dim bult tester as the sale old style bulbs is now banned in the uk

[ME]

as incandescent bulbs are rare now in the uk, would setting my variac op to 12 connected to 3x h4 bulbs on the variac op and have the dut in series with the variac 230v input do the same job as a 150watt dim bulb tester?

[Monkeh]

Heat lamps and oven lamps remain readily available.

[ME]

do 150watt oven lamps exist? ,I have a couple but they are only about 15watts!.

[coppercone2]

they may have bad thermal transient response compared to light bulbs.

With a light bulb ban my crazy idea of a tungsten wire rheostat comes closer and closer (adjustable light bulb built like a potentiometer)

[ME]

would my idea that i asked about ie using the variac in place of a dim bulb tester to power say 3 or 4 12v h4 halogen car headlamp bulbs, or would the inrush current be bad for the dut? , If so maybe with a soft start?.

[themadhippy]

as incandescent bulbs are rare now in the uk

are they ? https://www.lamps2udirect.com/standard-incandescent-light-bulbs/1

[ME]

I as told by the boss of my local hardware store its only legal to stock cfc or low energy led types now and its illegal to stock or sell incandescent household bulbs in the uk now, maybe that website is out of date?,i tried to order some and a red symbol came up.

[Andy Chee]

would my idea that i asked about ie using the variac in place of a dim bulb tester to power say 3 or 4 12v h4 halogen car headlamp bulbs, or would the inrush current be bad for the dut? , If so maybe with a soft start?.

Inrush can never be worse than direct mains connection.

Think about it.... how can adding resistance (dim bulbs) possibly make inrush worse?

[ME]

The bulbs are on the variacs output not its input!

[Gyro]

You're missing the big picture... 3 x H4 50W headlamp bulbs will pull 12.5A at 12V. You will be overloading the bottom section of the winding and carbon wiper of your new  2kVA Variac by roughly 50% if the load you have in series with it has a fault, maybe even on inrush (where the cold filament currents will be much higher).

Absolutely the best way to kill a variac, many 'unwise' people have gone before you. It is essential to fuse the output of a Variac (in addition to the input fuse). Depending on the country of manufacture, you probably want to rate the fuse conservatively - if it's cheap Chinese, probably by 50%.

[factory]

Yes they haven't been sold in high street shops to consumers for years, but are still available online, as was mentioned in your 400Hz variac thread, also appear at carboot sales, probably loads abandoned in attics/cupboard/sheds etc too, since people have moved to lower energy bults (whatever those are in your thread title).

I don't get the point of using them with a variac, as they are not going to limit the current useless they have enough voltage across them. Use one or the other.

P. S. This has reminded me, a friend was having difficulty finding one locally for an outside floodlight, told him to look online and he found loads on amazon.

David

[coppercone2]

You're missing the big picture... 3 x H4 50W headlamp bulbs will pull 12.5A at 12V. You will be overloading the bottom section of the winding and carbon wiper of your new  2kVA Variac by roughly 50% if the load you have in series with it has a fault, maybe even on inrush (where the cold filament currents will be much higher).

Absolutely the best way to kill a variac, many 'unwise' people have gone before you. It is essential to fuse the output of a Variac (in addition to the input fuse). Depending on the country of manufacture, you probably want to rate the fuse conservatively - if it's cheap Chinese, probably by 50%.

Fuse both sides of a variac, like I do? For some reason this makes people flip out lol. Pretty sure I ran into some ranty thesis on this forum about not needing variac fuses.

[mikeselectricstuff]

At least 100 listings for them on Ebay UK, also plenty on Amazon

[tggzzz]

I don't get the point of using them with a variac, as they are not going to limit the current useless they have enough voltage across them. Use one or the other.

Yes indeed. Understanding the basic principles avoids cargo cult assemblies.

Possibly relevant: if the OP is in the country indicated by his flag (i.e. the UK), his first post was in the middle of the night.

[factory]

I don't get the point of using them with a variac, as they are not going to limit the current useless they have enough voltage across them. Use one or the other.

Yes indeed. Understanding the basic principles avoids cargo cult assemblies.

Possibly relevant: if the OP is in the country indicated by his flag (i.e. the UK), his first post was in the middle of the night.

Reminds me of something on a Photonicinduction video, "don't drink electricity & play with beer", guessing might be why there are a high quantity of random threads from the OP.

The variacs here rarely get used, think the last time was for a device needing 100Vac input.
If I needed a lower voltage at higher current I used a transformer on the variac output, but this is no longer necessary since acquiring an educational grade AC/DC supply.

The lamp limiter gets used a lot for "new to me" vintage devices, to bring them up slowly to evaluate condition of parts that might write-off a repair. To go with this I have a selection of BC lamps from 5W to 300W (photo-flood type) and for tube/valve devices a solid state rectifier was built, as the capacitors could not be brought up slowly, as the rectifier needs full voltage to warm up & conduct.

David

[MariuszD]

Light bulbs aren't the only high-power "resistors." There are infrared heaters, very similar to light bulbs, and there are also many types of classic heaters.

[Zenith]

as incandescent bulbs are rare now in the uk, would setting my variac op to 12 connected to 3x h4 bulbs on the variac op and have the dut in series with the variac 230v input do the same job as a 150watt dim bulb tester?

They are not that rare. A quick look on ebay found loads of 150W incandescent bulbs. Four for about £12 is typical. A lot are Edison Screw, not bayonet, which may be a pain, and for this application plain is better than pearl, which cuts down the choice a bit. Small hardware shops may have a few round the back.

It seems a lot easier and cheaper to get hold of a few 150W incandescent bulbs than mess about with an alternative.

[coppercone2]

I can understand not wanting to spend 15 dollars on light bulbs for something as situational as a dim bulb tester. That will sit for 10 years and get used twice.

I would ask at work, maybe someone has a few in the closet or garage for free.

And for a traditional light bulb, you also need sockets... if there are no sockets to spare, a little project like a DBL becomes expensive

I waited for 2 years and finally found a light bulb in a box of junk someone was throwing away, and can combine it with ceramic sockets I found nearly a decade ago. LOL
A exciting quest. The project by itself is kind of depressing.... it looks like electricians wiring, not what you expect for hobby electronics lol, certainly not something you wanna spend money on, compared to something exciting like a microprocessor

[reodor]

A heating element will not work well as a dim-bulb tester. The heating element's temperature will not vary enough to alter the resistance sufficiently. In effect, it will be very close to a constant resistance. A light bulb, on the other hand, get so extremely hot that its resistance drops greatly when it gets hot. In effect, the incandescent bulb acts like a current limiter. At low current, it has low resistance, but at higher current, the resistance increases. I have seen constant-current battery chargers where the regulating element was a light bulb. Try measuring the resistance of a cold light bulb and calculate the expected current.

[coppercone2]

they mean infrared heaters, which are kind of light bulbs, but I don't know how fast it is

interesting if that would make a 'slower' dim bulb limiter, with a IR bulb, I don't know if the filament is different, I think so? They seem slow. So you can make different response times to 'wave shape'. I wonder if a normal light bulb restricts too  fast to test certain devices, where a heater bulb would work.


Kind of like fast vs medium vs slow blow fuses

[themadhippy]

And for a traditional light bulb, you also need sockets... if there are no sockets to spare, a little project like a DBL becomes expensive

Really? maybe thats the case in yanky land .Over here you can pick up a battern holder for less than $2,thats £1.50 in real money

[Zenith]

I can understand not wanting to spend 15 dollars on light bulbs for something as situational as a dim bulb tester. That will sit for 10 years and get used twice.

Unless you happen to have the materials available, or see them thrown away, everything of this nature is going to cost something. If you are starting from scratch i.e. with none of the necessaries at hand, it mounts up. If you wait for the materials to turn up, that has a cost. While the idea of a lamp limiter is simple, you'll want a base, socket, bulbs, mains connections, and you might not like the idea of a naked incandescent bulb which gets hot, and could be broken by accident presenting a shock hazard, so some sort of protective cover for the bulb. One design I saw published on the WWW, (so they weren't going to encourage anything dicey), used a bulkhead lamp holder - a fairly expensive item to buy new.

You could always codge something up for occasional use with an old table lamp and some bodge blocks, but you'd still need the old table lamp, the bulb etc.

 

[Fraser]

People do not seem to realise that tungsten filament lamps were not completely banned in the UK. Yes the sale of them for general use by the public was curtailed but tungsten filament lamps can be essential for some tasks in Industry where 50Hz flicker is a problem (Stroboscopic effect). Tungsten filament lamps remain available if designated as “Industrial lamps”. I still have a cupboard full of 100W and 60W bulbs from prior to my moving over to LED lamps. There are plenty of tungsten lamps available if a person just looks hard enough ! Search for Industrial Tungsten lamps and it becomes easier  The down side of Industrial tungsten filament lamps is that they are often a long life design with clear envelope, rather than frosted and tend to be more expensive as a “specialist” item.

Fraser

[Fraser]

I just searched for “Industrial 150W lamp BC base” and there are loads available at sensible prices. I do not see any rarity of this product.

Fraser

[Zenith]

I as told by the boss of my local hardware store its only legal to stock cfc or low energy led types now and its illegal to stock or sell incandescent household bulbs in the uk now, maybe that website is out of date?,i tried to order some and a red symbol came up.

CEF, which is a main supplier still sells them up to 60W. They are a fiver each.

The ban wasn't clear cut as there were a lot of exceptions, such as oven lights, artists daylight lamps and rough duty bulbs. Big suppliers such as Tesco were breathed on to go along with it. At the time CFLs were heavily subsidised and Tesco were selling them for 9p each. CFLs weren't that popular because people didn't like the warm up time or the quality of the light. The pound shops sold 150W incandescents described as rough duty bulbs, for some time afterwards.