LED gurus, your help is needed. How do I power LEDs from the batt w/o frying them?

[Insomniac119 10+ year member]

You still need a resistor though, no LED won't fry without one. Just place it anywere in the series.

 

[MetalMaxima 10+ year member]

You still need a resistor though, no LED won't fry without one. Just place it anywere in the series.

Not nessecarily. It the LEDs are only pulling 3V and have a max forward voltage of 3.5V, there you don't need one.

 

[req 5,000+ posts]

You still need a resistor though, no LED won't fry without one. Just place it anywere in the series.

thats absolutly not true.

the max forward voltage is 14.4v, if you wire the LED's in series, the whole array will use 14v. the LED's are usually 3.2v each, so if four of them are wired in series, each LED will get around 3.6 volts - wich is fine, considering that they arent constantly used 24\7. if you wanted to be on the safe side, wire up 5 led's for the array.

all the resistor does, is bump the 12v source down to 3.2v - while instead, you can just wire them all on one wire and not have to deal with the resistor.

resistors arent needed for every LED install my good sir. learn your electronics a little bit more //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

if you are still doubting me, ill make one up, hook it to my battery terminal with no resistor for 24hours and you can tell me if they fry... hows that? ill even send you $20 paypal if they do.

 

[Justin89T 10+ year member]

thats absolutly not true.
the max forward voltage is 14.4v, if you wire the LED's in series, the whole array will use 14v. the LED's are usually 3.2v each, so if four of them are wired in series, each LED will get around 3.6 volts - wich is fine, considering that they arent constantly used 24\7. if you wanted to be on the safe side, wire up 5 led's for the array.

all the resistor does, is bump the 12v source down to 3.2v - while instead, you can just wire them all on one wire and not have to deal with the resistor.

resistors arent needed for every LED install my good sir. learn your electronics a little bit more //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

if you are still doubting me, ill make one up, hook it to my battery terminal with no resistor for 24hours and you can tell me if they fry... hows that? ill even send you $20 paypal if they do.

You're absolutly correct! Although you can send me 20 bucks paypal for agreeing with you if ya'd like //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[req 5,000+ posts]

lol. you can send me $20 paypal for drawing that picture.

 

[88irocZ 10+ year member]

i am putting led's in my car this weekend also and i was wondering can you wire up more than four to a switch if so how?

 

[Spr0ket 10+ year member]

Use a series parallel circuit. You can branch the lead (Parallel) out as many times as you want and set each branch with the appropriate load (14.4V max Series). So if you wanted, you could have 16 LEDs run from one source using four branches of four. My dome light has a total of 16 LEDs but they are all wired parallel using 1/4W 560 ohm resistors for each cathode.

 

[Insomniac119 10+ year member]

thats absolutly not true.
the max forward voltage is 14.4v, if you wire the LED's in series, the whole array will use 14v. the LED's are usually 3.2v each, so if four of them are wired in series, each LED will get around 3.6 volts - wich is fine, considering that they arent constantly used 24\7. if you wanted to be on the safe side, wire up 5 led's for the array.

all the resistor does, is bump the 12v source down to 3.2v - while instead, you can just wire them all on one wire and not have to deal with the resistor.

resistors arent needed for every LED install my good sir. learn your electronics a little bit more //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

if you are still doubting me, ill make one up, hook it to my battery terminal with no resistor for 24hours and you can tell me if they fry... hows that? ill even send you $20 paypal if they do.

Well then good, I learned something. After reading that explonation, it makes sense to me now. I've never wired up multiple led's before, just one at a time, and so I didn't think that it could work that way.

 

[Justintoxicated 10+ year member]

haha I'm probabloy the LED expert on this forum

However I don't use notmal LED's anymore only Luxeon 1,3, and 5 Watt LED's I don't play with overpriced "superbrights" These things are not even rated in mcd just cd. So all you need is ONE.

As for running LED's off the Battery it is sorta difficult to power them correctly since your cars voltage changes from when it is on to when it is off 12.5-14.4

So a Resistor will not work quite right, if you don't want them to dim, and if you want them to always run at max voltage, what you want is a current limiting Circuit/resistor. If you know how to wire things up an LM317T from radioshack can be setup properly to provide the correct Current to your LED's with variable voltage. Basicaly if you wire your LED"s for their recomended Current (if it's 200ma then you set it for 200ma) then you can provide them anything voltage over their recomended voltage and it disipates the extra power as heat, should be fine for regular LED's since they have such a low current value.

The secreat to runing LED's is not to regulate them with voltage it is to regulate them with current. If you provide an LED's it's proper Current the voltage will automaticaly be correct. If you regulate an LED that needs say 500ma to be it's brightest it will not matter what the voltage is going to the Regulator the LED"s will be running at exactly what voltage it needs (The LED"s Forward Voltage)

People think I used hundreds of LED's on my ATV when I only used 4. This is a pic of my ATV with 2 3watt blue LED's for underlighting and 2 1 watt red's for the taillight.

I'd be glad to help you with an LM317T if you have any questions just PM me.

you COULD just use a resistor, and either slightly overdrive or underdrive your LEDs, but the LM317T can ensure you are running them perfect.

 

[orphe 10+ year member]

lol.
heres what ya do.

when the car is on, they will get 3.5v each - the array should only pull like 80ma of current, so dont worry about it, but make sure your wire can supply that. if you wanna put them in your dome light, you can just hook directly to the +\- of that bulb jack. if you wanna do accent lighting, you can hook into the fusebox in the dash on a switched wire (key on = power, key off = no power) and you can put some kind of switch (potentimeter? sp? lol ) on the negative lead to power them on or off depending on your mood.

hope that clears it up. anything more than 4v for a few seconds could possibly kill them. that might be your problem.

you shouldnt need any resistors if you just wire them how i have shown above by the way.

Your gonna burn up those LEDs if you wire them up like that... the apmerage on a car battery alone could fry them

put a 270 ohm resistor in the circuit and you'll be fine

like what, $0.89 at radio shack?

 

[Justintoxicated 10+ year member]

Your gonna burn up those LEDs if you wire them up like that... the apmerage on a car battery alone could fry themput a 270 ohm resistor in the circuit and you'll be fine

like what, $0.89 at radio shack?

Not true, the LED's will only use a certain level of current if you regulate the voltage (actualy you can only regulate voltage by regulating current is the reight wayt o look at it). Every LED draws a certain amount of current when a certain amount of voltage is provided.

Best to regulate the current though since car's voltage changes.

LM317T from Rat Shack and a the proper resistors to set it's current and your good to go.

Start here.

http://led.linear1.org/a-cheap-current-regulated-luxeon-star-driver-design/

and here

http://led.linear1.org/why-do-i-need-a-resistor-with-an-led/

 

[req 5,000+ posts]

technically, if you just set up the LED's to run at the max voltage for the car - ie 14.4 (like i used in my picture) you arent going to be frying anything, because it will rarely always be 14.4, and if it drops, thats even better for them.

so why go thru all the trouble. mine are working just fine.

and luxeon stars are all good with a bag of chips, but you have to heatskink them, and they put out an awful lot of light for 'accent lighting' //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[thylantyr 10+ year member]

You should try the LED Zeppelin brand of lights //content.invisioncic.com/y282845/emoticons/spank.gif.0d78e34d42ea8780359e903aeb6697d6.gif//content.invisioncic.com/y282845/emoticons/clap.gif.178cba2c538c68e720c727fcb024b19c.gif//content.invisioncic.com/y282845/emoticons/hide.gif.2d479cfd917eedfe201353b91522ceab.gif

 

[req 5,000+ posts]

they would be awesome. they emit light energy, heat enegery, and acoustical-all-up-high-on-the-tiny-strings energy!

alllllrigggghhhht!!!

 

[jujumantb 10+ year member]

technically, if you just set up the LED's to run at the max voltage for the car - ie 14.4 (like i used in my picture) you arent going to be frying anything, because it will rarely always be 14.4, and if it drops, thats even better for them.
so why go thru all the trouble. mine are working just fine.

and luxeon stars are all good with a bag of chips, but you have to heatskink them, and they put out an awful lot of light for 'accent lighting' //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Yes, in my experience, when an LED says 3v max it MEANS 3v max (imagine that //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif ) I went through the effort of soldering 2 long strings of them but never figured 12v vs 14.4 would be that big of deal when its only like .5 volt difference per LED, I was wrong, within seconds of the car on, one by one they bit the dust //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif Thats what we call learning the hard way...