1-10V fluorescent dimming

ban-all-sheds · 10 Aug 2010

1) Does anybody know of a controller which does on/off as well, e.g. using a pot with a push on/off switch?

2) If not, are the controllers anything more than a (47kΩ??) potentiometer? Could I just get one with a switch and put it on a blanking plate?

3) How susceptible is the control wiring to interference, how much screening needed?

4) Yes, I am too bl***y lazy to Google for this info.

Steve · 10 Aug 2010

ban, are you thinking about buying one of those PL downlights from qwikfast and transplanting its ballast?

flameport · 10 Aug 2010

The 'dimmers' are just a potentiometer, so no problem to make one in a box with a switch or whatever. The voltage to operate the dimmer circuit is created in the ballast itself.

When the resistance is lower, the light is dimmer (so ballast terminals o/c = full on, terminals shorted together = off.)

aptsys · 10 Aug 2010

If you buy one of the signal amplifiers that provide the 1-10V output from their own power source, you can use whatever pot you want, and can drive tens of ballasts without having to buy pots with higher power ratings.

The susceptibility of the signal lines depends on the impedance of the source, but unscreened cables are fine for normal distances (IIRC up to about 25m). The 1-10V control lines aren't SELV though remember, so you must still use mains rated wiring.

ban-all-sheds · 10 Aug 2010

Steve said:
ban, are you thinking about buying one of those PL downlights from qwikfast and transplanting its ballast?

Not really, as in no definite plans - dimmable ballasts aren't cheap, more a case really of "what would I need to do if....".

flameport said:
The 'dimmers' are just a potentiometer, so no problem to make one in a box with a switch or whatever. The voltage to operate the dimmer circuit is created in the ballast itself.

When the resistance is lower, the light is dimmer (so ballast terminals o/c = full on, terminals shorted together = off.)

Am I right about the 47kΩ? Presumably "o/c" in practice means "resistance > some-limit-or-other", which you'd want to be the max resistance of the pot and not a lot more - using one of several MΩ would have them go to full brightness almost immediately.

Linear or log?

Should I drive people mad by using a multi-turn pot?

aptsys said:
If you buy one of the signal amplifiers that provide the 1-10V output from their own power source, you can use whatever pot you want, and can drive tens of ballasts without having to buy pots with higher power ratings.

How would that work with a ballast that produces its own voltage?

The susceptibility of the signal lines depends on the impedance of the source, but unscreened cables are fine for normal distances (IIRC up to about 25m).

Not a problem in Bas Towers.....

The 1-10V control lines aren't SELV though remember, so you must still use mains rated wiring.

Or keep them segregated?

ColJack · 10 Aug 2010

I may be getting confused between my electronics education and my electrics education, but a potentiometer is usually connected to a source at both ends ( ie 0V one end and 10V the other ) and the "wiper" is the output..

how this would work for a 0-10V dimmer I can't say I've ever looked into it..

the one time I worked with 0-10v dimmable stuff was a "ring" of suspended fluorescents over what would be a board room table..

we had "push to dim" modules that took mains in and put out 0-10V depending on the amount of time you pressed and held the button..

if it's only 2 wire "0-10V" then I'd say it either accepts an external 0-10V source, or it's actually looking for up to a known resistance, which should be mentioned in the equipment documentation..

electronicsuk · 10 Aug 2010

ColJack said:
I may be getting confused between my electronics education and my electrics education, but a potentiometer is usually connected to a source at both ends ( ie 0V one end and 10V the other ) and the "wiper" is the output..

how this would work for a 0-10V dimmer I can't say I've ever looked into it..

I'd say you're right. It's possible to connect the wiper to one of the outers and be left with two terminals of variable resistance, more like a rheostat, but as BAS mentions a 0-10v dimmer I think it's fairly safe to assume that the two outers should be at 0 and 10v respectively with the wiper as a variable voltage output.

Some manufacturers may have their own ideas about how the system should work, but if the dimming level is based on application of a set resistance between two terminals then this most certainly is not a true 0-10v control system.

ColJack · 10 Aug 2010

after a bit of quick googling it seems that most "0-10v dimmers" actually take a mains connection and output the required 0-10v themselves, so not just a straight potentiometer..

ban-all-sheds · 10 Aug 2010

ColJack said:
0-10V

electronicsuk said:
BAS mentions a 0-10v dimmer ..... if the dimming level is based on application of a set resistance between two terminals then this most certainly is not a true 0-10v control system.

ban-all-sheds said:
1-10v

AdrianUK said:
I think the problem is that the dimmable ballasts in flories (or at least the ones Ive met) dont work with a 0-10V in the same way that a dimmer pack does.

The 0-10V connection on the ballast DOESNT expect or want a 0-10V input. What is required is a variable reistor between the '10V' terminal to the '0' terminal to pull it down. The unit provides its own power supply and dims in proportion to the current drawn between the terminals. It wont work with an anaolgue lighting desk.

flameport said:
AdrianUK is correct.
The lights you have will contain 1-10v ballasts which require a current sink to operate. (a resistor, or more usually an electronic control unit)
A typical lighting desk will be 0-10v and provides a variable voltage output (i.e. a current source).

See the last page of this: http://www.mkelectric.co.uk/Documen...Specifications/T18 GRID PLUS Tech 590-595.pdf

SUNRAY · 10 Aug 2010

flameport said:
The 'dimmers' are just a potentiometer, so no problem to make one in a box with a switch or whatever. The voltage to operate the dimmer circuit is created in the ballast itself.

The 'dimmer' (or dimmer pack) is the electronic unit connected between mains and the lamp (or other load), it has a control input which requires a variable control voltage. A common way of achieving this is to use a fixed 10v supply and a potentiometer to make it variable.
The 10v supply is most certainly not always created in the dimmer and sometimes it can be a real pita 'finding' 10v (or 12v) in a system to supply the pot.

flameport said:
When the resistance is lower, the light is dimmer (so ballast terminals o/c = full on, terminals shorted together = off.)

If you are describing a simple 2 wire circuit between the pot and the electronics then its not a 0-10v system.

edit - it took several hours to make my reply and I see others have made the points in the meantime

ban-all-sheds · 10 Aug 2010

SUNRAY · 10 Aug 2010

ban-all-sheds said:

Yes and the 'dimming controller' SUPPLIES 0-10v to the 'ballast' OR its not a proper 0-10v system [or 1-10v as shown in the drawing]

aptsys · 10 Aug 2010

Most of these ballasts have a 10V internal reference connected through a resistor to the "+" control line, designed to supply 0.6mA if shorted to ground.

The "+" control line is also internally connected to the actual circuitry which controls the brightness of the tubes.

The "-" control line is connected to ground. So when you have your resistor connected between the two control lines, you drag the voltage down with decreasing resistance. The internal resistor acts as the other half of the potential divider.

If you supply an external voltage to the control lines, you just have to make sure that they can sink greater than 0.6mA and overcome the effect of the built-in resistor.

I think almost all of these ballasts are 1-10V rather than 0-10V, and you cannot take the tube to 0% brightness without turning off the mains.

(I'm currently making my own microcontroller based controller for these ballasts)

Spark123 · 11 Aug 2010

The last ones I installed had a proper switch with pair of potentiometers in series, one PCB surface mounted in the back of the dimmer and one normal so one controlled the dimming function and the other controlled the minimum brightness.
iirc they are linear pots.
Setting both to zero didn't extinguish the lamp.
The fittings were also switched normally.

aptsys · 11 Aug 2010

They're usually log pots because of the response of the human eye.

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1-10V fluorescent dimming

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