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Thread: Electronic Edge Finder

Dec 17, 2021, 08:41 PM #2

Don42

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An LED driven by a 12-volt battery definitely requires a resistor if you want it to last. Most 5mm LEDs are quite happy running at 20 mA. A typical 5mm white LED has a voltage drop of 3.6 volts at 20mA, which indicates a resistor of 420 ohms. 430 ohms is a standard value. 470 would work fine too. Other colors have different voltages but 470 ohms would work OK with any of them.
A good source for LEDs is
https://www.ledsupply.com/5mm-leds
Good selection, reasonable small-quantity pricing, free first-class shipping.

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