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Plinth / From idea to a plan you can inspect

Know what to build.
Know what to check.

Parts, connections, and the next useful step. Plinth helps you reason through an engineering project with an AI assistant and editable planning tools.

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01 / An inspectable example

A little light. A clear first build.

Teaching sample · v1
No physical build recorded

A red desk indicator on a breadboard. Start with five parts, understand one tradeoff, then check what the calculation cannot tell you.

Connections / conceptual circuit

One loop, one current limit.

Desk indicator series circuitRegulated positive 5 volts to a 330 ohm resistor, to the LED anode, through the LED cathode, then back to ground. Diagram only, not a breadboard placement guide.5 V330 ΩRed LEDGND / return¼ WAK

A → anode (+). K → cathode (−). Symbolic illustration; glow does not predict measured brightness.

Read the connections as text
  1. Regulated 5 V → series resistor.
  2. Resistor → LED anode.
  3. LED cathode → supply ground.
  4. Disconnect power before changing parts; confirm the actual LED pinout and breadboard rail connections.
Check before power

Never connect this LED directly across the supply. The series resistor limits current. Verify polarity and the actual part ratings; this drawing is not a completed hardware check.

Parts / sample budget

Five things to gather.

$8.95USD estimate

  • 01
    Red 5 mm LED

    TLHR5400 reference; verify the actual part before substituting.

    $0.35
  • 02
    330 Ω resistor

    One ¼ W series resistor. Limits the LED current.

    $0.10
  • 03
    Mini breadboard

    A solderless place to check the first circuit.

    $3.00
  • 04
    Jumper wires

    A small set; check contact and rail continuity.

    $1.50
  • 05
    5 V power breakout + cable

    Connect to an existing regulated 5 V supply. Confirm polarity.

    $4.00

Illustrative unit estimates curated September 14, 2026. No supplier quote or stock check. Excludes the existing regulated supply, meter, tools, tax and shipping. Check pack sizes before ordering.

02 / Change one constraint

What if lower current matters?

Compare two resistor choices locally. Your notes and the example stay editable.

Indicator preference

Original reference

9.1 → 9.1mA calculated current

$8.95 → $8.95sample parts budget

Select Lower current to compare the resistor, expected current, and budget.

Then check: LED visibility at your desk, actual current, resistor value and rating. Lower calculated current may mean a dimmer indicator; brightness has not been measured.

Plan / next useful actions

Get one observation you can trust.

  1. Gather and inspect. Confirm the LED datasheet, resistor value and a regulated 5 V source.
  2. Connect with power off. Trace the loop and inspect polarity. Check for shorts before power.
  3. Measure, then decide. Record supply voltage, LED voltage and current. Check visibility. Only then consider a case or permanent assembly.

A proposed sequence, not a promised completion time. No firmware, PCB, CAD model, or enclosure is included in this sample.

Evidence / calculated, not measured

Here is what the numbers establish.

Assumptions
5 V supply; LED forward drop fixed at 2 V. Real voltage varies with current and temperature.
Example calculation result
(5 − 2) V ÷ 330 Ω = 9.1 mA. Resistor dissipation ≈ 27.3 mW, below the nominal 250 mW rating in this calculation.
Bench test
Not run. No measured current, photograph, or reviewer approval exists for this fixture.
Sources and assumptions · September 14, 2026

Vishay TLHR5400 reference datasheet ↗
Reference LED: 2 V typical forward voltage specified at 20 mA. Our lower-current calculation uses 2 V as an assumption, not a measured value.

Adafruit: Revisiting Resistors ↗
The series-resistor method: current is the supply-to-LED voltage difference divided by resistance.

03 / Make the next step yours

Start with what you have.

Use the example, describe your own idea, or bring a brief. You will review the text and your account allowance before creating a project.

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What can I take with me?

Export options depend on the artifact and plan. The example notes download is plain text. Circuit netlists and CAD starters still need review in the tools used to finish the design.

Who can see my work?

Project members can read assistant conversations. Publishing creates a public link; listing in Community is a separate choice. This teaching sample contains no user project data.

Is this a finished build?

No. It is a curated planning example with assumptions and calculated results. It includes no measured bench result, builder endorsement, or photograph of completed hardware.