Enlarger transformer and timer question

[gunner]

I have just piuchased an LPL 4x5 enlarger, it came with a transformer which has just a simple on/off switch, I have an old Rayco timer which can comfortably cope with the amperage, should I put the timer between the transformer and the enlarger or between the 240 volt supply outlet and the transformer or doesn't it matter

 

[Don_ih]

Timer plugs into the wall, the power supply for the enlarger plugs into the timer.

 

[gunner]

Timer plugs into the wall, the power supply for the enlarger plugs into the timer.

hi, thanks for that, all up and running fine

 

[Philippe-Georges]

What I did was mounting a relais (electromagnetic switch?) in between the enlarger's head, having 2 cooling fans built in and running on 110V/50Hz, and the transformer.
The relais worked on the net's voltage (220V) and switched neutral, so I had it command directly by the timer.
The transformer I am talking of is a 220V —> 110V/1200W (secondair)/50Hz, and connected to a 220V/6A Voltage stabiliser.
So by switching the secundair outlet circuit (110V) there was no 'delay' in the starting reaction of the cooling fans which caused some vibrations.
So the train was: Wall net outlet +/- 220V (not very stable) —> stabiliser (220V) —> transformer (220V to 110V) —> relais (working on 220V and switching 110V) commanded by timer (220V) —> enlarger head (110V).
The timer is connected to the stabiliser too.

I could have running the fans permanently on 110V and only switching the lamp on 220V by recabling the enlarger's head, but these fans ware so annoyingly noisy in the dark room...

 

[koraks]

So the train was

...a darkroom equivalent of a Rube Goldberg machine!

In 99.8% of the cases, just plugging the timer into the wall and the enlarger into the timer is all that's needed.

 

[Philippe-Georges]

...a darkroom equivalent of a Rube Goldberg machine!

In 99.8% of the cases, just plugging the timer into the wall and the enlarger into the timer is all that's needed.

Perhaps yes but it worked as a TGV (but not on 3 000V)...

And "plugging into the wall" was not an option as that "wall" was 220V and the enlarger 110V...

 

[koraks]

Yes, sometimes, a situation calls for a very specific solution.

Perhaps yes but it worked as a TGV (but not on 3 000V)...

Ah. Thalys. Fond memories. Still travel once in a while, but not as frequently as I used to.

 

[Philippe-Georges]

That enlarger is gone now, but I still use that relais, connected on the timer, to alternatively switch the darkroom safe lights, when I the enlarger is on, the red lights are off, which is easy for focussing and burning & dodging.

BTW, I forgot to mention that this relais is an industrial purpose one as it was the 'fastest' switching (the shortest dead moment) and the sturdiest I could find.

 

[koraks]

BTW, I forgot to mention that this relais is an industrial purpose one as it was the 'fastest' switching (the shortest dead moment) and the sturdiest I could find.

Yes. These days, you'd use a so-called 'solid state relay'. These switch at the zero crossing of the phase, are soundless, don't have a coil to drive them (so can be driven directly from a logic port) and have no mechanical parts whatsoever. They're also available in ridiculously large current ratings while retaining a very small package.

Coincidentally, my father has customized a pottery oven (this was already years ago) and its controls for my mom's ceramics hobby; part of the endeavor involved a big 3-phase relay to switch the coils. It's about the size of a child's head and when tripped, it makes the sound of 250 Hasselblads triggering at the exact same moment. The coil is a 230V one and needed to be switched with a smaller relay.

A year or so ago, they got an electric car and a charger to go with it. Of course I couldn't resist having a peek inside. The charger offers speed-charging and takes a 3-phase input, communicates (very rudimentarily) with the car and evidently also has to process significant currents. The entire electronics of the charger are about 1/3 the volume of that single 3-phase oven relay, and fit on a small PCB with only 3 inconspicuously tiny IGBT's to handle the power end.

Silicon has made a lot of things a lot smaller.

 

[Mal Paso]

Silicon has made a lot of things a lot smaller.

Except iPhones, apple can't make small ones any more.