LED Light voltage limiter

[Mylestec]

Greetings to all;

Please pardon me if I've missed this topic posted elsewhere but a quick search only found remote and tangential topics.

I've been in the process of re-wiring a 25' sloop with no engine driven alternator (pull start outboard). In an attempt to increase the efficiency of battery usage on board I've replaced all lighting with LEDs. I purchased a trio of waterproof LED light strips that I've come to discover could be damaged by voltage exceeding 12v.

I'm concerned that when charging my batteries, either via shore power or solar, that the LEDs could be damaged by +14v charge current (if someone switched them on). Does anybody know of a good, cheap, quick, (I know you can only choose two of the three!) solution to limit voltage? The total draw for each of the light strips is approx. 0.86amps.

Many thanks in advance for all your assistance!

-brandon

[marshmat]

Hi Brandon,

If you want to put a voltage regulator in your LED light circuits, it's a pretty simple and cheap part. Solid-state regulators are commonly used in all sorts of electronics, and a 1 amp 12 volt piece only costs a dollar or two.

Check out http://search.digikey.com/scripts/DkSearch/dksus.dll and search for "voltage regulator", then filter the results by the output current and voltage you need. For example, a Rohm BAJ2CC0T in a TO-220-3 package gives up to 1 amp at 12 volts, from an input up to 25 volts; a pack of 25 is about thirty bucks.

[Mylestec]

Thanks Matt!

Is this something like a Zener diode? Any suggestions on how to integrate it into my lights.... for example, would I solder it in line on the positive lead close to the light and encase in heat shrink?

Thanks again!

-brandon

[marshmat]

They're designed to be soldered to a circuit board.... one pin to hot, one to ground, and the remaining pin is the supply to the regulated circuit. True voltage regulators are somewhat more sophisticated than a Zener; there's plenty on the web about their innards if you feel like it. You could inline them, yes. But it'd probably be better to solder them to little scraps of circuit board material and encase in epoxy, leaving a place to clip your wires to of course. Frankly I'm surprised your light strips don't seem to have such a regulator built in.

[Mylestec]

Thanks again Matt.... in that case it may be best to make one epoxy encased regulator that can handle the entire load and feed it to a 12v regulated bus.

cheers,

-brandon

[pistnbroke]

If you have bought these as 12v units then they will be fine if you have the batteries on charge ..there is quite a large tolerance..all 12v equipment is really intended for 13.2v and all they are telling you is that they are not 24v...

[kroberts]

I agree with pistnbroke.

That said, you also have all your lights in the traditional wiring setups, right? Basically one or two circuits? Don't bother with a new regulator for each light, if you intend to regulate them. Get one regulator that will supply current for all your LED lights you have, plus all you might have. For example, cabin lights or some sort of reading lamp.

Frankly though I would be surprised if your lights won't accept 18v. Maybe you should try it with one light first, in order to test it.

[Mylestec]

@ Pistnbroke & Kroberts: I thought the same thing until a technical question to the vendor yielded a response that stated these types of lights are not compatible for automotive type uses since the +14v charging system would over-load the lights (despite being 12v and waterproof) the vendor further explained that the lights are intended for DC supplied by a regulated 12v power source.

An additional query to the vendor regarding acceptable voltage range has gone un-answered as of yet.

Before I posted here I found a few links regarding Zener diodes and thought a regulator was a simple diode, hence the in-line questions...

[kroberts]

A zener would work, but you want a regulator. You went to the extra expense to get LED lights, which is great. Adding a zener to regulate it would be to undo a lot of what you just did, and probably also add a bunch of weird noise to your electrical system.

There are all sorts of regulators out there. If you are max 12v, try dropping to a 10v subsystem for some safety.

Generally an LED light has a built-in resistor to enable a range of acceptable voltages. The LED is a diode (same as a zener, only different!) and the more current goes through it, the brighter the light. It will stop current from going the other direction, btw. Anyway, a "raw" LED will supply a vastly different amount of light depending on very small voltage differences.

So I guess what I'm saying is, you might have some lights with no such resistor. In that case, your cheapest solution would be to find a resistor which drops the voltage to 8-10 or so under batteries, and that will probably keep it under 12 when you are charging. Put the resistor in-line with the LED at each station, and you would be not only good to go, but also your nav lights won't dim when you turn on the cabin light.

[Luckless]

Question: How many lights are you going to have, where are you putting them, and how bright do you need each one? For LEDs, if you want brighter lights (safety running lights) usually it is easiest to just go with more, but in the case of those I would go with factory made lights that are ready to be wired to a power source and switch.

Stick with the integrated circuit regulators as was already suggested. They're usually cheap and reliable, and easy enough to install if you don't mind learning to solder and are willing to mess around testing electronics on your boat. Or else you should just buy a larger 12volt DC regulator designed for marine environments. LEDs are part of modern electronics, and like ICs it is a bad idea to run them outside of their factory specs. I've learned from experience that LEDs may be prone to exploding in an interesting manner if they get too much voltage for two long.

[pistnbroke]

This is all crazy YOU DONT NEED ANY REGULATOR ...if they are a simple sting of leds with a series resistor and spec is 12v they will be fine with a 12v battery even if on charge .
I recently bought some tail/stop/indicators units LED ones and each of the three led displays had its own regulator !! what are you doing regulating the regulated ..crazy just fit them and get on with your life ....

[Landlubber]

"When installing fixtures, arrays, strips, clusters or any LED product which have a total of 6 or more standard 5mm LEDs, always use a Regulated Transformer, and a dimmer even if you will not use the dimming function. The dimmer contains a PWM/pulse width modulation component which will allow maximum life of the LEDs."

http://www.theledlight.com/led-clusters.html

Very good site, and old friend of mine.......

[pistnbroke]

the life of a car type lamp is 1000 hours
the life of a led type lamp is 100,000hours ONLY 11.5 YEARS
so why would we want to increase the life ....CRAZY
You are misquoting your friend in the link ....he is talking about when using them on the mains ...for 12v he talks of a simple connection to an existing supply

WE CANNOT UNLEARN WHAT WE HAVE LEARNED

[CDK]

Some LED-lamps are working at maximal current to obtain the promised brightness. Especially low cost Chinese products can be damaged by voltages over 12 VDC.
I have replaced several units in my garden lights after they were subjected to 14 volts for several hours. Some started to blink, other were completely shorted. Because there are several LED wired in series, the shorting of one LED destroys the whole chain.

The best way to supply power to LED's is to use a current regulator, but that would require an extra 12 cents investment for one transistor and two diodes, as compared to a single resistor.

[TedZ]

I think CDK is absolutely right. Many combinations of components will work and i realize this may not be your thing.

Try http://www.freepatentsonline.com/6600274.html and read way down for a description of the components. R1 and R2 are the only issues. It would be great if you had a friend who knew how to bias a transistor and what the resistance was in the string of diodes.

All of this is probably unnecessary if you have very good LED's but if you want to forget it for 11.5 years regulation is a good thing.

Ted

PS using a single resistor in series with the LED's is a long way from voltage regulation if that is really what you want. A resistor is a current limiting device. With the resistance in the LED's you don't get much unless the power is fed to the circuit properly and then you get an unregulated voltage divider...maybe.