If you’ve ever paused mid-build to dig through datasheets just to figure out the right resistor for an LED, this one’s for you. We just put eight free maker tools on circuit.rocks – no login, no fluff, just calculators and helpers built for the kind of bench work we do every weekend.
Every tool runs in your browser and links back to the parts we stock here in Manila, so the math you do on the calculator can roll straight into a same-day order. Below is the full rundown of what’s live now and what each one is good for.
What’s new
- LED resistor calculator — Computes your current-limiting resistor for any LED, snaps to E12/E24 standard values, and recommends a power rating so you don’t fry a quarter-watt by accident.
- Pinout viewer — Interactive pinouts for ESP32 DevKitC, Raspberry Pi Pico W, Arduino UNO R3, and Raspberry Pi 5. Filter pins by function (I2C, SPI, ADC, etc.) instead of squinting at a PDF.
- BOM-to-Cart — Paste a parts list from a tutorial or your own project notes. One click adds everything to your circuit.rocks cart with live stock lookup. Designed for thesis-grade BOMs without manual searching.
- Voltage divider calculator — Pick R1 + R2 to drop any voltage from any rail. Shows power dissipation and current draw so you can spot a hot resistor before you solder it down.
- Resistor color code decoder — 4, 5, and 6-band picker with tolerance and temp coefficient. Lives as a tab on the LED calculator.
- Battery life calculator — Estimate runtime from capacity (mAh), active-duty cycle, and sleep current. Includes an efficiency factor for boost/buck regulator losses.
- Logic-level checker — Drop in a source and target voltage (3.3V to 5V, 5V to 1.8V, etc.) and the tool tells you whether you need a level shifter, a divider, or a direct connection.
- PCB trace width calculator — IPC-2221 minimum trace width for a given current, copper weight (1oz/2oz), and acceptable temperature rise. Useful before you hit Send on KiCad.
Why this matters
Most maker mistakes don’t come from bad ideas – they come from skipping the math. A wrong resistor value means a dim LED, a shorted GPIO, or in the worst case, a board you replace. The tools we just shipped exist to take the friction out of “I’ll do the math later” so you actually do it before the soldering iron heats up.
Every calculator also serves as a small lesson. The LED tool walks through Ohm’s law in real time. The voltage divider tool shows you why a high-impedance pair can give weird readings on an ADC. The PCB trace tool exposes IPC-2221 to anyone designing their first board, no textbook required.
Try it yourself
Head to circuit.rocks/pages/tools to see all eight tools in one place. Bookmark the ones you’ll use most – the BOM-to-Cart in particular pairs well with our learning tutorials on learn.circuit.rocks. We’re already building the next batch (capacitor coupling design, antenna length helper, op-amp gain), so tell us in the forum which tools you’d want next.
Frequently Asked Questions
Do I need a Circuit.Rocks account to use these tools?
No. All eight tools are free and run entirely in your browser. The BOM-to-Cart tool needs you to be signed in only when you press the ‘add to cart’ button at the end.
Can I save my calculation or share a link to a result?
Calculators run client-side and don’t persist results. You can copy the values from the result panel and paste them into your project notes. The BOM-to-Cart tool persists items by pushing them straight to your cart, which Shopify saves for you.
What will I learn if I use these tools regularly?
Ohm’s law applied to real LEDs, voltage-divider design with power dissipation, resistor color-code reading, IPC-2221 trace-width math, and battery-life estimation from duty cycle. These are exactly the fundamentals that show up on ECE board exams and in every real maker project.
