Adam Seychell <
a_seychell@...> writes:
> Whats the grid pitch ?
About 1.2 inches. Just enough to solder the leads together :-) That
means 99 LEDs in a 9x12 inch area, or 11 strings of 9 for the power
supply.
The density is about 0.2 leds/cm2.
> Whats the LED brand/model ?
The 395nm UV from BestHongKong. I got 100, and 100 of them worked -
perfect score! I built up a current regulator on a breadboard and
checked each one before inserting it into the board.
> I'm interested in your exposure times. I get 60 seconds with
> negative dry film, grid density 0.28 LEDs/cm^2, BestHongKong 390nm
> UV LEDs at 20mA, about 100mm PCB to LED gap, measured with inkjet
> transparency + 5mm window glass in light path.
I picked up a Stouffer step gauge (from stouffer.com - just call them,
they can ship direct, not expensive) so I'll know for sure. The
distance to board is about 5 inches, the current 20 mA. I calculated
about 30 seconds initial exposure based on the "math" of the setup,
but I'm sure reality will correct my assumptions there :-)
The next step is to laminate some resist and cut it into test strips.
I don't get a lot of free time for these, so stuff happens as I find
time to do it. I've got some photolith paper but it's not JetStar
(they sent the wrong brand but they're working on getting the right
stuff) and some glass of dubious UV qualities (cheap hardware store
glass). We'll see how it goes.