Gralab 451 and safelight set-up

Mike Té · Feb 6, 2023

Hi, all.

I have a new Gralab 451 timer, setting it up right now.
To my dismay, it doesn't have a dedicated safelight control output.

According to the very very brief instruction sheet, it does have a "logic level output jack":
"A logic level compatible signal is accessible through the output jack. An optically coupled transistor provides the signal.
Its on/off state parallels that of the AC outlet and provides a maximum voltage of 30VDC with 30mA of current."

Those are all new concepts to me and I have been searching around for answers.
Apparently few people do darkroom work these days....

What do I buy to set myself up?

Thanks!

Jimskelton · Feb 6, 2023

I looked this up at Gralab's website and they don't say it's specifically for darkroom use, but for "factory, lab, or studio." None of the accessories for it offer a normally on switch for a safelight. the output jack isn't meant for a 110v device, though may be able to be connected to a relay that control a high voltage lightbulb. The only way I can see making this work automatically with a safelight is to connect the output to a relay that has both sets of contacts for normally on/off, connecting the safelight to the former. It's not really a trivial project.

But, you could still use this just fine and manually switch off the safelight when enlarging if you like.

MattKing · Feb 6, 2023

I too find it frustrating when my enlarging timer doesn't have a (usable) control for the safelight. I've a similar Gralab, and when using it really missed having the safelights go off automatically when the enlarger goes on - it is a real benefit with complex burns and dodges.
If you find a solution, I'd be interested.
In the meantime, I've acquired a heavily used model 500 which has other challenges in my particular setup.

Kino · Feb 6, 2023

I have the very same timer and just use very dim safelights, leaving them on.

Of course, I use a slot processor, so it's not the same with trays.

MattKing · Feb 6, 2023

Whereas my darkroom is a bathroom with enlarger in one spot, paper safe in another spot nearby, paper cutter in another spot nearby and trays on a shelf over the bathtub on the other side of a dividing wall - bright safelight illumination is important for me.

Doremus Scudder · Feb 7, 2023

If you need your safelights off when exposing a print (e.g., for dodging and burning) and your timer won't do the job, rig up a switch for your safelights that is easily within reach from the enlarger. That's what I do. I've got bullet safelights on pull-chains and the larger Kodak model D safelight rigged with an in-line switch on the power cord that's only a step away from the enlarger.

Best,

Doremus

Sirius Glass · Feb 7, 2023

My Gralab has an outlet for the safe light to be on when the enlarger is off. Take leave me feeling left out in this discussion.

albada · Feb 8, 2023

Perhaps the easiest solution is to use the enlarger-output to control both a relay and the enlarger. The relay would be normally-on, and would turn off the safelight when the enlarger is on.
Such relays are common and cheap. Here's an example: https://www.digikey.com/en/products/detail/picker-components/PC113-2C-C1-120A-X/12318174
This solution is trivial for somebody comfortable with mains electrical work. For somebody else, it's probably not trivial.

Mark

Philippe-Georges · Feb 8, 2023

albada said:
Perhaps the easiest solution is to use the enlarger-output to control both a relay and the enlarger. The relay would be normally-on, and would turn off the safelight when the enlarger is on.
Such relays are common and cheap. Here's an example: https://www.digikey.com/en/products/detail/picker-components/PC113-2C-C1-120A-X/12318174
This solution is trivial for somebody comfortable with mains electrical work. For somebody else, it's probably not trivial.

Mark

That is exactly what I did, but I got an industrial relay with a ver fast, prompt, switching reaction, thus with a minimal 'death' time.
The death time is the time needed to switch beween contact A and contact B. Also it has a strong induction magnet coil driving the reinforced switch contacts.
It can be used on any enlarger timer.
It works on 230 Volt and switches 16 Ampère 50Hz, and it lasts for more than 30 years now.

Mike Té · Feb 8, 2023

Thanks to everyone for the thoughts and tips.

Gralab 451 and safelight set-up

Mike Té

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