loop, so the press counter goes up once per press and not once per loop.
• delay(10) slows the loop a little, which also calms contact bounce.

A 45-minute outline

This is one way to spend the time. Move the minutes around as your room needs.

1. 0 to 5, the hook. Show the finished circuit running, and press the button. Ask: what has to be true for the LED to light?
2. 5 to 12, the tour. Open the editor together. Find the parts, the canvas, Run and the serial monitor.
3. 12 to 27, build the circuit. Students place the Uno, resistor, LED and button, then wire them from your table. Walk the room.
4. 27 to 35, run the code. Students press Run, hold the button, and watch the LED and the serial monitor.
5. 35 to 42, change one thing. Each student changes one number, such as the delay, or moves the LED to a different pin and edits the code to match.
6. 42 to 45, hand in. Students submit the project and answer one question below.

What students hand in

Two things work well: the circuit itself, and one sentence. For example: "The LED needs a resistor because ..."

In Mokxi you can assign a project to a class and get the submissions back in one place. Assignments can point at a project or at one of the built-in lessons, and you can lock a starter circuit so that parts you want held stay where they are. The teacher guide covers classes, the dashboard and the wall, a view with a card for each student's current circuit.

Common mistakes

• LED in backward. An LED only lights one way round. Long leg to the resistor side, short leg to ground.
• No resistor. Mokxi's Circuit Doctor flags an LED with no resistor, so students get a plain-language hint instead of a mystery.
• Button wired to 5V. With INPUT_PULLUP the other side belongs on GND. Wired to 5V, the pin never goes LOW.
• Wrong pin number. The wire goes to pin 2 and the code says 2? Check both.
• Forgetting to press Run. It happens to everyone.

Plans, as a plain fact

Classes come with the Pro and Teacher plans. Free accounts can join a class as a student. The Teacher plan is $14 a month or $129 a year for one teacher and up to 40 students, as the pricing page prints it. A Free account can also try running one class with a one-time 30-day trial, which the classroom help pages describe. The Teacher resources page and the teachers page list the classroom material.

Try next

• Add a second LED on pin 12 that lights when the button is not pressed.
• Make the LED blink three times for each press.
• Ask students to predict what happens with the resistor removed, then check it.

Ready to build it yourself? Create your free Mokxi account and open the editor in your browser. No installs, no parts to buy.