Skip to content

Transistor Driver and Dimmer Circuit

Run the Transistor Driver and Dimmer Circuit MicroSim Fullscreen

About This MicroSim

A p5.js circuit diagram with two side-by-side panels, selectable via tabs:

Learning objective: Applying - the student can trace current flow through a transistor driver circuit and predict the LED brightness given a duty cycle.

How to Use

Use the on-screen controls - buttons, sliders, dropdowns, and clickable regions - to explore the idea. Every change updates the canvas immediately, so you can predict an outcome and then check it.

Iframe Embed Code

You can place this MicroSim on any web page by adding the following HTML:

<iframe src="https://dmccreary.github.io/moving-rainbow/sims/transistor-circuit-diagrams/main.html"
        height="402px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Grade Level

Grades 6-12

Duration

10-15 minutes

Learning Objective

Applying - the student can trace current flow through a transistor driver circuit and predict the LED brightness given a duty cycle.

Activities

  1. Explore (5 min): Open the MicroSim and try every control. Notice what changes on screen.
  2. Predict (5 min): Before each change, predict what will happen, then test your prediction.
  3. Discuss (5 min): Explain the idea in your own words and connect it to the LED code in Chapter 16.

Assessment

Ask students to describe, in one or two sentences, the relationship the MicroSim demonstrates and how it shows up when programming the LED strip.

References

  1. Chapter 16: Circuit Assembly — Resistors, Transistors, and Circuit Types - the chapter where this MicroSim is used.
  2. Moving Rainbow Intelligent Textbook - the full course this MicroSim belongs to.
  3. MicroSims Reference - the standards behind these interactive simulations.

Original Specification

Full specification used to generate this MicroSim 
Type: interactive-infographic
**sim-id:** transistor-circuit-diagrams
**Library:** p5.js
**Status:** Specified

A p5.js circuit diagram with two side-by-side panels, selectable via tabs:

**Tab 1 — Transistor Switch:** Shows a 2N2222 transistor schematic with labeled Base, Collector, Emitter. Connections shown: GP0 → 1kΩ resistor → Base; Collector → 220Ω resistor → LED → +5V; Emitter → GND. A toggle button labeled "GP0 HIGH / LOW" animates current flow (glowing arrows) and lights/dims the LED symbol. Clicking each component shows a tooltip: "1kΩ limits base current to ~2 mA", "220Ω limits LED current to ~14 mA", etc.

**Tab 2 — PWM Dimmer:** Same circuit but the toggle becomes a PWM duty cycle slider (0–100%). As the slider moves, the LED symbol changes brightness proportionally. Canvas: 700 × 400 px. Responds to window resize.

Learning objective: Applying — the student can trace current flow through a transistor driver circuit and predict the LED brightness given a duty cycle.