Led Lighting Problem

[333rocky333]

obvious to you john, i get confused with it all and so do people I encounter buying them.
some see the 12 volt stamped on the thing and judge it to be like a 12 volt transformer which most of us use for LV lighting
(Terminoligy used in the lighting world)
a lot of the constant current ones that I fit tend to not have a set voltage stamped on, but rather **volts to** volts which when seen rings bells to most people.

 

[JohnW2]

obvious to you john, i get confused with it all and so do people I encounter buying them.

It's the theory which is obvious to me, as it should be to most people here. As for the products we are talking about, I am as confused as anyone else! ...

some see the 12 volt stamped on the thing and judge it to be like a 12 volt transformer which most of us use for LV lighting (Terminoligy used in the lighting world)

Since I totally sympathise with your use of 'common usage' terminology, I'll let someone else tell you off If it has "12 volt" stamped on it, it must presumably be a (fairly!) 'constant voltage' supply - regulated to be 'constant' to a lesser (or no!) or greater degree!

... a lot of the constant current ones that I fit tend to not have a set voltage stamped on, but rather **volts to** volts which when seen rings bells to most people.

As I said, that's how it has to be. A constant-current source will apply whatever voltage it has to apply to the load (within its range of capabilities - the "**volts to** volts") in order to get the specified ('constant') current.

What may cause some confusion is that a load may say that it requires a constant current source of, say, 1A and at that current it will have about 12V across it. In that situation, if one connects a 1A constant-current supply to that load, it should, indeed, put out about 12V to achieve that current. However, if you changed to different loads, that same source may have to put, say, 6V or 24V across the load to get the specified/required ('constant') 1A to flow through the load.

Kind Regards, John

 

[333rocky333]

I will read that and try to understand it tomorow, i need to learn this driver stuff urgently, but cannot find much usefull info

I think most of our stuff has either 350, 500 or 700ma on it

Stuff like this

Input Voltage 180 → 254 V
Output Voltage 2 → 25V
Operation Constant Current
Output Current 0.7A
Maximum Output Power 17W
Dimming Operation 1-10 V

 

[Mikefromlondon]

Seems like your low voltage source supply is not adequately rated to supply the inrush current demand of all the 6 lamps, it is most probably too close to your load requirement, and does not have the ability to supply a short term high current demand or this demand exceeds the designed limits, so it trips into safe mode (current foldback) and so unable to switch the other 3 lights apart from the first 3 lights that managed to switch on. (Those 3 lights most likely met their inrush demand just in time before the power supply applied a current fold back mechanism)

this means you only had 3 lights working and 3 not, so when you unplug one of the 6th light the current fold back mechanism resets, and full power is restored again, and now it will reapply further inrush current to the other 2 lights which will now switch on, so you have 5 lights working, and when you plug in the 6th the inrush current is now 1/6 and the power supply copes with that as other 5 lampos don't require inrush current as they are already operating at their normal current level, so all 6 lamps come on.

So either you use a dimmer control so that your inrush current is smoothly controlled and avoids the current fold back mechanism to trip, or you use a more beefier power supply to your lamps. (power supply also means low voltage transformer, LV electronic transformer, or some even call it a driver, essentially a driver is anything that controls power levels that includes current control or voltage control or both)

(Current foldback is a mechanism where many power supplies protect themselves from constant over load conditions as they can get very hot, so a current fold back drops their output way back, and can only resume full power upon sensing part load being disconnected, as an example it can trip in at say 1 amp load, and then not reset until the load goes well below 1 amp, not just barely below 1 amp, so in other words if it trips at 1.00amps it won't reset at 0.99amps and can do so when the current goes well below to say 0.5Amps (kind of hysteresis built in) )

 

[JohnW2]

I will read that and try to understand it tomorow, i need to learn this driver stuff urgently, but cannot find much usefull info ... I think most of our stuff has either 350, 500 or 700ma on it

Good luck. As eric is always saying, the difficulty is often in working out, from the labelling (or even 'spec sheet') what some of these drivers/power supplies/'transformers' actually do.

A load, like an 'LED' which needs to be driven by a constant current should (obviously) specify what the required constant current is, but also what (at least approximately) applied voltage is required to achieve that current. Hence, if the LED says "constant current source 500 mA, 10V), you need to use a a 500mA constant-current driver which has 10V within its range of 'capable' voltages - so, a 500mA 5V-15V constant-current driver would do, but, say a 12V-20V one would not.

You should not really attempt to use a constant current source to drive more than one load in parallel, since there is no guarantee of how the (total) constant current will split between the two or more LEDs. You can use a constant current source to drive LEDs in series if the 'total required voltage of the LEDs was within the capabilities of the driver - hence you could, for example drive two or three "500mA 6V" LEDs in series from a "500mA 10V-20V" constant current driver.

If dimming is involved, the whole thing becomes much more potential complicated and confusing!

Eric feels that constant current sources should be called drivers, and constant voltage ones 'power supplies' (or, heaven forbid.'transformers' or 'electronic transformers'). However, I don't think you can rely on manufacturers sticking to that convention.

Returning to the theory, in case it helps ... if you have, say, a "500mA, 5V-15V" constant-current driver, then it will attempt to put 500mA through any applied load, applying whatever voltage (within its range of capabilities) is necessary to put that current through the load. Hence, if the load is 10Ω, it will put 5V (10 x 0.5) across the load, for 20Ω it will apply 10V (20 x 0.5) and for 30Ω it will apply 15V - in all those cases, the current through the load would be 500mA (0.5A). However, since it cannot generate more than 15V ("5V-15V") if the load is greater than 30Ω, then the voltage will stay at 15V (can't go any higher), so the current will fall to below 500mA. So, in this case, it would be able (just) to run three 10Ω loads in series (total 30Ω, total voltage across the three at 500mA = 15V).

Kind Regards, John

 

[JohnW2]

Stuff like this

Input Voltage 180 → 254 V
Output Voltage 2 → 25V
Operation Constant Current
Output Current 0.7A
Maximum Output Power 17W
Dimming Operation 1-10 V

You have my sympathies - without reading some (decent) documentation, I, for one. would struggle to work out what to do with that!! At a basic level, it's a 700mA constant-current source with a range of 2V-25V, hence a maximum output power of 17.5W (0.7 x 25). It's the 'dimming operation' part of it that complicates matters. What that does, and how compatible its method of dimming would be with any particular LED is anyone's guess. The "Suitable for range of DC operation 176-264 VDC" is also rather interesting, although I imagine irrelevant!

Kind Regards, John

 

[musszzy]

Found a nice article that goes some way to explaining what occurs inside an led downlghter especially when dimming.
http://www.ledsmagazine.com/article...-issues-to-ensure-compatibility-magazine.html

The application i have is a pelmet with 6 led downlighters so i have decided at this stage to not dim the downlighters (until the technology is clearer) and to use a concealed rgbw led strip around the pelmet for softer lighting ....(and i can also then have mood lighting .
There has been some great explanations/theories (and a lot of science) on this thread and i am extremely grateful.

Thanks to all
Dave

 

[333rocky333]

Stuff like this

Input Voltage 180 → 254 V
Output Voltage 2 → 25V
Operation Constant Current
Output Current 0.7A
Maximum Output Power 17W
Dimming Operation 1-10 V

You have my sympathies - without reading some (decent) documentation, I, for one. would struggle to work out what to do with that!! At a basic level, it's a 700mA constant-current source with a range of 2V-25V, hence a maximum output power of 17.5W (0.7 x 25). It's the 'dimming operation' part of it that complicates matters. What that does, and how compatible its method of dimming would be with any particular LED is anyone's guess. The "Suitable for range of DC operation 176-264 VDC" is also rather interesting, although I imagine irrelevant!

Sorry to impose on your thread musszzy

Thanks john very helpfull and apreciated.

The driver in the pic is supplied with lamps in two fittings we use.
like most fittings I see, they quote the current, but rather than any voltage they state the wattage.
in the example above they quote
9.5 watt at 350ma
18 watt at 700ma
so am i correct in thinking that equates to
9.5 w = 27.14 volt
18 w = 25.7 volt
Even though they are slightly out of the stated voltage range.

Am i right also to think, when one fails, theoretically they can be replaced with any driver rated
350 ma fixed with voltage range including 27.14 volts for the 9.5w version
700 ma fixed with voltage range including 25.7 volts for the 18w version

In addition on other fittings, if i failed to know the lamp wattage or voltage, but the failed driver stated 300ma, could i simply measure the output voltage of a same working fitting and if it measured say 18 volt, would it then be the case of just getting a 300ma fixed driver with a voltage range that includes 18 volt.

Sorry for the questions, but im trying to establish if their is a best driver with a common wide range, to help first time fix repairs on retail lighting.
Things are getting clearer now

 

[JohnW2]

Thanks john very helpfull and apreciated. The driver in the pic is supplied with lamps in two fittings we use. like most fittings I see, they quote the current, but rather than any voltage they state the wattage.
in the example above they quote
9.5 watt at 350ma
18 watt at 700ma
so am i correct in thinking that equates to
9.5 w = 27.14 volt
18 w = 25.7 volt
Even though they are slightly out of the stated voltage range.

You're welcome. Yep, your calculations are correct. However, what is the "9.5 W at 350 mA" all about. It's a 700 mA constant current source in your pic. Are they talking about putting two of those fittings in parallel, fed by a single 700 mA driver? If so, as I said, that's a little iffy, since one cannot necessarily guarantee that the 700 mA will be shared exactly equally between the two lights. However, if that's what they're suggesting then I presume that 'they' think/know that it's OK! ... or are you perhaps talking about two different drivers (one 350 mA and the other 700 mA)?

Am i right also to think, when one fails, theoretically they can be replaced with any driver rated ... 350 ma fixed with voltage range including 27.14 volts for the 9.5w version ... 700 ma fixed with voltage range including 25.7 volts for the 18w version

Yep, that's right - from the point of view of 'basic operation'. However, if you are planning to use the dimming facility of those drivers, then I'm out of this discussion, 'cos I haven't a clue!

In addition on other fittings, if i failed to know the lamp wattage or voltage, but the failed driver stated 300ma, could i simply measure the output voltage of a same working fitting and if it measured say 18 volt, would it then be the case of just getting a 300ma fixed driver with a voltage range that includes 18 volt.

Yep, that's right (again, assuming that dimming is not part of the equation!).

Any help?

Kind Regards, John

 

[ban-all-sheds]

It's the 'dimming operation' part of it that complicates matters. What that does, and how compatible its method of dimming would be with any particular LED is anyone's guess.

Presumably not by changing the current.

 

[ban-all-sheds]

However, what is the "9.5 W at 350 mA" all about.

That's what the light(s) is/are. As rocky said, that's what they get supplied with those Osram 700mA drivers, but I imagine they would work with a 350mA driver, or anything in between.

 

[333rocky333]

However, what is the "9.5 W at 350 mA" all about.

Oops my mistake john, my confusion
on that driver it does only state, as you say 700ma, i never noticed that, the pics of the net with the same model no as mine, yet on mine it says 700ma but also says it does 500ma with 18kohm resistor in the control port, hence, two currents, 500ma and 700ma (Not 350ma and 700ma as i misread)

This is the actual ones i have, i also note the output states 0-700ma just to confuse me more, i assume thats to do with the dimming side

Then in the fitting instructions is where my confusion came from, it says two wattages.
9.5 watt at 350ma as well as 18 watt at 700ma

At first glance i took that to be the two outputs as stated on the driver, but on further reading the instructions, the two wattages are actually two different fitting models, but using same fitting instructions and possibly do have different drivers.

So the maths was right, but relating to two seperate drivers/fittings, sorry

Any help?

yes, Very clear and precise, obviously I will endeavour to replace like for like, osram is easy but with so many other odd brand drivers out there, I need to know the basics to try and use more available drivers, hopefully the 1-10 dimming if involved, will be similar across the board and will just have to moniter how they perform

 

[ban-all-sheds]

If you are planning to go down the road of that solution looking for a problem, aka "home automation", then I would have thought that a 0-10V dimming system rather than 1-10V would be better.

 

[ban-all-sheds]

Found a nice article that goes some way to explaining what occurs inside an led downlghter especially when dimming.
http://www.ledsmagazine.com/article...-issues-to-ensure-compatibility-magazine.html

More info here: http://www.brilliantlighting.co.uk/wp-content/uploads/Lighting_Buyers_Technical_Reference_Guide.pdf

 

[JohnW2]

It's the 'dimming operation' part of it that complicates matters. What that does, and how compatible its method of dimming would be with any particular LED is anyone's guess.

Presumably not by changing the current.

One might have thought that - but in view of what Rocky has now posted, and the pic of a slightly different driver he has now posted, I'm not so sure. This second one is a 'constant-but-variable-current' driver, which seeming has a control input which allows the 'constant current' to be varied from 0 to 700 mA. If the first, very similar, one (with a 'dimmer' input' works similarly, it might well dim by altering the 'constant current' of the device.

It's not that unusual a concept. One of my bench power supplies has a constant current mode, but with a knob one can turn to vary the level of that 'constant current'.

Kind Regards, John