Auto shut off electricity precise timer

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hiroh

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Does anyone use these auto shut off timers for the exposure boxes? My exposure unit has two sets of UV lights, and it takes only 90 seconds for exposure, so every second is important. I have to click two buttons simultaneously at the same time, which is not a big deal, but I’d prefer to have auto timer so I don’t have to sit there and watch the countdown.

Anything I find is either too ”smart” and complicated for what I need, or it’s not so precise and have preset intervals of 15-30-60min.

I’d like to hear if anyone use timers, and have to recommend anything simple and elegant.
 
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hiroh

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Can't you just use a regular darkroom timer?

I don’t know, I don’t have one. Can I set it to precisely 90 seconds and will it shut of the electricity after 90 seconds? Preferably with two outlets, so I don’t have to use extension cords.
 

Donald Qualls

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That's exactly what a Gralab or other darkroom timer can do. You can actually interpolate a half second or a little finer on the Gralab (it's analog, with hands). Flip a switch, it starts, and it stops and shuts off then it counts down to zero.

Do, however, watch out for inductive load -- if your UV lamps are fluorescent, they'll look like a much higher draw to the contacts in a timer (60W fluorescent is equivalent to about 500 W resisitive load due to the inductance of the ballast).
 
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hiroh

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That's exactly what a Gralab or other darkroom timer can do. You can actually interpolate a half second or a little finer on the Gralab (it's analog, with hands). Flip a switch, it starts, and it stops and shuts off then it counts down to zero.

Do, however, watch out for inductive load -- if your UV lamps are fluorescent, they'll look like a much higher draw to the contacts in a timer (60W fluorescent is equivalent to about 500 W resisitive load due to the inductance of the ballast).

Hmm, this looks too bulky for what I need it. I understand why it has to be this large in a darkroom, but in my case, I even don’t have to see it if it’s going to shut the power at the given time. I imagined it would be some kind of plug with the display and few buttons. That’s how other looks, but their time increments are too large for what I need. Those that are precise to the second, seems unnecessary complicated with tons of other functions that I don’t need.
 

Donald Qualls

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There was also the tiny Time-O-Lite (similar form factor to an old mechanical kitchen timer, settable to one second and self-resetting to the same time after shutoff), but I'm certain the contacts in those won't handle high power fluorescent ballasts (turns out there are multiple Time-O-Lite models newer than the ones I remember). For LED, they'd work -- but they've also been out of production for decades and it's hit or miss if you buy one on eBay, whether it still works.

An enlarging timer is what you want, though -- fractional seconds are common, but electronic ones often suffer from "feature creep".
 

ic-racer

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Gralab is pretty small, 3.5" x 4" x 8"
Screen Shot 2022-11-14 at 10.21.43 AM.png
 
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hiroh

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But still… looks too big for the simple function.
This is the one that does exactly what I need but is only set to 30min. There are similar ones with different times.

67F82044-E337-483D-A3AA-CD7ADCC3BC13.jpeg


My UV is LED.
 

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koraks

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Those that are precise to the second, seems unnecessary complicated with tons of other functions that I don’t need.

When I started out contact printing with UV, I just got one of those Chinese timer modules off of eBay and wired it up the way I needed it. If you Google for "relay timer module" you should be able to find some. Yes, they offer all sorts of functions you don't need, but you don't have to use the other functions. The one I used for years had maybe 10 programs - I only used the simple countdown program. I had to read the manual once to figure it out and from then I just always used it the same way. It worked every time.

Another option (even better) is a light integrator. I don't currently use one, but they're ideal as they will compensate for a change in distance between your frame and the light source, reduced light output of your LEDs (which I wouldn't worry about anyway, but still) and anything else that makes the actual UV output vary.
 

Sirius Glass

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Does anyone use these auto shut off timers for the exposure boxes? My exposure unit has two sets of UV lights, and it takes only 90 seconds for exposure, so every second is important. I have to click two buttons simultaneously at the same time, which is not a big deal, but I’d prefer to have auto timer so I don’t have to sit there and watch the countdown.

Anything I find is either too ”smart” and complicated for what I need, or it’s not so precise and have preset intervals of 15-30-60min.

I’d like to hear if anyone use timers, and have to recommend anything simple and elegant.

Which enlarger do you have? I could recommend the timer which I have, but it works for a Chromega Dichroic II 5D-XL and might not work for yours.
 

Sirius Glass

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None, Sirius. This thread is about UV contact printing.

Rewiring the connections of enlarger times might be a viable alternative to consider.
 

Rick A

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So it has two outlets on the side, and by setting the time, it will shut both ?

One outlet is for the safelight the other for the enlarger, just plug into the enlarger outlet and it will do what you need. The Time-O-Lite is self resetting so when it hits 0 and shuts off the hand resets to the preset time. IRC the Time-O-Lite is only good to 60 seconds. The GraLab 300 timers are good up to an hour but lack the self reset and must be manually set every time.
 
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hiroh

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My exposure unit has two sets of UV lights ( I doubled it to shorten the exposure time), so I'd need a timer with two outlets. I guess I can use one for enlarger and another for safelight? My UV is LED, so I don't see the problem?
 

Rick A

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My exposure unit has two sets of UV lights ( I doubled it to shorten the exposure time), so I'd need a timer with two outlets. I guess I can use one for enlarger and another for safelight? My UV is LED, so I don't see the problem?

You can "piggyback" the two units on the enlarger side, the safelight side doesn't automatically turn off.
 
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My exposure unit has two sets of UV lights ( I doubled it to shorten the exposure time), so I'd need a timer with two outlets. I guess I can use one for enlarger and another for safelight? My UV is LED, so I don't see the problem?

You would need to plug both of your exposure units into the enlarger outlet as the safe light outlet will turn on when the enlarger is off. A short standard extension cord that has three outlets would work fine, but if you can find something fancier the should work as well.
 

Sirius Glass

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One outlet is for the safelight the other for the enlarger, just plug into the enlarger outlet and it will do what you need. The Time-O-Lite is self resetting so when it hits 0 and shuts off the hand resets to the preset time. IRC the Time-O-Lite is only good to 60 seconds. The GraLab 300 timers are good up to an hour but lack the self reset and must be manually set every time.

One outlet is powered at a time so one for printing and one for a safe light. A safe light might not be useful in the OP's work.
 

momus

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1/90th of a second is about...... it's really a short time. The point I'm attempting to make here w/o actually getting into the #!$!!! math is, it ain't much. If anyone can see the difference between an 89 second exposure, a 90 second exposure, and one for 91 seconds, I'd like to meet them.
 

albada

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I have two Time-O-Lite timers for sale in Photrio's classifieds here for $5 each. But these only go up to 60 seconds, and the OP needs 90, so he would need to set a Time-O-Lite to 45 seconds and start it twice (two exposures). He's running LEDs, so inductive flyback won't be a problem with any timer.
 
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Your problem is getting a timer that will do a long enough time. The digital Gralabs can be set in the minutes. Ones like the 645 and 900. Overkill for what you need but they do the job. I use the 900 these days with my UV box.
 

koraks

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@hiroh do you have a friend or family member nearby who can help you with very basic things, like connecting two devices to one outlet? That would make things a lot simpler for you, I think. He/she could then work out the functional suggestions given here into something that will work for you.
 
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koraks

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And I thus do not understand the discussion following.

Regular darkroom timers are often ill-suited for UV contact printing as their generally have too limited a timescale. For instance, with alt. process prints it's not uncommon to have exposures of e.g. 6 minutes or 10, or even much longer. Old-fashioned mechanical timers offer these kinds of periods, but are generally too low in resolution for good repeatability. Time switches intended for automatically switching on/off interior lighting often have user interfaces that aren't very suited to a simple 'countdown' scenario and depending on implementation may or may not be accurate/consistent.

The question really is a relevant one. Anyone who has done UV contact printing alt. process work will recognize it, I'm sure.
 
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