leds not working?

Reply Subscribe

Thread Tools

Search this Thread

Aug 15, 2008 | 05:39 PM

crestfallinman

Thread Starter

Laughing Gas

Joined: Dec 2007

Posts: 848

Likes: 1

From: Bethel Park, Pa

leds not working?

i hooked up 4 leds in my truck in the vents, and i spliced into the radio power and grounds

nothing works, is the ground wire too long?

any thoughts?

Aug 15, 2008 | 05:44 PM

Virto

Posting Guru

Joined: Jun 2007

Posts: 1,394

Likes: 0

From: Des Plaines, Illinois

I'm no electrical expert but knowing LEDs have very little draw, is the radio power maybe too much current for them?

Aug 15, 2008 | 05:53 PM

football3295

New User

Joined: May 2006

Posts: 12

Likes: 0

if you spliced into the speaker wires usually they will light up with the beat of the music because the higher the beat the more juice going to the speaker but there isnt allways a lot of juice pushing to speaker so i would hook them up to something elese.

Aug 15, 2008 | 05:56 PM

88F-150pimp

Senior User

Joined: Dec 2003

Posts: 298

Likes: 0

No offense, but I think you need to read up on LED's a little bit before you continue. Most LED's operate at around 2 volts and somewhere around 10 to 20 milliamps of current. This varies of course, but you get the idea. Hooking these directly to your 12V radio power will blow the LED's out in seconds. Secondly, you can wire the LED's one way, as they are diodes, not lightbulbs. positive to the anode, negative to the cathode. The anode is the longer lead of the LED. So....make sure your LED's are connected the right way, and wire in a resistor so that your LED's are seeing the proper voltage and being fed the appropriate amount of current. Of course make sure your ground is good (~ 0.0 ohms to battery negative) and you have voltage at your radio power wire.

Aug 15, 2008 | 06:34 PM

ArdWrknTrk

pedant

Joined: Jan 2008

Posts: 23,576

Likes: 38

From: EXTREME southwest CT

Quote:

Originally Posted by 88F-150pimp

So....make sure your LED's are connected the right way, and wire in a resistor so that your LED's are seeing the proper voltage and being fed the appropriate amount of current.

You need to know the voltage and current ratings of the LED's you're using and the source you're powering them with.
Then check this out in order to find the proper resistor to use w/ them.

hth,

Last edited by ArdWrknTrk; Aug 15, 2008 at 06:35 PM. Reason: highlight link

Aug 15, 2008 | 09:05 PM

crestfallinman

Thread Starter

Laughing Gas

Joined: Dec 2007

Posts: 848

Likes: 1

From: Bethel Park, Pa

oh i forgot to say that they are 12 volt led with 4 leds in each

i figured the radio would be good only because it turns on with the ignition and it was easy to splice into

Aug 15, 2008 | 10:41 PM

quaddriver

Cargo Master

Joined: Jan 2004

Posts: 2,512

Likes: 8

From: Cook Forest and Irwin PA

Most LEds use for decoration have the resistor cast in the lexan now. but they are P-N junctions - aka actual diodes (I freak people out by using LEDs to rectify AC)

anyways, your amp has 12v power source and likely has a built in inverter to run +12v/-12v at the amp rails - wide open. any less volume and the voltage is less. and since the amp output is actually a sin wave (ac current) you will get enough 'on time' each second to see it, BUT, since the speaker is 4ohm, and the LED is (how many watts or mA of current?) what is that kirchoffs? law (its been a long time since I studied) says most of the current by far will skootch down to the speakers.

just for grins, toss in a 1K resistor (just in case) and hook up to 12v and see if you get anything. btw - there are tri color LEDS (simply a red and a green nose to tail) that show yellowish under ac