NB resistor list

[weslynks]

Hey folks,

The arrival of the NB has me rethinking a build that was originally going to use a MR board. I have some questions about resistors though. My plan was to have both an illuminated blue dot switch and 1 accent LED style 3 in the build. If I use a NB, I'd run them in parallel from the LED line. If I have this figured out correctly that means I would need:

1 x 1ohm 1/8w resistor to the Rebel Star Deep Blue main LED. (3.4vlt at 1000mA)
1 x 18ohm 1/4w resistor to the blue dot switch (3.3vlt at 20mA)
1 x 68ohm 1/8w resistor to a green accent LED. (2.2vlt 25mA).

Does this seem correct? And since Tim doesn't sell a 68ohm resistor, can I use a 82ohm 1/4w resistor instead? I know that bigger is normally okay for ohms, but what about watts?

Thanks

[Skottsaber]

You have power (watts) and resistance mixed up. You can go over power without adverse results, but changing the resistance will make your LED either brighter or dimmer.
The formula for calculating power is P = IV. (Power is equal to Current in amperes multiplied by Voltage). So in this case for your first resistor you take your voltage (3.4v) and multiply it by your current (1A) and you have 3.4 watts of power. A 0.125 watt resistor like the one you posted will instantly burn if you put that amount of power through it. Therefore you need a 1 ohm resistor with a wattage greater than or equal to 3.4 W.

There are many other places to find resistors. TCSS only carries resistor values that are fairly common. With a little bit of searching you should be able to find a lot of reputable electronic component suppliers, but if you need help finding one, my email is in my profile.

[weslynks]

Yeah, I transcribed the values for the Rebel Star from my notes wrong. Though I I still came up with 1ohm 2 Watts as the solution. Is that correct?

[jedimastergarcia87]

Is this if you use an illuminated switch? I plan on using just a standard switch (22) on my build so I don't think I will need any resistors. I'm just using a P4 green led.

[FenderBender]

If you're using a single LI-Ion cell, you don't really need a resistor on the main LED (Unless its a red/amber). You just limit the drive on the config file to say....900, and you're good.