Interesting LED call

[gar]

150318-2337 EDT

Electric-Light:

I don't believe that Lutron explicitly defines what a CL dimmer is. but from their description one would be led to believe a better electronic control is used and that might imply the need for power for the electronics other than what is available from the series connection with the load, and that would require a neutral connection.

If there is no neutral, then to derive power for the electronics it is necessary to have some portion of the half cycle non-conductive (thus full brightness is not possible), or a current transformer is required to obtain energy from the load current.

Since you have close contact with many different Lutron devices I will then assume from your comment that there is no specific indication from general Lutron descriptions that a particular type requires a neutral. However, I believe that if you want a good dimmer, then there should be a neutral connection.


My comment on a magnetic dimmer was that it needs to produce very little average DC current. This can be accomplished with either a forward or reverse phase control. That Luttron does not make a reverse magnetic dimmer is not important to understanding what is the primary requirement for dimming via a controller on either the primary or secondary side of a transformer.


Incandescent loads are resistors that convert heat to light, and any way you can adjust the heat will determine the light output. No heat no light. Full heat full light. There are no electronics in an incandescent light, thus no special characteristics. No minimum voltage, no minimum current, no threshold points, no special requirements for phase information, and there is no disruption of the dimmer control because of the turn off phase point (it is the same as the voltage zero crossing).

The easier control of an incandescent is not because of its larger power requirement. I can phase shift control the brightness of a 757 pilot light as well as a 100 or 100,000 W bulb.


If one can obtain a basic understanding on how a particular dimmer functions, and the same for the loads being controlled, then one has a greater chance of putting together a successful system. We need basic knowledge, not just use A with B. We need to know why.

.

 

[Electric-Light]

150318-2337 EDT

Electric-Light:

I don't believe that Lutron explicitly defines what a CL dimmer is. but from their description one would be led to believe a better electronic control is used and that might imply the need for power for the electronics other than what is available from the series connection with the load, and that would require a neutral connection.

They market it as specifically designed to get along with dimmable CFLs and lol EDs.

If there is no neutral, then to derive power for the electronics it is necessary to have some portion of the half cycle non-conductive (thus full brightness is not possible), or a current transformer is required to obtain energy from the load current.

Now you're getting somewhere Some boxes do not have neutral, so not requiring a neutral is a very valuable feature in those cases.

Since you have close contact with many different Lutron devices I will then assume from your comment that there is no specific indication from general Lutron descriptions that a particular type requires a neutral. However, I believe that if you want a good dimmer, then there should be a neutral connection.

If you want a good dimmer, you don't power the device from "dimmed" power.

My comment on a magnetic dimmer was that it needs to produce very little average DC current. This can be accomplished with either a forward or reverse phase control. That Luttron does not make a reverse magnetic dimmer is not important to understanding what is the primary requirement for dimming via a controller on either the primary or secondary side of a transformer.

Those are specifically designed to have very little asymmetry. Reverse phase is still explicitly recommended against use with inductive loads.

Incandescent loads are resistors that convert heat to light, and any way you can adjust the heat will determine the light output. No heat no light. Full heat full light. There are no electronics in an incandescent light, thus no special characteristics.

The filament resistance decreases. So a 100W light bulb at full voltage is 100W, but at reduced voltage(RMS), it will be a lower resistance than a 100W heating element that do not change resistance all that much. I am saying that this works in favor of keeping the triggering stable.

The easier control of an incandescent is not because of its larger power requirement. I can phase shift control the brightness of a 757 pilot light as well as a 100 or 100,000 W bulb.

No, you fail to understand what I said. The dimmer sees a considerable minimum load even when the lamp output is barely visible. You need a much higher electrical turn down ratio to achieve the same visual turn down ratio when you're using LEDs, i.e. 10W down to 0.1W, as opposed to 60W to 10-15W as in the case of incandescent lamps.

 

[gar]

150319-1516 EDT

What I am trying convey with my comments is:

If you know how a particular dimmer works, and if you know how the load connected to the dimmer responds to various inputs, then you can judge the likely success of the combination.

To describe either the dimmer or load by some fancy name does not provide necessarily the required information. Much better to have a good basic understanding of how the source and load work.

.

 

[Electric-Light]

150319-1516 EDT

What I am trying convey with my comments is:

If you know how a particular dimmer works, and if you know how the load connected to the dimmer responds to various inputs, then you can judge the likely success of the combination.

To describe either the dimmer or load by some fancy name does not provide necessarily the required information. Much better to have a good basic understanding of how the source and load work.

.

I know that a centrifuge spins and spins and spins, but without a proper vibration elimination, it wouldn't function properly. The nuance in applied engineering to get it to spin correctly is quite different from knowing that it works by imposing a centrifugal force by spinning. So, I don't exactly know HOW dimmers make it stable with certain loads.

 

[gar]

150319-2346 EDT

Electric-Light:

If I have a centrifuge and know how it works, then as part of that knowledge I also know that it has to be sufficiently well balanced to not destroy itself. Does it require better balance for the process? That may require more study.

To build a low cost two wire dimmer it is necessary to depend upon load current in some fashion to obtain power for the electronic control of the electronic switch. This is incompatible with creating a stable firing point with different loads or startup conditions.

Adding a third wire so that a stable voltage source is available to power the electronic control circuit makes it possible to have a precise and stable trigger point relatively independent of the load, including no-load.

If the load is a transformer, then one knows that average DC current in any transformer winding must be kept small. Thus, any dimmer needs the ability to balance the average current of the two half cycles. Also one knows that if a reverse phase dimmer was used that it must be so designed that the inductive kick at turn off is snubbed. This is much more expensive to make, and thus, probably why only forward phase dimmers are made for so called magnetic loads.

Some CFLs labeled dimmable actually have relative stable light output when an adjustable sine wave voltage is applied. With a forward phase control dimmer and constant source AC voltage applied to the dimmer the bulb has a limited dimming range.

Other non-dimmable CFLs dim moderately well with variable sine wave voltage, and not well with a phase shift dimmer.

In contrast a Cree screw-in LED has a relatively good dimming range with both a forward phase dimmer, and variable sine wave voltage.

.