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LED wiring questions

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Serraph

Member
Joined
Oct 4, 2002
Location
Corinth, MS
I'm planning on running 3 5mm blue LEDs in series off of the 12 V from a molex connector. This is my first time soldering and wiring so I need some things clarified for me. There's probably not a 70 ohm resistor so what resistor is close enough? Can someone use paint or another image editor and make the appropriate wire connections? I'm not sure which ends of the wires go to where. Also I'm planning on having 2 of these. Is it safe to run them both off of a single powersupply molex using a Y-cable molex splitter or should I just have each one going to a separate power supply molex? Thanks.

Here's some LED specs: They are rated at 3.3 V each at 30 mamps. So I need (12-9.9)/.03 = 70 ohm resistor.

LED.jpg
 
OP
Serraph

Serraph

Member
Joined
Oct 4, 2002
Location
Corinth, MS
Thanks. One question though. Why does the resistor not come before the LED's? Won't the LEDs blow out if 12 V passes through them?
 

KILLorBE

Member
Joined
Mar 28, 2001
Location
The Netherlands
It doesn't really matter, there's a voltage drop over the resistor, and that's what counts in this circuit.

Electrons flow from the negative terminal to the positive, conventional current flows from the positive to the negative. They go in opposite direction, because conventional current was invented before they knew about electrons...Which one you use doesn't really have any major effect on simple circuits.

Hope that made things clear.