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In-wall rotary 0-10V potentiometer dimmer switch + RGBW module


Question

 

I already read

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 dealing with classical in-wall rotary dimmers and the Fibaro dimmer2 module, but I think the following combination would work better. Your advice would be very much appreciated.

 

The RGBW dimmer (FGRGB-101 / FGRGBWM-441) accepts 0-10V analog voltage input to control 12/24V DC low voltage lamps (LEDs or halogens):

 

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1/ Can a cost-effective classical 0-10V rotary dimmer pilot the RGBW module which would then dim the lights accordingly to the input rotation? Like this one for example:


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2/ If it works that way, how would the knob rotation of the 0-10V potentiometer behave with the direct control of the RGBW module from the Fibaro interface on a computer or mobile device? Suppose you have turned the potentiometer half the way to dim the lights up to 50%. Then you open the Fibaro app and switch off the lights. Do the lights switch off? If they are switched off, the potentiometer is still at 50%… What would happen then when you turn the potentiometer again?

 

3/ To prevent this apparent weird behavior, I looked for 360-degree (i.e. continuous rotation with no stop) optical or Hall effect absolute rotary encoders with 0-10V analog output, as a replacement for classical potentiometers:

 

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But in this case while the voltage varies linearly according to shaft rotation from 0V/0° to 10V/359° (1 turn) it also suddenly drops to zero at the beginning of the second turn (the voltage drops from max. 10V at 359° to 0V at 360°, just one degree further) like this:


10bit-analog.gif

This graph is for 0-5V but 0-10V acts the same way.

 

Not very handy for lights. It would have been more useful if the voltage stayed at maximum value of 10V after 360°.

 

4/ I then searched for incremental rotary encoders instead of absolute rotary encoders, but it seems an incremental version with 0-10V analog voltage output doesn't exist. 

 

Your thoughts?

 

 

Edited by flux_capacitor
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hi

you read my mind.......

i am looking at doing exactly this myself but am using a different approach.

ive done a small trial which seemed to have worked involving 'voltage divider' method.

i set the rgbw as 'output/input' type and choose device as 'input' and 'other'.

i then used 4 sets of resistors of different values to create different voltages between 1 and 10v and applied them to the inputs. the result was different light intensities depending on voltage level.  if i removed the voltage then the relevent channel went to full brightness so you have to keep the lower voltage connected to keep at a certain level.

now to take 1 step further i have ordered some rotary switches and then going to create a 11 positions with voltage levels 0-10v.

hopefully this will then enable manual control of the rgbw lighting instead of app.

watch this space......

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Hi all, hope this helps. The input required on IN 1 - 4 is purely a voltage signal. There should be little current involved. I would put something like the image supplied. R1 needs to be a high resistance to prevent excess current through the potetiometer then the voltage will vary on the potentiometer to trigger the module. I have a RGBW module and have some lights on the way. I will try and rig something up and get back with values. If you want to try yourselfe then it's back to Ohms law for you V=IR. Glad I went to school, knew it would come in handy one day.

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Hi

My thoughts were to use a potentiometer to vary the voltage but i couldnt get the correct balance betweem the r1 and suitable range on the potentiometer. also whether the increments will be linear or not, ie dimming quickly when u just start to turn the potentiometer and then too slow when u are near the high resistance end. also another factor was if the voltage output crept above the 10v mark.

My switches arrived and i chose a fixed r1 of 5600ohm and then 11 resistors starting at 10 ohm through to 22k ohm. this gave me 0.02v to 9.5v.

Following is what i used.

Power supply 12v

R1 5600 ohm

R2 on different switch positions:

1-10ohm 0.02v

2-470  0.93

3-1000  1.83

4-1500   2.54

5-2200   3.38

6-3300  4.45

7-4700   5.48

8-6800   6.58

9-8200   7.13

10-15000    8.74

11-22000   9.57

 

Will post a video on my channel once its fully installed hopefully in next 2-3 weeks as the kitchen is still being plastered.

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  • 47 minutes ago, morpheus75 said:

    My thoughts were to use a potentiometer to vary the voltage but i couldnt get the correct balance betweem the r1 and suitable range on the potentiometer.

     

    Did you specifically used a 0-10V potentiometer, or just ant standard voltage-varying potentiometer? 

     

    also whether the increments will be linear or not, ie dimming quickly when u just start to turn the potentiometer and then too slow when u are near the high resistance end.

     

    Seems you encountered the usual issue using LEDs with a linear pot, which doesn't play well when dimming around the lowest power range. A logarithmic potentiometer should be used instead of a linear one (it corrects this behavior, dimming slower i.e. over more increments around low dimming, and quicker around max range). I'm not sure about what version(s) you used, since you stated "whether the increments will be linear or not" so maybe you tried both?

     

    also another factor was if the voltage output crept above the 10v mark.


    Which points to my first question above about the 0-10V or standard potentiometer.

     

    My switches arrived and i chose a fixed r1 of 5600ohm and then 11 resistors starting at 10 ohm through to 22k ohm. this gave me 0.02v to 9.5v.

    Following is what i used.

    Power supply 12v

    R1 5600 ohm

    R2 on different switch positions:

    1-10ohm 0.02v

    2-470  0.93

    3-1000  1.83

    4-1500   2.54

    5-2200   3.38

    6-3300  4.45

    7-4700   5.48

    8-6800   6.58

    9-8200   7.13

    10-15000    8.74

    11-22000   9.57

     

    Will post a video on my channel once its fully installed hopefully in next 2-3 weeks as the kitchen is still being plastered.

     

    I'll look forward to that!

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    Hi

    i didnt use a potentiometer in the end. i decided on a rotary switch.

    see diagram below. the 11 resistors i used for R2 are detailed above but for simplicity i showed 7.

    R1 is 5600 ohm

    I made 4 of these for the 4 inputs IN1 to IN4 to control the RGBW channels independently

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    Edited by morpheus75
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  • On 28/10/2016 at 6:43 PM, morpheus75 said:

    Hi

    i didnt use a potentiometer in the end. i decided on a rotary switch.

     

    I understand your point and think your new setup is a brilliant idea. But I was asking if the problems you listed about using a potentiometer was either a consequence of some thoughts you had, of if you had ever reached the milestone of building a working prototype with such a conventional or 0-10V potentiometer, showing the voltage problems IRL, before switching to the rotary switch project?

     

    I am interested about the stage of your preliminary project when you ran into trouble with the pot, to see if the issues could be circumvented otherwise.

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    To be  honest the potentiometer i never actually tried it. its all from prior knowledge.

    also i couldnt find one that was around the 22k ohm mark. found some 10k or 47k but then trying to find a fixed for R1.

    I would have preferred to use the potentiometer as i would get a smoother response and more options rather than the 11 steps i have chosen.

    I will be posting pics and video as soon as i install in kitchen.

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    Try a 100k linear pot and a 20k resistor. That should give you a voltage variation of 0-10V on a stable 12V supply. I have tried it but not with the RGBW module yet. It varies the voltage perfectly. If the module inputs only require a voltage variation and no current it should do the trick. 

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    Thanks for values, saves me trying to work out. just found my local maplin stores have them in stock. so will try and get.

    the potentiometer will definitely be a neater finish than the rotary switch on the inside. 

    Will try it and report back.....

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  • Cool! I assume this will do the trick, as what have been said: V = I R, and most important, for voltage dividers: 

     

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    I needed to refresh my memory from school years… Keep up the good work guys :)

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    The input of a RGBW module behaves like a 18k resistor connected to 10.5 Volt. That resistance facilitates the use of switches: simply connect them between IN and GND, the 18k will pull the input "high" if the switch is open. But this resistor will alter your resistive divider (potentiometer)...

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  • I am not sure if the previous post by 

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     prevents the projected scheme to work, or if this is some difficulty that can be overcome.

     

    Whatever, I see a potential additional issue using a linear potentiometer. As said before dimming LEDs lower often goes too fast and is imprecise, and increasing light intensity to the maximum seems to take forever. 

     

    Using 12V DC of input voltage with a fixed 20k resistor and a varying 100k linear potentiometer as suggested by

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    , as a voltage divider assembly, the output voltage will indeed not vary linearly. Turning the knob counterclockwise from maximum intensity (360°) to switching off the lights completely (0°) will output a voltage variation according to the following diagram:

     

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    It will act like an old antilog potentiometer. But ideally, the curve would vary linearly, or better according to a log but the other way, i.e. faster near 360° and slower approaching 0°.

     

    Modifying resistances (to say 10k for the resistor and 50k for the potentiometer accordingly) would not change anything, as the output voltage would follow the exact same 0-10V variation according to the same curve.

     

    That's why I think a logarithmic (audio taper) pot should be used instead, or in a combination with a LED driver having a logarithmic or square dimming curve.

    Edited by flux_capacitor
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    Hi,

    This might improve the 0-10v range. Use a 10v zener diode to try and stablise the 10v to the top of the pot. I found that my 12v PSU actually delivers nearly 13v. zeners can be bought for a matter pf pennies from Maplin.

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  • As it seems I couldn't complete my own project due to electrical limitations (too much current over a cable too long, my switch and the LEDs being in two opposite sides of the room), I was wondering if I could uncouple the two parts, i.e.:
    - low voltage analog control from one side (12V DC RGBW module + 0-10V potentiometer) 
    - high voltage lighting (Dimmer 2 module + LEDs) from the other side of the room. 
    Using wireless sync. I started a

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    to know if this is possible. 

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    hi

    just received the pot's and 20k resistors and have created the voltage dividers and it does work.  However i can confirm that flux_capacitor is correct in the graphical representation of voltage/resistance.  This is what i had also predicted earlier aswell so im going to go back to the rotary switch method with the multiple resistors as mentioned in my earlier post. That method enabled me a close to 10% per switch difference.

     

    Now i need help in syncronising 3 of these modules.

    Im controlling 1 module using this method but i want all 3 to respond.. any thoughts please.....?

    thanks

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  •  

    19 minutes ago, morpheus75 said:

    However i can confirm that flux_capacitor is correct in the graphical representation of voltage/resistance.

     

    Can you tell us if the potentiometer you tried is linear of if this is an audio pot (logarithmic)?

     

     

    Now i need help in syncronising 3 of these modules.

    Im controlling 1 module using this method but i want all 3 to respond.. any thoughts please.....?

    thanks

     

    I think you need to associate the three modules together. Since you have an HC2, you can follow

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    .

    Edited by flux_capacitor
    2nd part to answer question
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    Hi 

    Its a linear pot i got from maplin

     

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    Re sync im trying to sync the rgbw with each rather than with a dimmer module. 

    So will use the rotary switches connected to 1 module but have 3 modules changing the colour identically. 

    Thanks

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  • That's why I think an audio taper pot is preferable, because its logarithmic curve would fight against the antilog variation of the voltage divider, so their combination may result in a linear variation.

     

    Dimmer association is about the same as RGBW association. See 

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    the manual was great thanks but it only sent on/off commands and not the colour commands like i wanted but i tried something else and that worked a treat.

    i connected all 3 modules to the 1 power supply unit and then connected IN1 to IN4 all together in parallel, ie sending the same voltage level to each module.

    this then effectively syncronised all 3 of the modules without the use of scenes and/or associations.

    the only thing now i need to do is get a 12v 15a power supply, as i was using 3 of 12v 5a supplies.

     

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  • Question: when the knob is completely positioned to the left (so the lights are switched off) the potentiometer resistance is maximum (100K) and output voltage of the voltage divider setup is minimum (0V) or the opposite: resistance is minimum at zero position and increases with CW knob rotation?

     

    EDIT: Dont bother. In the voltage divider setup presented above, we can use either the CW or the CCW pin of the potentiometer (using it as a rheostat) so we can choose the variable resistance direction.

    Edited by flux_capacitor
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