Correct setup of single led for Neutral switch

[xsPete]

G'day,

I'm thinking about running a single light for neutral mounted separate to the speedo.

My vast knowledge of what an LED and what a Resister is comes from about an hour on google last night.

So from what I can gather I need to know;

The Volts I'm using, I'm not sure on this whether to use the 12V which is the battery or what the bike will be putting out when It's finally running.

The mA that should pass through the resistor, how does 20mA sound (0.020Amps)

From what I can gather this is used to calculate what resistor to get.

So if the LED had a Forward Voltage (fV) of say 3.4 for argument sake.

Then to calculate the resistor (R), it goes,

R = (V-fV)/mA
R = (12-34)/0.20= 430 ohm resistor

So what voltage should I calculate it off &
is the mA something I'd get the info off the LED to have pass through it.

 

[pamcopete]

xsPete,

Use the voltage with the engine running and charging the battery, 14.5 Volts. Remember also that the LED is polarity sensitive.

 

[xsPete]

xsPete,

Use the voltage with the engine running and charging the battery, 14.5 Volts. Remember also that the LED is polarity sensitive.

Tks Pamco Pete,
I was fairly sure I had to take the engine running into account, now confirmed.

With the polarity senitive part, do this mean both the light and the resistor will be marked for + -. if not how would I test for it

I'm also still unsure of the mA that should pass through the resistor, would this info come with the LED or is there some standard rating for this type of thing.

 

[KeithB]

see this page for calculator...
http://led.linear1.org/1led.wiz
Also, there are LED lights that fit the stock "bayonette" style socket.
I removed all the indicator lights and just find neutral by feel.

 

[xjwmx]

I'm also still unsure of the mA that should pass through the resistor,

Somewhere on the package is "maximum forward current" or similar. Keep the current close to that to have it the brightest, but below it. So if mfc was 1ma and volts was 14 the resistor would be the solution to .001=R/14. You can get the watts for the resistor by using another formula.


Remember milliamps are 3 decimal places. The formulas are for amps without the milli....

 

[blackbetty]

I wired up a single LED on my setup:

http://k-four.net/Product.aspx?pid=68

Very straightforward. One lead to switched 12V, the other to the switch. I didn't do any calculations for it, I wired it in like a regular light. Works awesome.

I also have a blue LED wired in as a high beam indicator.

 

[xjwmx]

^You have high current leds or something. Some of them would immediately pop.

 

[blackbetty]

Looks like they are 12v, I posted the link from K4 Switches up there:

12 volt standard--6 volt add 6v to part no.--24 volt add 24v to part no.

black oxide coated brass housing

nylon insulator

4 1/2 wire leads

current--standard 30ma--flashing 70ma--estimated life 100,000 hours

.312 mounting hole

.375 bezel diameter

panel thickness up to 1/4 inch

led's are polarity sensitive--black wire to ground

 

[xsPete]

Thanks for all the responses, it's what I was looking for.

Now I just need to find the right led to suit.

 

[ReycleBill]

I wired up a single LED on my setup:

http://k-four.net/Product.aspx?pid=68

Very straightforward. One lead to switched 12V, the other to the switch. I didn't do any calculations for it, I wired it in like a regular light. Works awesome.

I also have a blue LED wired in as a high beam indicator.

Those dog bone risers are classic!