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Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire

p.kaczmarek2 546 3

TL;DR

  • The LZWSM16-2 is a two-channel Zigbee lighting controller for two switches and two loads, designed to work without a neutral wire and avoid relay clicks.
  • Inside, it uses a Tuya ZTU module, a rectifier bridge, extra rectifier diodes, an AMS1117 LDO, two BTA16-600BW triacs, and thermal protection instead of relays.
  • The unit is very compact at 39x39x19 mm, costs £65, and supports loads up to 200 watts.
  • Home Assistant via Zigbee2MQTT and CC2531 detected it as TS0012, and the switch worked noiselessly with a bulb.
  • Moisture traces inside raised some concern, and long-term stability remains unproven.
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  • Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
    Not everyone likes the distinctive loud click of relays accompanying the switching on of lights in most home automation products available. Nor does everyone have a neutral wire available in the box - in old installations it may have been unnecessary, and its absence makes it difficult to connect some of the 'smart' controls. The product shown here solves both of these problems at the same time.
    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
    I bought the LZWSM16-2 for £65 from the Polish importer. The LZWSM16-2 is characterised by its small size, only 39x39x19 mm. The device has two channels, can control two devices and allows two buttons to be connected. It supports a load of up to 200 watts.
    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
    The device normally works with the Tuya cloud, but I tested it with Home Assistant via Zigbee2MQTT and CC2531. It is seen as TS0012, but oddly enough, HA suggests it is powered by a battery.
    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
    However, this does not affect its performance. The whole thing is indeed noiseless and can cope with a connected bulb. I tested the whole thing quickly on a table before plugging it in, forgive the cottage industry aspect of the experiment.
    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
    This is where it could end, but I still wanted to look inside.
    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
    First we see the rectifier bridge, additional rectifier diodes (from the mode without neutral wire?) and the LDO AMS1117. The traces of moisture inside are a bit worrying.
    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
    After removing the whole thing from the case, you can see how everything has been nicely packed by the manufacturer. The communication module is a ZTU from Tuya. Next to it we have capacitors and two BTA16-600BW triacs. These triacs replace the relays. In addition, we have thermal protection.
    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire

    Device page according to my HA:
    https://www.zigbee2mqtt.io/devices/TS0012.html#tuya-ts0012
    Potentially a more fitting site (they may have updated the listing after I tested):
    https://www.zigbee2mqtt.io/devices/LZWSM16-2.html
    I recommend an update, because according to the LZWSM16-2 profile there are additional entities, allowing, among other things, to specify the type of connected button.

    In summary , the device looks promising. The whole thing is small, compact, and quiet and undemanding (literally - no neutral wire needed). The question, of course, is how it will be with the stability of operation, but time will tell.
    Do you use this type of switch?

    PS: I am enclosing the manual
    Attachments:
    • 30876_25700.pdf (706.73 KB) You must be logged in to download this attachment.

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    About Author
    p.kaczmarek2
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    p.kaczmarek2 wrote 14459 posts with rating 12468, helped 650 times. Been with us since 2014 year.
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  • #2 21896675
    Erbit
    Level 39  
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    p.kaczmarek2 wrote:
    Not everyone likes the characteristic loud clicking of relays accompanying the switching on of the lights

    I get the impression that by writing "loud" you are engaging in demagoguery.

    Somehow, "without automation", no one complained that the switch "clicks loudly" and yet the mechanical system of the light switch makes a sound.

    Of course, I understand that the use of an "electronic relay" instead of a mechanical one mutes the moment of switching on, just as the use of touch switches instead of key switches does, but why the demagogy about the "loud" clicking ? It is not that loud at all. It can be heard not much louder (or not louder at all) than the mere click of a normal mechanical switch.

    Added after 2 [hours] 46 [minutes]:

    p.kaczmarek2 wrote:
    Not everyone has a neutral wire available in the box either - in old installations it may have been redundant, and its absence makes it difficult to connect some of the 'smart' controllers. The product shown here solves both problems at the same time.


    In the test you used a classic incandescent bulb. Will an energy-saving bulb (commonly known as LED) also allow this circuit to work without the neutral wire ?
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  • #3 21902600
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14459
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    At my place, the relays on the smart switch are genuinely louder than when switching the lights with the classic switch.

    The LEDs are then connected to what is colloquially known as an "adapter", i.e. a capacitor. It is even shown in the first title picture.

    You can also see it in the instructions. Clearer graphics:
    Wiring diagram for a no-neutral Wi‑Fi switch with a power adaptor connected near the bulbs
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  • #4 21904125
    divadiow
    Level 38  
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    was there a boot log to be captured from the module? Maybe UART_TX - B1.

    Did you manage to dump firmware from the Z2/TLSR8258?

    I've a Z2 in a Moes bulb that I've not got round to scoping out yet.

    Which silent lighting controller on Zigbee? Two-channel LZWSM16-2 without neutral wire
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TL;DR: The Tuya LZWSM16-2 is a 39×39×19 mm, two-channel Zigbee controller that is "indeed noiseless" and works without a neutral wire. It suits people upgrading older light switches who want silent operation, Home Assistant support through Zigbee2MQTT, and a compact module rated for up to 200 W. [#21895380]

Why it matters: This module addresses two common retrofit problems at once: relay noise and missing neutral conductors in older lighting boxes.

Feature Tuya LZWSM16-2 Typical relay-based Zigbee controller
Switching noise Silent Loud relay click
Neutral wire Not required Often required
Output stages 2 Not specified in thread
Switching element 2× BTA16-600BW triacs Relays

Key insight: The most important takeaway is that the LZWSM16-2 achieves silent switching by using triacs instead of relays, while still fitting older no-neutral installations. [#21895380]

Quick Facts

  • Compact body: 39×39×19 mm, designed to fit behind a wall switch where space is limited. [#21895380]
  • Electrical layout: 2 channels, 2 button inputs, and a stated load of up to 200 W. [#21895380]
  • Tested setup: paired with Home Assistant, Zigbee2MQTT, and a CC2531 coordinator; the device appeared as TS0012. [#21895380]
  • Internal hardware seen on teardown: Tuya ZTU module, 2× BTA16-600BW triacs, AMS1117 LDO, rectifier parts, and thermal protection. [#21895380]
  • Purchase point and price from the thread: bought from a Polish importer for £65. [#21895380]

How does the Tuya LZWSM16-2 work without a neutral wire in an older lighting installation?

It is designed to operate in installations where no neutral wire is present at the switch box. The teardown shows a rectifier bridge, extra rectifier diodes, and an AMS1117 LDO, and the author explicitly links those extra diodes to no-neutral operation. In practice, that lets the module fit older wiring layouts that omitted a neutral conductor. [#21895380]

What makes the LZWSM16-2 silent compared with typical relay-based Zigbee light controllers?

It is silent because it switches with triacs instead of relays. The author found two BTA16-600BW triacs inside and noted that these triacs replace the relays. That removes the distinctive mechanical click common in many smart lighting modules. [#21895380]

Why does Home Assistant detect the Tuya LZWSM16-2 as a battery-powered TS0012 when it is mains-powered through Zigbee2MQTT?

Home Assistant detects it that way because Zigbee2MQTT exposed it as a TS0012 profile during the test. The author calls this behavior strange, because HA suggested battery power even though the module was wired for mains use. He also states that the incorrect power classification did not affect operation. [#21895380]

How do you pair the LZWSM16-2 with Home Assistant using Zigbee2MQTT and a CC2531 coordinator?

You pair it through Zigbee2MQTT with a CC2531, then let Home Assistant read the discovered device. 1. Put Zigbee2MQTT with the CC2531 coordinator into pairing mode. 2. Add the LZWSM16-2 and wait for it to appear. 3. Check Home Assistant, where it may show up as TS0012 and even suggest battery power. [#21895380]

What is the Tuya ZTU module inside the LZWSM16-2, and what role does it play in Zigbee communication?

"Tuya ZTU" is a communication module that handles the device’s Zigbee link, acting as the radio/control section separate from the power-switching components. In this teardown, it is the module the author identifies as responsible for communication, while the triacs handle the actual load switching. [#21895380]

What are BTA16-600BW triacs, and why are they used instead of relays in a silent lighting controller?

"BTA16-600BW triacs" are semiconductor switching components that control AC loads electronically, without moving contacts, which makes them suitable for silent switching. In the LZWSM16-2, the author found two of them and states they replace relays, which is why the controller switches lights without the usual click. [#21895380]

LZWSM16-2 vs a standard relay-based Zigbee switch module: which is better for silent light control without a neutral wire?

The LZWSM16-2 is better when silent operation and no-neutral wiring are your main goals. The author highlights both advantages directly: it is noiseless, and it does not need a neutral wire. A standard relay-based module still suits some setups, but the thread presents relay noise and neutral-wire requirements as the two problems this model solves. [#21895380]

How much load can the LZWSM16-2 handle in real use, and what kinds of lamps or devices fit within its 200 W limit?

The stated limit is up to 200 W, and the author confirmed it could handle a connected bulb during a bench test. That means ordinary lighting loads within that 200 W ceiling fit the intended use. The thread does not list exact lamp types beyond a bulb, so the safest thread-backed answer is to stay within the stated 200 W rating. [#21895380]

What extra entities or settings become available in Zigbee2MQTT when the device is identified as LZWSM16-2 instead of TS0012?

The LZWSM16-2 profile exposes additional entities, including settings for the connected button type. The author recommends updating because the LZWSM16-2 listing appears more accurate than the generic TS0012 identification. That matters if you want device-specific controls instead of a basic fallback profile. [#21895380]

How do you configure the button type for the LZWSM16-2 in Zigbee2MQTT or Home Assistant?

You configure it by using the LZWSM16-2 profile rather than the generic TS0012 profile. The author notes that the LZWSM16-2 listing provides extra entities and specifically mentions the ability to define the type of connected button. In Home Assistant, that setting would appear only after Zigbee2MQTT exposes the correct device features. [#21895380]

What could cause traces of moisture inside a new switch module, and how should that affect safety checks before installation?

The thread does not identify the cause, but visible moisture traces inside a new module should trigger a careful inspection before installation. The author explicitly says those traces are worrying. A practical thread-based takeaway is simple: inspect the interior, check the casing and board condition, and do not ignore residue in a mains-powered device. [#21895380]

Which wiring mistakes are most common when installing a two-channel no-neutral Zigbee light controller behind a wall switch?

The thread does not list common mistakes, but it does show the key installation constraints: two channels, two button connections, and operation without a neutral. In this device class, the thread-backed risk is connecting the wrong button or load to the wrong channel, especially in a cramped 39×39×19 mm module behind a switch. [#21895380]

What thermal protection is typically used in compact smart switch modules like the LZWSM16-2, and how important is it for reliability?

The LZWSM16-2 includes thermal protection, and that matters because the module is compact and handles up to 200 W. The author explicitly points out the presence of thermal protection during the teardown. In a densely packed controller using two triacs, that protection is an important reliability and safety feature. [#21895380]

Where can you buy the LZWSM16-2, and how does its price compare with other two-channel Zigbee no-neutral controllers?

The author bought it from a Polish importer for £65. The thread gives no price data for competing two-channel no-neutral Zigbee controllers, so it does not support a direct market comparison. The only confirmed thread value is the £65 purchase price. [#21895380]

What are people’s long-term experiences with silent no-neutral Zigbee light switches like the LZWSM16-2 in everyday home use?

The thread does not provide long-term user data. The author says the device looks promising after a quick test, but adds that stability over time remains an open question. So the only supported conclusion is short-term success, not proven long-term reliability. [#21895380]
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