LED bulb

Page 2 of 2  


mercury is what provides the initial ions for current to flow across the tube. it helps establish the arc.
I took apart a CFL and it only had two transistors,a tiny transformer,a couple of electrolytic caps,2 diodes and some chip caps. It rectifies and DOUBLES the input voltage,then converts to HF AC.
--
Jim Yanik
jyanik
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 5/5/2011 10:41 AM, Jim Yanik wrote:

Next time one of mine burns out, I'll take it apart. The diagram I saw looked complex for a light bulb. Sounds like what Wiki says:
Electronic ballasts contain a small circuit board with rectifiers, a filter capacitor and usually two switching transistors connected as a high-frequency resonant series DC to AC inverter. The resulting high frequency, around 40 kHz or higher, is applied to the lamp tube.
Also noted of late, cfl's I've bought have been little hummers. Can't recall in early ones. Maybe it's the cheap Walmart stuff I bought.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 5/5/2011 9:41 AM, Jim Yanik wrote:

Like other fluorescents, the mercury is mostly liquid when the tube is off. Starts on something more like argon. Heat from running vaporizes the mercury (which is why they may not be full brightness at start). The mercury arc produces a lot of UV, which the phosphors convert to visible light.
Other than the orange neon color ones, "neon" lights work the same, with cold (not heated) cathodes.

Switch mode power supplies, like in a computer, seem to be winding up everywhere.
--
bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Larry Fishel wrote:

According to the above link, this LED bulb consumes 8.6 watts to produce 429 lumens (49.9 lumens/watt).
That is not much less efficient than a 40W-equiv. CFL, which produces 450-500 lumens from 9 watts (50-55.5 lumens/watt).
As for why this LED achieves about 50 lumens/watt while there are now LEDs achieving 100-120 lumens/watt: I doubt the reason is filters:
1: My guess is that this LED bulb is a warm white one rather than a cool white one. Warm white LEDs produce less green spectral content and more red spectral content than cool white ones do. Not only is human vision less sensitive to red than to green, but also phosphors have higher "Stoke's loss" in producing red than in producing green light from the same LED chip.
2: The LEDs in this bulb may be high color rendering index ones. There is a recent trend for "warm white" LEDs used in lighting to have color rendering index of at least 80. Cool white LEDs of extremely high efficiency have CRI only 70 to low 70's, with some having extreme lumen/watt phosphors only achieving CRI in the 60's. Higher CRI requires the phosphor's spectral band to be wider, to include a fair share of wavelengths from slightly bluish green to mid-red. This is as opposed to a narrower phosphor band concentrating on wavelengths from slightly yellowish green to slightly orangish red. The wider band has more spectral content at deeper red wavelengths that human vision is less sensitive to, resulting in less lumens per watt.
3: The LEDs in this bulb may be less efficient than the most efficient ones available of a given color and color rendering index. The most efficient available LEDs have higher cost.
4: The LEDs in the LED bulb require a "ballast" or "driver circuit", for similar reasons to the ones why a CFL requires a ballast (included in usual screw-base CFLs). The ballast has some loss. When a 120V AC-powered "LED driver" has 91 or 92% efficiency, that is getting to be something to boast about. Merely fullwave- rectifying 120 volts AC to DC has a loss around 1.5%.
--
- Don Klipstein ( snipped-for-privacy@misty.com)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
---MIKE--- wrote:

Hmm, Few of them burnt out on me after couple years. Just like CFLs. Lasting 46 years is a myth to me.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.