Yes good call, I’ll be trying the slow route first and doing some wet sanding to avoid glass dust. If that takes too long I’ll have to find an alternative method.
Thankfully the edges of the lens are actually quite thin so it shouldn’t be too bad, got some extra long podcasts lined up 
Well that actually went better than expected. OD is now just a shade over 110.5mm
Took 240grit wet and dry emery cloth and about 3 hours worth of podcasts to get the lens down to size. 
very nice Linus your next pic will be of the sbt-70 through the lens :)
Can’t wait can’t wait can’t wait.
Epic City
Oh man, just held the lens up in front of the Sbt-70 for the first time…it’s….so….round… :heart_eyes:
Liar Liar Pants on Fire….pics or it never happened!
:bigsmile:
What he said ;)
Patience patience
I should be going to bed, but I’m just prepping up the pill and mcpb to do a test assembly. Gotta see this thing throw a beam now.
Yep, this is it. This light is f*cking amazing!
I really just slapped it together, eyeballed the focal length and mounted the lens with some tape. Pretty much got it spot on in focus for my indoor distances, at the maximum room length of 12meters it projects a lovely circular spot on the wall that’s only 15cm in diameter. I can’t quite get enough of looking at it.
Surounding the central spot is that very faint blue leakage pattern, hardly noticeable in real life but you can make it out in the photo. Then around that there is a very smooth corona fading out quickly to a slighlty bluer margin. Nothing at all unpleasant or ringy about it, just a lovely complement to the central spot.
This corona seems to be the light bouncing around inside the lens and then being scattered forward rather than a direct image of the emitter.
Much further out there is a number of rings, again this is light bouncing around inside the lens hood assembly itself and then hitting the lens at unintended angles. I haven’t done anything at all to combat any of that so I’ll see what I can do to reduce those but all of these artefacts are so minor compared to other aspherics I’ve built I’m not even that bothered.
I’m really delighted with it so far, this emitter was made for a light like this. It’s really an amazing light saber of light…and I’ve only run it at 1.5Amps so far
—
Edit: Here’s the light in action on the test bed.
Unfortunately getting a good look at the emitter itself is really hard, you have to hold the light at arms length and shine some light in there to really see it. Very tricky to get a good photo of it. But hey, with a beam like this that emitter can stay hidden all it wants, it makes itself very known as soon as you turn the light on.
That's awesome looks like a moon
I’m gonna have to break down and get another one of these beauties! Dadgum your hide! lol
12A, I wanna see 12A! Man, that circle of light is clean isn’t it? Aspheric projection of a round die, predictable but sweet all the same…
So, Linus, are we keeping up with total cost on this build? Or is it a secret from the bank accountant?
Last time I dared take a look a the spreadsheet, parts cost was around $200. Not too bad but the lens ordering shenanigans and the usual forgotten parts have probably pushed that closer to $250
And yes the hotspot is amazingly clean, usually photos are deceptive when showing bright hotspots. Hiding all sorts of faint coronal artifacts and other sins, but here that first image is exactly what I see. Super clean and defined even with the bits of sellotape in the lens and first attempt focus adjustment.
It’s awesome and what I always wanted from an aspheric beam.
Mouser is down from 12 available to 11…
:bigsmile:
Made a bit of progress on the driver today.
Wight’s Linear fet driver with an opamp flourish
This time a cleaner reflow build with less carpet fluff and flux residue, hope it still works as well as the prototype
Two 0.01Ohm sense resistors should net 10A. Though I may be persuaded to up that to 12-13A if initial tests go well and led temps are reasonably safe looking.
The fet will be mounted to the base of the copper pill with a strip of thermal tape. That should hopefully transfer enough heat away to keep the fet comfy and also isolate the fet drain from the rest of the light electrically. The little ram heatsink I had laying around and it gave me a good place to mount the fet and add some thermal mass to it at the same time.
The low vF of this emitter and the high drive current means there should be a fair amount of heat generated at the fet, but I’d think this setup should do a good enough job of keeping temps in check.
I settled on the T06N02 fet for it’s nice fast behaviour when used in conjunction with the 7136 and opamp, but I have better options on hand in terms of thermal and Rds On performance. I’ll see how this one fares and may upgrade it to something better later.
Finally I beefed up the tailcap section a bit to minimize spring resistance.
I like this external wire approach, keeps full compression on the spring or springs in my case and still gives a solid low resistance bypass.
Right straight over MY head! But it looks like you know what you’re doing so…Carry on!
But, might I ask… Why?
The straight build of Wight’s driver runs the SBT-70 very well and will run it at the amperage you’re looking for with no problem, so why all the work-arounds?
And why so much concern about the FET getting hot, you’ll be pulling 10A through a MOSFET designed for 150A, running 3.5V when 30V is it’s max. Baby stuff compared to what it’s designed for. In normal set-up it doesn’t get hot at all.
I think this is a different driver than the one you’ve thinking of.
I’ve built dozens of those, use em exclusively with triples and such.
The one powering my SBT-70 is one of the very first, the one that didn’t even have outer ground rings on the battery side. I just pulled 8.72A from a rested old 20R in that one. The Courui, with 3 parallel cells, can run that light with no effort. You might easily see 12A. That’s what modes are for, right?
Oops! Maybe not! That one has the 7136 chip on it, I see the outline now…thought you rigged that on there. Sorry, carry on.
Edit: Now I’m really confused. The A17DD-S08 +LDO is a variant of the board I’ve built lots of. Does the addition of the LDO cause the fet to run hot? I was looking at that driver when Wight announced it, I see it doesn’t seem to have taken off, is there a problem? I meant to switch over to this instead of Zener mods but totally forgot about it. (as if that’s not an everyday occurrence)
This is the one used here :