UV lightbox with UV leds physics?

Sacrifice 1 photoboard. Make a test jig with masking and expose areas with various exposure times. From that you can derive a scan rate.

Cameras takes pictures with a flash.. If the photo resist acts like film then pulse overdriving the UV leds may reduce the exposure time. That will increase the scan rate too..

Damn..I should have kept my old paper scanner...I could have converted it into a PCB exposer :( D from BC

And the problem with using the sun is...?

The sun is not as fun as UV LED's... :)

However...I should mention..I use a 500W halogen for PCB exposure.. Quick, cheap, simple, easy to get...

Some people just order the PCB from the PCB fab house. Heck..some people (managers) don't even order a PCB... "Hey you! Yeah... Order a PCB for me.." D from BC

I like to work at night when its cooler, and no one s bugging me on the telephone?

Do they have sun in Sweden this time of year?

But seriously, we have to save all that solar energy for Al Gore.

Best, James Arthur

I wanted to avoid experiments initially so I can just do the math and figure out how to dimension the build.

I think the photo flash is more like send all the energy in one go to exploit short exposure times. While the LED pulsing would be to exploit high peak values. Question is if the peak energy is more efficient than using mean energy ..?

I think junction temperature, LED current and LED voltage affect the lumens/watt efficiency. See the datasheet.. I dunno what wacky things a UV LED will do..

I'd guess taking an LED beyond it's spec current will reduce its lumen/watt efficiency.. The junction heat spoils the performance. But it still will be brighter!..for the moment..and that might increase the exposure efficiency. Exposure like this.. POOF...move...POOF...move...POOF...move The LED's get to cool down during the moving period..

But if the exposure time is long (more *flux/second) then I think continuous max UV LED current would be better.

Maybe mount them in a heat sink then. Without obscuring the light.. Though LED body is usually mad up of plastics wich is a poor heat conductor.

Have three sections of LED's, then light them in sequence?

Why not just mount some LED's in the printer head.

board

oard

Since you now have a ballpark figure of 8-9 minutes to work with, and this Nordic person at diyAudio was able to make an exposure in 2 minutes, it's time to move on to the next phase: experimentation, as D/ BC suggested.

Try using a single uv led and see how much area it will expose on a board. Vary the distance and exposure time. Then you can figure out how many led's you need, how close to space them, and how long to make the exposure.

Good luck,

Mark

p=2Es. did Nordic (from diyAudio) ever say what wavelength his led was? There is almost certainly a strong, nonlinear wavelength dependence here. What somebody did with a 390 nm led could take orders of magnitude longer (or be impossible) to do with a 400 nm led. At this point, the best way to find that out is to try with what you have.

How about converting a 24-pin type printer, far less issues with the existing drive electronics.