Generally: Many LED devices (not the LEDs themselves, but the full combination of LEDs, power socket and internal control circuitry) are NOT suitable for dimming. Most often, the internal circuit operates by sending pulses of predefined current amplitude through the light-emitting elements, and only a minority (the costlier ones) of those a suitable for dimming without causing inconvenience for the user, and/or damage to the unit itself.
1) A resistive dimmer switch:
This is not a switch as such, but a potentiometer, or regulator, for the ones who may not know what a potentiometer is.
2) Using a resistive dimmer between the main voltage and the transformer will damage the transformer:
A transformer will not be damaged by having a resistor in series with its primary winding, but possibly a low-voltage (switching) power supply might.
3) LED’s cannot be dimmed using resistive dimming; it will slowly damage the LED’s:
The main LED elements ARE controlled by limiting the current through, and will in many cases controlled by resistive limiting. In some cases, though, the LED element itself can be made to shine apparently brighter, by pulsing higher than average currents through the elements. This is mainly because the eye is sensitive to the peak light level, rather than the average level.
4) Pulse-width modulation works by switching the voltage on and off at a variable speed.:
Not necessarily. The term means that the source is on for a variable proportion of each cycle, while the frequency might well stay constant.
5) PWM – flickering:
Is more likely caused by the time the power is on becoming so short, that the internal regulation circuitry does not have “time” to “turn on” the light.
6) TRIAC Dimming:
The TRIAC is only able to switch off when the current passes through zero. (As opposed to IGBTs).
I have no comments to the remainder, as I have not studied any of that nature in the past.
I would also like to say DMX dimming is also possible from what I have read today.
I am half tempted to get a board and try it out with a dimmable LED bulb from Cree from what I understand it may work so as long as you do not dim below 10% so maybe a dimmer module used in conjuction with a relay to turn the voltage off if of course the only problem is flickering I see no point to go lower than 10% lighting really.
Where I buy my ESP8266 boards from... (Banggood)