Another video of the controller board in use... any one can do it...
I found a source for populated proto boards at Mouser...
If you google adriuno you get all sort of project ideas n free software
Very cool n versitile A/D IO board.
The thing I would like explained is the base exposure, in the video it set as stop (3.5 stops) I though it would be seconds then the rest is in stops calculate from that base time.
To make a more complicated example, and illustrate how dodges are computed, consider:
base = 3.5 stops = 11.314s
dodge 1 = 0.5 stop = 2^(3.5-0.5) = 8s (i.e. dodge for 3.314)
dodge 2 = 0.25 stop = 2^(3.5-0.25) = 9.514s (i.e. dodge for 1.8s)
Therefore, the base exposure once dodges are subtracted is 11.314-3.314-1.8=6.2s. When you perform the dodges, the non-dodged areas will get the originally intended base exposure of 11.314s.
The reason the base exposure is expressed in stops is it makes it easier to scale your paper size, or to shift the whole exposure darker/lighter by a certain tone. Say you figure out a good print at 8x10 and want to print 16x20, you just add two stops. And when you do a test strip in stops, the values will be equi-spaced, e.g. 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75. If you converted all of those to seconds, you'd get some really annoying numbers. It's also very easy to apply drydown correction; the software just needs to subtract a configured value, e.g. 0.08.
It also makes it easier to do stuff like grade changes when printing split-grade. My timer doesn't directly support that (i.e. it won't recompute the times for a grade change, or do a grade change while preserving a particular zone), but the use of stops to represent each exposure time makes it relatively simple for the user.
I appreciate this is a simple project to construct, but it would be helpful if you could post a schematic. Did I miss it? Thanks.
Thanks. For reference, here is the other thread: http://www.apug.org/forums/forum43/9...top-timer.html
It seems that only the C++ code has been released. The page given the OP doesn't have a schematic or a parts list.
I haven't posted a schematic yet, sorry. However, there is literally nothing to do except connect the Arduino to the LCD and Keypad according to the pin-definitions in the source file. I will get around to drawing one soon that shows how to interface a solid-state or coil relay.
PS: new code is uploaded, it now does test-strip (differential exposures for each step) and test-tile (complete exposures for each step) generation. Always 8 steps, but you get to choose the base exposure and difference in stops between steps. Test strips are the classic approach we all know and test-tiles are how I prefer to do exposure testing. Tiles take a little longer to expose but you get the same part of the image visible in each step of the test so you can pinpoint exactly the exposure you need for a particular highlight or shadow for example.
You'll probably have to shift-reload the webpage, which now has some "WTF is an F/Stop timer" explanation and a link to a Gene Nocon interview.
Perhaps such complex circuits are obvious to you and "literally nothing", but it certainly seems non-obvious to me.
So at this point, yes, you can really build it with zero external components except for the relay-driver circuit. That will change a little soon.