Traditional 0-10V for lighting control

[alexz]

0-10v controller how it works

Hi,
Can anybody explain in details how the traditional 0-10V dimming control for lighting works?

There are to inputs 0-10V+ and 0-10V-. What does it mean?
Wha do I connect to where and where do I change the voltage to dimm?

In particular I am looking into Atmel's kit "Dimmable Fluorescent Ballast".

The circuit is attached. I just want to understand it's operation and the input signals.

 

[plusminus]

software to control led 0-10v

This is only a part of the total schematic. Do you have them all?
Is this for fluoresent ballasts only? That will maybe explain ISO4.

In professional lighting the 0-10V control is not much in use anymore.
You compare a saw-tooth oscillator signal (which starts at each zero-crossing and runs to 10V as max in 10ms (50Hz mains)) with a comparator. At the output of the comparator you get a PWM signal with a duty-cycle in sync with your mains.
Now you can put the PWM signal (via a optocoupler) to a triac which regulates the power to the bulb.

There is something of this circuit to recognize in your circuit, 555 can be used as PWM generator, but the strange thing is the output(?) to ADC7 and PE2. Were is the controller part?

 

[alexz]

van dali naar 0..10v converter

Yes this is not the whole circuit, just the 0-10V part of it.
There is a PFC and inverter as well DALI and Swiss control.
I am just trying to understand how the 0-10V is working.
There are two signals I need to connect 0-10V+ and 0-10V-. what does it mean? what are they exactly? What should I connect to test the dimming?

PE2 is an I/O of a micro and the ADC7 is the ADC input of the micro.
The full schematic is attached

 

[plusminus]

Ok. I have found the original description of Atmel. I don't think this is a 0-10V control in the traditional way.
I think it works like this: Put a switch between 0-10V. At first the 555 will make a pwm signal that will goes up, if it is at a max it will reverse. Maybe the speed can be changed by changing the switch by a potentiometer. Opening the switch let's the pwm stay at the same duty cycle.

Do you have this demokit?
Please let me know if I'm right.

 

[alexz]

So 555 if for PWM.
Why do I need PWM?
why can it not be controled by a DC level straight to ADC?
And why do they convert voltage to current by this current source(Darlington) ?
Also, what are the isolators for?

 

[plusminus]

The isolators are for safety. The 10V is isolated from the rest of the circuit which is directly connected to mains voltage.

You need the PWM-signal to convert the analog (input) signal to a 2-level (on-off) signal which can be used to drive the led of the isolator. After the isolater the PWM signal is again converted to an analog signal by the RC network (R60, R61 and C35)

With the current source you mean Q9/Q10?

 

[alexz]

Yes the output of the current source is the input to the isolator and to ADC

 

[plusminus]

It is a regulated (by the 0-10V) current source / Current mirror.
You use a current source to get a nice lineair slope. (charging C36 with a constant current)

 

[alexz]

So what if I didnt have this current source?

 

[plusminus]

Then the 0-10V won't work. You can charge the capacitor also with a resitor, but the voltage curve follows a natural logarithm curve. (which looks not nice)

 

[alexz]

Why would it not work ?
And why does the ADC need PWM nad not a DC level?

 

[plusminus]

you need the pwm to transfer the signal over the optocoupler. A digital signal (PWM) is easier to transfer then an analog signal.
After the optocoupler you translate the PWM signal to an analog value. (R60, R61 and C35) (see my answer 08 Nov 2007 22:07) So you really use the ADC converter.

 

[alexz]

Why is it easier to transfer PWM through the optocoupler then DC?
The input voltage in the connector is DC isnt it?
The PWM is appearing after the 555 am I right?

 

[plusminus]

PWM is just on/off. Turn the LED on and the transistor will conduct.
The transfer ratio of an optocoupler is not linear. There are special optocouplers for analog signals but they are more expensive. So this looks like a strange solution but is very low cost to build.

The signal out of the 555 is the PWM signal and the input voltage of the connector is DC.

 

[alexz]

Why would you need on/off at the ADc input?
Why not to keep a constant DC presence there?
The other pin of the connector 0-10V + serves as on/off doesnt it?
Which is connected to an I/O of a micro through another optocoupler

 

[tom_hanks]

if you see the circuit...it is asking for a voltage between... 0-10V

and J5-pin3 is positive & J5-pin4 is negative wrt to pin3...

it is not asking two different voltage...


for other quiery..

remember Lamp,LED are current dependent device not voltage...
hence in short stable voltage donot give a proper result...

tc,
tom

 

[alexz]

Yes it is not asking for a voltage difference.
But what exactl is it asking for?

 

[tom_hanks]

connect positve of supply to J5-pin3 i.e +10Volt

negative/GND to J5-pin4.....

 

[p_g_18]

The transfer ratio of an optocoupler is non linear. There are special optocouplers for analog signals but they are more expensive.

 

[alexz]

connect positve of supply to J5-pin3 i.e +10Volt

negative/GND to J5-pin4.....

Are you sure?
So how would you control the dimming then?
I thought pin 3 is +10V or zero to indicate the 0-10V control is present, and the micro knows it by reading the I/O pin.
Pin 4 I thought is for dimming, to change the voltage(dont know the range) there isnt it?