Resistors!

[Ir0n]

So I'm building a B.mini and plan on doing a SIP mod on my switches, but I'm not really sure what resistors to pick up.
Which would be best for changing LEDs? Like going from white to red, or something.
If I go 1300 ohm would it just make white LEDs super bright, or dim? Never really messed around with LEDs before.. :[
It says 820 ohm can support all colors on a 60% style keyboards, but why just 60%?

Thanks!

[engicoder]

 The larger the number of ohms, the higher the resistance. More resistance results in less current flowing which means a dimmer led.  When current passes through an LED, which is a diode, the voltage drops by some amount. This drop is referred to as the "forward voltage". The forward voltage value, along with the source voltage and the resistor value can be used to calculate the current through the LED using the formula I = (Vs - Vf)/R. The resistor is chosen to yield the desired current.  Every led has a different forward voltage, but those with the same color tend to be similar. 

Red LED usually have a forward voltage of about 2.0V while White tend to be around 3.3V. Therefore to keep the current the same, and therefore similar brightness, you need to use a resistor with a lower value. That being said, it would be safe to use the same resistors. The LEDs would just be dimmer.

[Ir0n]

The larger the number of ohms, the higher the resistance. More resistance results in less current flowing which means a dimmer led.  When current passes through an LED, which is a diode, the voltage drops by some amount. This drop is referred to as the "forward voltage". The forward voltage value, along with the source voltage and the resistor value can be used to calculate the current through the LED using the formula I = (Vs - Vf)/R. The resistor is chosen to yield the desired current.  Every led has a different forward voltage, but those with the same color tend to be similar. 

Red LED usually have a forward voltage of about 2.0V while White tend to be around 3.3V. Therefore to keep the current the same, and therefore similar brightness, you need to use a resistor with a lower value. That being said, it would be safe to use the same resistors. The LEDs would just be dimmer.

Oh wow, thanks for the info! I definitely just learned something. I assumed a higher value would push more power lol glad I asked

[VinnyCordeiro]

How much current do you want to push on your LED? Btw, which LED are you using? What is its forward voltage?

You need these information before choosing a resistor value. For that you need to calculate the value solving the Ohm's Law equation:

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V = R × I
↓
R = V ÷ I

V = 5* - [LED voltage] ← This is important and usually overlooked
I = typically 20mA, but you can't exceed 500mA total from your USB port, so probably you will need less current

Resistors comes in standard value series, so it is highly possible that you won't find a resistor with the exact calculated value.
Pick the resistor with the closest higher value, to be safe.

* Assuming you are going to use an USB port.

Examples:
(1) A red LED typically have 2V of forward voltage and 20mA of maximum forward current. So the resistor is:

R = (5 - 2) ÷ 0.02 = 150 ohms

150 ohms is an standard value.

(2) A white LED typically have 3.3V of forward voltage and 20mA of maximum forward current. So the resistor is:

R = (5 - 3.3) ÷ 0.02 = 85 ohms

85 ohms is not an standard value, the closest higher value is 100 ohms.

[Ir0n]

Thinking I'll just pick them up at the zealpc site when I grab some switches (1.8mm ones) or else where.
I was using red and white as an example, but I'd to use what ever I want when I feel like changing them. go from say white to Blinky RGB. I had no idea LEDs was so complicated lol

Would 820ohms would be a safe bet?

Thanks!

[VinnyCordeiro]

Thinking I'll just pick them up at the zealpc site when I grab some switches (1.8mm ones) or else where.
I was using red and white as an example, but I'd to use what ever I want when I feel like changing them. go from say white to Blinky RGB. I had no idea LEDs was so complicated lol

Would 820ohms would be a safe bet?

Thanks!

It is safe, but it will make for a current between 2mA and 3mA, assuming typical LED forward voltages. That means the LEDs would be barely lit.

[W_hinklebottom]

I am doing a build with Sprit's FaceW PCB and I am putting SIP sockets in for the LEDs. I also am planning to solder smd LEDs to the bottom of the board for back lighting the acrylic case. Should I change the resistors to allow more current for both LEDs top and bottom or will it be fine just not as bright?