Dimmers not working - leading, trailing, TRIAC - very confused!

[ban-all-sheds]

I just checked out the description of the Maplin product - should I be concerned by its reference to Triac?

"Sudden interruption of current in an inductive circuit normally produces a high voltage surge. Damage to contacts occurs due to arcing. In thyristor or Triac Circuits incorrect functioning may result due to high dv/dt."

They are just warning you that things like a bulb blowing can produce a voltage spike ("high dv/dt" ≡ "a high rate of voltage change by time")

 

[ban-all-sheds]

I would have thought that many/most people familiar with differential calculus would be likely to write "dv/dt" as shorthand for "the rate of change of voltage".

They might. I'm as "familiar" with differential calculus as is anybody who did 'O' and 'A' level maths but has never used it in his working life, but I'm not sure I would choose to use that shorthand.

But the point is do Maplin really think that their target customers are familiar enough with differential calculus to know what "dv/dt" means?

 

[bernardgreen]

"Sudden interruption of current in an inductive circuit normally produces a high voltage surge.

the normal use of the device is to absorb the energy that creates a spark when a switch is switched OFF, Appliances with motors ( inductive loads ) create the largest sparks.

Each spark does a very small amount of damage to the contacts of the switch and eventually the switch will need replacing, suppressing the spark greatly increases the life of the switch.

The circuit to squench the spark ( capacitor and resistor in series ) is the same as the circuit to by pass the LED. Hence the same device can be used for both purposes.

 

[JohnW2]

They might. I'm as "familiar" with differential calculus as is anybody who did 'O' and 'A' level maths but has never used it in his working life, but I'm not sure I would choose to use that shorthand.

Fair enough - but you do use other 'steals' from mathematical notation - such as using "delta" to refer to a difference or change.

[In my day, 'O-Level' maths was not enough - one had to do O-Level "Additional Maths" (which I suppose was similar to an AS Level these days) to be exposed to any sort of calculus.]

But the point is do Maplin really think that their target customers are familiar enough with differential calculus to know what "dv/dt" means?

A valid point, but do I take it that you believe that most of them would know what "delta" means?

To be honest, although calculus has featured in various phases of my post-A-Level life, I would not normally dream of using the notation of calculus when addressing a 'general' audience - so I suppose I basically agree with you.

Kind Regards, John

 

[ban-all-sheds]

Fair enough - but you do use other 'steals' from mathematical notation - such as using "delta" to refer to a difference or change.
.
.
A valid point, but do I take it that you believe that most of them would know what "delta" means?

Fair point.

[In my day, 'O-Level' maths was not enough - one had to do O-Level "Additional Maths" (which I suppose was similar to an AS Level these days) to be exposed to any sort of calculus.]

My examination board split O-levels into two, so I did Pure Maths and Applied Maths. TBH I can't be sure that I did actually do calculus in PM.

 

[333rocky333]

I think its just another term evolved by lighting manufacturers.
To my knowledge theres 3 main types of dimming
Triac dimming
1 to 10 v dimming
Dali dimming.
The light makers tend to state what they are so you can match to your wiring.
A triac based light would need no extra wiring, whereas 1 to 10v and Dali will need control wires.
There has been instances were the wirings installed only for the lights to turn up and need control wires which have not been fitted
.
Some commercial dimmers will have both Triac outputs and 1 to 10v outputs so you can use virtually any fitting.

Years ago they termed Dimmers for Torroidal lighting transformers "Inductive dimmers" and I recall Bas at the time said that a true "Inductive Dimmer" is massive.
Then they introduced the term "Electronic Transformer.

May be worth looking at a 4 zone dimmer pack, located out the way, wired to a Remote wall switch with data cables.

 

[ban-all-sheds]

To my knowledge theres 3 main types of dimming
Triac dimming
1 to 10 v dimming
Dali dimming.

You can add 0-10V.

 

[JohnW2]

My examination board split O-levels into two, so I did Pure Maths and Applied Maths. TBH I can't be sure that I did actually do calculus in PM.

My school mixed and matched exam boards, as it suited them. At O-Level, we did no 'Applied Maths' at all (although we did some 'applied maths' in the name of Physics). O-Level "Additional Maths" (as I said, like an 'AS') consisted of calculus and 'co-ordinate geometry'. For A-Level the school chose the board that offered Pure Maths and Applied Maths as separate A-Levels (like your O-Levels), and some unis moaned, because, that way, we got 2 A-Levels for what other boards would have called one!

I think that sort of situation probably persisted. When my daughters did O-Level Maths (about 15-20 years ago), there was not a hint of calculus, although a few new things (like basic Probability & Statistics) had crept in.

I get the impression that A-Level Maths has been watered down over the years/decades. Neither of my daughters did it, but, at the time, I did show my old A-Level papers to some of their contemporaries who were doing A-Level Maths and most of them had difficulty in understanding a lot of the questions, let alone having any clue as to how to answer them!

Kind Regards, John

 

[stillp]

I would have thought that many/most people familiar with differential calculus would be likely to write "dv/dt" as shorthand for "the rate of change of voltage".

I would have thought that most people who have studied electrical engineering would use dv/dt for rate of change of voltage, whether they are familiar with differential calculus or not.

 

[JohnW2]

I would have thought that most people who have studied electrical engineering would use dv/dt for rate of change of voltage, whether they are familiar with differential calculus or not.

Indeed, but I imagine that if they have been taught that notation, they will very probably also have been familiarised with the concepts of differential calculus - either that or they lack intellectual curiosity, since I would expect them to wonder how dv/dt differs conceptually from Δtv/Δt.

Indeed, I would not have thought it possible to study electrical engineering at any significant level without some understanding of calculus (both differential and integral), would it?

Kind Regards, John
Edit: Silly Typo Corrected

 

[stillp]

Depends, I suppose, on what you consider to be a 'significant level'.

 

[JohnW2]

Depends, I suppose, on what you consider to be a 'significant level'.

I suppose a level sufficient to enable one to consider and style oneself as an electrical engineer.

At least in the past, it wasn't a school subject, so I suspect the lowest level of qualification was/is an ONC (or whatever that's called these days), or some equivalent (C&G?). There might well be an NVQ or suchlike these days, but I'm not sure what that would be good for. Personally, I would probably not be inclined to regardl someone 'an engineer' of any sort (electrical, electronic, mechanical, civil, structural, chemical or whatever) unless they were educated at least to first degree/HNC, or equivalent, level in the subject.

Kind Regards, John

 

[ban-all-sheds]

Δt/Δt

 

[JohnW2]

Whoops - typo has been corrected!

Kind Regards, John

 

[Deleted member 18243]

Thanks for a very informative thread about the problems encountered with LED lighting Bernard Green and John W2!

But, I'll stick with my traditional incandescents until LED technology is standardised / proved reliable / proved safe / cheap enough!