USFORCES

I ordered some 3mm & 5mm LED's the other day from Frozen, also 3mm & 5mm LED Harness 2 Pin Connectors that plug directly into the motherboards 3-pin connectors.

My question is do I need a resistors for them because they don't say anything about it at there site and it don't look like they have resistors on the wires.


LINK

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Capwn

More than likely yes. Average LED's to my knowledge are rated between 3 and 5 ish volts. A simple resistor will do you just fine.


Always remember the smaller prong inside the LED is always the positive.

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radodrill

The ones with the 2-pin harness are most likely 3.3V and will work without the need for resistors on the HDD-LED headers PWR-LED (with different connector) or any ~3V supply. If you want to use any of the LEDs on 12V or 5V you will need to wire them up either with a resistor or as an array (that may also include a resistor). The only downside is that FrozenCPU does not list the current draw of the LEDs (typically 20mA or 30mA) making it more difficult to calculate the right size resistor (unless you happen to have an ammeter).

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Why would they sell them like this, are the 3 pin connectors 12v?

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radodrill

I have no idea why they do not list the specs of them (voltage and current draw) as that is critical when custom wiring things; most any electronics warehouse either lists the specs on the product page or has a link to a datasheet with all that info.


The 3-pin fan headers are 12V; while the 3-pin PWR-LED is ~3.3V

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Thanks radodrill I'd rep you if I could.

I guess if they don't work Frozen can fix it because the way it's worded you just plug them right in to the motherboard.

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radodrill

I think they're primarily meant to replace the Power and HDD LEDs, and the harness is designed to plug right in to the HDD LED headers on the MB

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Found it!

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radodrill

cool; 3.5V @ 30mA

so you could wire 4 in series and connect them across the 12V rail


for 1 LED across the 5V rail the resistor in series with that has to be:
(5V - 3.5V) / 0.03A = 50R

for n LEDs in series with a resistor across the 12V rail the resistance is:
(12V - n * 3.5V) / 0.03A


once you compute the design resistance, round up to the nearest standard sized resistor.

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SR-1/2 radobases for Crazy Carl's Antec 900 mod

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