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Adding a Footswitch to a Durst Labotim Enlarger Timer
Adding a Footswitch to a Durst Labotim Enlarger Timer
A simple modification to upgrade your timer.
Published by Michael S
3rd August 2012
Default Adding a Footswitch to a Durst Labotim Enlarger Timer


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EDIT: Please take note of Richard's comment below and proceed at your own risk!:

Quote:
Not wishing to be a killjoy, but looking at the internals of that timer there doesn't appear to be any isolation of the electronic circuitry from the mains (e.g. a transformer). That means there is the possibility in the event of a fault that the exposed metalwork of the socket could become "live". It is unlikely but still possible. Just saying.
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Whilst I would love to own the ultimate timer, unfortunately the management has not seen fit to release the necessary funds (apparently 'food' and 'clothes for the children' are higher up the list).

So in the meantime I decided to see if I could modify my existing timer—a Durst Labotim—with the addition of a footswitch wired in parallel to the existing start button. I'm sure other brands of timer could be modified in a similar way. The Labotim has no socket for a footswitch and I was becoming increasingly frustrated during dodging and burning at the lack of another limb to trigger the enlarger while both hands were busy.

I am no electronics expert, but having soldered a few guitar leads and the like in my time, this project was well within my capabilities. It just requires the soldering of a couple of wires on to a jack socket, attaching the other ends of the wires to the circuit board, and then drilling a hole in the timer case and attaching the socket to it. Obviously if you choose to modify your timer you do so at your own risk, but please be careful: there are mains voltages inside the timer when plugged in.


What you will need:
  • A momentary footswitch (make sure you don't get the 'on/off' variety: the timer just needs the two button contacts connected briefly to start the timer).
  • A 3.5mm jack plug
  • A 3.5mm jack socket
  • A soldering iron and solder
  • A drill and 6mm drill bit (double check the drill bit size depending on your jack socket).

I got all my parts from Maplin for a grand total of around £10 (I already had the tools). I've linked to the parts I used but you will find equivalents readily available elsewhere. If you do get the footswitch from Maplin make sure you get part number DU99H (the momentary type) not DU98G (the on/off type).


Opening the Timer

First of all you must dismantle the Labotim. Make sure it is unplugged from the mains and then remove the four rubber feet and the four screws underneath. The screws have security-type heads but I found that a normal small bladed screwdriver would get them out fine.

Next remove the clamp (two screws) at the top of the timer which holds the mains cables.

In order to remove the circuit board from the case I used an open pair of long-nosed pliers positioned around the plastic posts which it sits on, and gently levered it free at each corner. The fit is tight but there is no glue: the board is held in by friction alone.

Once the board is out of the case, flip it over and you will see the two points we need to solder to underneath the red 'Expose' button.


Connecting the Footswitch Socket

On to the wiring. First cut the 6.5mm jack plug from the foot pedal. The reason being that there is no space inside the case for anything bigger than the 3.5mm jack I changed it for. Then snip off about six inches more from the wire to the footswitch and put it aside.

Solder the 3.5mm jack plug to the end of the remaining cable to the switch. I used a right-angle plug but a straight one would do just as well.

Next, take the six inch off-cut you just put aside and solder one end of the pair of wires to the jack socket. Make sure one wire is connected to the tip tag of the socket and one to the shaft tag: mine had two tags for the tip.

Strip the other ends of the off-cut wire and then solder these to the two points under the red button on the circuit board (see picture).
Next drill a hole in the top right corner of the bottom half of the case (or wherever you see enough space inside the case for the jack and socket). For obvious reasons make sure that neither the jack nor the socket will come into contact with the mains power terminals!

Reassembly

Place the circuit board back on its mounting posts with the new wire and socket threaded through underneath to the drilled hole at the top. Push the new jack socket through the hole and secure it in place with the nut supplied. Re-secure the mains cables with the cable clamp.

Put the top part of the case back in place and then replace the four screws and the rubber feet.
Plug the timer back in to your enlarger, plug in the new footswitch and test!

Possible Upgrade!

While I had the timer apart I tested the footswitch on the focus button and it worked there too. So I may add another footswitch to those terminals (ringed in red below) and another socket at the top left of the timer at some point in the future so I can operate that function 'no-hands' as well.
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  #1  
By Mike O'Pray on 3rd August 2012, 07:18 PM
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Nice job. Well done

Mike
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  #2  
By RH Designs on 4th August 2012, 10:00 AM
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Not wishing to be a killjoy, but looking at the internals of that timer there doesn't appear to be any isolation of the electronic circuitry from the mains (e.g. a transformer). That means there is the possibility in the event of a fault that the exposed metalwork of the socket could become "live". It is unlikely but still possible. Just saying.
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  #3  
By Rodinal on 6th February 2013, 10:27 PM
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Thanks for the article. I made this modification to mine many years ago.

If you have the guts to open and tamper this device, you might as well add a safelight control.

This unit has a relay output and only the NO contact of this relay is wired to control the enlarger. You can solder a wire to the NC contact and use it to supply energy to your safelight only when the enlarger is off (to focus more easily or to use an enlarging lightmeter).

As there is not much space inside, I used a four wire cord to have this connection available on the outside and replaced the flying female-plug for the enlarger with a box with two plugs, one for the enlarger and another for the safelight.

I cannot provide photos because, in time, I replaced this timer with a fantastic RH Stopclock Pro. My advice is that you try this only if you had the knowledge to identify the proper point by yourself.
Last edited by Rodinal; 8th February 2013 at 10:43 PM..
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  #4  
By Michael S on 8th February 2013, 10:12 AM
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Thanks for the tip Rodinal, I hadn't thought of that. I may have to open mine up again!
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durst labotim footswitch, enlarger timer, timer foot pedal, timer footswitch
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