Reduce 1-10V dimmer output voltage - Page 1
Forum section: electronics / beginners

author: mullet
author_rank: Newbie
timestamp: November 20, 2017, 04:14:12 pm
content: 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 examplehttp://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

author: Zero999
author_rank: Super Contributor
timestamp: November 21, 2017, 06:58:35 pm
content: It's not a transformer but a power supply with a constant current output,Using a module for the 0 to 10V control seems like a strange thing to to. Normally a 100k potentiometer on the dim input. is all that's required. The minimum brightness is determined by the driver module. If it can only dim down to 10%, then reducing the dim voltage below 1V will not make any difference.

author: ogden
author_rank: Super Contributor
timestamp: November 21, 2017, 07:44:40 pm
content: Quote from: mullet on November 20, 2017, 04:14:12 pmDepends on dimmer. If it is active dimmer able to deliver enough current for let's say 5K resistor on the output (between + and - of the output) still giving 10V on the output when set to 100%, then you can get away with resistor divider or just trimpot.  using resistors you cannot gain w/o losing. in case you gain low end, you most likely lose max power  Series resistor as you already noticed will not help 4sure. If it is not able to deliver enough current then things get complicated (yet still solvable) but then I would suggest you to throw particular dimmer away and use as Meanwell Say in their application note: "PWM signal and resistor type of dimming is rather straightforward and not the scope of this article."Would be nice if you test led driver (don't call it transformer please) using some other voltage source able to deliver whole 0.000 ... 10V range without trickery.

author: mullet
author_rank: Newbie
timestamp: November 21, 2017, 07:53:43 pm
content: Quote from: Hero999 on November 21, 2017, 06:58:35 pmNoted. I know there are options to control the dimming but I already have the 1-10V dimmers in place and they are only controls available from the Schneider series we are using. As said, the application note from Mean Wall actually says that the minimum dimming level is determined by the voltage and should go down below 1V (to 0.57V or so).

author: mullet
author_rank: Newbie
timestamp: November 21, 2017, 07:59:01 pm
content: Quote from: ogden on November 21, 2017, 07:44:40 pmI know it would be a lot easier with correct components (I really should be using the PWM series transformers from Mean Well instead of HLG series to get better dimming) but these are the things basically I'm stuck with. I think I try to come up with a voltage source of 0.6V or so and test the driver with this voltage. Then I would atleast see if this is something I'd like to pursue further. The dimmers in question (1-10V Renova series from Schneider) cost a ton and throwing a bunch of them away and replacing them would be a waste.

author: Zero999
author_rank: Super Contributor
timestamp: November 21, 2017, 08:42:52 pm
content: Quote from: mullet on November 21, 2017, 07:53:43 pmThe application note you posted refers to both 1V to 10V and 0 to 10V dimmable LED drivers. They are not the same thing. You can't just connect 0 to 10V to a 1V to 10V driver and expect it to dim all the way down to 5.7%. 1V to 10V dimmers are not specified to do anything, when given a voltage below 1V at the input. Unfortunately, the data sheet you linked to is the HLG-150H, a 1V to 10V dimmer, so even if your dimmer controller outputs less than 1V, it won't dim below 10% brightness.Quote from: mullet on November 21, 2017, 07:53:43 pmThe modules you posted the data sheet for, already do support PWM dimming. They just won't dim to below 10% of the full brightness. In short, the only way to get below 10% brightness is to replace the HGL-150H LED drivers, with ones which support 0 to 10V dimming.

author: mullet
author_rank: Newbie
timestamp: November 26, 2017, 04:37:25 pm
content: Quote from: Hero999 on November 21, 2017, 08:42:52 pmThanks for your help. With PWM, I meant PWM output, not input. For examplehttp://www.meanwell.com/productPdf.aspx?i=308AFAIK, they dim the leds with a better technique which also provides a better dimming range.As said, I've read the datasheet of the HLG driver and I know it kind of says that the dimming range starts from 1V (= 10%). I actually tested this with a 100k potentiometer. The datasheet says, that with a 100k pot, the 10% brightness would be with 10k resistance. By testing with a pot only, I get a better dimming range. It actually goes down to 3k or so before the leds die out. It looks much better on the darker end of the dimming range with a simple 100k pot than with the 1-10V dimmer.By looking at the datasheet only, similarly, it would suggest that with the 100k potentiometer the range from 3k ... 10k would have no effect but still, it does. I'd really like to test the driver by providing a control voltage range below 1V. To go back to my original question, would there be a simple circuit to achieve this with a 1-10V dimmer?

author: ogden
author_rank: Super Contributor
timestamp: November 26, 2017, 05:39:11 pm
content: Quote from: mullet on November 26, 2017, 04:37:25 pmPotentiometer + multimeter. Set dimmer on 10V and to vary output voltage - use potentiometer. Read actual voltage using multimeter. 2nd option - voltage divider using 2 resistors. For example 10k + 90K resistor will divide voltage 10 times and resulting output voltage range would be 0.1V to 1V.