Turning LWRF dimmer into an on/off.

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This topic contains 11 replies, has 11 voices, and was last updated by  JulsM 1 year, 4 months ago.

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     a201900 says:


    Okay this is a hardware hack question… I have a triple dimmer however one of the circuits feeds a PIR to some external lights… no no no i hear you say, you can’t do that. PIR won’t like the dimmer circuit, nor will the external lights, which are non-dimmerable; well you’re right, they don’t.

    My solution was to place a simple SPST relay on the dimmer switched live and have the relay provide a un-dimmed live to the circuit; this is where we run into the next problem. The LWRF dimmer puts out a small voltage to ‘detect’ load of the circuit, this load unfortunately triggers the relay even in the off position.

    What would happen if I put a resistor in parallel, would this be enough to meet the minimum load requirement? Does anyone have an actual figure for the minimum load?

     puckacostello says:


    Ive the same sort of problem with LED Strip Lights,

    Im going to use a Lightwave relay, Have the Gang Switch Always on and control the Relay via my smartphone or install a wireless switch

     Chris says:

    Key Master

    @a201900 I had a similar thought as you for controlling a fan in the bathroom which is currently connected to the lights. I wondered whether there was a way I could get the fan to stay off yet have the lights on a dimmer circuit. I haven’t tried this yet. My feeling though is that you may be better off just using an inline relay to control the circuit as suggested by @puckacostello.

    Chris Mills Founder and Editor - LightwaveRF Community http://cpmills.com/ http://lightwaverfcommunity.org.uk
     Majik says:


    I’m not sure a simple relay arrangement would work.

    I was considering whether a solid-state circuit could be built, e.g. with triacs which could create a triggered on/off based on a threshold using a voltage derived from the dimmer output, but it’s a bit beyond my current level of electronics competence. I’m sure an expert in this, such as the Engineers at JSJS, could quickly design something.

    It is my view that it would be a really good and popular addition to the range to have an official device like this. It could be installed at the device that needed switching and would be a great problem solver as it would allow the current ganged/slaveable dimmer switch range to be used for on/off switching applications, and the lack of ability to do this seems to be one of the biggest complaints about the current system.

    In my case, for instance, the inability to easily put a switch which controls an on/off load into the same faceplate as other wired dimmer modules is preventing me from upgrading a lot of my lights.

     Davey says:


    It goes back to the old problem that most houses in the uk don’t have a neautral at the switch. You cant trigger a on off relay without a neautral.

     Majik says:


    I was thinking of a module that could be installed at the other end (e.g. at the ceiling rose/junction box) where neutral is almost always present. It could be powered by the local Live and Neutral at that point, but also have a connection to the “Switched Live” from the dimmer module, through which it would receive the PWM dimmed signal. It would need some sort of circuit which could trigger a triac or similar switched output based on the received PWM level.

    As I said, I think this would be a great addition to the range. If I am anything to go by, it would certainly encourage me to buy a bunch of kit. I’m holding off at the moment because I can’t put together the setup I want with the current range, and I get the feeling a lot of others are in the same position.

     ScubyD says:


    Good idea, I like it! And you’re right in that there’s no technical reason it couldn’t be put together into a small package (needn’t be any bigger than the light switch module). Might have a look around and see if I can come up with something that’ll do the trick! Sadly I suspect the chance of Lightwave / JSJS doing this in the next 5 years is pretty much nil – they can’t produce the products they’ve apparently already finished, never mind designing new stuff.

     Node Zero says:

    Node Zero

    I emailed Jim at lw tech support about the benefit of a device like this, as it would enable us all to control any actual lamp or device with a wall dimmer. He responded that it was ‘in the pipeline’ , but make of that what you will.
    In the mean time I think all we really need is some kind of (variable voltage coil) Relay that energises at the voltage range put out by the dimmer (85v – 185v ?) with the addition of component that will ‘absorb’ the current required by the rf circuitry without energising the Relay when the dimmer is ‘off’.
    I’m sure someone with more tech know-how of how the trailing edge dimmers work will correct me if this is not poss, but if it is then if anyone can produce such a thing then they would flog a fair few per week on ebay etc. I read something a while back that said there are 16k LW user accounts in the UK and that this website alone received 55k+ hits from separate locations.

     daedalusminos says:


    To modify an existing dimmer module would be difficult – by their nature they require a permanent load in order to derive a voltage to power the Rx etc. Unfortunately it’s that load which needs to be switched and therefore when you switch the load off you no longer have a permanent load.

    Probably a better way would be to use a battery powered Rx with a latching relay output. LWRF used to sell a twin pack of battery powered wireless controlled LED lights for sticking in cupboards or under stairs, to be honest they weren’t very bright and fairly useless! However, these are useful for hackers in that what you essentially have is a low power battery powered Rx with manual override and digital ON/OFF output. It would take very little effort to add a latching relay to give the ability to switch mains loads.

    Even better is that this could all sit in a standard back box.

     Macman says:


    Those stick on wireless, battery powered lights are the one thing about my system that the missus actually likes. I stuck them on our landing at floor level and trigger them by PIR. When someone steps onto the landing at night to go to the toilet, the lights come on and are just bright enough for them to see where they’re going without waking up the rest of the house.

     arumustam says:



    I am just looking at this same problem, although now at the end of 2016 and wondered if it had been solved?


     JulsM says:


    No Rob! Although someone suggested a big resistor across the terminals…

    (So far: 12x wall dimmers, 6x relays, 5x door switches, 2x plugins 1x PIR & a dusk monitor.)
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