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Topic: Controlling ceiling light LEDs (Read 5457 times) previous topic - next topic

Wawa

#15
Apr 01, 2017, 10:29 pm Last Edit: Apr 01, 2017, 10:37 pm by Wawa
Found a 48volt/240watt supply here.
You can also get Meanwell circuit boards.
Leo..

MaxG

#16
Apr 02, 2017, 01:59 am Last Edit: Apr 03, 2017, 01:44 pm by MaxG
Don't know what's inside an 18watt light.
No, why I have ordered a 6, 9, 12, 18W each, to rip apart ;-) ... and to measure what is happening.

While I would prefer the same hole size, I understand the benefit of a low profile that these LEDs have; also less heat is wasted on this design compared to others.

As I said elsewhere, the issue I'd like to focus on is solely:
a) understanding how these LEDs and drivers work
b) developing a circuit which can control (on|off|dim) these LEDs efficiently
c) which includes appropriate / suitable power supplies

Someone said something along the lines" you wouldn't post on this forum if it weren't for a cheap solution; a statement I totally disagree with, because while I have seen cheap, but also brilliant solutions, within a wide range of requirements, and lots of brains put in to arrive at a solid solution.

So, touching on cost, I am after a well engineered solution, which I can build myself where necessary (e.g. build the driver, but buy the power supply); yes, cost saving plays a role, but 'cheap' is certainly not my motivation -- well-thought out is.

Thanks for all your help... I reckon I have to wait for the LEDs to arrive and then continue the conversation / discussion.
Mainly using UNOs. Everything needs to be defined.

septillion

Any system will have risks associated with it.
The dumb light will cater for a failure of the home automation (HA) system.
However, I could still make it controllable... :)
That's bull ;) You can still make light when the system doesn't what to. But that scenario is as likely as the system not letting you turn off light or randomly turning on light. An aspect most people don't think about. Don't know about you, but I think that's as annoying... :D Especially when you're in bed... Both cases you're forced to reboot the system / get it working again. Because although if the system is down you have some light n a room, I don't call a single light instead of a dozen of downloads to be a livable situation either...

And to be clear, don't criticize a design choice you made, just to make you really think about if it's indeed as good as a choice as you think it is :) When it comes to light an automation people tend to only fear sitting in the dark (even when we all have a flashlight on our phone_ but sitting in the light when you don't want to is as likely and in my opinion as big as a problem.

@Wawa, You're right, the scatter of the efficiently is bigger then I thought.
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

MaxG

Those ceiling lights have five 0.2watt LEDs in parallel.
Power rating of the light is how many of those groups of five are connected in series.
6 groups for a 6watt light, and 12 groups for a 12watt light.

A 12watt light (60 LEDs) would need a 36-40volt supply.
Meaning each of the these LEDs has 60mA, 5 in parallel = 300mA at 3.3V ~ 1W
60 LEDs in a 12W light is still 300mA, but now at ~40Vf

There is a number of circuits out there catering for up to 60Vin...

I understand the "ideal" scenario is to run LEDs in series to avoid overrunning parallel LEDs from overrunning when one LED dies. But given the design of the LED lights (where 5 LEDs are in parallel) this seems to be a risk  I have to live with.


Mainly using UNOs. Everything needs to be defined.

Wawa

They can sort off get away with that, because the LEDs are from the same batch.
And more important, they all have the same temperature, because they are mounted on the same heatsink.
(Vf of a LED drops with temp rise).

I'm using the ceiling lights you have linked to, and they have survived two years of normal use now.
Some hallway/entrance lights are running (dim) all through the night.
I have replaced several CF tornado lights in that time, but none of my LED downlights yet.
Leo..

guyco75

I know it's an old thread, but I have a follow-up question.

What is a reasonable maximum wire length between a 5v Arduino pwm pin and a constant current step-down driver? Is 75ft\25m reasonable for 500Hz over a cat6 or telephony wire? Should I worry about things like EMI, ESD, capacitance, resistance, etc.?

septillion

I think except from EMI you have to worry about all those things I think.

Aka, not a very good design to do so :)
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

guyco75

I think except from EMI you have to worry about all those things I think.

Aka, not a very good design to do so :)
What would be a reasonable length for that (5v pwm 500Hz)?

septillion

For a high impedance signal: keep it on the PCB.
For a low impedance signal (aka it has real load) < 1m I would say.
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

guyco75

For a high impedance signal: keep it on the PCB.
For a low impedance signal (aka it has real load) < 1m I would say.
High impedance.
What you're saying is that I can't use a pwm controlled CC led driver other than integrating it on a pcb together with the atmega chip?

At least Leo wrote on this thread he has them few meters apart..

Just to clarify, I'm considering Meanwell LDD drivers or something like this for smaller LEDs:
https://s.click.aliexpress.com/e/cZZ3KO40

Thanks
Guy

septillion

Actually, yes. But if you manage to make it a bit more low impedance (aka, have a resistor/filter an enough drive) you can do a couple of meter. But 25m without the possibility to have it pick up noise, that's getting hard. You can probably do it with a nice twisted pair and connect that to an opto. Opto gives you lower impedance, isolation gives you good advantage of the twisted pair.
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

guyco75

So would you recommend placing the drivers\dimmers together with the mcu and having 300mA dc running to the light fixtures (5-10 average, 25m furthest)? Any expected issues, other than some power loss and probably thicker wires?

septillion

If I would need to run them that far I would split the controls. Multiple combined driver + uC boards chained with something like RS485.
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

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