e-watt LED light bulbs - what has been your experience

FIRST General Forum
#49

This is an extremely true statement. While lumens are an important metric when evaluating light, there are often many other factors to consider.

When dealing with LED bulbs in particular, higher CCTs (color temperatures) result in a higher light output (for the same drive current). Essentially, higher CCT LEDs are more efficient than lower CCT LEDs because the phosphor conversion of blue light to white light is less dramatic.

Many companies will try and squeak a few more LPW (lumens per watt; essentially how efficient the bulb is) out of their fixtures and bulbs by bumping the CCT up a little bit and essentially gaining free light.

CRI (color rendering index) is another very important measure, albeit a controversial one at times. CRI basically tells you how well the light coming out of the bulb/fixture renders colors. The higher the CRI (max=100) the closer it is to natural sunlight in terms of color rendering. You can read more about CRI here: http://en.wikipedia.org/wiki/Color_rendering_index

One last measure which has a lot of play in LED lighting is lux. Lux is a measure of ILLUMINANCE, not LUMINANCE. Lux takes into account how much light is being emitted over a certain area. In situations which are a direct replacement for incandescent or flourescent bulbs (such as the FIRST bulb) it is not as useful, but for other LED retrofitting applications it is extremely useful. One example of where lux is extremely important is in streetlighting. Streetlighting has very specific requirements for lamps to meet so roads/sidewalks/parking lots are lit correctly. Just putting a big light source in a fixture will not necessarily give you the correct light output. To ensure the beam is being spread and shaped correctly, measuring lux at specific areas of illuminance will tell a better story of how well the light fixture is working.

These are some more metrics that can be useful when evaluating light, and LED lights in particular. As with most things, there are direct tradeoffs between things like cost and efficiency, CRI and output, etc. It is our job as engineers to find a balance that consumers will enjoy!

-Brando

#50

… and they do the opposite (lower the color temperature) with incandescents to create “long life” bulbs.

60 watt standard 840 lumens

60 watt “long life” 770 lumens

Don’t forget that the user can easily lower the color temperature and/or change the lighting pattern by selecting a different lamp. A different lamp can completely change the look and feel of the same bulb in a given room. A glass bowl or reflector which directs the light upwards to reflect off the ceiling produces a completely different lighting pattern than a lampshade that is narrow at the top and wide at the bottom to direct the light downward. And a white lampshade produces a different “feel” in a room than a dark color.

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#51

I have way less of an understanding of how incandescents work so I cannot speak to them as well as LED, but how do you tune the CCT of an incandescent bulb? Just curious, it seems like a pretty interesting thing to do.

Lighting is all about “feel” as you have said. Unfortunately its extremely difficult to put measurable metrics on feel, which is why lighting is sometimes a very tough market to penetrate. As you said, options must be available for users to make their own choices of what feels right to them.

I do have to say however, since I began working on LED lighting around 3 and a half years ago, I now prefer cooler feel temperatures (higher CCT). Nothing in the 4500K+ range, but a 2700K temp actually feels wrong to me now.

-Brando

#52

The user can change the color temperature of an incandescent bulb by dimming it.

The manufacturer makes long-life incandescents by changing the filament slightly so it doesn’t burn as hot. That gives a yellower light, and the filament lasts longer. And the bulb is less efficient (fewer lumens per watt).

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#53

Reported

#54

What kind of watt meter would you use?
What brand? Where would you purchase it?

#55

Our display has places for 4 bulbs so we can compare the color and directionality of the bulbs. Maybe we should get incandescent bulbs with the warm and cool designations to use in the display.

Karen - I can’t tell the difference in your photo. You may have found the perfect application for a 40 watt LED that looks like 60 Watt in one direction!

When I next see our display and /or the builder of it, I’ll get the details on the watt meter. All I remember it that it plugged into the outlet and had a digital read-out!

#56

Budget-conscious consumer electronics vendor Vizio is getting in on the act… reported here: http://www.engadget.com/2011/06/22/vizio-your-favorite-low-cost-tv-leader-introduces-a-light-bu/

“…A Vizio price…”

#57

Well, I got my first bulb yesterday, and boy are they directional. I have a standard lamp in the living room, and the LED bulb does not cast enough light downwards to read by - while a 60W incandescent is almost too bright.

On the other hand, in a downward-facing ceiling fixture, they are excellent.

Thank you PaW for the Vizio link; using a cheap bathroom light bar as my demonstration board will save me a bit of grief.

As for wattmeters: I am planning to get four $3 Harbor Freight digital multimeters, connect them to show Amperes for each of the four bulbs I want to display (LED, CFL, 40 or 60w Incandescent, 45 or 65W R30). People will see bigger numbers for the Incandescents, that’ll be all they need. Done, & done.

#58

I wish I could try one in our table lamp. However, we generally use a 150-watt 3-way bulb, so trying any 40-60-watt bulb replacement would not be a fair test!

#59

For a user friendly meter you could also use something like this for $21.

Kill-a-watt.jpg


Kill-a-watt.jpg

#60

I would watch out for those meters. I looked at some of the reviews and a lot of them said the meters were prone to breaking. And trying to show a potential costumer watts with a broken meter may not help you sell this product.

#61

That’s odd. The customer ratings heavily favored it with only 6% out of ~700 people rating it who disliked it.

I suppose it also depends on how much it gets banged around.
Cost comes into play too. A professional grade meter will cost more than one for casual home use.

#62

I use Kill A Watt meters often in my lab, in situations that do not require either (1) accurate data with traceable calibration, or (2) data sampling at a relatively high rate, such as might be required when we observe repetitive or pulsating load conditions. Most electric lighting tests satisfy both of the conditions above. (For tests that do not, we use much more expensive power metering equipment.)

We have not experienced failure of Kill A Watt in our tests. I would certainly use one for demonstrating e-watt light bulb power use.

#63

We just received a box of the led lights and man are they nice. There brighter than the 60 watt cfl bulbs I have, and they look cool. I thing this will be an amazing fundraiser for our team.

#64

We have sold a full case, and recouped a profit of 235ish dollars. The reason it is less is that we couldn’t get any purchases with 20 dollars, so we lowered it to 15, with 3 for 40.

#65

We are beginning to heavily get into selling these bulbs. I’m curious as to other teams experiences, and if they saw something similar to the above quoted text.

I’m wondering if it’s necessary to make $13/bulb (@$20 MSRP) on these when you could really get the volumes up while selling in the $15 range.

-Brando

#66

I have heard of selling light bulbs as a fundraiser. Where do people typically buy the bulbs from? I heard that you can buy them for $7.50 and charge $15 as a fundraiser. Is this something you can do through FIRST or do teams just do it on their own?

#67

It’s through FIRST. Dean talked about it at Kickoff, before the game was revealed (and it’s been going on for a year or two now).

Try http://www.usfirst.org/roboticsprograms/first-green-e-watt-saver-resources for more info (and I had a tough time finding it…)

#68

FIRST has an LED light bulb fundraiser
http://www.usfirst.org/aboutus/first-green-a-modern-day-twist-on-team-fundraising-methods