TA - thank you for this info! As i got halfway through reading your response i had the thought “what about dc fix on 1/8” plexiglass?” LOL, so i’m glad you mentioned that. That is probably what i will try for multiple reasons -
1. I do not have access to laser cutting or if i do it is too much legwork. unless i absolutely have to, in the event dc fix doesn’t work well enough.
2. I can cut plexiglass with my bandsaw (keeping the wrapper on it or cover it in painters tape to avoid scratching it on the saw’s table).
I had just assumed it was some diffuser material you had someone specifically engineer for the measurements of the tube. If that is not the case, and it doesn’t sound like it is, it seems that whatever gives the most consistent results is the best option. I feel dc fix and plexiglass will work fine for my needs.
Next question (since i have your attention lol) - Do you know where i can find calibrated lights like Maukka was selling?
Yeah, since you will be calibrating the whole sphere as a unit, the exact diffusing sheet you use is not super important as long as it does the job and does not cause anymore tint shift in the light then necessary. Most important thing is the calibration step.
DC fix should work fine, you will just have to play with how many layers to use. I ended up using 3 layers of the diffusion sheet I had to find I would not get any noticeable difference in readings when using different reflectors with the same LED. A sphere is better for this of course but a lot bulkier and expensive.
Maukka is the only source for calibrated lights that I know of, if he has some they are highly recommended.
Some types of the inflatable air pillow material used for filling voids in boxes when shipping packages is just slightly opaque / diffuse. This stuff is sold in rolls. Stack layer on layer to get just the right amount of blockage to fine tune the calibration to read 1:1. This may work best at the sensor side.
I used this method to calibrate a different lux meter for use with my TA tube and got it to read 1:1 to a Maukka light.
You might take a look at the photography world for diffusion material. You can find stuff that is uber consistent and easy to cut.
This stuff for instance. I got it from BH photovideo. Kind of expensive compared to the hardware store goodies. But so easy to work with. ,
And when TA says it took months to get the first calibration - believe it!
When I did my version, when I finally got in the ballpark, well the heavens opened and angelic choirs began to sing…
My version.
Want one? Get it from TA unless you like to fuss (and fuss (and fuss)) with stuff.
Important tip, if you do this - record every change, no matter how small, or you will go nuts trying to get repeatable results.
All the Best,
Jeff
Wow, Hoop and Jeff thank you for this info. Jeff - that thing looks like it belongs in Marty’s workshop in back to the future lol. I dont think i am capable of doing that setup, i mean i cant even understand your notes! boy… I may need to. They make it look so easy online. If i am not trying to go for a 1:1 with the calibrations lights, and im OK using a formula and with about 90% accuracy (to start), i wonder if i can just use some of the Photography diffusion stuff. I dont want to spend months doing it…
Oh, also, TA or anyone else - do you sand down the sheen of the inside? or paint it? or treat it with anything? or does the diffusion film help alleviate the need for that?
And even then, the meter will still have a +–10% deviation unless you spend hunderds of dollars for a professional calibrated meter.
As said, every change will impact the reading, even inserting a larger or smaller light affects the reading.
So the real question is, how accurate you want your readings to be?
Question 2 is how large you want your setup to be?
Question 3 is how much effort you want to spend for your readings?
If the diffusing sheets do their job and you spread them out over the length of the tube, there should not be any need for sanding the insides. This is part of why I hunted for the perfect diffusion material so long to save a ton of work on each sphere.
Even without that extra work I still get flashbacks to the weeks we spent building these spheres way back, learning as we went. Tubes all over the house in various states of completeness. Calibrations seeming to change just because someone else was testing it. Good times lol. Luckily I figured out most of the issues and got them consistent enough for our uses after a LOT of trial and error.
Without a proper sphere the real key was diffusing the light repeatedly, this removed most of the variance from light to light and made things much more consistent.
After that it was getting a proper calibration light to base the calibration off of. My home grown setup was WAY off and I had to send everyone some correction discs to fix it once I got Maukkas lights to do a real calibration.
Wow, thank you for sharing this hard won experience openly with us, and me! I bet it was a nightmare I. A way getting those setup properly in the beginning. This also makes me realize I really need to try and get the calibrated lights from Maukka …
I have always tried to be transparent about what I do and how I did it, at most waiting to release the full details until after I sold out of whatever it was I made.
My philosophy has always been that if someone wants to put the work in to do it themselves, more power to them, they are also the kind of people that would not consider paying for it pre-made from someone like me anyways. And if they did they would not be happy about it. So might as well help them out whenever possible.
I never want to be someone that forces people to buy something from me. I will build or DIY most things before even considering buying it pre-made, it would be wrong for me to not grant others that same choice.
The TA drives being a good example, I naturally could of kept those closed source and only available from me but instead I decided to release them publicly for those that wanted to DIY it and offered some for sale pre-made from me. Making them the most used modded light drivers ever as far as I know even years after I stopping making them.
That said one thing I have learned over the years is that sometimes, it is better to just buy something pre-made and be done with it unless the journey is something I want to experience lol.
Artiet59, there is very much uncertainty in building one yourself. If TA has one you can buy, get it !!
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I have spent a lot of time and money building 2 Lumen tubes. A 6” is calibrated with Maukkas lights, and it took months to get some consistant readings. Took it apart countless times adjusting, changing diffusers. When I tried the Big Throwers in it, well bad readings again. The 6” was only good for 2000 lumens or less. So I made an 8” lumen tube for the big throwers and used them to calibrate it with. There are no calibrated lights for 6000 to 30,000 lumens, so its a wide open guess.
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I tried to get help with lumen tubes, but not much interest at the time. LUMEN TUBES, pics, accuracy, opinions Please.
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EDITED : The reason I built mine is because I enjoy the challenge and there was none available for my big lights. Mine cost considerably more the TA was selling his, and I’m not really interested in lumen accuracy on my EDC.
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Getting the tube/lux meter to readout directly in lumens that are close to the actual value of the light really takes some fussing.
On the one I built, a few mm in pipe length throws things off. But that is also part of the calibration process on my tube. Changing one of the tube lengths moved me closer to my desired readings.
When I tried to use the hardware store diffusion stuff, how it was cut relative to the pattern made a difference. How it was oriented inside the tubes made a difference.
How tightly the tube sections fit together made a difference. I used thin spacer rings to adjust the fit for consistency and naturally this changed the reading too.
On my version the insides of the straight sections are lined shiny metal duct tape so very little light is lost. I covered the outside with the stuff initially. But I felt that more or less light was getting absorbed into the tube plastic depending on the throw of the light being measured. So I did the inside treatment.
And yes, just covering the outside of a tube with tape or foil - makes a measurable difference in the readings….
I found no need to scuff up the insides of the curved tube. The light is well defused by the time it gets to the elbow. But I did anyway because I wanted to get more consistent readings when changing the elbow sections. Different elbows had slightly different finishes.
I am still testing, I’ve got versions with the outside of the elbow covered in chrome paint. And another with chrome paint on the inside as well.
The project got put on hold for a while and I’m about to dive back in. I want to experiment with elbow finish.
I also want to add a photo diode at the end of the assemble so I can use the setup to get runtime plots that can be adjusted to the lumen values. I’ll use my USB O-Scope and logging software for this. My cheap lux meter hasn’t got a way to do data logging.
All in all it’s a good way to waste a goodly amount of time. Getting close and using a correction scale is a viable option.
If you are at all OCD, just step away, or keep the meds handy.
Or convince TA to build just one more…
All the Best,
Jeff
Exactly my experience Jeff!
I’d buy one from TA, but i’m frugal. But the time and money ive spent into my setup (tube and sphere) is worth more than TA’s price of the tube
CNCman, I completely missed the thread about your adventures.
I found the larger tubes harder to control, so I stuck to the 4” (actually 3” - had a brain fart and didn’t remember) for sanity and costs sake.
All the Best,
Jeff
Yeah, when I started, I thought “How hard could it be?” Still I’m glad I did it, I’m semi-retired and have always been a tinkerer.
When I get mine to a point to where I’m happy with the end product, I’ll do a DYI build POST.
Build one for someone else?
I don’t think so Tim…
All the Best,
Jeff
FYI, I don’t read BLF much anymore, so I never saw that thread CNC otherwise I would of been happy to help you.
Just a quick glance and I saw where some of your issues came from, those diffusion sheets in the pictures are no good. I tried those and had nothing but issues, 4 or 5 options later I found this local place that had some and it worked WAY better.
When you put the diffusor over the light in a room, you should not be able to see any simblence of a beam coming out of it, just a perfectly smooth wall of light. And even then multiple layers are important due to how the light reflects inside the tube.
For anyone interested, I did manage to find a few more lux meters (they need to be a specific kind of sensor body to fit properly and they are going out of production it seems) and I had someone order a tube awhile back that required me to get more stuff laser cut. So I do have the important parts needed to build a few more tubes if anyone wants one.
They will just take a week or 2 as I will have to order the rest of the parts.
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You have helped me on several occasions TA, :+1: Thank You.
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I had hoped there would be more input on the tread I started so I could learn more about why I was having so much trouble tuning it. In the end, it is clear to me the variables are not controllable to any satisfactory degree. The smallest thing can affect readings, so sensitive, I now just use them for fun, not accuracy. The work I do revolves around accuracy, that drives my thought process. Lumen tubes for me is a failure. Most of the time Lumens are arrived at by led type, voltage, and current for a ball park value.
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I Apologize that my frustration has offended anyone or everyone. :person_facepalming:
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CNCman, I don’t think anybody took offense at anything you said. Certainly not me.
Farting around with these things can be frustrating. I have pages (and pages) of notes taken of test builds and the results.
I got pissed off more that once as I made changes and seemed to be getting me further away from something that worked.
Just taking the tube apart and putting it back together yielded different readings.
I got that ironed out using spacer rings to control how tightly the parts fit together along with using witness marks to make sure the tubes went back together in the same orientation.
The diffusion stuff I used is so consistent, at least that wasn’t a problem orientation wise. Yet moving it in relation to the tube placement by 2mm made a difference in the reading.
On my setup, I found that room light did indeed make it into the test setup until I covered and/or lined the PVC tubes. So do your testing in a controlled light environment or shield the setup.
As TA said, even the smallest changes makes surprising differences in the readings.
All the Best,
Jeff
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