voltage greater than 14 for led panel

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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=100573
Printed Date: July 07, 2025 at 6:21 AM

Topic: voltage greater than 14 for led panel

Posted By: 68jimmy
Subject: voltage greater than 14 for led panel
Date Posted: December 30, 2007 at 12:52 PM

I have been using the led wizard to design an led panel for my truck. M problem is that I have anywhere from 14.2 to 14.5 volts. My panel will consist of 120 super bright red leds configured as 6 x 20. Is there a way to install a simple voltage regulator to keep a constant 12v across my panel?

Thanks in Advance!

donovan

Replies:

Posted By: KPierson
Date Posted: December 31, 2007 at 12:35 AM

You're best bet would be to go with a 5vdc regulator - like a 7805. You could possibly go with a 7812 (12vdc regulator) but you generally like to see at least two volts higher then your regulator output on the input at all times (so 14.0vdc on the input of the 12vdc regulator). If the car isn't running, you won't have the 14vdc. If you go with a 5vdc system you'll always have enough headroom. You can get a 7805 in a 1A package at Radioshack. If you need more then 1A you can wire them in parallel. If you are using over 100mA of current from a single 7805 you'll need to add a heatsink.

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Kevin Pierson

Posted By: 68jimmy
Date Posted: December 31, 2007 at 2:11 PM

After doing a bit more reading and research I was intrigued by perhaps using a 12v zener diode across the parallel/series setup. Have you had the opportunity to try such a setup? It looks good on paper but I'm not sure that my calculations are correct and that I really need as big a diode... Thought?

Thanks.

Posted By: KPierson
Date Posted: December 31, 2007 at 2:45 PM

I would still go with a 5vdc regulator.

If you go with a zener you will need to completly isolate the LED voltage from the battery voltage, because you don't want to zener clipping the output from your alternator (not that you would ever get a zener diode with that much current capacity). You would probably need a large power diode and then a large current, but low resistance load resistor or something along those lines.

With the 5vdc regulator all you'll need is the regulator, a couple optional (but recomended caps) and your current limiting resistors for each LED (or each bank, however you choose to do it). I always recomend individual resistors, but with 120 LEDs I might put one resistor for 2 or 3 LEDs. Remember, if you use one resistor for 6 LEDs if something in that leg fails the entire segment will go out.

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Kevin Pierson