Faulty switch?

[securespark]

Inside my dimmer is a fella running around with an evil-looking circular blade?

 

[JohnW2]

The word is triac though maybe the spell checker changed it. It is what domestic dimmers use.

Yes, I think we all know that (just as you know what an OP means when they refer to a 'transformer') - but you're meant to be the one who is obsessed about the use of correct terminology.

Kind Regards, John

 

[securespark]

Whats an SMPT

Switch Mode Power Supply.

Interesting abbreviation - sounds more like a mistype of SMTP

Kind Regards, John

You turn on the light and emails pour out?

 

[RF Lighting]

I've been running the five lights in my bathroom on the exact same dimmer and transformer combination for nearly fifteen YEARS. Three of the five lamps are still original, as are all the transformers and the dimmer.

I don't know where you've got your opinions from, not sure if it's tittle tattle over hear in the wholesalers or what, but the majority is not right, and some is just downright wrong.

There is NOTHING worng with dimming halogen lamps, and it is NOT detrimental to their life. Ifact if you use a soft start dimmer ilke the one in the video it will actually EXTEND the life of a halogen lamp.

Another thing, the transformers used for 12v halogen lights have poor regulation and will over volt is not run at full load. Running a 20 watt lamp on a 50 watt transformer will shorten the lamp life. That is one advantage of a SMPS.

12V 50W lamp

12V 20W lamp

Wow the voltage is constant. More poppycock from winston.

 

[JohnW2]

You turn on the light and emails pour out?

Not quite - SMTP is about sending e-mails, not receiving them

Kind Regards, John

 

[JohnW2]

I've been running the five lights in my bathroom on the exact same dimmer and transformer combination for nearly fifteen YEARS. Three of the five lamps are still original, as are all the transformers and the dimmer. ... I don't know where you've got your opinions from, not sure if it's tittle tattle over hear in the wholesalers or what, but the majority is not right, and some is just downright wrong.

RF, have you got an oscilloscope there?

Some of what winston says about possible reasons why there could be problems running a wire-wound transformer from a waveform-chopping (akak triad ) dimmer makes a certain amount of theoretical sense. I therefore wonder whether a large inductive load may actually appreciably 'tidy up' the waveform coming out of the dimmer.

If you had the ability, it would therefore be interesting to see what the ('dimmed') waveform coming out of the dimmer looked like with a resistive load and with your (true!) transforming+lamp setup.

Kind Regards, John

 

[winston1]

There is NOTHING worng with dimming halogen lamps, and it is NOT detrimental to their life. Ifact if you use a soft start dimmer ilke the one in the video it will actually EXTEND the life of a halogen lamp.

From Wikipedia:
A halogen lamp, also known as a tungsten halogen, quartz-halogen or quartz iodine lamp, is an incandescent lamp that has a small amount of a halogen such as iodine or bromine added. The combination of the halogen gas and the tungsten filament produces a halogen cycle chemical reaction which redeposits evaporated tungsten back onto the filament, increasing its life and maintaining the clarity of the envelope.

More:

Halogen lamps are manufactured with enough halogen to match the rate of tungsten evaporation at their design voltage. Increasing the applied voltage increases the rate of evaporation, so at some point there may be insufficient halogen and the lamp goes black. Over-voltage operation is not generally recommended.

THIS HERE>

With a reduced voltage the evaporation is lower and there may be too much halogen, which can lead to abnormal failure.

At much lower voltages, the bulb temperature may be too low to support the halogen cycle, but by this time the evaporation rate is too low for the bulb to blacken significantly. There are many situations where halogen lamps are dimmed successfully. However, lamp life may not be extended as much as predicted. The life span on dimming depends on lamp construction, the halogen additive used and whether dimming is normally expected for this type.

 

[JohnW2]

winston1, I'm not really sure why you have thanked me for my post to RF.

As you presumably understood, I was suggesting that, although there is a certain amount of theoretical sense in your suggestion that feeding a wire-wound transformer from a waveform-chopping dimmer could present problems, the fact that it actually works in practice suggests that there is some flaw in your argument ... and I was suggesting that the flaw might be that the effect of a large inductive load might actually be to considerably clean up the waveform which would otherwise (with a resistive load) be coming out of the dimmer.

Kind Regards, John

 

[winston1]

winston1, I'm not really sure why you have thanked me for my post to RF.

As you presumably understood, I was suggesting that, although there is a certain amount of theoretical sense in your suggestion that feeding a wire-wound transformer from a waveform-chopping dimmer could present problems, the fact that it actually works in practice suggests that there is some flaw in your argument ... and I was suggesting that the flaw might be that the effect of a large inductive load might actually be to considerably clean up the waveform which would otherwise (with a resistive load) be coming out of the dimmer.

Kind Regards, John

Waveform chopping produces lots of harmonics. Transformers for domestic mains are not designed to cope with harmonics so could overheat. Some may be OK, others not. Also the secondary load will affect things. A fully loaded secondary will reflect a mainly restive load to the primary, a lightly loaded secondary will be all together different.

Basically it is not good practice, and with so many unknowns a sample of one that appears to to work is meaningless.

 

[winston1]

[/quote]

12V 50W lamp

12V 20W lamp

Wow the voltage is constant. More poppycock from winston. [/quote]

All transformers output vary with load due to IR losses and iron losses. Some are better than others. Your meter only seems to measure to the nearest volt, so at 12 volts that could represent a variation of 8% rather than constant.

A sample of one is not exactly scientific.

 

[JohnW2]

Waveform chopping produces lots of harmonics. Transformers for domestic mains are not designed to cope with harmonics so could overheat.

Again, reasonable theory, but I'm not sure what happens in practice, and I would certainly like to see the waveform with inductive loading - not the least to see how 'harmonicy' it really is with such a load. In any event "could overheat" has moved an awfully long way from "transformers cannot be dimmed" ... and ...

Basically it is not good practice, ....

..."Basically not good practice" is probably even further from "transformers cannot be dimmed". I sense a lot of wriggling!

...and with so many unknowns a sample of one that appears to to work is meaningless.

It's not a sample of one. I, for one, have known of a good few people who have done it, long-term, without any apparent problems.

Kind Regards, John

 

[JohnW2]

All transformers output vary with load due to IR losses and iron losses.

Can you explain to me what "IR losses" are ... Infra-Red, Insulation Resistance, Current x Resistance or what? You really should try to be more precise with your terminology.

Kind Regards, John

 

[333rocky333]

Been doing shops, pubs and restaurants since 12V dichroics first came out in the 80's in them days always toroidal or multi output transformers, nearly always dimmed via lutron grafix eye dimmers, virtually always trouble free.

Though i do recall the sales gumf at the time recomended loading them up near the max and that using 1x 20 watt lamp on a 50va Tran was rumored to effect the lamp life

It became common to pair the spots up, but then when inadvertently 50 w lamps were fitted, the trans then cut in and out on overload,

At home i have 300 Va toroidals on Lutron 500va dimmers the size of a 1 gang plateswitch and although dimmed constantly I dont recall changing a lamp since before the millenium

 

[winston1]

All transformers output vary with load due to IR losses and iron losses.

Can you explain to me what "IR losses" are ... Infra-Red, Insulation Resistance, Current x Resistance or what? You really should try to be more precise with your terminology.

Kind Regards, John

Current x Resistance.

You got third time. I'm surprised you had not come across this term, also known as copper losses when referred to a transformer.

 

[JohnW2]

Can you explain to me what "IR losses" are ... Infra-Red, Insulation Resistance, Current x Resistance or what? You really should try to be more precise with your terminology.

Current x Resistance. ... You got third time. I'm surprised you had not come across this term, also known as copper losses when referred to a transformer.

I obviously have "come across the term", otherwise I would not have included your intended meaning in my list!!!

Kind Regards, John