Blue Series Dimming Tech

I’m not an electronics engineer; I think I’d call myself an intermediate hobbyist, amd I’m not really knowledgeable about the details of dimmer switches. In particular, I get the general concept of how the switch works in non-neutral mode, but definitely don’t know the specifics of what limitations that introduces. But in my mostly-uneducated opinion, what he’s saying sounds reasonable to me.

I’m surprised they are using the dimming mosfets for zero cross detection. I’ve mostly seen dedicated/isolated circuitry for that. Perhaps theress no room/cost of components, but then you’re free to use trailing edge dimming.

So the relay is energized the entire time the switch/load is turned off? Seems backwards, but i guess relays can fail in either position.

It only has to operate for dumb switches. You don’t really enable it for dumb switches, when you select 3-way with a dumb switch mode it starts operating because it has to.

1 Like

Well, the switch doesn’t click when you turn power on, right? It makes sense for the relay to only be on in dumb 3-way mode when the traveler is in use. That would keep it off in 1-pole mode and aux switch mode so off in most modes. The click was added just so you could hear a click when you turned it on or off. Well, it might keep the MOSFETs turned-on so the relay click immediately connects the MOSFETs to the load. That part can’t be determined from looking at output waveforms.

Not sure, I’ve not installed mine yet! :slight_smile: They were slated for ballast loads and plans changed once I started reading that it wasn’t what I remembered.

The relay swaps the MOSFETs output from being connected to the load terminal to the traveler terminal. For the dumb three way the AC has to swap terminals to work but for a single way installation that is optional as the MOSFETs are used to interrupt the AC so it is not required to switch it from the Load to Traveler terminal. Ideally the design would have had a second relay that bypasses the MOSFETs for ON/OFF operation but it seems there was not enough room.

It is energized because that is the state for the incoming AC to be passed from the Line to Traveler and not Line to Load.

Ya, kind of exactly like the explanation I posted first in this thread describing what the relay does. You’re not telling me anything I don’t already know.

Honestly the more I see how these devices work the more I really wish it was multiple SKUs

People who are buying HA gear typically don’t want or care that the other switch in a 3 way needs to be smart.

Get rid of the relay (or make the relay actually bypass the MOSFET’s), use the traveler for communication, this can still work in dumb mode but it means the smart switch has to be at the load wiring. There is no reason you need to be switching line power to/from the traveler.

1 Like

For an on-off switch, to me it should

  • require a neutral
  • have a physical or solid-state relay with pure sine wave output

For dimmers, I always buy the neutral version (if available) as my locations all have it. Dimming seems to just work better with one.

I hope the next series of Blue products have the same SKU as the Red series did.

1 Like

For an on-off switch I’d actually prefer the simplicity and increased current carrying capacity of a relay.

1 Like