Jump to content

Demux not dropping to 0v


Recommended Posts

We've just installed some IGBT dimmers for control of GU10 LED house lights (retrofit allowing existing fittings and wiring to be used). These are from 0-10V control and have an optional in-built dimmer should the attached fixtures not dim correctly to 0V. The dimmers can be either fed from a Demux or a variable Pot adjusting the voltage. When we use a Pot, we get a pretty nice dim down to just above off then a snap at the last 1-2%. This is perfectly acceptable. However when we use the Demux we purchased, we are unable to dim below 6% as the demux itself won't reduce it's output voltage below 0.6V. I have checked the unit isn't in 1-10V mode as when it is set, it outputs a perfectly smooth 1V at the bottom and 10V at the top.


What I'm after is a way to effectively reduce the voltage through the dimmer's 0-10V inputs. I don't need the top 20% at all so could happily live with something that reduces the effective output down to 0V to 8V say. I've got a regulated 15V PSU feeding the Demux which I can take power from if required.


I've tried a resistor inline with the positive terminal along with a simple potential divider circuit with a pair of 10K resistors as proof of concept. In both cases, perhaps counter intuitively, the measured voltage across the terminals actually increases up to 1.2V ish.


The dimmer positive control terminal is also a voltage source of 10V so I think I may need to put a transistor between this and ground and drive the gate of that with the demux output? I'm a bit rusty with my electronics though!


Any thoughts would be appreciated.



Link to comment
Share on other sites

Try putting a 1k pulldown resistor to gnd on each dimmer input. Demuxes often have diodes on the outputs which can cause things like this.


(what model of demux is it? Are you measuring the voltage with it connected to the dimmers?)

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.