OT Electric supply

We try and buy branded makes where possible, then we don't get failures like the cap pins falling out and so on. GE and Osram seem to be quite reliable.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web

Thanks for the input. I wasn't suggesting spikes, as they would have a much more noticable impact. I just wondered if the voltage could be a litle high thus shortening bulb life.

Unfortunately almost all the fittings have the small bayonet fittings, and all the low energy bulbs I've found have been standard bayonet. Anyone know where I can get small bayonet energy saving bulbs.

As another alternative would it be worth fitting dimmer switches and never turning them right up?, with all the bulbs we don't need the full power. For example the lounge has two light fittings, each with five bulbs in (and it isn't that large a room!).

Regards

Kevin

Tim I suspect what causes the fuse to blow is that, at the moment of the filament breaking, a cloud of tungsten vapour is released from the break point and an arc forms from the broken ends of the filament, the arc then rapidly expands to the support posts as these have a very low resistance compared to the filament and will therefore have a higher potential between them. The arc has very low impedance and will draw 10s or 100s of amps for a few milliseconds, thus blowing the fuse. This is reinforced by the fact that when a bulb blows, there is often a bright blue flash inside the bulb. Martin

The gap in the breaking element arcs - it has the whole 240V across it - causing the ends of the element to turn into tungsten vapour, which expands and conducts well - the arc then spreads along the outside of the element, eventually arcing directly between the lead-in wires - then the hotter the arc gets the less the resistance, causing it to get even hotter in a vicious cycle, so the arc gets very hot and low resistance - and low resistance ->

high current.

Household blubs (technically "lamps") have fuses in them, which perhaps used to be better quality, to cope with the end-of-life current surge (it can get into the hundreds or even thousands of amps if unfused).

Cheap lamps now mostly just have a thinned section of lead wire which acts as a fuse, expensive ones have small glass fuses filled with ceramic powder or small spheres of glass, which surround the fuse wire in the fuse and quickly cool and extinguish the arc caused when the fuse blows. This means that the arc is cooler (and thus higher resistance -> lower current) and lasts less time, and the spike of current is lower and shorter, but the lamps are more expensive.

Dimmers are not designed to last for ever, by the way.

Maybe there's your answer. We have a couple of reading lights which take SBC bulbs. Despite only being used for an hour or so each day, the bulbs' average life is less than 6 months.

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Well, they're certainly not 'blubs'

But surely nothing is? In what way is their design life limited?

Cheers Tim Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

I bet they're made in somewhere like Hungary. Anyone know why manufacture of these things seems to have become concentrated in that general area? Is it just a couple of very big factories?

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Same problem here.Five and six bulb fittings,10 and 12 feet up in the air,bulbs vertical,lit all the time.Buy bulbs buy the carton(100). Currently using Osram 100w made in Indonesia.Have tried all the well known makes and have noticed no difference between them and the really cheap ones.Sometimes they trip the breaker when they go sometimes not.I occasionally wonder what causes this but as someone else usually gets fed up waitng on me changing bulbs and does it herself I don`t normally think about it for long. Regards,Mark.

On

Could it be that the SBC bulbs, with physically less bulk in them, run hotter than standard size bulbs? -less of a heat sink

Regards

Kevin

Yes - a 5% voltage drop should roughly double the life.

Light output changes as the 3 1/2 power of the supply voltage and power consumption varies as the 1 1/2 power of the supply voltage so you'd have about 20% less light and use about 8% less power.

Jim

Have a look at

So if a small percentage voltage drop gives large lifetime savings on bulbs maybe it is worth putting a constant voltage transformer in the lighting circuit set to give (say) 230v.

Not sure if it is still the case but a few years back the electronic junk shops were full of constant voltage transformers - looked like an elongated normal transformer with silver end caps. I understand that they have an extra winding that is tuned to resonance but I've never pulled on apart to see how they work. Claude Lyons iirc made them

AWEM

Kevin Steele brought next idea :

Hi Kevin,

Ordinary light bulbs are especially sensitive to the voltage they are presented with, which is why (one reason) at one time it was possible to buy such lamps in different voltages as well as wattages. You could get them in 10v steps (210, 220, 230, 240 and 250v). A 240v lamp on a

In the UK the nominal voltage is now 230v as of 1st January 2004. In practise nothing has changed since we were on a nominal voltage of 240v and you can still expect to measure approximately 240v across your mains supply. The 230v nominal is simply to bring us in line with the EU. The supply should be within the tolerance of 230v +6% to -5%. Or approximately between 218 and 243v.

If it is regularly higher or lower than these limits then you have good cause to complain.

To check your mains voltage, you need an accurate AC voltage meter. Modern digital ones are cheap and usually very accurate. The voltage needs to be checked close to your mains Dis-board, or on a circuit which is not already loaded (to eliminate voltage drop). Very brief surges over voltage will make little difference to a lamp, because they have a few milliseconds of thermal lag, but longer periods over 243v will have a noticeable effect on lamp life.

Every appliance you turn on in your home, will cause the voltage to change. Even turning the kettle on will cause a measurable dip of a few volts, which can be seen as noticeable change in the light output of a lamp.

It might also be worth checking the voltage stamped on the lamps themselves. These should be marked 240v. I recently bought a pack of four halogen lamps marked 230v, they lasted just a few weeks before they blew. Not until the third change of the lamps did I notice the voltage stamped on them.

| | So if a small percentage voltage drop gives large lifetime savings on | bulbs maybe it is worth putting a constant voltage transformer in the | lighting circuit set to give (say) 230v. | | Not sure if it is still the case but a few years back the electronic | junk shops were full of constant voltage transformers - looked like | an elongated normal transformer with silver end caps. I understand | that they have an extra winding that is tuned to resonance but I've | never pulled on apart to see how they work. Claude Lyons iirc made | them

No incandescent bulbs are *very* dim on low voltages! The light output is dependent on the voltage to some power. Use energy saving lamps.

Can't think of anything.

The actual life limiting factor, if there is a single one, depends on the cost of the components. The following would apply to a medium production volume high end dimmer designed for long life, but the situation might well be different with a mass produced cheap one: I don't know for sure, never having designed a domestic dimmer. Mass production designers will do weird, unexpected and even outrageous things to save 0.01p on a component, and any life after say five years in service is not of much interest to them.

It is quite likely that in real life another component will fail first, either the potentiometer (the bit that the knob attaches to, which moves) from mechanical causes like wear or abuse, or the circuit board from prolonged heating; but there is a limitation on the life of the main switching element, called a triac, and the other components will (in theory, just maybe) be chosen to have a just-a-bit-longer life.

A triac is a bit like a transistor, except (simply put) it switches off and on without in-between states, it latches in the "on" state until the current reverses with the AC cycle, and it switches mains voltage AC rather than DC. The dimming action comes about when the triac is only switched on part of the time.

Like a transistor, it is made of doped silican.

Triacs do not last forever, especially when operated near their limits. The dopant atoms slowly spread out from their manufactured places in the silicon and mingle. This is encouraged by the high current density and the heating.

This spreading (diffusion) actually happens with all silicon semiconductor devices, whether powered on or not, even processors and memory chips: but it is usually very slow. It is much faster and more noticeable in high voltage and high current devices like triacs, and especially when operated at high temperature.

More, triacs in dimmer enclosures tend to get hot, which speeds this up, further lowering the life of the triac (and the potentiometer, and the circuit board).

I wonder what design life is for something like this? I paid quite a bit extra at the time for MK dimmers, as they were the only type I could find with a switch separate from the pot, and the setting isn't affected by switching on & off. The one which isn't bypassed has been in daily use for 15 years without trouble, maybe the extra expense is now proving worthwhile?

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

OK, bulbs are considered good.

What do you say regarding "old or oxidation or wearied or no-more-silvered switch contacts and/or "burnt" copper wires... connection screws and... maybe... "mice"... ?

WinXP

I had a classic example of this the other day. I had to fit a new cable to a Makita 110V angle grinder, which had a factory-fitted yellow plug. I've got a reel of proper power tool cable, but it's 3-core, the grinder only needed 2-core. I was debating with myself whether to snip the earth lead short at both ends, or wire it in to the plug and only snip the tool end, until the decision was made for me. Mind you, either option is probably a hanging offence these days There were no earth terminal screws in the plug. The pin was drilled & tapped, but no screws. I'm guessing that Makita negotiated a discount for the supply of x thousand 110V yellow plugs without the earth terminal screws!

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

On Sun, 30 Jan 2005 14:42:01 +0000, Tim Leech wrote:>

OT, but I confirm your opinion.

All engines on Mower are bolted to the frame by means of four Screws, Washers and Nuts (four bolts).

Toro, the wellknown US Brand,is/was requiring specific "made-by-order" Tecumseh engines with mounting bores of reduced diameter just to use "single" self-tapping screws.

So it is sparing at least 4,000,000 of washers and 4,000,000 of 5/16" Nuts every one million of Mowers.

US Mart produces about 6,500,000 engines for Mowers yearly...

WinXP