Using a Qubino 0-10V Dimmer and a Voltage Comparator to Automate commercial LED lights

I love A LOT of light (3000K to 4000K range) in general, but especially where I work on my projects. I replaced the meager light in my ceiling fan with an LED module that outputs 2200 lumens (the ceiling fan still looks stock) but it points downwards only so it created harsher shadows and was not bright enough for my purposes.

I set out to find the perfect light to point to the ceiling so I can get some reflected / diffused light, and one to point straight down on a second desk that is a makeshift electronics workbench.

The perfect lights (length, lumens, and narrow construction) were the Commercial Electric WS-WR2A50A1-40 which output 5000 lumens at 4000K.


The issue I ran into is that all of the suitable dimmable candidates required the commercial 0-10V dimming. I was hoping that when set to 0, the light would turn off, but it turns out that at the lowest dimmer settings (really 10% and under) it just stays at the same very low dim setting, but never turns off. The dimmer performance is awesome, but I really needed a way to turn the lights out…

I installed the dimmers inside the light fixtures, and added SmartThings Zigbee outlets to power down each light. The issue that bothered me was that this also powered down the Qubino Zwave 0-10V Flush Dimmers thus potentially causing mesh network issues (and I don’t need more of those!!) and it doesn’t result in a user friendly setup as setting the dim level will not do anything unless you power the lights up first.


The voltage output of the Qubino dimmer was mapped to the dim percentage so as that each 1V was equivalent to 10% dimming therefore 1V was 10%, 5V was 50% and 10V was 100%. Since the dim levels below 10% seemed to do nothing, I figured I needed to find a way to keep the Qubino dimmer always powered, but to cut power to the LED driver when the module output 900mV or less (9% or less).

The component I needed was a Voltage Comparator that could control a mechanical relay or an SSR. The biggest issue I had was how to isolate the mains voltage going to these components in the tight space inside the light fixture. In the end I settled for something that is NOT perfect but should be safe enough. It is an LM393 based voltage comparator with a 10A 250VAC mechanical relay.

The safety issue I am concerned about it related to a trace that goes from the relay common to the rest of the circuit:

If used in DC applications it would be ok, however if the 120V were to arc over to the DC part it would be a big issue… Since these boards came in the form of a kit, I obviously did not install the jumper, however the best thing for me to do is to cut and lift the trace that I marked in the image. This should introduce enough separation between the AC and DC parts of the circuit. I can then also paint the large relay traces to minimize chances of anything making contact there. Any electrical/electronics engineers out there have any comments? (Disclaimer: I am neither).

Some may wonder where I am getting power for this board since the fixture has a constant ~30V voltage / variable current driver in it. I added a small 12V LED driver to power this board and the Qubino dimmer. The 12V are also used as a reference which I thought might lead to issues given it is not very good quality (lots of ripple too).


Overall I am super happy as this solution resolved my problem 100%. When I turn OFF the lights or set them to anything under 9%, the relays turn off. This has been very consistent. Due to small variations, the two lights don’t always both turn on at 10%, but if I set them to 11%, they do. I am sure I can make the threshold a bit more accurate/consistent between the two, but it really doesn’t matter. These lights mirror the dim setting of the main light, so if I want to have a very dimly lit office in the evening, I set it to 9% and the extra lights turn off - always.

In the event manual control were needed, I added a push button on the light fixture that connects to the Qubino dimmer.

Adding pictures/video soon.