# LED's

Discussion in 'The Projects Forum' started by jimbu, Nov 22, 2008.

1. ### jimbu Thread Starter New Member

Nov 22, 2008
3
0
What are the pro's and con's of using LED's with built in resistors?
I am building a project with 69 LED's in series.
I previously built a project with 120 LED's in series and used a resistor on every 4 LED series. It would seem much eaiser and less parts without the seperate resistors.
Would a + & - lead have to go to each LED with the built in resistor?
Thanks for any suggestions.
jimbu

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
293
It's the way to go if they are all in parallel, but, as you said, a waste for series strings.

One way to beat the system, though. Use a string of LED's with one having the limiting resistor in it. Arrange for the voltage to be just high enough for all LED's to conduct, but also that the current limiting resistor in the one LED is limiting for all in the string. Can't get neater than that.

3. ### Bernard AAC Fanatic!

Aug 7, 2008
4,949
551
LED's with built-in resistors are disigned for a specified V.Example:3 V LED @ 5 V op. X 23 = 115 V; 3 X 23 +10 =79 V. Taking 23 strings of 3 ea.;3X3 +1=10 V, a little safer.

4. ### jimbu Thread Starter New Member

Nov 22, 2008
3
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I should have mentioned that the voltage source is 12 volt.

I, last night joined in series 6 LED's that draw 2.9 volts each and hooked them up, they alll so far seem fine with no resistor in line. I will let them burn 24-7 to see how long they last.

5. ### jimbu Thread Starter New Member

Nov 22, 2008
3
0
Wel trash that idea. They burned 22 hours and poof!!!!