# Will a resistive load make LightwaveRF dimmer work with 30W transformer? [closed]

I have 2 sets of 12VDC LED strip lights (4.8W per metre) - (LED Lights).

Each strip is 3M in length. They are both connected in parallel to a LED Power Supply Driver Transformer (36W, 12V DC, 3A) - (LED Transformer).

If I switch the mains on to the other side of the transformer the lights work perfectly.

However, I would like to use a LightwaveRF switch so I can remotely control the lights. Unfortunately LightwaveRF only make a 'dimmer' switch and not just a regular on/off switch. (LightwaveRF Switch)

When I connect the lights to the dimmer the LEDs just flash on quickly and then off for around 1 second and then back on quickly.

After doing some reading on this someone mentioned putting a 'resistive load' in circuit (I presume with the mains coming in to the transformer?). They recommended this resistive load (10W Resistive Load).

Firstly, I just wondered if anyone knows whether this would work or not?

Secondly I wondered if anyone knows whether there's a smaller resistive load that could be used as this one is 59mm diameter so quite large.

Thirdly, does anyone who understands why this isn't working have any other solutions for getting this to work?

Thank you.

## closed as off-topic by PeterJ, tcrosley, Daniel Grillo, Adam Davis, Dave Tweed♦Feb 23 '16 at 13:38

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – PeterJ, tcrosley, Daniel Grillo, Adam Davis, Dave Tweed
If this question can be reworded to fit the rules in the help center, please edit the question.

• If you turn the dimmer to full brightness before you turn it on do you still have problems? – EM Fields Feb 21 '16 at 11:20
• The lightwave RF switch is not designed to run that LED transformer. Please contact the manufacturer of the lightwave RF switch for compatible products. This question doesn't really fit on this site because you're trying to receive support for a consumer product, so it's likely to be closed. – Adam Davis Feb 23 '16 at 12:49

It's not working because what you linked isn't a transformer, even though they describe it as one. It's really a switching mode power supply intended for powering LEDs. Attempting to dim it leads to it trying to compensate for the dropping voltage until it is unable to do so, causing the on-off behaviour. The choppy waveform created by the dimmer might stress the components of the power supply to failure as well.

Mains dimmable constant voltage LED drivers do exist. They are also switching mode power supplies, but are designed specifically to work under triac- based dimming. They function by monitoring the incoming waveform and determine how much dimming is being applied.

• Thanks for this info. Would this one be suitable? I have 2 strips of LED lights, 3M each wired in parallel. They pull 4.8W per metre. I'm just concerned this one says minimum load 33.6W? I'm not sure my lights would pull that?? amazon.co.uk/gp/product/… – John T Feb 21 '16 at 18:25
• If your LED strips don't draw that much you need to buy a different one. Calculate the power draw and find your driver. For example, a 10W one: amazon.co.uk/Aurora-Dimmable-Constant-Voltage-Driver/dp/… and a 0W to 40W one amazon.co.uk/…. You will quickly see that they are significantly more expensive than the non-dimmable ones. – jms Feb 21 '16 at 18:39
• Thanks again. I've found this one.. amazon.co.uk/… Which I think (*read - "Hope!") will suffice :-) – John T Feb 21 '16 at 19:28
• @John T: I'm confused here. Do you want to be able to dim the LED strips or do you just want to turn them ON and OFF? – EM Fields Feb 21 '16 at 19:43
• @EMFields I just want to be able to turn them on/off. LightwaveRF only supply a 'dimmer'. It is meant to be able to be used as a switch on/off but doesn't work with my set up. I'm guessing due to the resistive load not being enough. Hopefully changing the transformer to a dimmable one will allow the LightwaveRF switch to function. Not bothered about them being dimmable but, if that is a by-product, then that's fine too. I've already got a lot of Lightwave stuff in the house so would prefer to get this dimmer working if possible (it cost me £24!) :-) – John T Feb 21 '16 at 20:26

What you've been told is largely gobbledygook.

If you turn the switch ON and it won't stop the blinking and it was cranked to maximum brightness before you turned it on, what you need is a single-channel RF switch, sans dimmer, which you interpose between the mains and the LED supply, which is $\style{color:red;font-size:100%}{not}$ a transformer; it's a DC power supply (or an AC to DC converter if you like) regardless of what the illiterati would have you believe.

Amazon UK has a 2 channel unit here, which would work for you and provide an extra channel if you needed it later, for something else.

If you only wanted a single channel unit they're all over the web and Amazon UK might even have one; I didn't look past the 2 channel unit.

Yes this does work. I use this resistive load trick all the time (Although, I just use one regular incandescent light bulb on the AC line and have the rest be LEDs). The dimmers in my house all use triacs. I'm guessing that lightwaveRF also does as well. Basically, triacs depend on having linear loads in order to correctly control the voltage wave form of mains AC going to the load (more on that here). LEDs are anything but linear, not to mention that your LED transformer is likely a switching power supply with it's own non-linearities. As far as I know the resistive load should be around (1/4)->(1/3) the load at minimum (Although I've never tested below 1/4 personally). I run mine at 1/3 for personal and availability reasons. Yes you should attach the resistive load between the LED transformer and main (well, in parallel with the LED mains input to be more precise.)

Suggestions for getting it working

1. Linear load: I like lightbulbs cause they at least provide some amount of light in exchange for regulating the load. Resistors and the like also work, just make sure to follow electrical code and practice safety.
2. You can hack the unit to control a micro-controller or other IC on the LED side of the LED transformer which dims your LED strips directly.
3. Buy a switch that works with your LEDs. I don't know if these exist.