Noticed that several electronic timers mention that they don't work with energy saving fluorescent bulbs - would this be the case if a 240V mechanical relay sat between the timer and the bulb or must the timers have a load of 40W or more?
Examples of timer
Thanks
I think you will find that some of these timers 'leak' a small current through the bulb and that gives them the power to operate. That works with restive loads such as incandescent bulbs but not with inductive loads such as energy saving ones. At least you found that out before you bought one..
Jim
think a teensy resistor across the lamp sorts that one out.
What size do you recommend?
Jim
I dunno. Trial and error.
Won't work either way. They're trying to source a neutral from somewhere, and doing it by seeing a high-current load as effectively a connection to neutral (they only need a tiny current themselves). An incandescent bulb is fine, but a low-energy bulb or a relay isn't.
What you want instead is a controller with a deliberate neutral connection. These are now becoming common, because of the need to do just this, with low energy bulbs. OTOH, you also need a neutral connection to your switchgear, which is a problem for anything mounted on a wall switch.
the timer I use works with a CFL, so there must be some 'leakiage'.
I cannot imagine it matters if you use a relay after all a relay is just a switch. Brian
I cannot see the point in using current through other devices. Surely if you have mains, then you have mains and there would be no need to use a cludge to power a switch. If its a properly wired ring at any rate.
Brian
The need for these devices arrises if you are trying to add a timer in the place of a sight switch. Light switches rarely have a nearby neutral - that's been left in the ceiling.
A link to a Maplins' product:
I got one from John Lewis (cheapest I could find online) last week to switch a 20W low energy lamp and it does exactly what you want. Works a treat.
Scottish Power, from methane?
Light switches usually only have three wires: earth, live in, and switched live out, and no neutral.
You could fit an incandescent lamp and measure the current, I, which flows through it to get an idea of the current the timer or PIR controller requires. And you might measure the voltage across the filament lamp under the same conditions, but that will probably be near enough to zero volts. You then need some trial-and-error to find out what minimum voltage the timer needs to operate properly. You might begin with 60/I ohms if I is in amps, with a wattage of about 60 x I watts. (Probably the values will be in Kohms and milliwatts.)
If the watts used are too high (wasting electricity) you could probably use a capacitor (plus a small series resistor to limit surges) instead. Capacitor-resistor combinations are available as interference suppressors. As a wild guess, you could try a 0.1 microfarad capacitor plus 100 ohm series resistor, and work up from there. But get it wrong and you might zap the timer. It might be wise to hook a surge suppressor aka varistor across the timer.
There are said to be timers which work only with filament lamps, and others (probably more recent designs) which work with more or less anything.
The timer/security switch linked above has a specification of: Conforms to directives 72/23/EEC & 89/336/EEC Permissible loads Filament 40-300W Low energy 20-150W (electronic & iron ballast) Fluorescent 18-76W Low voltage 20-200W Battery back-up 1000hrs by factory fitted rechargeable battery Temp range -10C to 40C Operating voltage 220-240V AC Dusk start 1-5 Lux Terminations suitable for 1mm sq & 1.5mm sq solid conductors or stranded equivalents Control type 1Y
NOT suitable for discharge lighting e.g. SON & Metal Halide Will fit a 16mm deep box
Hope this helps
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