LED Light Question

[Wylie_Tunes]

Originally Posted by yurtle

I guess my question is really, can a high powered LED get brighter and dimmer based on voltage? All the itty-bitty LEDs I've played with are either on or off. I'd like a headlight that has "Bright" and "Dim" mode, like I have now. I can't really call them high beams and low beams, as their focal point doesn't change, but two 55 watt halogens in series is a lot less obnoxious to parked carters than two in parallel.

I can say that yes, an LEDs intensity does change with voltage. I custom cut/wire a ton of waterproof LED strips, as well as use a variety of other LED pods, etc. I bench test all my strips before installation and then again once installed. This is typically long before the vehicles/vessels battery is put back into service. I use a 9V battery for testing and they are noticeably brighter with 12V and then again with 13.5 when the alternator is charging. On some applications, we use a dimmer POT switch so the intensity can be controlled.

[Bull203]

Originally Posted by JohnnieB

Being semiconductor devices, LEDs operate on amps rather than volts, so light output can be varied by varying the resistance in series, as well as varying the voltage applied to the series chain, or by varying the duty cycle of the applied voltage.

You asked earlier about it having one LED. It might be in one package, but to get white light, you have to have more than one PN junction since white light is the combination of Red, Green and Blue light and the color of light emitted is determined by the energy band gap of the PN junction and is monochromatic.

beat me to it

BTW, well said Johnnie, amazed at the knowledge on here sometimes.....

[yurtle]

What's your background Bull? Some of y'all are electrically trained, and some of us have just picked up info along the way. I'm a civil engineer, but have been playin' with electrical stuff for 40 years, much of which was WAY before the Internet. My Dad gave me a 15 kV 30 ma neon sign transformer when I was around 10. Think he was tryin' to off me?

[yurtle]

I haven't played with bright LEDs too much. I bought 100 bright white LEDs a couple of years back, but don't even remember why, other than they were really cheap.

I remember a neighbor who's an electrical engineer telling me his LED MagLight kept dying, so he returned it to Home Depot a few times, before figuring out it was just dying batteries. With my old-school Krypton (I think) incandescent MagLights, I could tell when batteries were conking out, as they got dimmer and dimmer. Apparently with my neighbor's Maglight, it would basically leave him stranded, as it gave no dimming warning, or at least not noticeable.

[Springlake]

Originally Posted by yurtle

Got'em in my hoarded clutter. Thanks!

I thought you cleared all that H Clutter out?

[yurtle]

Originally Posted by Springlake

I thought you cleared all that H Clutter out?

Got rid of a lota stuff I'll prolly regret, like my 40s or 50s era aviation gyro, but I still got WAY more crap then I need, but have a LOT more room. I'd be shocked if I got rid of less than one ton a stuff over the past five months.

Every time I toss sumpin', I usually need it within a month AFTER gettin' rid of it.

As I told family, with eBay, I'm re-balancing free stuff I already have, vs. space.

[Knothead]

Yurtle, I have these exact lights, too. I also have them hooked up as "brights", with some lower watt LED's used as "lows". These eBay lights are capable of input voltage of 10-30 volts, so I'm positive they won't "dim" using a lower voltage, nor "brighten" using a higher voltage. Just a heads up.......

I can vouch for the fact that they are well-built, & are PLENTY bright enough for a cart. They're bright white, & will illuminate stuff @ 100-150 yds. easily....

I considered hooking them up in series, & using pack voltage to supply them, without using the reducer. In theory, they'd handle 20-60 volts hooked in series, so my 48 volt pack would be right in the middle....

[Sethjamto]

Cree LED's are quality LEDs, and yes, LEDs can be dimmed. Aquariums use them all the time and I'm about to put about a $1000 worth of LEDs onto my 300 saltwater reef tank that can be dimmed from 1%-100%.

[cgtech]

While yes, leds can be dimmed, but these particular lights clearly have some voltage/current regulator built in to each housing. There is no way any led can withstand 30v, without some regulation. There are no leds that are 12v natively either. This probably means that the lights will cut out pretty quickly when the voltage is not sustained above 10v to the regulation system.

[gornoman]

Originally Posted by Sethjamto

Cree LED's are quality LEDs, and yes, LEDs can be dimmed. Aquariums use them all the time and I'm about to put about a $1000 worth of LEDs onto my 300 saltwater reef tank that can be dimmed from 1%-100%.

The way LED's are dimmed nowadays is to pulse the voltage to the LED. Changing from a high frequency pulsation to a lower frequency pulsation will result in the LED being excited for less overall time. Very similar to a modern golf cart controller.