We keep hitting the same wall in maker projects: the reference material is either a 900-page datasheet, a decade-old calculator on a domain that now sells something else, or a forum thread with three contradicting answers. So we started building the tools we needed. Free, no signup, no tracking. The set started at six; it is twelve now, and here is what building them taught us.
The tools
ESP32 DevKit V1 pinout (38-pin): interactive per-pin reference with the warnings the datasheet buries. GPIO 6-11 are wired to flash (using them crashes the board), strapping pins (0, 2, 5, 12, 15) get read at reset, and GPIO 12 pulled high can stop 3.3V flash boards booting entirely. Per-pin anchors so a forum answer can deep-link exactly the pin in question. Prints clean for the bench.
ESP32-C3 SuperMini pinout: the $2 RISC-V board's own traps. GPIO 2/8/9 strapping, the flash bus at 11+, and why "my board won't flash" is almost always BOOT pulled by your circuit.
USB-C pinout (24-pin): the 5.1k resistor rule that makes chargers output 5V, all 24 pins, the four VBUS and four GND pins, and what USB 2.0-only breakouts leave out.
Resistor color code calculator: 4/5/6-band decoder with tolerance range and nearest E-series value. The result is saved in the URL, so pasting it into a forum answer reproduces the exact numbers.
Capacitor code calculator: the three-digit ceramic codes (104 is 100nF), RKM notation like 4n7, and the tolerance letters. It also explains the MMFD trap in the old tables.
SMD resistor code calculator: the tiny codes on 0603 parts, E24 and E96, RKM notation, and the zero-ohm jumper.
LED resistor calculator: supply, forward voltage and current in, the resistor out, with the nearest standard value and the wattage check that stops the smoke.
Voltage divider calculator: pick R1 and R2 for an output, see the current drawn and how much a load pulls the output down.
IoT battery life calculator: the "how long will my ESP32 run on this LiPo?" tool, duty-cycle aware with deep-sleep presets. This is the one we could not find anywhere. Generic battery calculators do not model wake and sleep cycles.
WS2812B / NeoPixel power calculator: PSU size with headroom, fuse rating, injection points. Realistic 20mA average vs the 60mA worst-case toggle every LED-strip thread ends up re-deriving.
Voltage drop & wire gauge: 12V wiring with the 3% rule, round-trip modeled. 5A over 5m of 18 AWG is 9.6% drop, and the calculator says undersized before the LEDs do.
Wire gauge (AWG) chart: the AWG table with mm2, resistance per metre and both ampacity columns, plus the rules worth memorising: three gauges doubles the cross-section, six doubles the diameter, ten multiplies resistance by ten. The worked example shows why 18 AWG can carry 16 A and still brown out a 5 m strip.
All twelve, free, no signup: tinkernews.com/tools
What building them taught us
Unit bugs hide in plain sight. Our battery calculator was 1000x off on first build, milliseconds converted to seconds where the formula wanted hours. The fix was a one-line change; proving it took an evening of hand math. Every calculator now gets click-tested against hand math before it ships.
Shareable state is the killer feature. Forum answers need a canonical URL that reproduces numbers. Putting the inputs in the query string turns every answer that cites the tool into a permanent, verifiable reference.
"When not to use this" earns citations. The battery calculator publishes its assumptions (regulator quiescent current, cold-weather loss, retry storms) and says when to trust it instead. That is what makes writers comfortable linking a tool.
Safe-GPIO warnings are content. The pinout pages get read because they say "never use GPIO 6-11" at the top, not in a footnote. The warnings are the product; the pin grid is the reference.
We run TinkerNews, a free weekly roundup of DIY electronics builds, and these tools came out of the issues. If any of them are wrong, tell us and we'll fix that first.
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