PDA

View Full Version : Improving CF bulbs for task and shop lighting



Evan
08-17-2007, 04:40 AM
I used compact fluorescent bulbs for the headlights on my lawn tractor. To make it work I designed a simple reflector that concentrates as much light as possible to make a flood light. I did this because the ready made CF flood lights suck. They have a diffuser and are always soft white, at least that is all I can find. They also don't perform half as well as my design.

With a simple reflector a CF bulb can provide twice as much light or more where it is needed. It isn't a spot light but a flood light with very even distribution and no hot spot. I realize that for many this is a very simple project but not everyone has experience with even simple sheet metal work.

The reflectors are made of standard aluminum flashing which is then polished to a reflective finish. If you have a reasonably priced source of what is called "reflector sheet" then that would make an even better reflector. I checked around here and the only way to buy some is to order an entire 4 x 8 foot sheet at about $200. That's too rich for me so polishing aluminum flashing is how I do it. I will point out that even highly polished stainless steel makes a very poor reflector as the maximum reflectivity of SS is only around 50% while the reflector shown here is about 80 percent reflective.

Below is a series of pictures. I will refer to the pics by number.

In pic 1 are some 8.5" discs cut from standard 9" flashing by stacking up five to ten 9" squares and cutting them in a vertical band saw using a center pivot. Easy to do and a wood cutting blade works fine for this.

Pic 2 shows the tools needed for polishing. I use one buffer wheel to apply Mother's Aluminum Polish. Then the second wheel is used to remove the residue. The disc is screwed down at the center so it doesn't turn into a Frisbee of death.

3: About 5 minutes buffing gives a good reflective finish. Be careful not to catch the edge with the buffer turning toward the center of the disc. Always brush away from center.

4: A method is needed to fasten the reflector in it's final shape. I find that the best and easiest solution is to make some bent clips from thin mild steel sheet, These clips should be prebent so that all that needs to be done is a final squeeze with some Visegrips.

5: The polished reflector is marked for cutting the center hole for the CF bulb. A hole diameter of 2.5" is about right. You can use a compass or the cap of a rattle spray paint can is the right size. Cut out a pie shaped piece to give access to the center cut. This is where you can use that $5 set of aviation snips to cut.


6: Warp the sheet around into a cone and press on a clip on the OD with the locking pliers, squishing it flat to hold the metal. The center hole should be made slightly smaller than the ballast OD of the lamp this is meant for. About 1/16" smaller is good. This is accomplished by varying the amount of overlap of the sheet metal. Add two more locking clips, one to the OD and one to the edge of the hole.

7: Snip a series of 1/8" long cuts around the center hole. This makes it possible to press the reflector over the base of the bulb and stay in place.

8: This is how it looks when installed over the base of the bulb. It should be positioned as close to the top as possible

9: The finished reflector should look like this with the reflection of the coils of the bulb filling most area.

10: This is a picture of a plain bulb (the left) and the same bulb with a reflector (right) as installed in a plain fixture in the unfinished ceiling of my basement. The images were taken with my Nikon 4300 in manual mode with all exposure settings locked and the flash enabled.

11: On the left is the scene looking down the basement stairs with a plain bulb installed and warmed up. Exposure is locked at 1/60 second and f 2.8 with no flash. On the right is the same scene with the same settings but with the reflector bulb installed. Absolutely no processing except cropping and resizing has been used on these photos.

As can be seen the reflector is very effective. This cannot be achieved by using an ordinary fixture with a normal shroud around the bulb even if it were as reflective. The distance and slope of the reflector won't be correct unless mounted as is shown here. By using the bulbs with such a reflector mounted the apparent brightness is approximately doubled which can either greatly improve task lighting in the shop or reduce the power consumption by requiring smaller bulbs. The reflector may even extend the life of the bulb somewhat by acting as a heat sink for the ballast unit which is where most of the heat is generated. It's also much cheaper than the equivalent CF bulb floodlight.

http://vts.bc.ca/pics2/reflector1.jpg
http://vts.bc.ca/pics2/reflector2.jpg

http://vts.bc.ca/pics2/reflector3.jpg

J.Ramsey
08-17-2007, 05:14 AM
Evan
I have never heard it called reflector sheet before, in the race car world it's called hi polished or mirror finished and yes it can be used as a mirror.
Here in the midwest it's up to about 120.00 for a 4 x 10 sheet x .032.
If you need any drops in the future holler at me because I go through ten to fifteen sheets a year and usually have quite a bit of small scrap lying around.
Don't have any idea if it would be worth the freight.

Mike W
08-17-2007, 05:24 AM
That was pretty cleaver Evan. I had no idea that would make such a difference.

Evan
08-17-2007, 05:33 AM
Reflector sheet aka Lighting sheet is a special product used mainly for lighting fixtures. It has a reflectivity of up to 98 percent and is made of specially optically coated aluminum.

http://www.anomet.com/reflective_aluminum.html


Hi polished aluminum is good enough but for maximum efficiency reflector sheet is the material to use. It's expensive.

lenord
08-17-2007, 05:53 AM
Evan,

The local home depot has a new kind of CF. It is suppose to have a light that looks just like sunlight. I got one and love it ! You can really tell a difference. There are also CF flood lights available IIRC. They are expensive though.
Since I have a dozen or so of the old kind in the shop, I'll try out your method. I can always use the extra light. I tried this before, but did not polish the metal at all. And I did not make a cone, I just made a cylinder. Will try something like what you did.


Lenord

Mike W
08-17-2007, 06:00 AM
How do those CF flood lamps compare with the old type has far as brightness?

J.Ramsey
08-17-2007, 06:06 AM
Evan
Looked at link that's the same stuff I use, the suppliers up there are sure hosing
you guys.

Evan
08-17-2007, 08:30 AM
Looked at link that's the same stuff I use, the suppliers up there are sure hosing you guys.

That's a very common problem here. I just priced out exchanging my acetylene B bottle and the cheapest I can find is $43. Keep in mind that the Canadian dollar is almost the same as the US dollar now so that works out to about $40 USD. The price in the US is around $12 to $15 for the same thing.

Evan
08-17-2007, 08:56 AM
How do those CF flood lamps compare with the old type has far as brightness?

That depends on the type of CF bulb. There are a lot of cheap ones that don't work that well. I use NOMA Electric brand as they seem to be very reliable. Noma has been around since the 1920s.

Look at the lumens that the bulb is rated to produce. The cool white bulbs are more efficient than the soft white bulbs and are what I use. In general the CF bulbs are around 4 times more efficient so a 15 watt CF bulb is about equal to a 60 watt incandescent.

A.K. Boomer
08-17-2007, 10:34 AM
Amazing difference! I have a couple of the CF floods, they have built in reflection so a backing would not help, but I think they are more concentrated than what you produced, good pics on "how too" Evan.

A.K. Boomer
08-17-2007, 10:54 AM
3: About 5 minutes buffing gives a good reflective finish. Be careful not to catch the edge with the buffer turning toward the center of the disc. Always brush away from center.

]


A wittle buffing Twick, (my best elmer fud impression)

I noticed buffing all around the edges of the aluminum where it meets the plywood and wanted to comment on a short cut I often take (if the "part" is uniform and will allow it, maybe you already tried and it wasnt, but you can always set it on top of a uniform spin plate underneath)
For grinding or buffing sometimes you can leave the center screw loose so the object rotates, then you start buffing for direct spin, once the object starts spinning then change the vector of the buffing wheel to control objects speed, Ideally you want a very slow but uniform object speed and while your buffer is kinda Crosshatching,,, very uniform and nice results, keep in mind the vector angle has to be changed as you go from center to outer, but it allows you just a small linear movement of the tool instead of covering the entire surface, you can also "cant" it in the direction that it never catches the outer lip of the material...

J Tiers
08-17-2007, 09:55 PM
I guess on the tractor is won't matter as much when the CF bulbs start smoldering............ :D

Sorry couldn't resist, I'm up to two burned-up ones now, and expecting more. Made in china, of course.....................

J. Randall
08-17-2007, 11:48 PM
Evan , it must depend on location if you can get a bottle that cheap in the U.S. I just exchanged my acetylene bottle last month, 43.00 here in NW Okla.
James

andy_b
08-17-2007, 11:58 PM
Evan,

do you need to coat the aluminum with anything to stop it from re-oxidizing? if you didn't coat yours, how long do you think they will stay shiny? i haven't played around with polishing aluminum lately, so i'm just wondering if the reflectors will need to be pulled off and re-polished every few months, or if you think they will stay reflective for a long time (the life of the bulb, optimally).

andy b.

Fasttrack
08-18-2007, 12:25 AM
I dunno if you'd want to, but i think you should submit your article to the magazine. I would think it would be popular with the whole "save the environment and use less electricity" fad (not that i'm not all for helping the environment but some of the stuff seems pretty political) and its an easy but rewarding project for a beginner.

just my two cents....

Mad Scientist
08-18-2007, 12:32 AM
Contrary to what one might expect, unless you are trying to focus light into a pencil beam. A reflector, for general illumination, painted a bright white will reflect more light then a mirrored surface.

Think of it like this, what reflects more light a light colored surface or a dark one? Which of these surfaces is lighter in color? A sheet of white paper or a silvered (gray) mirror?

J Tiers
08-18-2007, 01:53 AM
Not sure you are thinking about that right, Mad.....

The specular reflecting surface will reflect "more", but it may not be as "usable" as the white surface, due to the more diffuse light reflected by the white surface.

The shiny surface is somewhat "stealth".

In my prior job, the owner wanted the logos of the product (guitar amps) to be shiny to reflect lights and show up better. I tried to convince him to make them textured, but no dice.

We called them "stealth logos", because the specular reflection generally did NOT reflect in a usable direction that could be seen. They looked black.

A diffuse reflection from texture would have more chance of light reaching the eyes of an observer. Same with the white. THE PAINT ACTUALLY ABSORBS MORE OF THE LIGHT, AND REFLECTS LESS, but due to wider and more even dispersion of the light as a diffuse glow instead of a specular reflection, it tends to light more area, even though the total light reflected is less.

Evan
08-18-2007, 02:16 AM
Contrary to what one might expect, unless you are trying to focus light into a pencil beam. A reflector, for general illumination, painted a bright white will reflect more light then a mirrored surface.

Not in this instance. The standard for non specular reflectance (White surface) is titanium dioxide fume on a glass substrate. It exhibits a visible spectrum reflectance of 94%, Ir reflectance of 88% and UV of 13%.

The best reflector is silver with a maximum visible reflectance of 99%. Polished aluminum alone is virtually flat across the bandwidth of IR to UV at about 88 to 92 %. With appropriate coatings aluminum reaches 98% broadband reflectance. White diffusing coatings cannot approach this.

The nature of the light for illumination purposes depends on the source. In the case of a CF bulb the source is a large area diffuse emitter. Using a specular reflector (mirror) produces maximum reflectance without hot spots because of the diffuse nature of the source. No advantage would be obtained by using a non specular white reflector as it would be less efficient and there is no need to provide additional diffusion.

darryl
08-18-2007, 02:57 AM
And where does one get these 12v cf's? :). Does your garden tractor have a 110 vac output?

Those are almost completely identical to the ones I made for my light bar. Made from flashing, cone shaped, but held not with clips but with its own material as rivets. One edge of the pie shaped cutout has 1/4 inch holes in it, and the mating edge has the mating locations punched with a spike. When the cone is formed, the spiked holes are placed over the drilled holes, then the spike is wobbled around in the hole, spreading the little fingers. A few taps with a hammer and walla- self-made rivets. I did NOT polish mine- yours look much reflectier, (ha ha, spell check doesn't like that word).

It's a good idea, and it does keep the ballast cooler. Mine are zap strapped to the ballast. I did intend to experiment with the shape of the cone to get the right angle, but I got what I needed right away- I'll call it a wide angle spot.

I wanted to fit something around the edge, but so far I haven't found anything elegant enough to use. Making a rolled edge on it would be good, but I doubt many of us have the equipment to do that. I don't.

J.Ramsey
08-18-2007, 02:57 AM
[QUOTE=

Think of it like this, what reflects more light a light colored surface or a dark one? Which of these surfaces is lighter in color? A sheet of white paper or a silvered (gray) mirror?[/QUOTE]

Mad Scientist
Do you own a real good flash light or spot light? I'm sure you do so take it and shine it on a white surface (you're choice) and then point it at your bathroom mirror while looking into it.
Bright Dip,Hi-Polish,Reflector material what ever a person wants to call it is as good of a reflector if not better than a glass type mirror.
Have you looked at the windows used on sky scrapers in the last forty plus years? they're not painted white.
Light colored surfaces absorb less light than dark colors,thats why most people wear lighter colored clothing in the summer.
For that matter what does the reflector in the above mentioned flashlight resemble.

jacampb2
08-18-2007, 04:48 AM
Pretty slick Evan! Now if you could just invent something to keep the metal dust out of my CF ballasts. I have 30 47W (?? I think, they are 150W incandescent equivalents) and I average about 4 months per bulb. They always fail from metallic dust from grinding/plasma cutting. I have had ballasts start smoking, I have had them melt the bulbs off the base, had one melt a hole right in the middle of the CF element. Pretty cool, but ultimately irritating having to climb up and change them every week. Fortunately, my local home depot, where I bought them is so far honoring the 7 year guarantee written on the packages (which I saved). At $10 a bulb, I wish I got better life out of them, but as long as they keep giving me freebies, I am not complaining.

Later,
Jason

Evan
08-18-2007, 06:47 AM
Does your garden tractor have a 110 vac output?

Yes, full details in the lawn tractor mods thread.

Evan
08-18-2007, 07:15 AM
Jason,

It sounds to me that you have an air quality problem, not a light bulb problem. Are you breathing that air too? This must be fume you are talking about. I can't see metal grinding dust rising to the ceiling.

I don't have any trouble with the 35 or so 23 watt CF bulbs in the ceiling of my shop. I have been burning up to 2 lbs of wire in a day some days. I use two turbo fans to blow the welding fumes out the open shop doors.

I run two fixtures like this one in the shop as well as several more "redneck chandeliers" with 4 to 6 bulbs apiece. Since I renovated the shop and installed the bulbs early this year I haven't had even one bulb fail yet.

http://vts.bc.ca/pics2/clights1.jpg

http://vts.bc.ca/pics2/shopg1.jpg


Perhaps what you really have is a light bulb quality problem. How do you know that metallic dust is the issue? I use four CF bulbs directly over a 10" diamond wheel in my grinding shop as well as a buffer, linisher, grinder and a horizontal belt sander. I think I may have had one bulb fail in the last two years.

CF bulbs also don't last long if they are switched on and off constantly. They are a poor choice for any location where they will only be turned on momentarily.

A.K. Boomer
08-18-2007, 07:21 AM
Evan,

do you need to coat the aluminum with anything to stop it from re-oxidizing? if you didn't coat yours, how long do you think they will stay shiny? i haven't played around with polishing aluminum lately, so i'm just wondering if the reflectors will need to be pulled off and re-polished every few months, or if you think they will stay reflective for a long time (the life of the bulb, optimally).

andy b.


I thought this worth bringing up again, Andys got me wondering the same thing, although the pores of the aluminum are sealed more it will start to oxidize, wonder how long a good wax would last or if you need to skip that and put a clear coat of enamel on it?

Evan
08-18-2007, 07:30 AM
Sorry, I forgot to answer that. Thanks for reminding me.

Aluminum forms a clear oxide layer within seconds of being exposed to oxygen in the air. That layer protects the surface indefinitely as long as it isn't exposed to chemicals that can attack it. Of course nothing will stop the reflector from becoming dirty but the shine will last indefinitely. There is no need to coat it with anything.

edit: Aluminum doesn't "oxidize" in such a way that is harmful to the finish. The oxide is crystal clear and once an oxide layer develops a few atoms thick it stops growing. It takes some sort of airborne chemical attack to change the layer properties.

IOWOLF
08-18-2007, 07:43 AM
As an amateur photographer i am surprised you didn't get out your Light meter and show all of us how bright you are.........


making your shop. :)

Evan
08-18-2007, 08:20 AM
I don't use a light meter. The one I have has been broken for decades. I thought of building one but the Nikon 4300 has a fully manual mode where the photographer has control over everything. It even does time exposures up to one minute with automatic dark field noise subtraction of hot pixels.

When you take a time exposure it automatically follows the exposure with a second exposure with the shutter closed and then uses that dark field to adjust every pixel to the same equivalent sensitivity. Of course that can be turned on/off.

Mad Scientist
08-18-2007, 04:35 PM
Mad Scientist
Do you own a real good flash light or spot light? I'm sure you do so take it and shine it on a white surface (you're choice) and then point it at your bathroom mirror while looking into it.
Bright Dip,Hi-Polish,Reflector material what ever a person wants to call it is as good of a reflector if not better than a glass type mirror.
Have you looked at the windows used on sky scrapers in the last forty plus years? they're not painted white.
Light colored surfaces absorb less light than dark colors,thats why most people wear lighter colored clothing in the summer.
For that matter what does the reflector in the above mentioned flashlight resemble.

I did just that a few years back when I was designing a light source for a photographic enlarger, actually I designed and build the entire enlarger.

The goal here was to squirt as much light through a 9” square piece of film as possible and without any hot spots. Measuring the reflected light with a light meter, a white surface gave a substantially higher reading then a mirror surface and without the hot spots.

I did not have any “Bright Dip” at that time so I can not say how it would behave. But my guess is that it would have produced some hot spots.

Evan
08-18-2007, 08:17 PM
Comparing the absolute reflectivity of surfaces must ignore such effects as "hot spots". That's an optical quality issue and not related to the degree of reflectivity. Diffuse reflectors and specular reflectors operate on different principles. A specular reflector (a mirror) maintains the coherence of the incident light and follows the rule that angle of reflection equals angle of incidence. A diffuse reflector such as a matte white titanium dioxide surface reflects mainly via the backscatter principle. Angle of reflection is not dependent on angle of incidence so coherence is not preserved. Backscatter is inherently less efficient than specular reflection. The details of why are beyond the scope of this thread but can be found in the book QED, Quantum ElectroDynamics, By Richard Feynman.

jacampb2
08-18-2007, 10:08 PM
Jason,

It sounds to me that you have an air quality problem, not a light bulb problem. Are you breathing that air too? This must be fume you are talking about. I can't see metal grinding dust rising to the ceiling.

Perhaps what you really have is a light bulb quality problem. How do you know that metallic dust is the issue? I use four CF bulbs directly over a 10" diamond wheel in my grinding shop as well as a buffer, linisher, grinder and a horizontal belt sander. I think I may have had one bulb fail in the last two years.


Yeah, I am breathing that air. I use a respirator though when grinding. It is definitely not fumes. Most of my ballast's have a fine layer of metal dust on them when I pull them out. I have metal dust everywhere in the shop.

Here is a picture of the amount of dust I collected just off my 2'x5' welding table with 2 3" magnets. This is from one day of work. I sweep my floor every couple of weeks and get about 1/5 of a 5 gallon pail of metal dust off the floor. Plasma cutting makes more incredibly fine metallic dust then you could imagine. Add to that, that most of my exterior welds need blended and smoothed for my customers, I generate a crap load of dust. I have yet to come up with a reasonable approach for removing the dust from the shop. I suppose some squirrel cage fans ducted to a narrow grate at floor level and exhausting outside would be a good approach, but I can barely heat the shop in the winter as it is, and that is my busiest season...

Here is the pic...

http://www.rollmeover.com/bronco_fab/odds_n_ends/dust.jpg

Later,
Jason