I agree with the above: dimming is way smoother on the Blue Series for me — none of the “steppiness” that I saw on the Red Series (and it works better with my low-wattage loads so I don’t need to set the minimum level higher, which probably made it worse on the Reds, though this will depend on your bulbs).
I can’t answer what kind of dimmer it actually uses inside, MOSFET or TRIAC Given that it can be used in either dimmer or switch mode, the answer might be more complicated that. A search here doesn’t seem to reveal anything, either.
I’d be curious to hear more about the dimmer capabilities. Not much is mentioned in the manual.
IIRC, the red was forward-phase (leading edge) only. Can the blue do reverse-phase (trailing edge) dimming? eg, The Lutron DIVA is reverse-phase, and its LED compatibility is really good. Adaptive/universal dimming would make this a best-in-class switch.
I’ve noticed that if I use Home Assistant to set the brightness to 1 (out of 100), my LED lights are still fairly bright. I was able to dim them lower with my old switch, a Lutron Diva DVELV-300P. The switch’s Minimum Dim Level parameter is set to 1. It’d be nice if it could dim even lower–I’m guessing the electronics can do it, but the firmware is enforcing a minimum brightness where 1% doesn’t actually translate to the power being on 1% of the time?
That’s similar to the Red dimmer. You can see the current waveforms into a resistive load I measured here.
I’m curious what the fascination is with building leading edge dimmers using MOSFETs which are only needed to build trailing edge dimmers. Leading edge dimmers could be made with cheaper TRIACs. LEDs are generally happier with trailing edge dimming and when the hardware has the capability to do trailing edge it seems odd it’s not implemented.
I’m pretty sure the relay switches the output of the MOSFET dimmer circuit between the load and traveler terminals.
If you look at a 3-wire with a dumb switch wiring diagram, the dumb switch connects the light load to either the load terminal or the traveler terminal depending on which direction it is switched. So, in the dimmer device the dimmer circuit output which is normally connected to the load terminal has to be switched to the traveler terminal. Hence, the relay is needed to do this switch.
I believe this means if the device is used in single pole neutral mode and set to use the relay that the relay click simply switches the MOSFET dimmer circuit to be powering the traveler wire when the device is turned off which disconnects the MOSFET dimmer circuit from the load terminal and doesn’t allow it to power the load. The relay isn’t in parallel with the MOSFET dimmer circuit so it doesn’t bypass it.
The same thing can be done in a RED by setting it to 3-wire dumb switch mode even when it’s a 1-pole neutral wired application. The internal relay starts clicking when it’s turned on or off.
This also explains why this device can’t do a fan. The internal relay isn’t bypassing the dimmer so the dimmer would have to power the fan, which just isn’t done.
So according to that, Single Pole, Dimmer using MOSFET + Relay is an option:
I’m not clear on what that would do exactly though. And I don’t know how to configure the switch between the two modes either. I see in ZHA a “Disable relay click in on off mode” parameter, which I assume is 261 Disable Relay, “Click” Sound:
In neutral on/off setups, the default is to have a clicking sound to notify you that the relay is open or closed. You may disable this sound by creating a, “simulated” on/off where the switch only will turn onto 100 or off to 0.
But that says it’s only for on/off setups. I have that setting disabled on my switches (which is the default)–disabled the disabling, so the relay click is enabled. On the switches set up as dimmers, there’s no click. And on the on/off switches, it does click.
I guess it might be cool if at 100% brightness, the relay clicks on to bypass the MOSFET dimming and connects the line directly to load, but I have no idea if the internals are wired so that’s possible.
I have mine set up in smart bulb mode. If it didn’t bypass the dimmer wouldn’t that cause a problem with my zigbee bulbs? I guess it’s possible my bulbs could be compensating for that brief off period but idk.
Huh, I just checked the waveform with the switch in On/Off mode, relay enabled and clicking, and to my surprise, it looks like it does when in dimmer mode at 100% brightness–it’s actually still using the dimming circuitry and not sending out a pure sine wave From what I understood from the previously-linked thread, this is not behaving as expected: “We were able to add the relay function … so that there’s more of a, “hard on/off” for single-pole settings.” “… we haven’t had any complaints around flickering or safety concerns in on/off mode, at least there will be an override if someone experiences this.”