Skip to content

Moving Rainbow Wiring Diagram

Run the Moving Rainbow Wiring Diagram MicroSim fullscreen

About This MicroSim

Three wires. Power, ground, and data. Two minutes with this before a kit gets powered is worth twenty minutes of debugging afterwards.

The one that catches everybody is the data wire. A NeoPixel strip has a data-in end and a data-out end, and the little arrows printed along it show which way data travels: each pixel reads its own colour off the front of the message and passes the rest along. Wire the Pico to the DO end instead and everything is electrically fine, nothing gets warm, no error appears — and not one pixel lights. That is a far more confusing failure than a wrong pin number.

The one that gets left out is ground. When the strip has its own power supply, the ground wire back to the Pico looks redundant. It is not. Data is a voltage measured against ground, so without a shared ground the strip has no reference for what counts as a 1 or a 0, and the output is anything from nothing to flickering garbage.

And the power wire has a limit worth knowing. VBUS is the USB supply passed straight through, which is fine for a short strip. A NeoPixel at full white draws about 60 mA, so thirty of them is nearly two amps — more than a USB port will give you. Long strips need their own supply, with the grounds still tied together.

How to Use

  • Click any wire to see which Pico pin it leaves and which strip terminal it lands on.
  • Look at the arrows printed along the strip. They point away from DI, which is the end the data wire must go to.
  • Turn on Check my wiring. The labels disappear, and you are asked to click the wire that carries each named connection.
  • Reset turns the quiz off and restores the labels.

Lesson Plan

Bloom level: Apply (L3) -- demonstrate

Learning objective: Given a Pico and a NeoPixel strip, the learner demonstrates how to wire the power, ground, and data connections between them, including which end of the strip is the data-in end.

Before the session (5 min). Every mentor runs one quiz pass. It takes two minutes and it is the difference between spotting a backwards strip immediately and watching four students conclude their Pico is broken.

With students (10 min). Hand out the parts and have pairs wire it from the diagram, then swap benches and check each other's before anything is plugged in. A wiring check by a second pair of eyes is a habit worth building early.

After (20 min). Run the rainbow. Then deliberately move the data wire to the DO end and watch nothing happen — the failure is much more memorable when you caused it on purpose.

Check for understanding. Ask: "Your strip has its own 5 V supply, so you only need two wires to the Pico. Which two?" Data and ground — and a student who says "just data" has missed the reference that makes data mean anything.

Embedding This MicroSim

Paste this into any page of the book, adjusting the relative path to docs/sims/ for the page's depth:

<iframe src="../../sims/moving-rainbow-wiring-diagram/main.html" width="100%" height="502" scrolling="no"></iframe>

Specification

The full specification below is extracted from Chapter 19: Raspberry Pi Pico, MicroPython, and the Moving Rainbow Kit.

Type: diagram
**sim-id:** moving-rainbow-wiring-diagram<br/>
**Library:** p5.js<br/>
**Status:** Specified<br/>
**Template:** https://github.com/dmccreary/moving-rainbow/tree/main/docs/sims/neopixel-wiring-diagram

Purpose: Let a mentor click each of the three Pico-to-strip wires and confirm the correct pin and terminal before powering a kit for the first time.

Bloom Taxonomy: Apply (L3)
Bloom Taxonomy Verb: demonstrate

Learning objective: Given a Pico and a NeoPixel strip, the learner demonstrates how to wire the power, ground, and data connections between them, including which end of the strip is the data-in end.

Visual elements: A drawn Pico board and a drawn NeoPixel strip with three labeled wires (power, ground, data) running between them; the strip's DI and DO ends clearly marked.

Interactive controls: Click any wire to highlight its two endpoints and show a labeled tooltip ("5V to Power," "GND to Ground," "GPIO 0 to Data In"); a "Check My Wiring" quiz mode that hides the labels and asks the learner to identify each wire.

Default parameters: All three wires shown and labeled; quiz mode off.

Behavior: Clicking a wire highlights it in a distinct color and shows its tooltip; enabling quiz mode removes the labels and scores the learner's clicks against the correct wire-to-terminal mapping.

Implementation notes: p5.js canvas with fixed coordinate endpoints for the Pico and strip graphics; click-detection based on distance to each wire's path.

References