LED Bling

[tktige']

Anyone replacing their interior running lights with LEDS? I have a 2001 21V. I know they use less power that the old bulb lights. Can I still use the same factory switch, I know I need an inline fuse per LED.

Anyone install the swim plat form LEDS.

Thanks TK

[Boarder_X]

You shouldn't need a fuse for the LED's ... (unless it specifically says so). They should be able to handle the same current as the original bulb. They are just more efficient, and that's why that last longer. They also don't use as much power.

Quick electricty lesson:
P= IV/ IIR
V=IR
P = Power (Watt)
V= Voltage
I= Current
R= Resistance

The LED has less resistance, but handles the same current (that's why you don't need a new fuse). The voltage is a constant (comes from the battery). Because the resistance is lower, that also means the power consumption is lower.

[gman]

Could you please explain how you get less power consumption with less resistance if the voltage is the same?

[Boarder_X]

http://ourworld.compuserve.com/homep...tt/elect34.htm

Electricity is very wierd. It can be likened to a garden hose. The voltage is the speed of the water, and the current is the area. The speed at which you can fill a 5 gallon bucket depends on both. You can raise either, or both. Just because the water is moving fast doesn't mean anything (It could be moving through a drinking straw).

[raythompson]

According to the link you provided "If the value of the resistor is halved the the current is doubled." So if you double the current, using the same voltage, you are actually doubling the amount of power consumed. Power is current times voltage. That goes against your original post stating "Because the resistance is lower, that also means the power consumption is lower."

In fact, a properly biased LED will exhibit much greater resistance than a wire bulb. LED's are reversed biased and you need to overcome the resistance to get them to light. You also have to a current limiting resistor to prevent them from self destructing from too much current flowing. When properly configured the LED will exhibit significant (with the current limiting resister) resistance, more resistance than a bulb, less current than a bulb, therefore much less power consumption than a bulb.

LED's emit most of their energy in the visible spectrum. White LED's are actually blue with a yellow phosphor to convert the blue to pseudo white. Wire bulbs produce most of their energy in the infared spectrum where it cannot be seen, only felt. This is a lot of wasted energy.

I have some LED flashlights that use 5 watt LED on a 3 volt battery. These lights are pulling up to 2 amp in current draw from the battery. They do get hot and require heat sinking and thermal protection.

[gman]

Boarder_X Take and keep the voltage the same. Then do calculations with different resistors. Say 10 ohms and 6 ohms using a constant 12v. You will find that the power is less with 1o ohms than with 6 ohms. If you use 10 ohms than the power is 14.4 watts. If you use 6 ohms than the power is 24 watts. More power with smaller resistor.

[Boarder_X]

I am sorry guys.

I was told in class they use less power. Then someone asked why, and the teacher said they have a lower resistance, and blah blah.

When gman asked how, I did some research, and foud exactly what ray said. .... I know, I know. Assume the teacher is right, and it's still an assumption.

I am a recent college grad. (Dec) I am learning (this is just another example) that research is better done for one's self, rather than going with the word from a teacher that does necessarily teach that information.

I still think to answer tk's question the LED's should be able to handle the current load from the old circuit. To confirm this, look at the data sheet for the LED's, and check the Id charactaristics. Compare this to the current running through the wire currently (using and Ammeter). If the max Id is less, then a fuse will be required.

http://www.roithner-laser.com/All_Da...HCA_series.pdf

This is an example. It is an LED with 7-8cd. On this data sheet they use Ifp instead of Id. However you see that peak current it 80mA, and a continuous current (If) of 20mA will not hurt the unit. These are the numbers you are looking for, when you change from bulbs to LED's.

[lee]

I thought it was pie r square and cake r round.

[raythompson]

Originally posted by Boarder_X
I am sorry guys.

Not to worry. Teachers are not always correct. I have had more than one myself. Don't ever try to correct them as they sort of get angry and that ruins the rest of the class. If you can substantiate your position, you would need to do it carefully. Even then you may have made an enemy. Not good when they control your grade.

I still think to answer tk's question the LED's should be able to handle the current load from the old circuit.

The current is never the issue unless you start pulling more than the circuit is designed to handle. Then you stress wires, blow fuses, etc. An LED light will have the proper limiting resistor to limit the current the LED draws to keep the LED safe. A device will only draw as much current as it needs or is designed for. Voltage is the main issue. If the LED's are designed for 12 volts they will work without modification in place of any 12 volt wired bulb.

I have some very high end LED flashlights that are brighter than the brightest 2D flashlight on the market. The lights are smaller than the 2D flashlight and contain a computer chip that regulates the output, manages the power, prevents thermal problems, and provides multiple programmable settings. There is also a boost circuit that boosts the voltage from the 3 volt cell to almost 5 volts.

It is amazing to see how far LED lights have progressed. The lights are incredibly bright, and surprisingly, generate a significant amount of heat. One light has a 5 watt LED, running on a 3 volt cell, that is drawing almost 2 amps from the cell.

[Matt Garcia]

lol at lee...

[lee]

Matt,

I was wrong, this morning my wife said pie r round also.

[dogbert]

Originally posted by lee
I was wrong, this morning my wife said pie r round also.

LOL, Mr. Know it All trumped by his wife...classic!