Fitting resistor into lighting ring to stop flashing

[LazyD]

Hi,

I think this probably isn't the type of thing that gets asked on this forum, probably more for an electrician but I think people here will probably know anyway. I'm not an electronic engineer of any sort or an electrician, but soldering is part of my work so I'm confident in soldering.

I bought a 5 of these time delay switches for our communal stair well as several of the other rubbish pneumatic ones had completely failed:
http://www.eterna-lighting.co.uk/product/tls1440/

I'm switching 2D fluorescent lamps, so definitely not LED, and the exact model and wattage have been confirmed to work by the original manufacturer.

So once the light is turned on anywhere, the lamps flash, usually they stay on for a few seconds and then flash roughly every half second or so until they turn off again. The original manufacturer have stated that I should 'fit a 100k/2W resistor into the circuit' to prevent this issue.

As far as I can tell, this item is available for 19p from Maplin:
http://www.maplin.co.uk/p/metal-film-2w-100k-ohm-resistor-d100k

Could anyone please advise, is this the correct item? And what wires in the lighting circuit should I solder this into? The rough plan in my head is to pull up a bit of lighting cable where I can find a bit of slack behind one of the switches, solder this in and then put some shrink tube over the component? Am I going about this wrong?

Thanks.

 

[Tha fios agaibh]

The problem is that these timed switches don't draw their power conventionally from line and neutral, instead they derive their power from being the open portion of the circuit and rely on the continuity of the load.
So when the light turns off, a parasitic load from the timer switch acts like a partially closed switch and sends a small amount of power to the light fixture causing it to flicker.
I can't vouch for the size of the resistor but if the manufacture recommended it I have no reason to doubt him.
I preface this with a warning that it's likely not compliant with local electrical codes.
This resistor can be placed across the line side of the lighting ballast (parallel) to help bleed off the parasitic load caused by the timer. This should help kill the small current after light is off.
I would add an inline fuse to the fixture to limit the current (if there isn't one) just incase something goes wrong.
Never solder electrical connection like this without making a strong mechanical connection first. Reason being, solder can blow out with higher currents.
I would just crimp the connections and use heat shrink on any exposed conductors.
You may want to experiment with higher values first. Example, start with 200k, then try 150k, etc. But stick with 2w or higher.

 

[Alec_t]

Be aware that a 100k resistor will be dissipating ~600mW and will get hot, so any adjacent materials and wire sleeving (heat-shrink seems unsuitable) should be non-combustible. The resistor should be well-spaced from other things to allow adequate ventilation.
You should check with a qualified electrician on the safety/legal aspects of adding the resistor, especially as this is to be used in a communal setting.