Calculation of resistor resistance for LEDs (20 pcs.)

Anton asks:

Good afternoon, experts. I make a child’s garage for cars and I want to add LEDs. I bought 20 FYL-3014UWC1A diodes on the chip, asked to count a resistor for them in 3 each in series, given 470 ohms. He calculated through an online calculator that he writes what is needed for 120 ohms. The question is, can I connect 3 through 470 ohms or not? I plan voltage from 8 batteries.

The answer to the question:

Good afternoon! And what are the 8 batteries? It can be finger-type at 1.5V, then it is 12V, and maybe there are 8 batteries of the “crown” type at 9V ... We need to clarify this. These are ordinary output LEDs with a consumption current of 20 mA. A typical voltage drop across them is 3.2V, if there are still 8 batteries of 1.5V each, then the total will be 12V, we consider:

(12-3.2) /0.02=440 Ohm,

Better is the greater resistance in this case, the current will be less, the LEDs will live longer (and there are no 440 Ohms in the standard series, if I'm not mistaken). So it turns out that 470 ohms is normal and this is the standard rating.

Perhaps in the calculations you set the wrong voltage on the LEDs or the wrong current.

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