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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 25th Oct 2020, 12:42 pm   #1
Polybus
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Default Dim Bulb Tester

I'm new to the hobby and want to build a Dim Bulb Tester.

It is quite difficult to get incandescent globes (or if you can, they are VERY expensive) now in Australia - they were banned (in a very round about way) years ago now.

I know I can't use LED Globes (and understand why), or any of the low energy type globes, but can I use a Halogen globe to build a Dim Bulb Tester? I'm not entirely sure. A halogen globe is a type of incandescent globe - but is it the right type??

Also I'm looking at some Halogen globes, they are rated at 42W(60W)

What does that refer to? What value would I use for calculations 42w or 60w?

Thanks
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Old 25th Oct 2020, 1:02 pm   #2
paulsherwin
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Default Re: Dim Bulb Tester

Yes, you can use halogen lamps.

The first number is the actual wattage used by the lamp, and the second is the wattage of a conventional incandescent lamp producing the same amount of light (so a 42 watt halogen is as bright as a 60 watt conventional lamp).

This sort of terminology was widely used when novel lamps first arrived as it made their brightness easier to assess, but manufacturers are increasingly quoting the brightness in lumens, particularly for LED lamps.
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Old 25th Oct 2020, 1:07 pm   #3
snowman_al
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Default Re: Dim Bulb Tester

Yes Halogen lamps are still incandescent filament types.
They use less energy to produce the same light. So a 42watt Halogen is equivalent in light output to a 60 watt standard filament lamp.
So a 42/60W it will draw 42 watts use that for your calculations.
Have you searched for Hard or Heavy Duty filament lamps. They are the only ones still available in the UK, but do carry a premium...

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Last edited by snowman_al; 25th Oct 2020 at 1:08 pm. Reason: beaten
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Old 25th Oct 2020, 1:17 pm   #4
Polybus
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Default Re: Dim Bulb Tester

Excellent - thanks so much for the fast, and very helpful replies.

Exactly that advice I needed.

Cheers.
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Old 25th Oct 2020, 2:12 pm   #5
Silicon
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Default Re: Dim Bulb Tester

Oven bulbs may continue to be available for some time.

I don't know of any other type that will withstand the heat.
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Old 25th Oct 2020, 3:46 pm   #6
broadgage
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Default Re: Dim Bulb Tester

Daylight bulbs are another possibility, confirm by inspection that they are a standard filament lamp with bulb made of blue glass and not any form of LED or CFL.
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Old 25th Oct 2020, 4:28 pm   #7
crackle
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Default Re: Dim Bulb Tester

Other specialist bulbs are a possibility, but it is getting difficult to find them.
https://www.tlc-direct.co.uk/Main_In...amp/index.html
https://www.tlc-direct.co.uk/Main_In...amp/index.html
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Old 25th Oct 2020, 5:41 pm   #8
deswradio
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Default Re: Dim Bulb Tester

Another possibility is to keep your eye on the local freecycle/freegle groups. Lots of people seem to be offering their collections of filament bulb spares now they have moved to leds.

Best wishes
Des
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Old 25th Oct 2020, 6:50 pm   #9
emeritus
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Default Re: Dim Bulb Tester

I am not familiar with the expression "dim bulb tester" but I assume it is what I know as a "lamp limiter", a series-connected filament lamp whose normal operating current is much greater than that of the equipment to be tested, and so only glows dimly if the equipment is OK. If the equipment develops a short circuit, the current is limited to the current drawn by the lamp, which will then glow brightly. The highly non-linear temperature coefficient of tungsten means that it doesn't drop much voltage when it is only glowing dimly because the equipment under test is not faulty. Thus, as noted above, you are only interested in current limiting ability rather than light output, it is the actual wattage of a halogen lamp that you will be interested in, and not its equivalent wattage.

If you can't get a single tungsten lamp of suitably high wattage, you could use several 15W or 25W oven bulbs in parallel to get the equivalent resistance of a higher-wattage bulb.

Last edited by emeritus; 25th Oct 2020 at 7:03 pm. Reason: Typos, clarification
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