Re: Resistor value for LED


>> R = E / I = 3.2 / 0.020 = 160 ohms.
>>
>> They don't make 160-ohm resistors, so use either 150 or 220.
>
> Again, you've missed the boat. The 160, 1.6k, etc., 5% resistor values
> are no harder to get than 1k or 2.2k. Standard resistor values can be
> found here. _Read_and_remember_them_.
> http://www.rfcafe.com/references/electrical/resistor_values.htm

I know what the standard values. Some people have to shop at Radio Shack,
which has 220 but not 160 or 150 available singly. Radio Shack has
assortments that have 150 but not 160. Admittedly, "they don't make" was an
erroneous oversimplification.

I have actually not seen 160 (or 1.6, 16, 1600, etc.) very often at all.
Not all of the 5% standard series is equally widely available.
Long-established good practice, even with 5% resistors, is to prefer the
values in the 20% series first, then the 10% series, then the 5% series.

The 20% series goes: 1.0, 1.5, 2.2, 3.3, 4.7, 6.8, 10.

I spent a long time writing construction project articles for magazines and
developed a fairly strong aversion to hard-to-get parts. That, and I
started designing things back when resistors were 10% carbon composition!



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