I see, I'll have to see once the power supply is ready to be moved into the darkroom for further testing. But it doesn't look that complicated.
Thanks for the photos!
There were at least two different types of shutter mechanism. In one case the microswitches contact a rotating cam. In the other case the microswitches contact the actual lever that moves the shutter. You should be able to look up there and see which kind you have. They should both function the same. The logic function of the two micro switches and the relay is not outlined in the service manual I have. You might have to figure it out for yourself or see what Gary knows about it and how he programmed the shutter motor function via the arduino.
View attachment 385834
Thank you again, Gary!The picture is wat happens across the 22 ohm resistor in the startup fase.
The challenge is to not trip the safety circuit of the Kemo power control. It’s a very nice feature of the Kemo. It saved me and the Kemo more than once. But also very vast. It will trip almost immediate when the current exceeds (10A ?) only for some milliseconds. Despite the output is only 16V RMS it still peeks at ± 90 V. After all it’s just a PWM signal. 22 Ohm is just enough to keep the current under the tripping level.
The resistor will naturally not come to a fully developed thermal flow but I like to be on the save side. The potential over the resistor peeks at 28.5 volt rms in the startup phase. The potential over the resistor is not the same as over te bulb. Once the bulb has the minimum temperature keep it there for the time the unit is turned on. You don't need the resistor after the initial startup.
All options have their pros & cons. Ultimately I settled for a boring old 20x4 alphanumerical character display on my present controller. The reason is mostly because I could hack/modify these pretty easily to install a red, amber and a white backlight (the latter was already there; I just added the red & amber). Since I do both color and B&W, I wanted red for B&W work and amber (very dim!) for color.
E-ink is certainly possible, but as you said, the refresh rate is somewhat limited, which is the main reason I also skipped that option. You can do refresh rates of maybe 4Hz or so on e-ink, which doesn't allow for very smooth cycling through numerical values (you need about 10Hz or so to have a smooth user experience).
Initially I used 7-segment displays, which is fine if you're OK with having a single color. If you only do B&W work, then just use a red 7-segment display and call it good. You can put some additional rubylith on top to filter out the smaller wavelengths. It'll work just fine that way. If you also want to do color, you could use amber, which will also work reasonably well for B&W work as long as you keep the light level down. Some papers won't mind (Ilford) while some will fog to amber 7-segment displays (Foma). Note that you can NOT filter an amber 7-segment display to red etc. These are essentially LEDs, so fairly narrow wavelengths. If you put a red filter over an amber LED, you see virtually nothing.
I've seen projects where reasonably fancy red backlight dot matrix displays were used; you could e.g. use something like a Nokia 5110 display (these are quite popular in DIY circles) with a red backlight if you can find/hack one. There are bigger/nicer graphic displays with red backlight as well, but in the DIY community they're few and far between. I think for you it would be ideal if you could just use a ready-made module that you can interface with through SPI or I2C and for which a solid Arduino library is available.
I'd steer clear of IPS displays; they're nice in principle, but the backlight will be a (big) problem. OLED may work if you can find actual RGB displays (most DIY OLEDs are white, blue and/or yellow) and then use only the red channel for your enlarger. This may or may not work well for B&W printing (it'll be useless for color work unless you're OK with the display being off during exposures); the main issue will be the wavelength of the red, which is likely around 620nm (and it'll usually not be specified to begin with, or you have to look very hard to find it). For a B&W safelight it's nicer to steer towards 650-660nm LED. If you hack a cheap 16x2 or 20x4 or so, you can pretty much pick any color LED you want. Plus, they're cheap, easy to control from Arduino projects and it's relatively easy to replace the backlight LED with something of your choice.
One more question I've got for you is the following; Is the Kemo actually required? Is the only down sight to not having an idle mode lamp life?
Your pictures look promising !
There are probably 1000 ways to solve a problem like this one. I only needed one. Can it be done better ? Certainly. My motivation to use the kemo was that it opens the possibility for incorporating a ZMPT101B if there was / is drift in print density. According tot information in the internet from Durst USA using the bulb at 117V instead of 120V prolongs the bulb live with 100%.
In the past I have worked on at least 10 EST1000 boxes. Al had multipull problems. Possible caused by the high inrush current.
This is what I got out of chatgptSadly we kan’t ask Jens Jensen why he claimed the prolonged bulb live. The only thing that interests me is that it worked for my color and BW with 8x10” Durst's the past 20 years. But you can setup your gear any way you see fit.
The only worry I have is: I phase cut 230Vrms to 120Vrms in order to use it with my 120V bulbs. That doesn't feel right.
Does this make any difference in a practical setting
Can anyone specify what is critical for color enlargements?
I don't see a problem with it from a perspective of the bulb, quality of the light etc.
Not meaningfully so.
Consistency more so than the 200K difference in the temperatures you mention. You may see a difference in color balance going from a 3000K to a 3200K bulb with all other parameters kept the same. But you can print with the full gamut the paper, film and dichroic filters allow for with either bulb.
Have you printed color before? A real issue would be a lamp that varies between 3200k and some other value during a string of identical prints or between test print and final. Otherwise. your color pack will account for the lamp with a constant K value.On another note,
The ISO 6846 for BNW paper sensitivity calls for a 3000k tungsten halogen light source. The lamps I found are 3200K. Does this make any difference in a practical setting. In theory, as far as I can tell, the 3200 should just release more visible light and more blue light. (Also more UV)
As far as I can tell, that ok for BNW. Can anyone specify what is critical for color enlargements?
Have you printed color before? A real issue would be a lamp that varies between 3200k and some other value during a string of identical prints or between test print and final. Otherwise. your color pack will account for the lamp with a constant K value.
I don't know about the device you are building, but the original Durst CLS1840 power supply was a pulse wave modulated system, but the lamp does not flicker, it maintains heat during the off part of the duty cycle.
If is’s any reassurance the Durst CLS1000, CLS1840, Optimo and Optopa al drive a 120V bulb with a phase cut 120Vrms from 230Vrms
The Durst Laborator 1840 Repair Instructions might come in useful reverse engineering the durst controller boxes.
The Durst Laborator 1840 Repair Instructions might come in useful reverse engineering the durst controller boxes.
I see, that's quite similar. Weird how they had different designs for this, on such similar machines.Here is the shutter on my 2000. I wonder what Gary's looks like. View attachment 386204
Ha! Same burned resistor!
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