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Connecting LED's to car battery

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Cazzo

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YOoooooooooooooooooooooooo

Hello, simple circuit

I have a strip of LEDS i want to connect to the inside of my boot. i know where the wire is for the boot lamp so it only turns on when the boot is open but.

If i connect LEDS to 12V car battery they will just explode everyware right. what do i do so that they will always work?

-Also, will it matter the way i connect the LED'S?? Series or parallel which is best??????

and will this circuit depend on the amount, i think it will. If i have some in my boot, some under the dash board, some here, some there. and they have 12 LED's on them, or 6, or 8 etc how will the circuit change, and how can i know this so everytime i connect LEDS of a certain amount, i will make it work.


Separate but related matter
- Having LED's in the boot flash to music at the flick of a switch..

--> Same LED's in boot that are controlled off the boot switch, i want to be connected to a music to LED sync circuit that i can flick a switch and they will go.

Hope you know how to help brah
 
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The exploding was a joke, and yes i know i need to limit current but im asking how... use resistor..what value? how many?

How do i measure the amount of resistance needed (a resistor) depending on how many LED's i have

Please guys if you actually know how to explain an answer can you do that. and not direct me to other sites.. this is electronics forum, im askin bout electronics.

If you dont know the answer, its fine. If you know but cant be bothered to tell, dont comment. Thanks boiz
 
  1. Determine the forward voltage of the LED. Check the datasheet, it is most often called Vf
  2. Determine how many LEDs can be strung together without exceeding 12v
  3. Determine the maximum current rating of the LEDs
  4. Calculate the minimum value of the resistor

Example:
Assume you chose an LED with a Vf of 3.5v. 3 LEDs in series would give you a total Vf of 10.5v. When the car is running, I believe the battery voltage is around 13.8v. 13.8-10.5 = 3.3v. If the maximum current rating of these LEDs is 200mA, the resistor value you'd use is 0.2A = 3.3v / R or R = 3.3v / 0.2A = 16.5 ohms.

If the car is running, your LEDs will be driven at 200mA given the above example. With the car off, the battery voltage will be much lower, around 12v. (12v-10.5v)/16.5ohms = 90mA. This is likely be MUCH dimmer. You can get around this by using fewer LEDs and a higher resistor value. This isn't a perfect solution, but it will improve regulation.

Another solution is to use a constant current source. Check out page 11 of this datasheet on how to build a simple constant current source:
https://www.electro-tech-online.com/custompdfs/2012/01/CD00000469.pdf

Now if you want to blink to music, that'll be a bit different. Here is a simple solution I found on Instructables:
https://www.instructables.com/id/Music-LED-Light-Box/

Whatever you come up with, create a schematic for it and post it here on the site. People will offer suggestions on what you can do to improve it. Cars can be terrible environments for electronics. A circuit will need adequate protection or it could fail quickly.

Edit: Running an LED at 200mA was only an example. 200mA LEDs are often very bright and require heat sinking to run at that current. Depending on what you're trying to do, 200mA may be extreme overkill (and very painful to look at up close).
 
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You have LEDs in your boot??
I have my foot in my boot. You talk funny down under, MATE! (a smilie dosn't work anymore)

A sub-woofer is in the trunk of my car, not in my boot. Sometimes my car passes trucks on the road, not lorries.
The engine of my car is under the hood, not bonnet.
I drive on the RIGHT side of the road but you drive on the left RONG side.
My car runs on inexpensive gasoline (not petrol) and yours runs on taxed-to-death stinking diesel.

NEVER look at Instructables circuits that are designed by 12 years old little kids who know NOTHING about electronics.
The link shows a transistor that shorts the stereo because it is missing a series base current-limiting resistor so the stereo and/or the transistor might blow up.
It also shows no current-limiting resistor for the LEDs so they also might blow up.
It shows four 3.5V blue LEDs in series. Then the supply must be at least 14V. It also shows a photo of six 3.5V white LEDs in series. Then the supply must be at least 21V.
 
You provide the data for the LEDs you have (as mentioned) and myself or someone else will help you and show you how to choose a resistor. LED Forward Voltage Vf and Forward Current If.

Ron
 
NEVER look at Instructables circuits that are designed by 12 years old little kids who know NOTHING about electronics.
The link shows a transistor that shorts the stereo because it is missing a series base current-limiting resistor so the stereo and/or the transistor might blow up.
It also shows no current-limiting resistor for the LEDs so they also might blow up.
It shows four 3.5V blue LEDs in series. Then the supply must be at least 14V. It also shows a photo of six 3.5V white LEDs in series. Then the supply must be at least 21V.

I am in 100% agreement with the idea that instructables are written by people that don't know what they're doing. But that's one of the main reasons why I told him to create a schematic and post it.
 

A trunk is something elephants have hanging on their noses.
We have trucks too :)
A hood is something little red riding hood wears on her head.
The right side is the wrong side.
Gasoline, petrol and diesel are all taxed-to-death here :)
 
G'day MATE!
You are VERY far away from me in Canada so of course you have a very strong accent. In other far away countries they speak a completely different language and yours is almost completely different from mine.
 
use a 1k ohm resistor on a single led..cant go wrong..
Ive run single 5mm leds on 12v with a 470 ohm.. a pair 200ohm, three 100ohm. 1/2 watt resistors 1/4watt resistors will do fine.
To make them beat to the music..LM3915.. you'll get your signal either from a speaker out or an auxillary audio out on the stereo.But if your having a little difficulty with leds..the LM3915 circuit may overhelm you a little...
not to mention youll have ten leds going,per side on two 3915 circuits even better if you can get the signal from a low pass,,nothing but bass flickering looks really nice.
 
Thanks guys, very detailed helpful instructions :)

lol accent, boot, trunk watever. What i am doing is having coloured LED's wired around my subwoofers and boot lining to have a sick as neon glow around the subs as they blast. instead of a single boring boot lamp it will be fully sickas..

Audioguru you probs know me, im Chris15 from Allaboutcircuits ;)

And again, thanks for those who took the effort to help, appreciate it.

Also, it dosent matter that they are bright, or will need heatsinks. they are for boot lamp. they will only be on for when the boots open, and if im drunk and leave it open all night, then HAHAHAHAH to me.

Simple Minimal, anyone can say i need a resistor to limit current... see how the other commenters took the time to help. your comment did nothing for me, so i kindly ask that in future if you dont feel your comment will benefit me, dont comment :) Thanks
 
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Simple Minimal, anyone can say i need a resistor to limit current... see how the other commenters took the time to help. your comment did nothing for me, so i kindly ask that in future if you dont feel your comment will benefit me, dont comment :) Thanks

YouTube video link I gave to you was worthless ? :D
 
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Nope, quiet helpful but im talkin bout ur first comment and how i had to get the link out of you. even then you didnt explain it. dw bout it, i got help from others. i cant change people like you and i dont really care.

I'm talkin about reading everything i wrote and trying to answer every aspect of my question to your best ability. not say i need a resistor... dw brah.. live your life as you do, if it works for you then good on ye :)

DELETED MODERATION: Abusive
 
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use a 1k ohm resistor on a single led..cant go wrong..
Ive run single 5mm leds on 12v with a 470 ohm.. a pair 200ohm, three 100ohm. 1/2 watt resistors 1/4watt resistors will do fine.
To make them beat to the music..LM3915.. you'll get your signal either from a speaker out or an auxillary audio out on the stereo.But if your having a little difficulty with leds..the LM3915 circuit may overhelm you a little...
not to mention youll have ten leds going,per side on two 3915 circuits even better if you can get the signal from a low pass,,nothing but bass flickering looks really nice.

i like the sound of your circuit. is there any more you could explain about it, or give a schmatic?

im assuming bass would have a good voltage to monitor compared to constantly changing music. so the circuitry would be simpler, and as you said just bass will look sick
 
Just google LM3915 VU meter.
This one looks promising

https://www.servicetron.com/vu-meter-circuit.html

look at VU meter 4....Experiment a little that's what I did to tweak it just right
using a 2n3906..you can load 3 or six leds to a segment channel..
Toot my own horn but I have the LM3915 driving 10 relays on 10 sets of christmas lights..using the low pass filter/amp from an old set of sub/sat computer speakers..
built my own FM transmitter,got an old portable stereo from the 80's
,transmitting on 89.1 FM..I can have ZZ Top blaring in the house and the lights kicking to the base outside..Viva Las Vegas is killer.

Oh ..and experiment with the bar and dot mode,,rolling bass can offer up a cascading effect in dot mode..
 
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