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Ohm's Law at the Bench: Picking the Resistor That Saves the LED
Volt

Nilikha ni

Volt

23. Setyembre 2026SE
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Ohm's Law at the Bench: Picking the Resistor That Saves the LED

One equation does most of the arithmetic a maker ever needs from electronics, and it is three letters long. What makes it worth a rung of its own is that the three commonest beginner disasters — the LED that dies instantly, the resistor that cooks, the divider that sags under load — are all the same equation applied carelessly. An LED is the sharpest example. It is not a resistor: past its forward voltage the current rises almost without limit, so connecting one directly across a supply destroys it in a fraction of a second. The resistor beside it is not a formality, it is the only thing deciding the current. Every SIK circuit published here that lights an LED has one, and this is why.
Baguhan
3 hours

Mga Tagubilin

1

Size the resistor for an LED, and see why it is not optional

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Mga materyales para sa hakbang na ito:

Kit ng LEDKit ng LED1 piraso
Kit ng RisistorKit ng Risistor1 piraso

Mga kailangang kasangkapan:

Lapad na PansubokLapad na Pansubok
KalkuladorKalkulador
MultimetroMultimetro
2

Check the resistor will survive the heat

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Mga materyales para sa hakbang na ito:

Kit ng RisistorKit ng Risistor1 piraso

Mga kailangang kasangkapan:

KalkuladorKalkulador
MultimetroMultimetro
3

The divider that works until you connect something

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Mga materyales para sa hakbang na ito:

Kit ng RisistorKit ng Risistor1 piraso

Mga kailangang kasangkapan:

Lapad na PansubokLapad na Pansubok
MultimetroMultimetro
KalkuladorKalkulador
4

Measure it, and find out what your parts really are

Build the LED and its resistor on a breadboard, then measure: the supply, the voltage across the LED, and the voltage across the resistor. They should add up to the supply. Then work out the current from the resistor's voltage and its measured resistance, and compare it with what you calculated. The LED's real forward voltage will not be exactly the table value — it varies by part, by colour bin, and with current — which is why the calculation is a starting point and the measurement is the answer. This also demonstrates Kirchhoff's voltage law without naming it: around any loop, the voltages sum to zero. Once you have seen it on a meter it stops being an abstraction and becomes a tool for finding where a missing volt went.

Mga materyales para sa hakbang na ito:

Kit ng LEDKit ng LED1 piraso
Kit ng RisistorKit ng Risistor1 piraso

Mga kailangang kasangkapan:

Lapad na PansubokLapad na Pansubok
MultimetroMultimetro
Panustos ng Kuryente sa MesaPanustos ng Kuryente sa Mesa

Mga Materyales

2

Mga Kinakailangang Kasangkapan

4

Kaugnay na Blueprint

Ang mga blueprint na ito ay nagbabahagi ng kaalaman — mga teknik, materyales, o prinsipyo

Driving an RGB LED — SIK Circuit 3

Driving an RGB LED — SIK Circuit 3

ni EdFI

Digital

93
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Driving Multiple LEDs — SIK Circuit 4

Driving Multiple LEDs — SIK Circuit 4

ni EdFI

Digital

91
0
0
0
0
0
Wheatstone Bridge

Wheatstone Bridge

ni EdFI

TEKNOLOHIYA

38
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CC0 Pampublikong Domain

Ang blueprint na ito ay inilabas sa ilalim ng CC0. Malaya kang kumopya, magbago, mamahagi, at gumamit nang walang pahintulot.

Suportahan ang Maker sa pamamagitan ng pagbili ng mga produkto sa kanilang Blueprint Komisyon ng Maker itinakda ng mga Vendor, o lumikha ng bagong bersyon ng Blueprint na ito at isama bilang koneksyon sa iyong Blueprint upang ibahagi ang kita.

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