Fridge interior lamp

[xl5]

Don't last very long! I thought if i carefully removed the glass from an o/c lamp gaining access to the terminals to install a large led or two... mains driven cct sealed in a transparent enclosure.

Or should i just remove the existing fridge diffuser cover to allow me to and screw in a low wattage long life lamp, what do you think!

 

[Reloadron]

OK, I don't know about fridge lamps in Scotland but around here with normal open / close use the lamps last for years. I can't even remember last time I changed one. You are sure when you close the door it really does go out?

Seriously, I would remove and replace with a known good bulb.

Ron

 

[MikeMl]

Besides, the lamp runs on AC. You will have to jump through some loops to make LEDs work.

 

[crutschow]

You are sure when you close the door it really does go out?

That sound funny, but there is a small chance it could be a stuck/broken switch.

To check, just leave the door closed for a few minutes. Then unplug the fridge, open the door, and feel the bulb. If it's warm, you know it's been on.

 

[xl5]

Fridge lamp

Mmm! Incandescent lamps are prone to regular failure even on Venus lol it is said that if a lamp with a continuous supply is left on it might well last for many a year without failure... so if that was fact the lamp in my fridge staying on due to a push to make release to break sw being faulty wouldn't count!

Also the lamp doesn't stay on when the door is closed because my cat Pugsy told me it didn't!... As for the lamp obviously working with alternating current conversion to direct current is even less of a problem than the ac lamp it would seem to be that the cold enviorment that our ac driven lamp takes exception to the sudden surge applied to our Scottish filaments

NB: Perhaps we in Scotland open & close the fridge door more regular than you do doh!

 

[crutschow]

It's a fallacy that turning an incandescent lamp off and on frequently will significantly shorten its life. They often do fail at turn-on near their end of their normal life due to the shock of heating up a weakened or narrowed filament, but the bulb was due to fail shortly anyway.

So, you locked your cat in the fridge to check the light?

Edit: I had halogen bulbs fail in two different locations in my microwave shortly after I purchased it. I attribute that to a batch of faulty bulbs that came with the microwave.

 

[ronv]

Want to make it last a long time? Stick a diode in series with the lamp. It will be a little yellow but it will last a long long time. And the cat may be able to sleep when it's on.

 

[KMoffett]

Want to make it last a long time? Stick a diode in series with the lamp. It will be a little yellow but it will last a long long time. And the cat may be able to sleep when it's on.

You used to be able to buy diode buttons that were placed in the lamp socket, under the bulb, for "saving energy". I don't see them anymore.

Ken

 

[xl5]

Thank's for all replies it's just that i seem to be replacing lamps regular ie oven.. fridge... extracter.. and don't like paying exorbiting prices for common filament lamps. Myself & my assistant Pugsy will persevere.

 

[crutschow]

It is unusual to have to replace all those bulbs that are not on much. I can't remember the last time I had to replace one of those (outside of the microwave which I already mentioned). Is the line voltage normal in your house?

 

[Boncuk]

NB: Perhaps we in Scotland open & close the fridge door more regular than you do doh!

Yes, I can imagine that.

You must make sure the little guy inside the fridge (switching on and off the light) hasn't quit his job because of under payment.

Boncuk

 

[Mr RB]

Crutschow- It's a fallacy that turning an incandescent lamp off and on frequently will significantly shorten its life. They often do fail at turn-on near their end of their normal life due to the shock of heating up a weakened or narrowed filament, but the bulb was due to fail shortly anyway.

Do you have any material to support this crutschow? I'm not calling you a liar on it, just that it seems counterintuitive and goes against my experience.

I've had huge problems with failing incandescents over the years, sometimes after only a few weeks (my mains here can typically be 254v AC).

When I've done the sums; a 100w globe at room temp the filament = 50 ohms, often less. If it gets turned on at mains peak the instantaneous filament power is E squared over R; 254*254/50 = 1290W.

I get your point about a weakened thinner filament being more likely to blow due to turn-on surge but surely repeated cycles of 1290W in a 100W filament are going to shorten its life? If not then why would my brand new bulbs blow at turn on after only a few weeks use?

 

[Boncuk]

I've had huge problems with failing incandescents over the years, sometimes after only a few weeks (my mains here can typically be 254v AC).

Your mains voltage is an exception to the rule.

I had all filament type lamps blowing in Turkey when mains voltage was increased to 285V at 75Hz because of a malfunctioning power plant.

Filament type lamps have a low cold resistance and on/off cycles shorten their life considerably converting the filament wolfram wire to metal steam settling on the glass with a black deposit.

They also don't like vibration and mechanical stress very much as I found out in my shop located in the main road in our city. Passing heavy trucks took care of monthly lamp replacement regardless of the lamp wattage.

Boncuk

 

[crutschow]

It's true there is a large power surge when you first turn on an incandescent light, but that just causes the filament to heat up more rapidly to its operating temperature, it doesn't overshoot that temperature or cause undue stress on the filament. It isn't turning on and off that causes the filament to evaporate and deposit on the bulb, it's the continuous operation at high temperature.

I have a headlight modulator on my motorcycle which rapidly turns the two lamps off and on about 4 times a second. I've have had it for about 6 months and both bulbs are still working. The information on the modulator states that bulb life is essentially unaffected by the modulation.

 

[Diver300]

I think that repeated turning on and off can reduce the life. The problem is not that the filament heats up rapidly, but that it heats up unevenly. If some parts are colder, and lower resistance, while other parts are at normal temperature, the lower resistance parts do not limit the current as much as they should. Therefore the current is larger than it should be and the parts at normal temperature will get too hot, until the colder parts heat up.

 

[Boncuk]

I have a headlight modulator on my motorcycle which rapidly turns the two lamps off and on about 4 times a second. I've have had it for about 6 months and both bulbs are still working. The information on the modulator states that bulb life is essentially unaffected by the modulation.

Hi Carl,

six months of operation of motorcycle headlights are probably equal to one month of continuous operation, limited to the time between refueling stops for an on cycle.

Automotive lamps are at least halogen type lamps the filament of which also partly evaporates, but when the lamp cools down the vapor will settle on the filament again.

Halogen lamps also don't like vibration and shock - which might be acknowledged by Citroen 2CV (pronounced: deu-je-vo) owners. Their headlights were mounted on a relatively long metal rod vibrating with the two cylinder engine running.

Regards

Hans

 

[Mr RB]

Thanks Carl (crutschow) for the clarification. I think it is a very different situation with a 12v bulb. They are low volts high amps, and the difference between cold and hot filament ohms is much less difference than the 12:1 ratio in a 240vAC mains bulb. Also the E squared / R power of the cold turn on is so much lower with 12vDC squared vs 340vDC (peak) squared.

I would imagine that a good headlight modulator also does a soft start or ramped flashing of the headlight, or maybe modulates the bulb from half-on to full rather than cold to full?

I know that good turn signal flashers incorporate resistance to reduce the cold surge current to the flasher bulbs, and some bikes even use rather thin wiring for the turn signals which helps increase turn bulb life too.

Sorry i made a mistake too, I said;
"the instantaneous filament power is E squared over R; 254*254/50 = 1290W"
it should have been;
"the instantaneous filament power is E squared over R; 355*355/50 = 2520W"
for obvious reasons.

 

[crutschow]

Well, until I see some testing proof, other than anecdotal evidence, I'm not convinced that turning an incandescent bulb on and off frequently, significantly affects its life. I believe the filament heats up evenly (albeit rapidly) when the bulb is turned on without overshooting it's normal temperature, thus having no significant effect on its lifetime. I've had bulbs in refrigerators that have lasted for many years (I don't ever remember having to replace one).

The hot/cold resistance ratio has nothing to do with the bulbs operating voltage. It's caused by the hot/cold difference in resistance of the tungsten, which is determine by the bulb operating temperature. If the 12V bulb has the same operating temperature as the 240V bulb, then its hot/cold ratio will be the same. Similarly the peak power is the same, since the inititial resistance of a 12V bulb is proportionally lower than the 240V bulb.