PAGE 034 OF 150 · POWERING LEDS
Standard Resistor Values
Round up to the next preferred value for a safe margin.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Why standard values exist
Resistors are made in preferred series, so you cannot buy every exact value. Choose the nearest standard value to your result.
The E12 series
10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68 and 82, times 1, 10, 100 and so on. The E24 series adds in-between values such as 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75 and 91.
Common LED picks
- 220 ohms and 330 ohms for 5 V
- 470 ohms for 9 V to 12 V
- 1 kilohm for dim indicators
Rounding up gives slightly less current, which is safer for the LED.
REMEMBER
The resistor sets the current, so the resistor sets the safety.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
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