OLcontest, modified light: 20cm fresnel lens thrower

Running out of clamps, I need three more. Have to wait for glue to dry to free some clamps :frowning:

Most structural work is done. Everything fits and the slider that focuses the led seems to work fine. It still needs a handle and a cover for the lens. And then the cosmetic work: final touches, sanding, painting and such.

The led is still underway from China to Amsterdam, so I can not work on the electric side of the build, but it will not be before monday anyway before I have time to continue.

Nice work bench. Looks like your almost finished. :beer:

Nice! Very retro looking and the use of plywood is very cool.

It is monday and mondays bring hours of time without people telling me what to do.

Today I made the thing work!

A few days ago I received the SBT90.2 on a chunky Noctigon from Hank, so I could do the electric stuff.

First the battery carrier was adapted. The driver board of the SD2 was cleared of components using a heat gun, then handy traces (near multiple via’s) for picking up batt+ and batt- were enlarged by scraping off some extra solder mask. Then led+ and led- wires (about 15cm of 18AWG silicon wire) were soldered on the board, so this light will be uncontrolled direct drive, with the current limited a bit by the long led wires.
Initially I bypassed the driver spring (see pic), but that limited the travel of the spring so much that the battery did not fit anymore. So I removed the spring and soldered a thin brass washer instead as batt+ contact (no picture of that).

I also glued the battery tube in the hole of the aluminium plate (with arctic alumina adhesive because that is strong glue and was at hand), so that it is fixed in place. The tail section of the battery tube was sanded a bit shorter so it does not fix/makes electric contact against the aluminium plate but against the tube as it should.
I still need to saw a bit off the head of the SD2 because it hits the lens when zooming out and thus limits the flood.

Now the spot was marked on the heatsink that is exactly centered behind the fresnel lens. I already found out that the centering is not extremely critical, a few mm off is not noticable in the beam. But still…
Then I did several attempts at drilling two 2mm holes in the heatsink to make M2.5 threads for the screws that fix the ledboard in place. But I did not get that done. Not sure what type of aluminium this is but the drills kept digging in the material and then break off in the hole :person_facepalming: . Had to sand everything flat again, twist the heatsink 90 degrees, mark new holes, and fail again. In the end I decided on using two existing M2.5 threaded holes in the heatsink with some creativity with a small steel plate. Behind the board is a thin layer of AS5 for best thermal contact with the heatsink.

The thick wires come from the battery, the thin wires go to the little fan, it is simply wired parallel to the led and the ledboard had a convenient extra set of solder pads to connect the fan.

The lens thusfar was fixed in place with two small pieces of tape, but that needed a bit more permanent solution if I wanted to check out the workings of the decice, for the time being that will be four little screws. I think eventually a new clean lens will be glued into the frame.

A handle was added. I planned aluminium, but found with how this thing looks, a wooden handle was better.

The device still looks very basic, I’m not sure if I can ever make it look fancy, but some cosmetic stuff is still in the planning for next monday.

But now it is ready for some testing!

On a 50E battery I got 15-something amps, a bit low. On a 30T I measured 17-something amps. Although I would have liked 20A, this is good enough for some intial throw measurements. I can still bypass the tail spring, although is is already a copper-alloy one.

The fan works, even with the lagging voltage caused by the led, it makes a faint humming sound as it spins quite slowly. With the light running for about 8 minutes on a 30T, the fan suddenly stopped, it appeared that the voltage had become too low for the fan to run. The battery at that point appeared to be 3.08V resting voltage, which is fine for recharging. So maybe the fan works as a sort of low voltage alarm, if it stops the battery needs recharging. Not sure yet if that works just as nice for a 50E battery.

After the draining of the 30T, the heatsink and aluminium plate were only hand-warm, maybe I could have got away with one size smaller heatsink.

A quick and dirty throw measurement at 5.5 meter (led focused at that distance) showed 3.9 Mcd. So a few things seem to be working! :sunglasses: . The beam is way better than the beam from the 36cm fresnel thrower, that, and the SBT90.2, explains why the throw number is better than you expect when you go from 36 to 20 cm (which is a 3.2 times surface reduction).

Aiming the beam on the small square where I live is fun, but making a beamshot proves a challenge. Here is one at 70 meter, I kept the background lighting as I see it in person, but then the spot is totally overexposed. When all is finished I will try some proper beamshots.

Next week the light will be dismantled again, the interior will be sprayed black, the exterior will be sanded and maybe touched up a bit, a lens cover must be fabricated, and I have not decided on an outside colour yet.

Awesome work! :+1: :+1: :+1:

Awesome!
I love these build threads

Awesome! Following intently.

I’m in the design phase of what may become a 1000-1500 watt MH HID based searchlight with a 24” parabolic reflector. Horribly inefficient and messy, but I’m looking for the most visible beam possible, not max CP or max throw. I also have a cheap A4-sized fresnel and an old 250 watt halogen incandescent worklight that I’m experimenting with. It’s only 4000 bulb-lumens and a filiment length of about 100mm, so I don’t expect much. But we shall see.

:smiley: You mad bastard. I mean that in the nicest possible way. :beer:

Nice build! That box needs a few coats of paint or lacquer, as well as a name / model number and a logo! (And a groupbuy!) :wink:

At your service :slight_smile:

Today was a quiet sunday in partly lockdown Amsterdam, and I could do a couple of things.

First a lens cover. The nr1 vulnerability of a plastic fresnel lens lamp is that the grooved side of the lens is on the exposed outside of the lamp, and any dirt/grease/fingerprint will be impossible to remove without damaging the surface. So a cover is essential for any moment that the lamp is not in actual use. I made the cover from polycarbonate which is tough and flexible. I used a small slat to create a groove at the underside of the lens that exactly fits the cover thickness, so that the cover can be slit in the groove while bended a bit and when it is pushed down it springs into position against the lens.

Now I removed the slider, the fan and the fresnel lens and did some cosmetic things to the box and painted it. I likely would not have done this if not because it is for a contest, which shows what a contest does to people, or just me :partying_face:
Knowing well that this is a plain square plywood box, and that any attempt making it look like a slick light is quite hopeless, I still went for some detailing, and by making it bright red it might even give a slight impression of being fast and furious? Probably not :person_facepalming:

The inside was spraypainted with a matt black paint sold as “camouflage” :sunglasses:

The outside received a base-paint first, and then after some slight sanding, bright red!

That is all for today. Next job will be shortening the battery tube by chopping part of the head of the SD2 off, so that a wider flood can be obtained. And changing the long 18AWG ledwires for 14AWG ones, in the hope to get the 20A sweetspot for a well-cooled SBT-90, but I can not do that yet because the 14AWG wires are still somewhere in the mail between Hobbyking and my place.

And I have a cunning plan for a fun detail… :smiley:

looking at the box that looks so innocuous, one can only be amazed at what emanates from it. Scary.

:smiley:

Well done! :+1:

That box looks great now.

I’m looking forward to your long-distance beamshots. :sunglasses:

The fan is because most of the light never exits the lamp and is absorped by the dark-painted wood, that is maybe 20W of heat. The fan causes a minimum of air circulation to get rid of some of it. I do not expect much heat to build up in the lens, maybe a bit in flood position when the led is closer, so the lens is cooled a bit too. The fan is parallel because that was easy, it draws maybe 100mA so it does not eat much of the current. The alternative was a dedicated battery for the fan, but it seems not needed sofar.

Your solutions using glass plates and such sound very fancy, I’m not sure if fancy is needed, it was certainly not my intention and everything works as it is.

Sweet :heart_eyes: :star:

Yes, a collimator could be useful for making better use of the light coming from the led, and in this design there is enough space and mounting opportunity for one.

But the original purpose of this lamp was pure throw, and every added optic will reduce that number to some extend.

If more light is needed: I placed the light engine on a slider, so that with the led moved closer to the lens, a flood beam is created, in the closest position I expect light extraction to be fairly good.

Wow! Somehow I completely missed seeing this thread when it first appeared. Great stuff, makes me want to get my hands on an aspheric lens and see what develops.

:+1: :beer:

“Relax Honey! We don’t need to call the police! Its just that crazy flashlight guy on the other side, testing out his latest ISS signaling device creation. Just like the other time, we will hear all about it in a few days on the NASA channel.”


What happened to the die projection? Did you burn a part of the phosphor?! :wink: