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Topic: Dimmer and correct circuit (Read 1 time) previous topic - next topic

PelleS

No.

Did you actually read (and make sure you understand the circuit in) the tutorial I linked to? Or one of the thousands of other tutorials about the subject...
Yes, I read it very thoroughly. I didn't mean to offend you. I am sorry.

wvmarle

Your circuits don't make sense. It's not even a copy of what's posted in that tutorial.
That particular resistor is where normally your load would be.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

PelleS

Your circuits don't make sense. It's not even a copy of what's posted in that tutorial.
That particular resistor is where normally your load would be.
Maybe we are talking about different things. The resistor that's where the load would be, I put it there in order to simulate the load in LTspice. So it is the load.

PelleS

Could someone please take a look at the image I attached. Without the ZC, what is the difference between this and the circuit in the page I linked to? I really can't see it. Maybe I'm just too stupid for this.

TomGeorge

Hi,
What load do you want to switch with the Triac?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

wvmarle

That looks good - except for that ground connection on the mains voltage side. That has to go.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

PelleS

That looks good - except for that ground connection on the mains voltage side. That has to go.
Super! :) The difference between this circuit and my previous one is that I replaced the resistor with the word "Load". I had the resistor there to simulate load (fail on my side). Same with ground, so that will be removed.

PelleS

Hi,
What load do you want to switch with the Triac?

Thanks.. Tom.. :)
Hi, Tom :)
Halogen and incandescent loads. I would like to dim LED bulbs as well, if possible, but I don't know much about that. Can it be done the same way, with the same circuit? I know they have some inbuilt circuitry themselves, so that might complicate things.

wvmarle

Incandescents: no problem.
LEDs: may or may not work depending on how the LED's circuit reacts to the load.
Halogen: normally has a transformer, making it a HIGHLY inductive load, and that's a problem, unless you connect this on the halogen (low voltage) side of the transformer. You'd have to adapt the circuit, especially the zero crossing, to the lower voltage.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

PelleS

Incandescents: no problem.
LEDs: may or may not work depending on how the LED's circuit reacts to the load.
Halogen: normally has a transformer, making it a HIGHLY inductive load, and that's a problem, unless you connect this on the halogen (low voltage) side of the transformer. You'd have to adapt the circuit, especially the zero crossing, to the lower voltage.

Thank you for the info. Do you know how dimmers can work with both Incandescent and Halogen lights and still be wired the same way? I have a dimmer here where it says it works with both.

Paul__B

Thank you for the info. Do you know how dimmers can work with both Incandescent and Halogen lights and still be wired the same way? I have a dimmer here where it says it works with both.
This is the most mind-bending discussion I have seen here for some time!

A Halogen lamp with a transformer is essentially a resistive load.  The only inductance of concern is the leakage inductance of the transformer.  The common series-wired two wire dimmer does not even notice the difference.  A microprocessor-controlled phase controlled dimmer should work just as well.

If however you have halogen down-lights, the best thing is to replace them with LED luminaires - much more efficient means less heating; you can get dimmable ones which will work just fine with phase dimming if they are so specified.

A zero-crossing optocoupler such as the MOC3041 completely prevents phase control for dimming.

PelleS

This is the most mind-bending discussion I have seen here for some time!

A Halogen lamp with a transformer is essentially a resistive load.  The only inductance of concern is the leakage inductance of the transformer.  The common series-wired two wire dimmer does not even notice the difference.  A microprocessor-controlled phase controlled dimmer should work just as well.

If however you have halogen down-lights, the best thing is to replace them with LED luminaires - much more efficient means less heating; you can get dimmable ones which will work just fine with phase dimming if they are so specified.

A zero-crossing optocoupler such as the MOC3041 completely prevents phase control for dimming.
I guess "mind-bending" in this setting is negative? :D I know I can't use a zero-crossing opto as soon as the zero-crossing circuit was being mentioned. I probably should have said that.

I do think most people here are replacing the halogen ones for led. I didn't know phase control dimming could be used for leds as well.

Paul__B

I didn't know phase control dimming could be used for leds as well.
"Mind-bending" in terms of the zero crossing matter, dodgy circuits dredged from who-knows-where and somewhat misguided attempts to use circuit simulation software.  :smiley-eek:

There are better and worse approaches to the circuits in LED luminaires.  If they use simple capacitive "ballasts", then their power factor is bad and phase control becomes very difficult; they are generally labelled as "non-dimmable".

If they use a switchmode regulator with a reservoir capacitor (like a computer PSU), then that capacitor charging to the peak voltage resists phase control and again, the power factor is undesirable.

The best design for both dimmability and power factor, is a switchmode regulator without a reservoir capacitor.  This simply makes do with the instant voltage at each point in the waveform and behaves more like a resistive load.  And leaving out the capacitor is actually cheaper.

I have not yet dissected any LED bulbs (if for one, because they rarely "burn out"!) so I cannot say what circuit they are using.  I do however have two failed LED downlights - non-dimmable - awaiting my attack.  They have this pattern of lighting almost fully, dimming progressively out, waiting and then "popping" back on.  Presumably heat cycling of a switchmode converter IC.  That they failed within two years in service is most disappointing.

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