PL-L refector shapes

To all those with flat top reflectors, read on!

Trying to achieve mimimum light loss for 3 pll bulbs in a space only 20cm wide, here is what i have come up with:




(protective plastic not yet removed). Used 0.5mm aluminium sheet. Easy to make:











Why only 20cm wide? there will be 3x 36W bulbs i will fit into a pc case. More on that later - after some hard work it is almost ready.

A preliminary test:


-using flat surface of same reflector material






-and now for two lights from one, at least from a vertically down viewpoint:




None of the horizontal light from the side ends of the tube gets reflected but for a reflector 6.6cm wide this is a necessary sacrifice.


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Here is an idea stolen from hydro scrog in another thread :

Hydro-Soil said:

That look great!
I was curious if we'll get even more light output if we turn the bulbs so they're vertical in the reflector. Wouldn't it put out more reflected light if only one little portion of the lamp was shining into the top crease?

Everything else would bounce off the reflector and down to the plants.

Unless, of course, if the double exposed element gives off more lumens than the double reflected element?

Click to expand...

I have been thinking about reflector design for a Pl-l bulb for days and never did i think of that. Its counter intuitive to rotate the bright face away from you - i think its serious lateral thinking there buddy. Anyways, I was so interested by the idea that i decided to do a little test using some card.





a coating of aluminium foil tape (the best tape ever invented?):



voila:




and flat on:



As you can see the reflected area is brighter with it flipped but with a flat face the optimal shape for a reflector is much harder to make because it should have curves or many small folds in the bit directly above the top face. This reflector has the advantage of being easy to make, very easy infact, and may even be better. restrike is extremely low.

it could also be made more compact. the upper V should be the diameter of the tube in width but ive managed to fold it slightly larger. all turns are 90deg.

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I would love to use the bulb flipped upwards like that but you need at least 6 cm either side to reflect the light from the two faces downwards. Alas, not suitable for my pc, but great for high effieciency lighting.

....And finaly after all that, holy crap do i need a smoke

So....... What is the absolute best reflective surface to use for these lamps?

I have to build a hanging reflector and I'd like to use the most reflective, including UVB, that I can.

Is there a paint that would work on sheet metal that's killer reflective?


The reason I'm concerned is I'll be looking into the edge-on alignment. Since the main element won't be exposed to the plant, the reflection efficiency will be doubly important.

This will be for a Scrog or LST setup so I'm not interested in penetration as much as saturation.

Good question, one i tried to answer myself but I still dont know the best solution for reflectivity of the actual surface. Mylar is most reflective but I wouldnt trust the adhesive over time - it might start peeling off, contact the bulb and create potential fire risk. I cant see how the bulb would get hot enough, however. What is the best heat tolerant adhesive to stick mylar to sheet aluminium i wonder?

As for paint, I read somewhere that someone uses white paint mixed with barite?

You could have the most reflective nasa engineered material but unless you have the right shape what's the point - its just more light restriking the bulb. The commercially available reflectors available in the grow shops are just that.

Here is the reflector i have built and mounted in a pc case.




I carefully put aluminium foil tape on the surface. Its advertised as highly reflective to light and heat resistant to 180C. Before applying the tape I compared the tape to the sheet metal by reflecting a table lamp both onto a wall and using my eyes. The tape definately came out on top. I couldnt tell the difference between the tape and mylar. Perhaps I did find the best solution after all with my rudimentary method.


With the lights on and from a perpendicular viewpoint its hard to differentiate between the bulb and the reflector. Its one massively intense light panel.

As much as i like your idea for reflector shape, if I were you i would build something like this :



Its easy to build, perhaps not as easy, but you wont have to worry so much about the reflector surface because you are not relying on so much to be reflected.


About UVB, the tape will reflect that very well but as far as im aware there are no PL-L bulbs sold with a UVB spectrum. I have tried and found some for terrariums that are 5800k and emit a small amount of UVA - £20 each!. Also if you build it as one panel with multiple bulbs, how can you raise a UVB emiting bulb away from the plants without moving the whole lighting system, as ive read too much can burn them.

D.I.trY said:

Good question, one i tried to answer myself but I still dont know the best solution for reflectivity of the actual surface. Mylar is most reflective but I wouldnt trust the adhesive over time - it might start peeling off, contact the bulb and create potential fire risk. I cant see how the bulb would get hot enough, however. What is the best heat tolerant adhesive to stick mylar to sheet aluminium i wonder?

As for paint, I read somewhere that someone uses white paint mixed with barite?

You could have the most reflective nasa engineered material but unless you have the right shape what's the point - its just more light restriking the bulb. The commercially available reflectors available in the grow shops are just that.

Here is the reflector i have built and mounted in a pc case.

I carefully put aluminium foil tape on the surface. Its advertised as highly reflective to light and heat resistant to 180C. Before applying the tape I compared the tape to the sheet metal by reflecting a table lamp both onto a wall and using my eyes. The tape definately came out on top. I couldnt tell the difference between the tape and mylar. Perhaps I did find the best solution after all with my rudimentary method.


With the lights on and from a perpendicular viewpoint its hard to differentiate between the bulb and the reflector. Its one massively intense light panel.

As much as i like your idea for reflector shape, if I were you i would build something like this :

Its easy to build, perhaps not as easy, but you wont have to worry so much about the reflector surface because you are not relying on so much to be reflected.


About UVB, the tape will reflect that very well but as far as im aware there are no PL-L bulbs sold with a UVB spectrum. I have tried and found some for terrariums that are 5800k and emit a small amount of UVA - £20 each!. Also if you build it as one panel with multiple bulbs, how can you raise a UVB emiting bulb away from the plants without moving the whole lighting system, as ive read too much can burn them.

Click to expand...

I have to say that it's bad-ass. I'm definitely appreciative of your posting that stuff. I'll be working on something here for a 220w array. Barite, eh?

Hydro-Soil said:

I have to say that it's bad-ass. I'm definitely appreciative of your posting that stuff. I'll be working on something here for a 220w array. Barite, eh?

Click to expand...

thanks , at least somebody is!

Got a quick question for ya. (Hope you have measurement tools)

I'm looking to duplicate what you've done and am interested in the measurements of your folds and such.

Length of downside, Width between ends of reflector, width of flat section at top, height of angle piece that sits above the bulb and so on and so on.

Would that be too much to ask? Just using one of your excellent drawings and adding in the dimensions would rock!

BTW, ran across something called "GORE™ DRP® Diffuse Reflector" and it's supposedly the most reflective substance on earth to date. Expanded PTFE that doesn't yellow or break down under UV exposure. Supposedly ok up to 280C as well, so definitely a great light material.

I'm looking for a source to get sheets of it. Cover my reflector surfaces when I'm done.

I second Hydro's request for measurements I'm getting my cab close to completion and I know the improtance of proper reflections for CFLs, as my 240watt spiral grow had none and I can't wait to see the difference.

Hi I'm sorry I didn't check this thread earlier because im pleased to help.


Ive quickly put in some measurements of the reflector i think you're asking for.



As you can see by the diagram which is to scale the reflector is just a few milimeters from the bulb. the higher you put the reflector the wider you will have to make it. Do a sketch and you will see why - plus i see no benefit of putting the reflector higher. You can see its perfectly in line too when bulb and reflector are so close.


Here are dimensions for the reflector I built myself that you see my post above mounted in a pc. Even though i have sufficient cooling and the bulbs can be touched comfortably, the sheer amount of light just radiates heat onto everything below it. Its intensely bright but i admit I'm still learning to harness its potential.

D.I.trY said:

Hi I'm sorry I didn't check this thread earlier because im pleased to help.


Ive quickly put in some measurements of the reflector i think you're asking for.



As you can see by the diagram which is to scale the reflector is just a few milimeters from the bulb. the higher you put the reflector the wider you will have to make it. Do a sketch and you will see why - plus i see no benefit of putting the reflector higher. You can see its perfectly in line too when bulb and reflector are so close.


Here are dimensions for the reflector I built myself that you see my post above mounted in a pc. Even though i have sufficient cooling and the bulbs can be touched comfortably, the sheer amount of light just radiates heat onto everything below it. Its intensely bright but i admit I'm still learning to harness its potential.

Click to expand...

Sweet! Thanks a bunch

As for the heat, set up your ventilation (possibly even mounting a fan at the end) so that the airflow goes across the bulbs from the tip to the base. The base is where they get the hottest and that air should go straight away from the plants.

Edit: Looks like it's too wide for my cab I have 19" max and that's at least 21" for 4 of those side by side. Damn! Gonna have to come up with something similar but slimmer. GAH!

D.I.trY said:

Hi I'm sorry I didn't check this thread earlier because im pleased to help.


Ive quickly put in some measurements of the reflector i think you're asking for.



As you can see by the diagram which is to scale the reflector is just a few milimeters from the bulb. the higher you put the reflector the wider you will have to make it. Do a sketch and you will see why - plus i see no benefit of putting the reflector higher. You can see its perfectly in line too when bulb and reflector are so close.


Here are dimensions for the reflector I built myself that you see my post above mounted in a pc. Even though i have sufficient cooling and the bulbs can be touched comfortably, the sheer amount of light just radiates heat onto everything below it. Its intensely bright but i admit I'm still learning to harness its potential.

Click to expand...

D.I.trY: nice work on those reflectors! Makes mine look even more hack than they really are :smile:


I'll try to get a better shot of the reflector from the side and some measurements for you. They are similar in design to yours (i.e a dual parabolic). Mine are not nearly as consistent as yours are as they bow out a bit in the middle. I think this is due to the gauge of metal I chose to work with (thin sheet aluminum/roof flashing).
Anyway it is good to see that these PL-L's are really starting to catch on with our fellow growers. Each 55w PL-L is basically a 4' HO T5 bent in half (hence the same reason they both work with the same ballasts). While they may not compete directly with HID's for light penetration etc., they do provide awesome even light distribution. Plus they are nice and shallow using up very little head space (4" or less including reflectors) which makes them very appealing to small setups like mine.
Sorry for rambling. Nice thread! :smile:
-bakelite

Hi Bakelight a big thanks from me for enriching this thread with your great looking reflector. That's a beatiful sight of the white colour of the reverse side of the bulb in the mylar. I do hope the adhesive is permanent for you. I'm sure this aluminium foil tape i used will never come off but it doesnt look as nice as mylar. I just ran out of the stuff because its so handy it absolutely wipes the floor with duct tape for sealing etc and its waterproof, and of course reflective.

The 0.5mm aluminium i used still took me a bit of strength to bend the thing with a hammer. Its a pity i didnt use a flash and took some CRAP looking photos! Oh, and yeah your measurements would be helpful i'm sure - looks like yours are slightly wider. Hope you show us the buds

D.I.trY said:

Hi Bakelight a big thanks from me for enriching this thread with your great looking reflector. That's a beatiful sight of the white colour of the reverse side of the bulb in the mylar. I do hope the adhesive is permanent for you. I'm sure this aluminium foil tape i used will never come off but it doesnt look as nice as mylar. I just ran out of the stuff because its so handy it absolutely wipes the floor with duct tape for sealing etc and its waterproof, and of course reflective.

The 0.5mm aluminium i used still took me a bit of strength to bend the thing with a hammer. Its a pity i didnt use a flash and took some CRAP looking photos! Oh, and yeah your measurements would be helpful i'm sure - looks like yours are slightly wider. Hope you show us the buds

Click to expand...

D.I.trY, contributing is the least I could do in return for what I have learned here on ICmag. Excellent observation about seeing the back of the lamps in the reflector....cripes I didn't even catch that myself lol! And that was the whole point of it There was intent in my design with the angles and measurement I chose. I did a bunch of drawings tracing the light path from the source (bulb) towards its intended target. Technically fluorescent bulbs differ from HID as they are diffuse source of light whereas HID are point source, but I think the same basic principles can apply though.

I'm keeping an eye out on the effectiveness of the spray adhesive in a hot environment myself. I'll keep you posted. I tried using a flat white spray on the reflectors as everyone is always saying that it is the best etc. etc., but a quick check with my trusty el-cheapo light meter said otherwise. The flat white diffuses the light better which throws off the light meter. I chose to use Mylar as I am just trying to direct as much of the light as possible out from the back and sides of the bulbs and down to where the plants are. I did however switch to flat white on the insides of all of my cabs (I used to use mylar). IMHO flat white is better than Mylar there, the whole cab now glows when I open it up :smile:

I'll try to get get some pics and measurements for you ASAP.

-bakelite

Ok here is a hack drawing of the reflectors I fabricated for my PLL fluoro's. These aren't exact but are reasonably close in detail. The Left and right edges/flanges that are 3cm long are not drawn to the correct scale/ratio if that makes sense. In reality they would be a little shorter.

where did you get the polished aluminium sheet?

I feel like people aren't making a big enough deal out of this. I had never seen this before, and it seems like a major evolution in lighting. A reflector for HID lights that is ideally shaped, a computer-designed curve, could be a very marketable item. You could literally add 25% power to almost any light.

Efficient reflectors already exist for hid lighting. This is more about the intricacies of reflecting the dual tube system that pl-ls use.

ScrubNinja said:

Efficient reflectors already exist for hid lighting. This is more about the intricacies of reflecting the dual tube system that pl-ls use.

Click to expand...

yeah after I posted that I looked at my old 400w reflector and it uses this exact principle. oopsie.

Anyways it's still a big deal for the PL-L's because it makes them even MORE efficient, when they were already a huge improvement over spiral CFL's. I am now planning on doing my PC grow with a single 24w pl-l. I think my girls will get the same amount of light as if I used dual 23w spiral cfl's. Perhaps even better. It's like quadruple the exposed bulb of a spiral cfl with flat reflector, in a growing situation like this

Has anyone ever found a source for Miro 4 aluminum??

There are some nifty reflectors available on the net for PL-L lamps but they're about $100 for 4 of them. (Just the reflectors). I'm interested in a supplier in the U.S. that sells rolls of flat stock, about 5 to 6 inches wide.
(I'll see what I can do about finding that link. They're aquarium light kits.)

ahh hello guys, i didnt realise this thread had been resurected

I agree with you architechno that people arent making a big enough deal about the reflector for pll lights. If we can use nearly all the light from a cfl as is possible with the shape of a pll then i believe we can rival an hps, finally! I attribute much of my recent success in a pc case to the reflector, and i wouldnt be at all surprised if the 24w pll with nearly all the light properly directed can outperform 2 of the equivalent spirals, and would be much easier to ventilate.

I didn't know about miro 4 aluminium hydro. Did a quick google and the top result comes up with a supplier for those in the states. Its a super reflective polished aluminium so its perfect! I do hope that the premade refelctors avaliable take into account the specific geometry needed to reflect the top face of each bulb. Many just use a very reflective material and think thats enough, when clearly the right shape needs to be made. the little V over the centre of the two tubes is critical. I think using standard avaiable to buy aluminium sheet like 0.5mm thickness and covered with aluminium tape will achieve a similar thing. The tape is very polished and reflective itself and super adhesive.

oh and bakelight, its been a while! but thanks alot for the sketched diagram!

Awesome! Thanks for the search tip.... last time I did that, only pre-made kits came up.

This link

Is for a 24" x 48" sheet for $60!
You could make 6 reflectors out of that and still have working material so you're not saving every scrap.