Outdoor LED lighting...

[hurron]

Hey all,

I am looking to power waterproofed LED light units for outdoor use. I have a landscape lighting transformer with 12V AC output. Most of my research indicates typical use of 12V DC for LED lighting, however, the transformers on sale at home depot, etc. that are specified for LED outdoor lighting have outputs of 12V AC.

Bottom line question...Do LED lights run off 12V AC? Is it that they only use one side of the electrical waveform?

Thanks...

 

[BlackBII]

They can run off AC or DC, depends on how you set it up...

This is a good site, overpriced, but it will give you some ideas of what to look for

http://www.superbrightleds.com/

 

[rickf92592]

The LED drivers (think ballasts for flourescents) are available in a variety of inputs.
Most landscape lighting products are AC, automotive products are typically 12VDC.
All modern LED products use a driver, sometimes it is incorporated into the fixture, sometimes it is a seperate part.

 

[exbass94]

Is it that they only use one side of the electrical waveform?

Yes, current will only flow one way through an LED. AC power switches polarity many times every second. A typical wall socket is 60 Hz. So, the LED would flicker on and off 60 times per second. It may or may not be noticable, I've never tried it.

 

[hurron]

I have seen mention of people using computer power supplies as a transformer from 120V AC to 12V DC. Has anyone applied this for LEDs in a non-computer application? Outside?

 

[rickf92592]

I have seen mention of people using computer power supplies as a transformer from 120V AC to 12V DC. Has anyone applied this for LEDs in a non-computer application? Outside?

Why?
The non-automotive LED fixture's drivers all are AC power in various voltages.
Maybe I don't understand what you're trying to accomplish.

I'm pretty well-versed in LED, we sell tons of it in my regular job (electrical supply distribution) and I also help build off-road race lights.

 

[4x4junkie]

Are you making lights from straight LEDs? Or are these LED lamp assemblies you've bought? If the latter, I would think they'd say on the package or the lamp itself what their power requirement is.

If you're using straight raw LEDs, then they need a DC circuit for sure. A bridge rectifier can be used to convert the AC to DC, though it'll be a ripply or "pulsed" DC which might result in visible pulsation of the light (a capacitor across the line would smooth it out).

 

[rickf92592]

The point of a driver is the LEDs need for Constant Current.
A bridge rectifier will not provide constant current.

Drivers are explained very well here: http://www.national.com/portal/site...195b9f0210VgnVCM1000000a18c1a5RCRD&videotag=1

 

[4x4junkie]

I know what a driver does.

A simple current limiting resistor can easily be used for it in many cases as well.