LED info needed

billzie · Post by **billzie** » July 17th, 2005, 12:17 am

I just need some basic LED info. Not for exterior. I just want tot replace some of my interior lighting and add some to various places.
I know that they are not 12vDC and need something soldered in. But, I need to get specifics.
Thanks for your help. Bill.

Post by **Custommx3** » July 17th, 2005, 12:31 am

search for LED lights on google. people sell replacements bulbs with LEDs instead of filaments.

Dominicanchu_Nmbr1 · Post by **Dominicanchu_Nmbr1** » July 17th, 2005, 12:56 am

i think someone on here was selling some. mostly, i think you'll need resistors soldered to'em. there are even colorchanging ones.

billzie · Post by **billzie** » July 17th, 2005, 1:00 pm

I'm just looking for the info to DIY.
LEDs are as cheap as 5 cents and resistors as cheap as 1 cent.
I think those guys selling those ones you're talking about are raping us.
So for a 194 replacement LED that probably has a mfg cost of 20 cents, they charge $3.
That's insane.
If anyone has the info do DIY, ie picking the appropriate LED for brightness and how to hook them up with the appropriate resistor (for singles and runs), I'd really appreciate it.
Thanks for your help.
Bill.

billzie · Post by **billzie** » July 17th, 2005, 1:12 pm

And, I just saw the prices on the bigger bulbs like the 1156, 1157. $10, rip off. And, they're all probably POS built.
I did buy some LED replacements for my car trailer from a small USA shop in MI, they did great work, but all of their stuff is basically for the trucking industry (mainly running and tail/stop lights). They only used high quality Made in the USA LEDs and circuit boards. They have a highly resplected reputation in the trucking and home 12v lighting industries (for alternative energy homes like solar). And heck, if I can find their brochure I'll share the name.

Bill.

happyclown · Post by **happyclown** » July 19th, 2005, 10:04 am

I'd really like some of info on this too... I'll do some looking around, but if anyone has any input please share!

FlyVFR · Post by **FlyVFR** » December 28th, 2005, 1:44 am

billzie wrote:I just need some basic LED info. Not for exterior. I just want tot replace some of my interior lighting and add some to various places.
I know that they are not 12vDC and need something soldered in. But, I need to get specifics.

No easy answer because it depends on the LED used and it's electrical properties. The resistor can be calculated to solve for a resistance value by using OHM's law once the LED is selected and it's electrical properties are known. Also the resistor's *power rating must be calculated once the voltage and current values are solved. These 2 values must be known before the proper resistor can be selected. Now there is a lot more to resistor selection but it is beyond the scope of this basic OHM's law calculation example.

OHM's law:
E=IR
Solve for current
I=E/R
Solve for resistance
R=V/I

E= DC Voltage
I= Current flow
R= Resistance in ohm's

WARNING-DISCLAIMER: I do not recommend the wiring of custom LED circuits to work off of a 12V car electrical system directly unless one is familiar with resistor circuits, it's power selection and proper fuse protection as using the wrong values and or parts poses a fire hazard. The posted above calculation in OHM's law is for educational purpose only!

ariesdude · Post by **ariesdude** » December 28th, 2005, 12:22 pm

FlyVFR wrote: basic OHM's law calculation example.

OHM's law E=IXR
Solve for I=E/R
Solve for R=V/I

E- Voltage
I- Current flow
R- Resistance in ohm's

A general formula for calculating the necessary resistance (for 12v supply) will be
Resistance R = (12-Vf) / If

where "Vf" is the (forward) voltage of the led - this is usually indicated on the led packaging and ranges from 1.6v - 2.5v (sometimes upto 3.1v)

"If" is the current required by the led could be anywhere from 10mA to 300mA

If your calculation comes up with a resistance of 123.45 ohms you can round out to the nearest (commercially available) value which would 120 ohms

Connecting more than 1 leds in parallel means the current should be added ( If = I1+I2+I3+....) and the voltage is the same. If you connect them in series then the voltage should be added and the current is the same. Generally serial connection is not recommended if you plan to have more than 7 or 8 leds.

Another important thing is choosing resistor power which can be calculated by
power = (12-Vf) * If
and its always given in watts (w) - so if the above formula gives you a result of 0.1w then you are safe with a quarter (1/4) watt resistor (because 0.25 > 0.1). Resistors are commonly available in 1/4w, 1/2w, 1w, 10w etc ratings. This is a very important calculation because if you underestimate the power requirement (even if you did everything else right) then the resistor would definitely burn and will pose a fire hazard.

http://digikey.com
http://jameco.com
have cheap good leds and resistors and other accesories - but if you have a lot of money and dont know how to spend it - then you can always check out http://radioshack.com (from personal experience in this case high price does not mean good quality)

FlyVFR · Post by **FlyVFR** » December 28th, 2005, 2:57 pm

Very good ariesdude. I see you studied OHM's law as well as basic series and parallel DC.

Since you took the time to abridge OHM's law into a circuit desisn crash course, we may as well also mention all about resistors and why it's important to choose not only the correct value and power rating, but also the type of resistor (core material) and tolerance rating that have not been mentioned. These values must also be taken into consideration when designing circuits. Core material and tolerance are very important in specific circuit design for safety and precision.

We also did not mention how to read resistor values? Oooops we also need Watt's Law.

Introducing Watt's Law.
Where P is power in Watts.
P = I² R
P = VI
P = V²/R

V= DC voltage (joules per coulomb)
I= current
R= resistance

For the non-electrical engineering crowd if it's getting a bit involved I will leave the subject now by quoting airesdude.

ariesdude wrote: but if you have a lot of money and dont know how to spend it -

I am available to design custom circuits, such as multiple LED sequencers or more advance projects.

WARNING-DISCLAIMER: I do not recommend the wiring of custom LED circuits to work off of a 12V car electrical system directly unless one is familiar with resistor circuits, it's power selection and proper fuse protection as using the wrong values and or parts poses a fire hazard. The posted above calculation in Watt's & OHM's law is for educational purpose only!

jschrauwen · Post by **jschrauwen** » December 28th, 2005, 4:04 pm

OMG, I'm impressed. More electrical "Guru's". Next lesson will be on circuit board cooling and value changing of resistors due to heat ....LOL
I love it!!!!

Nd4SpdSe · Post by **Nd4SpdSe** » December 28th, 2005, 4:12 pm

So for the non-electrical engineering crowd if it's getting a bit involved I will leave the subject now by quoting airesdude.

I used this back when i was just hearning electronics, and still do cause it's really easy

http://led.linear1.org/1led.wiz
http://www.bit-tech.net/article/68/

FlyVFR · Post by **FlyVFR** » December 28th, 2005, 5:26 pm

Nd4SpdSe wrote:
So for the non-electrical engineering crowd if it's getting a bit involved I will leave the subject now by quoting airesdude.
I used this back when i was just hearning electronics, and still do cause it's really easy

http://led.linear1.org/1led.wiz
http://www.bit-tech.net/article/68/

I agree, it's a very simple and easy LED web site. IMO it should have a disclaimer. BTW I noticed the second link is no longer available.

FlyVFR · Post by **FlyVFR** » December 28th, 2005, 5:43 pm

jschrauwen wrote:OMG, I'm impressed. More electrical "Guru's". Next lesson will be on circuit board cooling and value changing of resistors due to heat ....LOL
I love it!!!!

I hate it when that happens... resistance value changing due to heat build up (AKA thermistor). Hope it will not result is a resistor flambe'... LOL

Taras · Post by **Taras** » January 4th, 2006, 2:57 pm

http://www.hidplanet.com/forums/viewforum.php?f=3

You have to be a registered user to read the stuff. Read the stickies and past threads (especially the big ones) there is a lot of info for 12v specific applications. Oh and serach before you ask simple questions.

Also:
http://www.luxeon.com/products/line.cfm?lineId=4
This is what's used in OEM automotive applications, under Quicklinks on that page, read the Documentation:
http://www.luxeon.com/products/line.cfm?lineId=4#docs
Especially, this one:
http://www.luxeon.com/pdfs/AB20-3.pdf

This should keep you busy for a while.

FlyVFR · Post by **FlyVFR** » January 4th, 2006, 6:40 pm

Taras wrote: Also:
http://www.luxeon.com/products/line.cfm?lineId=4
This is what's used in OEM automotive applications, under Quicklinks on that page, read the Documentation:
http://www.luxeon.com/products/line.cfm?lineId=4#docs
Especially, this one:
http://www.luxeon.com/pdfs/AB20-3.pdf

Good products