Circuit Design using CAD Software
How does CAD software help us design, test and share a circuit before we build it?
- Draw a schematic in Tinkercad Circuits or Fritzing
- Simulate the circuit and verify the output
- Export a clean schematic image for the design journal
Overview
CAD (Computer-Aided Design) tools let you draw a circuit, simulate it, and only then build the real thing. Tinkercad Circuits runs in a browser and is free; Fritzing is a desktop app with breadboard, schematic and PCB views. This week you will design an LED driver and a voltage divider in CAD.
Schematic capture
Schematic capture is the act of drawing the circuit using standard symbols. Every connection is a labelled wire; every component has a part number and value.
Simulate first, solder later
In Tinkercad you can press 'Start Simulation' and watch the LED light up. If it does not, you fix the drawing — much cheaper than replacing a burnt LED.
PCB layout basics
Once the schematic is correct, some CAD tools help you arrange components on a printed circuit board. This is beyond this week but is where professional designers head next.
LED driver + voltage divider in Tinkercad
- In Tinkercad Circuits, build an LED driver (battery, resistor, LED) and calculate the resistor for a 5V supply and a red LED (Vf ≈ 2V, If ≈ 10 mA).
- Add a voltage divider that outputs about half the supply voltage.
- Simulate, take a screenshot of the schematic, and paste it into your design journal.
- What does CAD stand for?
Reveal answer
Computer-Aided Design.
- Why simulate before you solder?
Reveal answer
Mistakes caught in software cost nothing; mistakes on a real board burn parts.
- Calculate R for a 9V supply driving a 2V LED at 20 mA.
Reveal answer
R = (9 − 2) / 0.02 = 350Ω.
Design a two-LED traffic light in Tinkercad that alternates red and green.