little LED lights

misfitsfiend · Post by **misfitsfiend** » February 28th, 2005, 10:50 pm

i got some little led lights i want to stick in my ac vents... how would i get a 12 v wire from somewhere to light these little guys up?

DJsMX-3 · Post by **DJsMX-3** » March 1st, 2005, 5:17 am

Uhmm how about from the illuminationwires in your car

Remember a resistor and to calculate the value of it correct, so you wont overload it when you turn your dashlights up to max..

misfitsfiend · Post by **misfitsfiend** » March 1st, 2005, 1:25 pm

thats a good idea.... but which colour wires would be the ones that provide the energy.. and which ones would be to ground ?

Grants · Post by **Grants** » March 1st, 2005, 3:44 pm

So you just got the LEDs? Not the ones with the cigarette lighter plug? Make sure you do what DJsMX-3 said about the resistors or else you'll burn them out.

Theres wiring diagrams on my web page if you want to look up the wire colours but the ground you can pick up anywhere on the frame. Personally though, I'd put them on a switch and run a new supply from the fuse box.

DJsMX-3 · Post by **DJsMX-3** » March 2nd, 2005, 9:14 am

Okay i cant remember the wire colourcombination but you can see that behind your dimmer, or read it in the online shopmanual now that its back on, then either run wires from dimmer to your LED's or try to get to the wires of the bulb behind the HVAC

Ill put this in for others to allthough i have written it on here before i think, so searching could help finding out how to calculate resistors for LED's..

But in order to calculate the resistors right you need the technical info on them first "forward voltage, max current"

Oh and ALLWAYS get LED's with a Wide viewingangle 30-60Degrees, theyre the best for allmost all purposes, dont get fooled by ebaylistings of LED's with 10000mcd of light and 10Degree viewingangle, they just make very bright dots whereas a 700mcd 45Degree LED spreads the light much more and still has a very bright lightoutput

Ordinare LED's use 1.5-2.1VF but Blue UV and Highpower LED's have a VF from 3.5-5volts so you need the VF..

Way to calculate is: UB - VF / A = Ohms
If you have a 12v supply, LED with a VF of 3.6 and a maxcurrent of 20mA you get 12-3.6/0.02 = 420

Nearest resistorvalues are 390 and 470 Ohms, since 390 would exceed the max current the 470 is used and the actual current of the LED is found by calculating backwards: UB - VF / Ohms = A

12-3.6/470 = 17.8mA

NB: this is NOT the value for this application, just an description on how to find the correct value

Allways keep in mind that Voltage in car exceeds 12V and you need to calculate the resistorvalue with "worstcase" in mind, thats the maximum of Voltage comming from the Batt. if not you could ruin the LED with excessive current because the restistor was based on a 12V input..

In this case you have to keep in mind the dimmer never opens completely,at maxsetting it still "eats" 2V, so if the incar voltage was a constant 12V you'd have to calculate your resistor with 10V as max

mx3frik · Post by **mx3frik** » March 3rd, 2005, 6:04 pm

awesome write-up, I was going to post a linkie to nasioc.com but I guess that post cleared it up

One thing to keep in mind is that a 12V battery is 'full' at 12.7V. When the car is off it's safe to assume 12.4V, and when the car is on the alternator charges the battery at 14.5V or so.

I was playing around w/ LED's for my engineering project and for my HVAC lighting in my legacy, one thing I foud is if you just clip the top of the LED (clip off the round part) you will get a really wide and almost uniform beam coming out, angle at roughly 120 or larger.

happy lighting

Eugene

93SOHC · Post by **93SOHC** » March 4th, 2005, 1:55 am

DJsMX-3 wrote:Okay i cant remember the wire colourcombination but you can see that behind your dimmer, or read it in the online shopmanual now that its back on, then either run wires from dimmer to your LED's or try to get to the wires of the bulb behind the HVAC

Ill put this in for others to allthough i have written it on here before i think, so searching could help finding out how to calculate resistors for LED's..

But in order to calculate the resistors right you need the technical info on them first "forward voltage, max current"

Oh and ALLWAYS get LED's with a Wide viewingangle 30-60Degrees, theyre the best for allmost all purposes, dont get fooled by ebaylistings of LED's with 10000mcd of light and 10Degree viewingangle, they just make very bright dots whereas a 700mcd 45Degree LED spreads the light much more and still has a very bright lightoutput

Ordinare LED's use 1.5-2.1VF but Blue UV and Highpower LED's have a VF from 3.5-5volts so you need the VF..

Way to calculate is: UB - VF / A = Ohms
If you have a 12v supply, LED with a VF of 3.6 and a maxcurrent of 20mA you get 12-3.6/0.02 = 420

Nearest resistorvalues are 390 and 470 Ohms, since 390 would exceed the max current the 470 is used and the actual current of the LED is found by calculating backwards: UB - VF / Ohms = A

12-3.6/470 = 17.8mA

NB: this is NOT the value for this application, just an description on how to find the correct value

Allways keep in mind that Voltage in car exceeds 12V and you need to calculate the resistorvalue with "worstcase" in mind, thats the maximum of Voltage comming from the Batt. if not you could ruin the LED with excessive current because the restistor was based on a 12V input..

In this case you have to keep in mind the dimmer never opens completely,at maxsetting it still "eats" 2V, so if the incar voltage vas a constant 12V you'd have to calculate your resistor with 10V as max

Faq worthy?

Grants · Post by **Grants** » March 4th, 2005, 4:31 am

No offence as its good information but its very generic. Not specific to MX3s at all.

I'd like to see it written up as a pdf file or something and linked from this site. Hey maybe it already is somewhere??? Probably.

I'd like to see a lot of this sort of generic info available but it needs to be on a site that ain't gonna fall over. No good putting it here - this is MX-3.com and theres enough specific information to keep this site full and admin busy. Thats the frustrating thing - how many links from this site don't work any more? Nobody here's fault but things change and the web is very fluid. We should consider ourselves very lucky Jeff has been so consistant.

I'd like to say I'd host it but how many generic topics are there? Thousands? Millions? And I still might get run over by a bus!

Maybe we should start a thread to consider our options to compliment this site with information on these general issues? Work with Jeff and tie together extra resources???

Ha! Why did I say this here??? The only people who read it are expecting something on "little LED lights"!

DJsMX-3 · Post by **DJsMX-3** » March 4th, 2005, 9:55 am

Well it wasent written to be put in the FAQ but youre argumenting that it wasent MX-3 specific, but it is

Dont know if other cars dimmer work in the way i described, thats why i wrote it He he...

If somebody on here really wants something about LED's for the FAQ lighting section i could do it right, it would be my pleasure to do something for the community, but what i put into this post covers the most basic of it

Grants · Post by **Grants** » March 4th, 2005, 4:45 pm

Its good info DJsMX-3, maybe write it up again, add the wire colours and post it under a new heading "Calculating LED Resistor Values" or something? That way it could be easily searched for and be a complete reference. It would also be a good format then for the FAQs.

Maybe even add a couple of sample calculations for the different voltages for specific installations, ie on the dimmer or on a switch...

Someone else could do it but I reckon your the man for the job!

Edit: And what about a calculation for LEDs in series? That might be good to add as well?

Chiggles · Post by **Chiggles** » March 8th, 2005, 1:20 pm

Check this out: http://www.varad.com/products/products-index.html Click on the HyperLED ILKs (5th from the left)

I came across those while browsing around and remembered this thread regardding the possible necessity of using resistors while installing the LEDs, but an install guy at work said that it's probably not necessary with these since there's just a wire for ground and a wire for power that runs them. He believed you should just be able to splice into a regular 12V line and go. The only thing he could think of that might be necessary was to upgrade the fuse(s) to something more powerful, but a resistor probably wasn't necessary. What do you guys think?

DJsMX-3 · Post by **DJsMX-3** » March 8th, 2005, 5:37 pm

Well if you click on the pic where theres a coin besides the LED to illustrate the size, you can actually see the little black SMD resistor through the orange plastic

So yes theres a inline resistor...

But why waste mony of thoose? their narrowangled as hell anway "you see that if you click the picture with the array of diffrent colours"

Go to ebay instead "if you want narrowangled LED's" and you can get 100 30Degree viewingangle LED's in your desired colour and lightintensity including resistors and schrinktube at super costs if you search around

Grants · Post by **Grants** » March 8th, 2005, 5:52 pm

I came across those while browsing around and remembered this thread regardding the possible necessity of using resistors while installing the LEDs, but an install guy at work said that it's probably not necessary with these since there's just a wire for ground and a wire for power that runs them. He believed you should just be able to splice into a regular 12V line and go. The only thing he could think of that might be necessary was to upgrade the fuse(s) to something more powerful, but a resistor probably wasn't necessary. What do you guys think?

If you get the ones in that link you won't need to add more resistors. Thats what the little orange box is for - to house the resistor. You definitely will need to add resistors if you get the LEDs only - not possibly but definitely.

They use such a small amount of power, to need to upgrade the fuse you'd have to install several hundred of them. Please don't do that

mx3frik · Post by **mx3frik** » March 8th, 2005, 9:14 pm

if you're curious to see how LED's pop then hook them upto 12V supply straight up...it's kinda nifty when you have a few lying around

Chiggles · Post by **Chiggles** » March 9th, 2005, 12:58 am

mx3frik wrote:if you're curious to see how LED's pop then hook them upto 12V supply straight up...it's kinda nifty when you have a few lying around

"Pop"???? Huh???