El Cheapo LED Nav Lights

If it were me, I would go over the exposed leads with liquid electrical tape.

Other than that, it looks good. Will it be bright enough?

 

that looks pretty slick branden,curious to know where you 're gonna mount it.post a pic after the install.i have been thinkin about some led's for lighting but also cant force myself to pay what they want, i dont care what color it is or if its as bright as the sun.i might have to try something like yours,if you have'nt pattened it yet:big_smile:

 

Brandon

I'm a little surprised you would need a resistor, as LED's typically need 3.2-3.7 voltage for native operation. Five LED's in series like that would be considered under driven at anything under about 15-16 volts. Perhaps the resistor does add some spike protection though.

I would run the lights for about 10 minutes and make sure the resistor doesn't heat up. If everything stays cool and it's bright enough you should be in good shape. Cool idea!

 

Of course I may have spoken too soon, I just found some green, red, and yellow leds that are rated for 1.8-3.0 volts. :embarassed: Bottom line, if they are bright enough with the 100ohm resistor then you should be in good shape.

 

So what is the total cost for the settup? I am wanting to run BLUE LEDs inside my boat for Night Fishing Lights. I found some at Wally World that are strips around 6" and have Chrome ends on them, and they only cost around $10! I am thinking of running 3 Around the Lower Deck. BUT if your Idea is Cheaper I might Borrow it from you!!! :wink:

Looks like they will work out fine!!

Drew

 

If I had done this project I would have wired them in parallel; I don't know why, as I have never worked with LED's. I guess it just seems more logical to me.
Is there a reason that they should be wired in series? Thanks...W

 

I would suggest you google search for the USCG Rules and Regulations. Depending upon the size of you boat, the navigation lights must be visible for a distance of 1 to 2 miles. Be a shame to put all that effort into the project if they won't meet the base requirements.

 

Branden, I am coming up with more like a 130 ohm resistor for your 5 LED series circuit. Of course I am assuming some values to be 2v per LED and a desired current of 15 milliamps.

LED's vary widely in their voltage drop and optimum operating current. You need to know these values to correctly size your resistor. White LED's will differ from Blue, which differs from Green, which differs from Red etc.....

Basically you need the specs off of the package on the LED's you are using.

In your example, you had a source voltage of 12v, I assumed a voltage drop of 2v per LED. This leaves 2v for the unknown resistor to dissipate. Assuming you want your LED's to conduct at 15 milliamps, you will calculate as follows, E/I=R or Voltage/Current=Resistance, this will then be 2v/15ma(or .015)= 133.33 Ohms.

P=IE Power = Current times Voltage. In this example your power dissipated= 15ma or .015 x 2v= .03 watts, in other words not squat. A 1/8 watt resistor for example will handle .125 watts, a 1/4 watt resistor will handle .25 watts etc. Although it is not a good idea to use a resistor at its full power rating. Once you get past around 60% of a resistor wattage rating just bump up to the next size. You can put your finger on your resistor all day long, it will not get warm in this case. I guess thats one way to 'test' your circuit but it's easier to just do the math!:smile2::smile2::smile2:


Metalman: We could get into a lengthy discussion over LED's in parallel but basically it just isn't a good practice. You can in fact run strings of series LED's in parallel and that works great, as long as each string has their own series limiting resistor.

Class over!:wink:

 

An advantage of parallel would be redundancy. If one fails, the others continue to shine. LEDs are often rated for up to 100,000 hours, but failures do happen. Wired in series, if one LED fails, the entire light goes out.

Disadvantages of parallel would be that it's a lot less efficient, as a bigger resistor would have to be used for the step down from ~13 volts to ~2 volts. And variations in the vf (voltage forward) of the individual LEDs could cause big variations in brightness between them. That takes care of itself a little better when they are wired in series.

Using a resistor isn't the most efficient way to reduce voltage for an LED, but it tends to be the simplest, which is an advantage in harsh environments such as a boat.

 

15mA seems pretty low, I figured he was calculating at 30mA and 2 volts. Those little green and red LEDs are usually rated for a fairly wide voltage range, but you wouldn't want to push the voltage and current too high above rating.

 

Sorry Branden, hope I didn't offend you. I was just trying to post a little info on how to calculate for the correct resistor. I see that you did a fine job.

Forgive me, brother from the West!:big_smile:

 

They will probably bust you for having 5 little green lights instead of 1 big one, and then ticket you again because the one green one they deem to be your legal light isn't bright enough by itself. :0a26:

Seriously though, it's a cool idea.