I am trying to install recessed, dimmable LED lighting in the living room. We're talking about an end solution of maybe 15-20 spot lights. My home has 120V/60Hz.
Currently I am experimenting with a single spot light, a 4 x 1W warm white LED LemonBest 120V AC. Besides the main lamp the device has a small box which is labelled 'LED driver'.
I installed a Leviton slide dimmer in the wall and the spot light into its hole in the ceiling. There is functionality. The light can be turned on and dimmed.
However, the light that is produced has a flicker in it. It is especially noticeable when the light is dimmed. This flicker is not an option. I am trying to get rid of the flicker.
Since this is the 2nd dimmer I am trying I gave up on a solution a la 'just get the right dimmer'. This problem needs to be solved differently.
Measuring the output of the 'LED driver' results in 25V down to 15V DC depending on the setting of the dimmer. Now, I guess that the 'LED driver' contains a rectifier and a resistor. I further guess that the flicker is a result of voltage as a function of time which probably goes like in the image (the resistor is not shown). The LED has probably a minimum voltage that is needed for operation and on a frequency of 120Hz this minimum voltage is not provided. Thus, the flicker.
My question is: Is there an inexpensive, but still professional way to achieve a non-flickering LED light? E.g. would a capacitor added to the wiring at each lamp smoothen the voltage? Or is the only solution to add a 25V DC source to the wall and 'dimm' the DC current (and remove the 'LED driver' at each lamp)?
EDIT:
The LED lamps are designated as 'dimmable' and the dimmer slider I use is designated as for the use of LEDs. As I said, the lights are dimmable and for most use cases it's fine. But in a very ambient setting (low dimmer setting) and when uses as the only light source in the room, one notices the high frequency flicker. (If I fan my finger in front of a book page I see a stroboscope effect). This is annoying and I'd like to solve this before installing ~20 of these lights.
I opened the 'LED driver' and took 2 photos. See below. Not sure what the brown-ish thing is. A capacitor maybe?
EDIT:
And this is the lamp:
And the other side (with the LED driver connected):
For completeness the specs of the lamp (source Amazon):
Specifications:
Power: 4W(4x1W LEDs)
Input Voltage:AC 100-145V
Dimmable: Yes
Material: High Strength Aluminum
Color Temperature:Warm White(2800-3500K)
Luminous Flux:480-650LM
Beam Angle:45 degree
Life Span:50000 hours
LED Working Temperature:-25°C - +65°C
Size:D3.39*H1.65inch
Cut-out:2.68inch (68mm)
EDIT:
I looked up what a PWM is and it basically puts the signal periodically to zero on a high frequency simulating a 'dimming' effect. The signal would look like:
Thus for the dimmable LED lights to have the best result one needs to go for the highest frequency (or fast-acting) PWM. If the frequency is high one should not notice the flicker. But what would be high? As I see it, right now I guess my flicker is at 120 Hz and it is annoying. (Honestly I think it's at 60Hz but technically I can't explain 60Hz, so I say 120Hz, comes from the two zeros per sinus wave). Guessing I need a PWM at at least 240 Hz. Does this make sense?
Best Answer
I sort of have an answer but it may not be one that you like.
I have the same problem in a mobile audio recording truck that I am working on. The person with whom I am working has tried every combination of every single LED fixture and wall-mount dimmer that was available locally as well as several units purchased online.
All of these have some degree of flicker at the low end of lighting.
My solution is sort of drastic. I'm going to rip the electronics out of every LED fixture in the control room and install a very-fast-acting PWM constant-current driver inside each fixture. Then I'm going to use one of the standard PWM LED dimmers that we build and simply supply 12V PWM to each fixture.
I have the freedom to do this - I was worried that flicker might be a problem (past experience) and made sure when wiring the control room that I would be able to isolate those particular lighting runs from the 120 Vac supply and instead use DC.
My particular case is fairly unique in that I have several hundred Amp Hours worth of 12V battery in the truck's battery compartment from which to draw power. You would have to find somewhere to install your DC power supply, whatever voltage you want to use.
I have two standard LED PWM frequencies that I use: 977 Hz (1024 us tick rate) & 4 KHz. Both work well and I have never experienced a flicker problem with either. I'll probably wind up using the 977 Hz version just to give the constant-current LED drivers a fighting chance of working well.