About CircuitNote

CircuitNote is a free collection of electronics calculators, built by an electronic engineering student to replace the calculations that come up again and again in lab work and projects. It is meant for lab reports, student design projects and hobby builds such as Arduino work.

How the calculators work

• Everything runs in your browser. Nothing you type is stored or sent anywhere.
• Each result shows the formula used, so you can check how the number was reached.
• Unless stated otherwise, parts are assumed ideal. For a real design, check tolerances, temperature and ratings in the datasheet.
• Reference tables are generated with the same formulas as the calculators, so the tables and results always agree.

Standards and references

• Preferred resistor and capacitor values: IEC 60063 (E24 and E96 series)
• SMD resistor markings: the EIA-96 code
• PCB trace width: the current and temperature-rise relation in IPC-2221
• Wire sizes: the AWG definition, with copper resistivity of 1.724×10⁻⁸ Ω·m at 20 °C
• 555 timer: the astable equations from the NE555 datasheet

Who makes it

CircuitNote is written and maintained by one electronic engineering student. The first tools were the ones needed again and again in circuit theory, electronics and digital logic labs: the pre-lab calculations and the post-lab comparison of theory with measurements. Each calculator page also lists the practical pitfalls and common mistakes that come up on a real bench.

How pages are checked

• Every change runs an automated check that opens each page in a browser, compares each calculator's default result with a hand-verified value and checks the layout on a phone screen. Nothing is published unless it passes.
• Worked examples and reference tables are generated by the same formulas as the calculators and cross-checked against them when a table is added.
• After each release, every address on the live site is checked daily.

About the lab guides

The lab guides use measurements from undergraduate experiments the author carried out, and explain with numbers why measured values differ from theory. Measured values are used as recorded, never adjusted. Names, student numbers, the school, instructors, group numbers and photos are never published. The guides do not write discussion or conclusion sections for anyone's report; they are meant to help you understand the circuit and interpret your own data.

Updates and corrections

Confirmed errors are fixed promptly, and when a calculation changes, the page's explanation and examples are updated with it. Results are a starting point for design. For anything safety-related (mains wiring, high currents, battery charging) check the component datasheets and the relevant standards.

Report a problem or suggest a calculator

If a result looks wrong or you need a calculator that isn't here, write to circuitnote777@gmail.com. The contact page explains what to include. Fixes come first, and the most requested calculators are added next.