AR1  ·  DC Circuits  ·  Final Project

Design &
Simulation

MCQ  ·  Quick Check

Quick check.

Question 1
Which function models the HIGH and LOW times in our circuit?
  • A t = I·R
  • B t = 0.693·R·C
  • C t = V/R
  • D t = P·t
Question 2
In our circuit, t1 depends on: (select all that apply)
  • AR1
  • BR2
  • CC
  • DAll
Question 3
In our circuit, t2 depends on: (select all that apply)
  • AR1
  • BR2
  • CC
  • DAll
Before You Build

Check your design.

Confirm that your circuit meets each requirement before you pick up a component.

  • Your circuit switches between two values of R1 to produce two different pulse widths.
  • R2 stays the same, so the low time remains constant.
  • C stays the same, so the total period stays consistent.
My Design

Here are two approaches that work.

Version 1
555 timer circuit with diode-switched R1, version 1
Version 2
555 timer circuit with diode-switched R1, version 2
How do we know either approach works before building it?
The Problem with Skipping Ahead

Jumping straight to building creates avoidable problems.

  • You may spend several class periods rebuilding a circuit that was never verified to work as designed.
  • Without a known-good signal to compare against, debugging becomes guesswork: every symptom looks like every other symptom.
  • Some faults stay completely hidden until you actually measure the output with an oscilloscope.
What Simulation Does

Simulation answers the important questions before you build.

  • Test whether your timing formula gives the pulse widths you calculated, with no components required.
  • See the output signal on a virtual oscilloscope and verify it matches your design.
  • Catch and fix mistakes in seconds rather than rebuilding on a breadboard.

Use simulation to verify your design works before you build.

The goal is to confirm, not to guess. Simulation is the check before the build, not a shortcut around it.
Getting Started

Open Tinkercad.

  • Google Classroom: open the Tinkercad simulation assignment in your class stream.
  • Sign in: use your .gse account when Tinkercad prompts you to log in.
Join the class meet
Live Demo

Follow along.

1 Power first: place and configure the power supply before adding any other components.
2 Measurement tools matter: add an oscilloscope so you can see what the circuit is actually doing.
3 Add the 555: place the 555 timer IC and connect it to the power rails.
4 Add the diode: the line on the diode matches the line on the schematic.
5 Prep for servo: Make a place for the servo to connect.
Your Turn

What you will build in Tinkercad.

In Tinkercad

  • A 555 timer circuit with your calculated component values.
  • Two values of R1, switchable with a button.
  • One R2 and one capacitor C that stay fixed.
  • A servo connected to the 555 output pin.

What to Look For

  • Does the output signal change when you press the switch?
  • Does the pulse width match your timing formula calculations?
  • Does the servo move between the two positions you designed for?