led keep buring out
Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=80414
Printed Date: May 02, 2024 at 10:54 PM
Topic: led keep buring out
Posted By: zzachattack2
Subject: led keep buring out
Date Posted: July 17, 2006 at 6:52 PM
I have a set of relays which work fine but as soon as i connect a set of relays (1 200 amp stinger and 2 80 stinger which are fairly large) which turn on from the same 12v power wire as the led's, several of the led's stop working, permanantly. Any ideas? It was suggested to me that the large relays might be drawing a quick large surge which could be burning out the LED's. Could this be true? If so what can i do about it?
Replies:
Posted By: zzachattack2
Date Posted: July 17, 2006 at 6:53 PM
Sorry at the beginning that was supposed to be "I have a set of LED's"
Posted By: killer sonata
Date Posted: July 17, 2006 at 7:59 PM
sounds like a voltage problem. Make sure that the voltage that you test the leds on is the same to the voltage they are being connected to.
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"People with mullets live 40% longer" - Ricky Bobby
Posted By: zzachattack2
Date Posted: July 18, 2006 at 4:31 PM
It is the same voltage, they only difference between when they work fine and when they burn out is the relays are connected to the same 12v power wire
Posted By: killer sonata
Date Posted: July 18, 2006 at 4:51 PM
are you saying its the same because you have actually tested it with a DMM or jus tthink its the same because its connected to a 12V?
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"People with mullets live 40% longer" - Ricky Bobby
Posted By: zzachattack2
Date Posted: July 19, 2006 at 3:38 PM
No I'm just saying its connect to the same physical 12v wire. They seem to burn out when i connect the relays to that same power source (12v wire). I'm going to try connecting it to a seperate 12v wire and see if that does anything.
Posted By: killer sonata
Date Posted: July 19, 2006 at 4:42 PM
thats what im saying. Test the voltage output of the relay that the leds are connected to so you make sure its definitely 12V. The only other thing I can think of is that you have the relay hooked up wrong and its blowing the leds.
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"People with mullets live 40% longer" - Ricky Bobby
Posted By: zzachattack2
Date Posted: July 20, 2006 at 3:47 AM
Alright sorry I must have confused you, the relays don't actually drive the LED's powersource, but they are turned on by the same 12v wire that powers the LED's. They carry a much heavier 4-guage wire from the battery. However being that they are very large relays, its reasonable to assume that they draw a considerable current for the time they are engaged.
Posted By: KPierson
Date Posted: July 21, 2006 at 12:57 PM
Do the LEDs burn out when the relay energizes or drops out? What kind of resistor do you have inline to the LEDs to limit current?
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Kevin Pierson
Posted By: 12vdeej
Date Posted: July 23, 2006 at 9:15 AM
If the the leds burn out when the relay switches off then i am fairly certain i know why. The coil in the relay is essential an inductor, and when a current stops flowing through it, a phenomina known as 'back EMF' takes place causing a high voltage spike on the power lines which can easily blow leds. This is why you see diodes connected accross relay coils, as it allows a low resistance path for the current to flow away from sensitive components. The diagram below is not for your specific situation, but shows how you should connect a diode in reverse polarity accross the relay coil. hope this helps 
Posted By: zzachattack2
Date Posted: July 23, 2006 at 5:53 PM
Ok thanks that makes alot of sense. Could i solve this problem by connecting the 12v line that powers the LED's to another wire isolated from the wire that turns on the relays? (For example the dome light 12v power source or something like that)
Posted By: stealthone
Date Posted: July 29, 2006 at 6:26 AM
Your problem sounds like too much in-rush current. Try recalculating the resistance of the current limiting resistor using 14 volts as your supply instead of 12 volts .
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