Educate me on LEDs

[intothewild]

Ok, so admittedly, electrical is not my strong suit. I have been wanting to replace my reading lamps inside my Astro with LED's. I was just poking around, and had one of those LED flashlights that harbor freight is always giving away. It's got two settings, 3 LED on one side, and 24 LEDs on the other. I pulled it apart, dropped the reading lamp from the roof. I left the button engaged on the LED Light board, so that when I would turn the reading lamp switch on, that it would power on automatically.

Anyways, long story short.

It worked. HOWEVER, it got very hot, very fast and would even start smoking.

I am guessing that I am missing a middle link somewhere, the factory wiring I assume is too much power for the LED's thus causing it to get HOT very fast. The board still works, but I literally only left it hooked up for a split second before it got super hot.

So, am I on the right track? Is there something I can place in between the LED light board and the factory wiring to back the power down a notch? I like that this simple idea could have some merit and be a nice functional/cheap upgrade, but I am not burning my rig down in the process. :sombrero:

 

[mgmetalworks]

Here's a decent tutorial on LEDs....

http://electronicsclub.info/leds.htm

Basically, the LED you have is probably designed to work at a much lower voltage than the 12V car system. Over driving an LED will cause it to heat up and eventually destroy itself. There is a specific resistor needed in the circuit for the amount of supply voltage you're running through the LED. You're better off getting an LED bulb designed for a 12V system since they are relatively inexpensive.

MG

 

[intothewild]

Thank you, that give's me a starting point. Surprisingly, the LED still functions just fine.

 

[dwh]

LEDs will burn out if run at too high a voltage. Your truck's battery is gonna be somewhere between 12v-14v and the flashlight will probably have either 2 or 3 1.5v batteries in series. So the LEDs from the flashlight are designed to run at either 3v or 4.5v depending of if it has two or three batteries.

So the little doohickey you need is a voltage regulator. LM78xx series. Here's a pic of an LM7812, which limits the voltage to 12v. If your LEDs needed say 4.5v, then you would want an LM7805 which would limit to 5v.




Radio Shack carries them:

http://www.radioshack.com/product/index.jsp?productId=2062599

Don't forget to screw it to a heat sink...

 

[bobDog]

This could turn into a very interesting thread. since I know nothing....I'm subscribing.

 

[intothewild]

LEDs will burn out if run at too high a voltage. Your truck's battery is gonna be somewhere between 12v-14v and the flashlight will probably have either 2 or 3 1.5v batteries in series. So the LEDs from the flashlight are designed to run at either 3v or 4.5v depending of if it has two or three batteries.

So the little doohickey you need is a voltage regulator. LM78xx series. Here's a pic of an LM7812, which limits the voltage to 12v. If your LEDs needed say 4.5v, then you would want an LM7805 which would limit to 5v.

View attachment 165161


Radio Shack carries them:

http://www.radioshack.com/product/index.jsp?productId=2062599

Don't forget to screw it to a heat sink...

Awesome, thank you for that! I will be visiting radio shack later, I will just start with one and see how it works out. If all goes well, I will do more.

 

[silvrzuki77]

I converted all my campers lights using my buddies mod. Works awesome and cheap!!!
http://www.pirate4x4.com/forum/tow-...r-cheap-led-interior-lights-build-thread.html

 

[DaveInDenver]

A voltage regulator like the LM7805 will work to drop the voltage to the LED board but don't forget that the heat still needs to go somewhere, so probably be a good idea to mount the regulator to a heat sink. The 24 LEDs will draw a fair amount of current, I'd guess in the 500mA range. So the regulator will be dissipating a few watts (12V - 5V * 0.5A = 3.5 W), which if you tuck it away where there's not a lot of air flow might shorten its life. Doesn't have to be fancy, a piece of aluminum, maybe right on some sheet metal or something with a bit of thermal grease.

 

[Accrete]

Yes on what's been said by others on voltage match and such.

On an LED related note...If you happen to want to replace your rig's standard interior bulbs this next info might be the ticket...it worked well for me.
I went from bumper to hitch on our 38ft 5th wheel and our 15 foot fiberglass TT and replaced all the 12v fixture's standard lighting with these guys: They will fit the bayonet mounts or the clip type.

Thom

 

[pugslyyy]

Yes on what's been said by others on voltage match and such.

On an LED related note...If you happen to want to replace your rig's standard interior bulbs this next info might be the ticket...it worked well for me.
I went from bumper to hitch on our 38ft 5th wheel and our 15 foot fiberglass TT and replaced all the 12v fixture's standard lighting with these guys: They will fit the bayonet mounts or the clip type.

Thom

I like the Green LongLife products. I just installed a bunch of these ones - I liked them a bit better because of the tidy packaging



I've also had good luck buying LEDs through DHGATE. Some of the prices you can get are ridiculous.