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LED''s In Series..... — Parallax Forums

LED''s In Series.....

ArchiverArchiver Posts: 46,084
edited 2001-04-16 00:29 in General Discussion
I have a question about wiring LED's in series. LED Requirements:
Voltage Drop of 2.4V at 20mA. Supply Voltage: 12VDC. I'd like to put four
in series using just one current limiting resistor. I understand that I
should add-up the total voltage drop for the four in series, but my question
is, should I divide this by 20mA or by 80mA to calculate the resistor value?
In other words should the series be allowed 20mA total or should I figure
20mA for each LED?

2.4V x 4LED's = 9.6V Total Voltage Drop.

12V - 9.6V = 2.4V Remaining.


2.4V / 20mA = 120 Ohm Resistor?
OR
2.4V / 80mA = 30 Ohm Resistor?

As always, thank you for your time and consideration - especially with the
"rookie" questions.

Tim
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