Choosing an LED Series Resistor for 5V and 12V Circuits

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A guide explains why LED circuits often fail in early builds, such as treating forward voltage as fixed or ignoring resistor heating. Because LEDs have a nonlinear current-voltage curve, a series resistor is needed to limit current from a voltage source. The article gives the basic formula for a single LED and for a series string, using the difference between supply and forward voltage divided by the chosen current. Worked examples show a 300 ohm (rounded to 330 ohm) resistor for a 5 V supply with a red LED, and a 470 ohm resistor for a blue LED on 12 V. The examples also compute resistor power dissipation and note that resistor power differs from LED power.

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US LTL Freight Class Density Scale Changed in July 2025, Many Calculators Outdated

The National Motor Freight Traffic Association rewrote the density scale used to determine freight class for most US less-than-truckload shipments, effective July 19, 2025. The revised scale expanded from 11 to 13 density-based classes, and many commodities that once carried a fixed class now classify by density alone. The developer of CheckFreightClass reports that numerous online calculators still rely on the old table, some even producing a class 500 result that the current scale cannot generate. The article explains that density is calculated by dividing weight by volume, including pallets and overhang, and recommends classing each piece individually rather than blending densities. It also advises shippers to verify outputs against published test cases, since boundary values are where calculators most often diverge.

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ProgrammingDEV Community ·

Flutter developers target jank-free 120Hz rendering with DevTools profiling and leak fixes

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ProgrammingDEV Community ·

Fixing nginx 'host not found in upstream' error in Docker

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ProgrammingDEV Community ·

Bubble Shooter Game Adds Symbols So Color-Blind Players Can Match Bubbles

A relaxing Flutter bubble shooter called Bubble Pop was built to remain playable for people with color vision deficiency. Each bubble carries a distinct symbol alongside its color, letting players match by shape as well as hue. Symbols are enabled by default and the game supports deuteranopia, protanopia and tritanopia. The design avoids timers, pressure and purchases, and saves progress locally without requiring an account. The article presents the approach as a general principle that any app should follow when color carries meaning.

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