Shelly RGBW2, Dimmers & 2.5s - Help please!

squanch

Novice Member
I’m about to have my electrician install lighting in our kitchen (just refurbed) and we are going to have quite a mixture going in - including a few runs of LED strips (e.g. under worktops, around a recessed ceiling) and pendant lights (e.g. above island, above dining table). NB: The LED strips will be white (not RGB) - in particular these: DuoFlex Dual Colour Flexible Strip

I’m planning to have him install Shellys but I have so far experimented with just a basic on/off Shelly 1 in a spare bedroom and it works great (and I’ve successfully homebridged it to HomeKit with a Raspberry Pi).

My (initial) questions (bear with me as I’m a mathematician not an electrician!):

1. If I have two pendants and two LED strips being controlled from a four gang switch can I use a Shelly Dimmer 2 (for the pendants) and a RGBW2 (for the two two-channel LED strips) in that to do the job. My aim is to be able to turn these lights on and off from the ‘dumb’ wall switches as well as via ‘smart’ functionality.

2. I broadly understand how Shelly 2.5s work as a pair of binary relays. Is the Shelly RGBW2 essentially ‘always on’ from its DC input but the DC voltage output by the four channels to the LED strip is effectively throttled down to zero using its dimming function? What purpose does the AC input switch serve on the RGBW2 and is that the terminal that would be wired up to the four-gang switch somehow?

3. Are Shelly Dimmer 2s completely inappropriate for LED strip lighting usage?

4. I see references to ‘momentary’ switches, press-and-hold dimmer switches and the like. I’m not 100% sure on what the former is. Would it be possible to use the rotating knob dimmers for the above use cases?

5. What other questions should I have at this point?!

Any help greatly appreciated!
 

Seb Briggs

Distinguished Member
1. If I have two pendants and two LED strips being controlled from a four gang switch can I use a Shelly Dimmer
2 (for the pendants) and a RGBW2 (for the two two-channel LED strips) in that to do the job. My aim is to be able to turn these lights on and off from the ‘dumb’ wall switches as well as via ‘smart’ functionality.

Do you want to control the pendants separately if so then you would need 2 x Dimmer 2 and 1 x RGBW2 for the LED Strips. If pendants being used together then just 1 x Dimmer 2 required


2. I broadly understand how Shelly 2.5s work as a pair of binary relays. Is the Shelly RGBW2 essentially ‘always on’ from its DC input but the DC voltage output by the four channels to the LED strip is effectively throttled down to zero using its dimming function? What purpose does the AC input switch serve on the RGBW2 and is that the terminal that would be wired up to the four-gang switch somehow?

Yes that is correct, though by adding the AC Input Switch adapter you can add a AC switch to turn the strips on/off from a switch but also turn them back on by App, Scene Voice etc





3. Are Shelly Dimmer 2s completely inappropriate for LED strip lighting usage?

Yes , Dimmer 2 is 230v AC, RGBW 2 is 12/24v DC

4. I see references to ‘momentary’ switches, press-and-hold dimmer switches and the like. I’m not 100% sure on what the former is. Would it be possible to use the rotating knob dimmers for the above use cases?

The best switch to use with a Dimmer 2 is a retractive 3 way centre off switch. Then you can turn on/off at the switch (up for on down for off) but also dim up and down by holding the top for dim up and bottom for dim down.

YOU cannot use rotary knob switches at all

5. What other questions should I have at this point?!

Does your electrician know what he is doing :} ?
Ideally get them to run a neutral to the light switch


Any help greatly appreciated!
 

Seb Briggs

Distinguished Member
LED Strip Wiring with switch

1641349885755.png
 

Seb Briggs

Distinguished Member
Just checking the specification on the LED strip, are you buying it with the controller if so you wont be able to add the Shelly. If not i dont see them as being the best value for money.

The shelly module doesnt support changing tunable LED strips (different types of white)


WIth the Shelly RGBW 2 module and LED Strips I would go for 14.4W/m 24v Tape, and a suitable driver (PSU), ie if a total of 5M then a 100W Driver is required

I use this company but plenty of others

 

squanch

Novice Member
@Seb Briggs this is supremely helpful, thank you. I’m a fair bit clearer now and will look for alternative LED strips that are not tunable white… we’ll just have to settle on a temperature in advance.

If you don’t mind me asking a follow-up, what should I be weighing up in choosing between strips of different wattages per metre? My kitchen is going to have strip lights all around the island (c 10m perimeter), and under all counter tops as well around a recessed ceiling detail (c. 24m perimeter).

I’ve seen COB strips and wonder whether these are potentially a bit intense for domestic use (as above), any views on that?

Thanks again
 

Seb Briggs

Distinguished Member
No problem

If a total of 34m then still use 14.4w/m but you will need a bigger driver (psu) and also I will need to check the maximum that the Shelly will take per channel.
 

Seb Briggs

Distinguished Member
Each channel on the RGBW2 is 90W for 24v so around 6M for 14.4W/pm

Therefore I would split the two LED Sections and use a RGBW 2 module for each

Module 1 (10m) - 2 x 5M runs

Module 2 (24m) - 4 x 6M runs
 

squanch

Novice Member
@Seb Briggs Is it possible to use a retractive three-way centre-off switch with a Shelly RGBW2? My electrician isn’t sure of the wiring to the AC dimmer inputs to the Shelly and suggesting it isn’t possible. Thanks!
 

Seb Briggs

Distinguished Member
You can wire that type of switch to rgbw2 but both up and down do the same thing as both sides are wired to the same input.

If I remember correctly then a Single click on then single click off . Click and hold dim up 2nd click and hold dim down.
 

squanch

Novice Member
You can wire that type of switch to rgbw2 but both up and down do the same thing as both sides are wired to the same input.

If I remember correctly then a Single click on then single click off . Click and hold dim up 2nd click and hold dim down.
Thanks - much appreciated!
 

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