IC for directly wiring LEDs to mains voltage

Submitted by W2PAW on Wed, 08/31/2016 - 14:44
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If you don't generally read data sheets for ICs, you may want to skip this one.

https://www.fairchildsemi.com/datasheets/FL/FL77944.pdf

One thing I've been wondering about is where are the inexpensive LED replacements for florescent bulbs? Sure they exist, but the time to break even on power savings makes them impractical,

What if you could easily connect a string of LEDs to mains power without a boatload of parts? A new $1.76 chip from Fairchild does just this. Besides the LEDs and the chip, designs will need a bridge rectifier a couple of resistors and a capacitor.

A big advantage to strip LED lighting vs. LED bulbs is heat dissipation. Because the LEDs are not clustered all together, cooling is simpler and more efficent.

Hopefully some manufacture will put UL listed, four foot, $4 LED replacement bulbs on the market soon. Retrofitting should consist of merely removing the old ballast, bypassing it, and installing new bulbs. Done.

Florescent lights can be big RFI generators, and LED bulbs are also frequently a problem. I've been advised to buy "consumer grade" lighting ballasts in the meanwhile to try to cut down on generated RFI.

W1TTM - Thu, 09/01/2016 - 23:23

We built out a new office (a good sized floor in an office building) And they purchased full sized led fixtures. They had two strips of High intensity leds and used the same tricks they use on florescent tubes to spread the light. Those things were $300 per fixture.

They make exactly what you're talking about, but they're a couple times more expensive at low quantitiy

https://www.earthled.com/collections/led-t8-tube-replacements-replace-yo...

W3BX - Fri, 09/02/2016 - 10:17

I installed 4 ft hybrid T8 LED tubes last month in my garage. I got tired of replacing florescent tubes and ballasts. I guess the temperature fluctuations take a toll. Anyway, I replaced the tubes in two 4-tube fixtures with Euri Lighting Model ET8-1140H units. I got them from 1000bulbs.com for $10.49 each. I chose to wire them directly to 110VAC, so I removed the ballasts. So far, so good. They're doing OK in the heat. We'll see how they do over the winter.
- Joe AB3PZ

W2PAW - Fri, 09/02/2016 - 15:14

It's good to hear that they're getting cheap. How is the RFI?

I think removing the ballasts is the way to go here to save energy and remove one failure prone part out of the whole system. I can see however that some people are going to want that drop-in functionality.

Shipping for a few bulbs is kinda expensive from that seller.

Edit to add: back of envelope calculation seems to show it would take a week worth of daily use of two LED tube (@ $30 delivered) to save one kilowatt of power (worth about 15 cents) so the break-even point looks to be about 4 years down the road.

If the original standard T8 bulbs in the light are still working, keep using it until it doesn't at those prices. The bulbs are coming down in price and you'll probably save money by waiting.

wa2mqk - Sat, 09/03/2016 - 08:14

So I glanced up at the rows and rows of fluorescent light fixtures while shopping in the supermarket and wondered whether they will eventually install complete new LED light fixtures or just a fluorescent tube to neon tube retrofit. Without Googling it for info (that would be cheating) my guess is that the ballasts waste energy and are failure prone so that we can expect some kind of complete new standard neon replacement light fixtures in place of the old fluorescent units. New building construction should be using those now and when the production costs fall we need the LED fixture company that advertises the lowest EMI and acoustic noise pollution specs.