Hardware Components for 0-10V Input

[Tico]

Please excuse my electrical engineering ignorance. I'm in need of some guidance for a 0-10V sensor input to the miniserver that will be used to control a lighting circuit.

I intend to use the 24V supply of the Miniserver via Cat6 to an appropriate wall mounted potentiometer. I don't have a circuit diagram to refer to, so if anyone has guidance, I would welcome it.

A few questions -

1. I assume I will need two pots? One to drop the voltage initially to 10V before the second pot. The second pot will be the wall mounted controlling device. I'd like to get the full range of sensitivity throughout the available movement of the pot.

2. What value of resistances are needed to have 10V at one scale of deflection on the pot2 and 0V at the other scale of deflection?

3. The Cat6 runs about 30 metres through the house in proximity to some mains cables. I've done my best to avoid close proximity with the cables and have crossed them at right angles. What are people's experience with voltage fluctuations on the 0-10V input in a residential environment?

Is this diagram remotely correct?

[Jedi Tek'Unum]

The lack of response is likely because this is not as simple as it seems. I'm not an electrical engineer but I'll make a few observations.

I personally wouldn't run inputs like that through my house. I wouldn't go further than within a cabinet or to a nearby cabinet. My assumption (possibly incorrect) is that the input doesn't have a lot of protection and probably isn't isolated. One mistake (shorting to 24V or, even worse, line voltage) will fry an expensive piece of equipment.

I assume that you've got pot 1 there so that you can compensate for voltage loss over the cable run? (Besides the obvious of being a way to drop the voltage.) If so, I don't think you're going to see a noticeable voltage drop over 30m since the current here will be almost nothing. Pot 1 could be replaced with a voltage regulator or a voltage divider circuit (consisting of 2 fixed resistors). At a minimum I'd suggest dropping the supply voltage down to something that can't overload the input before going to the pot (I have no idea what the tolerance is on the analog input - but I would think 12v would be a lot safer). I'd note that even if slightly less than 10V max is seen that you can compensate for that in software settings - you're not going to miss a few 10ths of a volts range.

Your circuit won't have any current of consequence so the resistance value of the pot(s) isn't all that important. The only real concern is too small a value could potentially draw to much current. Just look up a basic ohm's law calculator (http://www.ohmslawcalculator.com/ohms-law-calculator). Put in 24V and the resistance you're thinking of and it will tell you how many milliamps. I'd aim for less than 1ma.

As I suggested, a better solution would be a fixed resistor from 24V to pot 1. The resistance of pot 1 would be the other part of a voltage divider. Try http://www.ohmslawcalculator.com/voltage-divider-calculator to find values. Your challenge will be to find the right balance of available fixed and variable resistors and target current.

[Andras]

How about a 1-wire sensor? I believe the DS2438 (smart battery monitor) is able to monitor voltage, albeit in the 2.4V-10V range.

[Duncan]

the analog 0-10v inputs of the server and extensions are 24v tolerant - they can be used at 24v digital inputs so no need to worry about it

bearing in mind that 0-10v is controlling a lamp so 1%=0.1v change, you might find that induction and variations in voltage will result in the light changing its brightness/flickering which may well be annoying.

why do you need an analog control of a lamp brightness via 0-10v? there are other ways of achieving dimming such as 2 buttons dimming up/down

[Tico]

Thanks all for the inputs.

The device (a MiLight) has a wifi app with control of a number of features by sliders. The interface to the light is Loxone => Node-Red => MiLight WiFi iBox2 Contoller.

The analogue control is not essential. The idea of a rotating knob seems a bit more intuitive for control of Brightness, Kelvin and Saturation. And I really want a physical control for convenience.

I was also planning to have a digital input directly adjacent to the pot to cycle through various modes. The option of 2 buttons for dimming is certainly viable and a good idea.

There's enough cores in the Cat6 to experiment with both options if induced voltages prove to be an issue. I think I'll definitely use a 10V voltage regulator in lieu of Pot 1.

Regarding the 1-wire sensor idea - I don't think the polling rate of the 1-wire could provide sufficient granularity for movement in the pot. You would need to rotate the pot - wait - rotate - wait - etc...

And if anyone has knowledge on MiLight-NodeRed, here's another question -

Milight integration with Loxone

[Jedi Tek'Unum]

Possibly interesting circuit for S Curve pot.

[Tico]

Thanks.