120 VAC to drive XRE's?

[lotsaluck]

May sound like a dumb question but in doing some testing I would like to ask the members how many XRE's in series could you drive at 120 vac (looking for 350 ma) and what simple dropping resistor would you use instead of fully regulating the circuit?

yeah, I know all the hazards, just need the info for a little something special.

thanks...

 

[JohnR66]

You probably want to drop about 75 volts through the LEDs and the rest through a resistor. This is not efficient, but you don't want to try to drop nearly the full voltage through the LEDs and the rest through the resistor because the circuit would be more sensitive to voltage spikes and the peak voltage of 120vac is about 170. Also the LEDs would strobe like crazy since they are on for a small part of the cycle.

It would be far better to rectify the ac to full wave dc and filter it.

 

[Illum]

I'd recommend something like a xitanium driver of some sorts

http://www.theledlight.com/led_drivers.html

 

[Gunner12]

LEDs are designed to run on DC, not AC. There are a few that you can hook up to a 120v DC current but those are essentially two strings of LEDs in series, one string has an opposite polarity.

What are you planning on doing?

 

[Marduke]

There are some LED's made specifically to run on 120VAC, perhaps you should look at using one of those instead. Something like the SSC Acriche, which requires no additional circuitry.

Otherwise you could use a common off the shelf converter to get to 12VDC, then use a small drop resistor to run 3 XR-E's in series.

 

[blasterman]

I'd like to add that a good deal of the retrofit LED light kits I've tested that work with regular 120volt light bulb sockets *aren't* rectified and flicker like crazy.

 

[Illum]

60Hz can drive you crazy....

 

[Marduke]

Could use something like this:
http://www.dealextreme.com/details.dx/sku.13552
http://www.dealextreme.com/details.dx/sku.13554