OLcontest, modified light: 20cm fresnel lens thrower

[MascaratumB]

I guess these could be handy
https://www.aliexpress.com/item/32920891109.html

[MRsDNF]

@djozz

@Skylight

Are you going to project the legendary ‘bat signal’ with this flashlight? Or better a ‘BLF signal’? :smiling_imp:

I could have a try on the bat signal, but it must be cut out of a strip of metal within a 10x10mm area

You know you can do it. I’d suggest a beer to the student that makes the best batman stencil.

@MtnDon

Wow! Great stuff, makes me want to get my hands on an aspheric lens and see what develops.

:+1:

I’d love to do the also MD but you know as well as I do it wood never work.

[MtnDon (Don Miller)]

@djozz

@MtnDon

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:

The big optics invite woodworking over metal work (too heavy, too much expensive material), so these lenses are right in your league

What/who was your source?

[kennybobby]

you can harvest big lenses from old projection TVs at the thrift store and cut them down to size, and people will nearly pay you to come haul them out of their house.

The liquid light film slides can be made mixing insoluble liquids such as water and oil with color tints of either paint type between two panes of glass. Another example is to use air to blow a drop of water across some fresh oil-based paint and enjoy the patterns that develop. Fun stuff to do on drugs…

[djozz]

@MtnDon

@djozz

@MtnDon

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:

The big optics invite woodworking over metal work (too heavy, too much expensive material), so these lenses are right in your league

What/who was your source?

I bought it a few years ago actually, on aliexpress. They are cheap (under 10 dollar for a 20cm diameter lens) and pretty good, here is a link, I expect it to be the same quality as the ones I got. I chose 200mm focal length as a compromise between the amount of light catched by the lens, and image quality (a very short focal length lens will catch/transmit a large percentage of the light but also show a lot of image distortion at the edges which will negatively affect the beam and throw).

https://m.aliexpress.com/item/32650652778.html?spm=a2g0n.productlist.0.0.19d315a3EZSPBz&browser_id=66b1ef171b05438fb64eff5ede7df8ad&aff_trace_key=8a9fcaee55ca4f97ad04c20e01d01302-1603223217706-05977-UneMJZVf&aff_platform=msite&m_page_id=uwt5f3ysax4carj3175b3e1b8271a9c5879ed5cc9b&gclid=&*imgsrc*=ae01.alicdn.com%2Fkf%2FHdaa45cc53f114786a1a4c40ca2433fd0A.jpg_640x640Q90.jpg\_.webp

[MtnDon (Don Miller)]

Thanks.

[CNCman]

@djozz

This is how the star is made.
Because I built in some tolerance, the die is focused at infinity when the slider is still 12mm short of the backside.

So when the slider is fully retracted, the focal plane of the lens is 12mm in front of the led, and the die projection is out of focus, creating a fuzzy larger spot instead of the smaller sharp square of the focused die.

So I positioned a cutout of a star (made from the lid of a coffee tin) 12mm in front of the led, which is sharply imaged at infinity by the lens, and because the led is only little out of focus, the throw is still not completely ruined (although I think it went down from 4Mcd to just 1Mcd).

Of course for maximum performance of the lamp, the cutout must be rotated out of the way.

If I find the patience I may have a go at a batman cutout, but it must be tiny, and the metal is tough.

.
That is amazing, very well done djozz :+1:
Now that is thinking outside the box ! I never thought a Fresnel lens could do that !
You could do a Batman thingy in the clouds too.
No doubt this years competition is heating up :smiling_imp:
BLF has other forums beat easily
.

[MtnDon (Don Miller)]

This is very cool…. something to think about

[djozz]

I tried a bat stencil, sawn out of thin aluminium with a fret saw, but I made it too big, the edges of the wings do not receive enough light so they appear not sharp.

So it must be made tinier, not sure if that can be done nicely with a fret saw. And I’m not sure about batman either, maybe I will end up with something entirely different

[MtnDon (Don Miller)]

Cool!

[djozz]

Jeff51 just posted about a batman projection contraption that uses a 100,000 lumen Imalent flashlight as a light source, and a 25cm fresnel lens with fairly long focal length. Pretty cool too, but not as silent, and maybe a bit less throwy than this one.

The Bat Signal

I suppose this could go toward the OL build contest, But he’s not part of the BLF (I think). But I couldn’t resist adding this. [How to Make a BATSIGNAL (For Real!)] All the Best, Jeff

[CNCman]

The sky is the limit

[Skylight]

Looks pretty good actually!

[CRX]

[MRsDNF]

Good effort djozz.

[djozz]

Tnx.
Today I got the 14AWG wire in so I could finish the battery carrier. I chopped the front section off the flashlight head 4mm above the shelf and sawed two grooves in the remaining rim to lead the ledwires to the side. Had to ream the holes in the shelf to 4mm diameter for these quite massive wires. Smoothed everything with sand paper so there were no sharp edges to cut into the wires. The wires were fixed in position with a good bit of kapton tape, does not look extremely profi but you are not going to look inside the lamp daily.
In the picture I show the old 18AWG wires too, so that you can see that 14AWG is a whole lot thicker.

I was lucky because with a 40T at 4.12V I measured 19.85 amps now, precisely what I was hoping for

So now that the battery tube was shortened, I could check the maximum flood setting of the lamp, with the slider towards the lens with the battery tube touching it.

In the picture the flood looks a bit less wide than in reality because of the wide field of my phone camera. Trees are at 25 meters as always. (it looks like I borrowed Flahoholic’s van for the beamshot )

[MtnDon (Don Miller)]

Nice

[Xandre]

WoW

The beams are really awesome

Regards Xandre

[Grigio]

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

I missed the last update from a few days ago but “Wow, nice work, sir!” (Mooi rood is niet lelijk, toch?)

[djozz]

mooi rood is niet lelijk herinner ik me uit de jaren 70 volgens mij, zegt iets over je leeftijd