Hi all,
I have a question which I hope the solution is a simple one. I'm building a cottage with some LED strip based lighting fixtures. I have a number of dimmable led drivers from Mean Well HLG-range, for example
http://www.mouser.com/ds/2/260/HLG-150H-SPEC-806071.pdfThe drivers have a 3-in-1 dimming input which accepts various different control signals to control the dimming level of the 12V led output. I have a number of 1-10V dimmer knobs attached to the drivers. The dimmers and drivers are connected as pictures in the attached wiring diagram.
I've managed to get everything to work except for one problem. The dimming range of the dimmer is quite low. When I set the dimming level to max, the strips are nicely bright but when I adjust the level to the minimum, the strips still produce much more light that I'd like them to produce.
The dimmer knob has two trimmers to control the min and max voltage of the output. I have adjusted these trimmers to the best possible setup but still, the dimming range is not ideal. I've read from the web that the ideal dimming input voltage range depends on the load of the transformer (i.e. if the transformer is loaded with too little number of leds / watts, the dimming range is much less than 1-10V). I've adjusted one transformer with the trimmers and metered the dimmer output. It produces a dimmer control voltage of ~ 1 - 3 volts when the dimming range is the best I can get.
I stumbled upon this application note from Mean Well:
http://www.meanwell.eu/ExclusivePDF/DIMMING-NOTE.pdfIt basically says that the dimmer input of the transformer might support lower control voltages (0 - 10V). The application note says that the dimming circuit should go down to about 0.57V for minimum brightness. This got me thinking that if I could somehow lower the voltage of the dimmer knob with for example half a volt, I could produce something like 0.5V - 9.5V from the dimmer and adjust it with the trimmers for a better dimming range.
I tried experimenting with resistors a bit with no luck. The Mean Well datasheet says that "Dimming source current from power supply: 100 microamps (typ.)". I did my calculations and put a 10k resistor (in series) between the dimmer knob and the transformer and noticed that the voltage metered from the dimmer input actually rose with one volt. I think this is logical if the transformer has a constant draw of 100 microamps from the dimmer so from Ohm's law as V=RI and I increase the resistance the voltage actually rises. I experimented with a simple voltage divider by adding another 10k resistor between the (+) and (-) of the dimmer input but then the voltage went all awry (it dropped a bit but the dimmer adjustment had very little effect on the actual dimmer voltage produced).
So, my question basically is that is there a simple way to drop (or halve) the 1-10V control voltage level of the (standard) 1-10V dimmer I could try?
Thanks a ton in advance,
Marko