Projector Cyanotype and Chiba python digital negative.

[imgprojts]

Uh! Aliexpress delivered the wrong part sooner than expected. I got the chip and not the assembly. So I gotta think about how to cool this thing. On the plus side, its not 10mm, all the emitters fit in a 5mm square.

 

[calebarchie]

I suppose so, conventionally the lenticular effect is only on a single axis.

Not sure about specialty resins, any UV will will destroy polymer chains and they all usually have inhibitors. Fused silica/quartz is the better choice.

You may also want to look at reverse or solar fresnel, not sure if they make one that small in glass though. Although I think anything infront of the chip will just reduce output too much relatively.

The smaller chip looks ideal, good luck.

 

[koraks]

how to cool this thing

Solder with a hot plate to a copper core PCB, heatsink that and put a fan on it. There's no other way.

 

[imgprojts]

Solder with a hot plate to a copper core PCB, heatsink that and put a fan on it. There's no other way.

Yup. I went to HD and got a bag of very expensive copper straps. How did copper straps go from a buck fifty to five bucks? I dremeled that sucker into the right shape. Soldering was pretty straight forward. At work I use a PID hot plate or a reflow oven. But in my basemen living room garage, I have no respect for science. So I torched the baseplate. Then I carefully soldered the leads. I tested it for a couple of seconds at full power and only half of it lit up. It turns out that half the COB is pointing in the opposite direction. Then looking at the board online I realized the two sections must be in series. So de-soldered and re-soldered it.

Wow, I'm really impressed. I mean both are 50W but the little one has a good 4 or 5 times the light/power intensity. Up close, 1cm, it develops new cyanotype to full Prussian white in 4 seconds. Using the 50mm lens at 25mm from the COB It is able to expose new cyanotype in 10 seconds to Prussian white. Its crazy good, 385nm supposedly. The cyanotype paper makes crinkling noises when it develops. This COB needs cooling. The little heatsink seems too small but if you think about it, it is the combination of fin area and air volume that does the cooling. So it works nice and cool piggy backed on the big fan's air stream. I'll 3D print a duct for a fan before testing the projection system. Oh man, I'm glad I got my red safety glasses for this.

 

[koraks]

t if you think about it, it is the combination of fin area and air volume that does the cooling.

Yes, moderated by heat transfer from the COB to the radiator and from the radiator to the air. The latter is mostly determined by geometry of the radiator and airflow; the former is determined by how you mount the LED to the heat sink (and whichever mounting interfaces are between those points). That part of the construction isn't entirely clear to me, but I have some concerns there.

Note that I've used high-power SMD LEDs with iffy DIY mounting only to find out that failure is something that happens gradually and within a timescale that's really inconvenient - i.e. you *think* you have a working setup, and then the LEDs start to die one by one. Maybe your setup is perfectly fine; I cannot judge. It's just a word of caution.

 

[imgprojts]

Yes, moderated by heat transfer from the COB to the radiator and from the radiator to the air. The latter is mostly determined by geometry of the radiator and airflow; the former is determined by how you mount the LED to the heat sink (and whichever mounting interfaces are between those points). That part of the construction isn't entirely clear to me, but I have some concerns there.

Note that I've used high-power SMD LEDs with iffy DIY mounting only to find out that failure is something that happens gradually and within a timescale that's really inconvenient - i.e. you *think* you have a working setup, and then the LEDs start to die one by one. Maybe your setup is perfectly fine; I cannot judge. It's just a word of caution.

Its fine really. It's just another few bucks down the road. I think my setup is probably very good because without the airflow the aluminum block got hot very quickly; within 5 or 6 seconds it becomes uncomfortable. So the conductivity at the joint which is the usual problem is good. They have this poor LED sitting on thin copper traces insulated by epoxy over aluminum. All the LEDs sit on a single piece of brass 4mmx4mm. So I made a strap that had a central cut out 4mmx4mm. Then I flattened it, filed it flat and polished it to 8000 on the contact side. I then cut a small piece of flux core electrical grade solder and I flattened that. I placed the LED, solder and copper on a wooden clamp such that only one copper mount wing was exposed. Then I hit that with a mapp torch watching the color change carefully. Once the LED dropped over the copper, I stopped heating and quickly used a wooden stick to correctly place the LED. Somebody wished me luck and I used all of that plus I tossed the neighbor's cat and caught it in the air thereby gaining one extra life.

When I found out I had one of the polarities backwards, I should have bonded that jumper to the 4mm ground plane. Oh well. I went searching for the picture of the board to try and guess how they did it and I wound up discovering that there are 405nm LEDs with similar footprint that go up to 400W. I am really not sure 405nm would work since 395 didn't, but these things work by specific wavelengths so it might be worth a try in the future. Hopefully I can find a 100W 385nm and run that at 50 to 80W to extend it's life next time. I'm actually not sure really what the damage threshold for all the coatings is. Their spec Max indicated 24W/mm^2 on a "similar" chip for ~400nm. 50W x1/2 over the first beam splitter minus all the light that doesn't hit the DMD and the light absorbed at the Fresnel is probably close to the limit. I'll have to judge by the results. In the previous test only 1+ pads showed on the projection @1W each. Based this new setup might get me 30W worth of pads showing.

 

[koraks]

Sounds good; I agree that by your description the heat transfer should be excellent.

 

[imgprojts]

Sounds good; I agree that by your description the heat transfer should be excellent.

Reverse psychology. It works! This time I measured the actual temperature with the large heatsink the temp is staying pretty solidly at 43C. In the 30 seconds that measurement took, the rest of the 8.5"X11" sheet went almost fully Prussian white. Now I need a new adapter for the projector. You'll notice I mounted the chip at some angle (45 degrees). This will make the little light squares line up with the DMD chip.

I figured going to the big heatsink will be saving time. And time is definetly something everyone can put a value on. Even me. I'm old. Middle aged. I could still date my wife if she wanted to. I bought a new heatsink for the other LED which I don't need at this moment.

 

[mshchem]

I've got to go back to the beginning of this thread. Fascinating!