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prolong halogen lamp life (burns from 240V AC)

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smilem

Member
Prolong halogen lamp life (burns from 240V AC)


Hi, I have problem with halogen lamps, they are rated for 230V AC.

However I have 240V AC at day time and at nights 245V AC.

I was thinking to use 100Ohm 5W resistor for 40W lamp
and 33Ohm 10W for 100W lamp. The only disadvantage is that the power is wasted (used to heat the room :( ).

Is there any other way besides using resistor to make correct 220V instead of 240V AC?
 

sailorbob

New Member
You could use a dimmer switch. Halogen lamps work fine with them. Then you could throttle back to about 180V with little noticeable drop in light output and a dramatic increase in lamp life. Or, depending on how much light you really need, you could add a diode in series with the light and run it on half voltage. I did that with all my outdoor security lighting here. One of them has run dusk to dawn, 365 days a year, for 20 years and it's still running .... Now that's a dramatic increase in life expectancy.
 

MikeMl

Well-Known Member
Most Helpful Member
Use a Lutron Maestro or equivalent dimmer. Even if set to full intensity, these have a slow turn-on/turn-off over about a 3 sec period. I have been using these on a transformer-powered 12V halogen lighting system in my kitchen, and haven't lost a MR-12 or G-4 halogen bulb since I added the dimmers. btw- the dimmers I am using are rated for "magnetic" service, meaning transformers. The deliver a symmetrical waveform so the transformer doesn't buzz.
 
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sailorbob

New Member
Right. I read the original post as saying the lights ran on line voltage. If there's transformers in the mix, then a dimmer that will handle the inductive load will be required. After that, the results will be the same. Running incandescent/halogen lights at reduced voltage makes a dramatic difference in life expectancy. Naturally, running them over their rated value reduces their life. Actually, that's how the manufacturer tests them. They can pin the expected life of that batch of bulbs in a matter of a few hours by seeing how long they burn at very high voltage.
 

MikeMl

Well-Known Member
Most Helpful Member
Its the start-up inrush that kills them. Using the soft-start on the dimmer is what makes the difference. I'm not reducing the final operating voltage; just the start-up inrush.
 

smilem

Member
Its the start-up inrush that kills them. Using the soft-start on the dimmer is what makes the difference. I'm not reducing the final operating voltage; just the start-up inrush.

Thanks.

Perhaps somebody knows any simple soft-start circuit I could use for this?
 

mneary

New Member
They make NTC thermistors to limit inrush on TVs and PCs. Maybe you could find one that would work for a lamp. Maybe the "hot" resistance high enough to reduce your 245 to 230.
 

smilem

Member
They make NTC thermistors to limit inrush on TVs and PCs. Maybe you could find one that would work for a lamp. Maybe the "hot" resistance high enough to reduce your 245 to 230.

To reduce ~240-245V to 220V for 40W bulb I need 100Ohm 5W resistor.

I understand that I neet NTC thermistors to make resistance low when the lamp heats up.

I found this:

EPCOS - B57236S800M - THERMISTOR, NTC, 80R, 1.6A

EPCOS|B57236S800M|THERMISTOR, NTC, 80R, 1.6A | Farnell LT

I wonder how can choose them if they have such values like

Steinhart-Hart Thermistor Calculator
 
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