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Topic: LED PWM Dimmer Circuit (Read 9338 times) previous topic - next topic

lcornelius

Hi all,

Please point me in the right direction if this question has been asked before.
I did allot of reading on the forum, but can't seem to find a answer.

I'm building a light hood for my 2m x 1m marine tank.
Will be using about 196 CREE 3w LEDs. Will use Cool White, Blue and Royal Blue LEDs.

The problem is that I will need 14 individual Mean Well drivers, 2 per 300mm x 300mm section.
So I think this is not the best way to do it. I would rather run 3 big drivers, one for white, one for blue and one for royal blue.
Now I need a circuit to dimm each block of LEDs.

I would like to controll each sections white, blue and royal blue.

I'm no designer, just a programmer. Is there such units available for sale?
Or how easy would it be to build my own?

Apreaciate your input.

Regards,
Lean

dc42

You said the leds are 3w, but what voltage and current?
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

lcornelius


You said the leds are 3w, but what voltage and current?


Driver at 700mA 3.2 volt
Driver at 1000mA 3.3 volt

The CREE model numers:

Neutral White Cree XP-G LED (XPGWHT-L1-0000-00FE4)
Blue Cree XP-E LED (XPEBLU-L1-0000-00201)
Royal Blue Cree XP-E LED (XPEROY-L1-0000-00B01)

Thanks for your response!

lcornelius

#3
Sep 18, 2011, 08:16 pm Last Edit: Sep 18, 2011, 08:18 pm by lcornelius Reason: 1
To give you more info:

The design will have 12 sections.
Each section contain:

  • 14 White LEDs

  • 8 Royal Blue LEDsp

  • 6 Blue LEDs



I would have run a Mean Well driver for each color.

Magician

Someone used "Meanwell ELN-60-48P driver".
http://arduino.cc/forum/index.php/topic,66070.0.html

lcornelius


Someone used "Meanwell ELN-60-48P driver".
http://arduino.cc/forum/index.php/topic,66070.0.html


Hi Magician,

My original plan was to use these drivers, but I will need 14 - 16 of them to control all the LEDs.
I was just wondering if there is a alternative to using so many drivers.

Was hoping to use only 3 big drivers to power the LEDs and then use a circuit to dim the power of each LED section.

dc42

I can see no easy alternative to using commercial LED driver modules for that system. LEDs need constant current supplies, and you can't modify the output of a constant current supply with PWM the way you can with a constant voltage supply (well, in theory you could do it by having the PWM short out the LEDs, but the constant current supply will almost certainly object to that). In view of the amount of power involved, you won't want to use series resistors because of the associated power wastage and heat, so you need to use switching regulators with inductive ballast. Also, your strings of white LEDs will need about 45v, which is not a voltage you can get from a low cost commercial power supply.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

Magician

Design with just 3 drivers would require V = 64 x 3.5 = 224 volts DC, I don't know if commercial
solution you can find. Alternative is to split leds in groups , to drop down voltage, and it would require more current. Telecom power supply -48, or even PC +12 V ( with more groups ) will works, but it wouldn't be cheaper, as you will need modify them to current constant supply.

lcornelius

Thanks for the responses guys.
Looks like I will have to use 2 drivers per section.

Is there a way to add aditional PWM output pins to the Arduino mega?

ibourdon

You could use TLC5940 ICs to increase the PWM outputs.

lcornelius


You could use TLC5940 ICs to increase the PWM outputs.


Great thanks, how about: http://www.practicalmaker.com/content/pwm-shield-assembled
Would that work?

bmcmvox

#11
Sep 22, 2011, 05:40 pm Last Edit: Sep 22, 2011, 05:44 pm by bmcmvox Reason: 1

Hi all,

Please point me in the right direction if this question has been asked before.
I did allot of reading on the forum, but can't seem to find a answer.

I'm building a light hood for my 2m x 1m marine tank.
Will be using about 196 CREE 3w LEDs. Will use Cool White, Blue and Royal Blue LEDs.


Well first off, 196 seems like a lot of LEDs for a 6 foot tank. To put that into perspective, the Vertex uses 192 for a 6 foot fixture and they are only run at 700ma, not 1000ma. I am not sure of the way you have them laid out, but if you are going for depth penetration (the tank is 1m tall or wide?) then you can cut down on the LEDs and use optics on LED sections which are above SPS sitting at the bottom of the tank. To put this into perspective again, the Aqua Illuminations sits at about 76 watts per unit and has a feasible foot print of 2'x2' with optics. These are tested and true ultra high powered LED fixtures that will cook your corals at full power. So for starters, you can eliminate some of those mean wells by eliminating some LEDs

EDIT: Looks like you will be running at 700ma, I was confused by the 3watt, you are actually only running 2.4 watts. I still think you can do away with some LEDs though, but really there is a big diff between 1000 ma and 700ma :)

Quote

The problem is that I will need 14 individual Mean Well drivers, 2 per 300mm x 300mm section.
So I think this is not the best way to do it. I would rather run 3 big drivers, one for white, one for blue and one for royal blue.
Now I need a circuit to dimm each block of LEDs.


Well, your choices are limited, due to the fact that high power LEDs gobble voltage, you are pretty much stuck unless you want to go into heavy duty commercial power supplies and have some specialty divers made. However, Thomas Reseach has a 120w driver out that tops out at 114volts and runs at just over 1000ma. It has a 10v dimmer circuit. Feasibly, you can run 32 3watters. The only place I know that has them, is Nanotuners, I believe they have exclusive distro rights in NA. They are also substantially more expensive that the 48v mean wells. They are between 80 and 130 dollars.


Quote
Driver at 700mA 3.2 volt
Driver at 1000mA 3.3 volt

The CREE model numers:

Neutral White Cree XP-G LED (XPGWHT-L1-0000-00FE4)
Blue Cree XP-E LED (XPEBLU-L1-0000-00201)
Royal Blue Cree XP-E LED (XPEROY-L1-0000-00B01)


If I were you, I'd consider using a cool white LED instead like XPGWHT-L1-0000-00H51. It will push you to between 5000k-8000k. Also, you get better lumen output from that chip

That being said, I have a question while I am here,

Can you daisy chain all the blue or white drivers together into one PWM channel or does each driver need it's own channel?

lcornelius



Hi all,

Please point me in the right direction if this question has been asked before.
I did allot of reading on the forum, but can't seem to find a answer.

I'm building a light hood for my 2m x 1m marine tank.
Will be using about 196 CREE 3w LEDs. Will use Cool White, Blue and Royal Blue LEDs.


Quote
Well first off, 196 seems like a lot of LEDs for a 6 foot tank. To put that into perspective, the Vertex uses 192 for a 6 foot fixture and they are only run at 700ma, not 1000ma. I am not sure of the way you have them laid out, but if you are going for depth penetration (the tank is 1m tall or wide?) then you can cut down on the LEDs and use optics on LED sections which are above SPS sitting at the bottom of the tank. To put this into perspective again, the Aqua Illuminations sits at about 76 watts per unit and has a feasible foot print of 2'x2' with optics. These are tested and true ultra high powered LED fixtures that will cook your corals at full power. So for starters, you can eliminate some of those mean wells by eliminating some LEDs

EDIT: Looks like you will be running at 700ma, I was confused by the 3watt, you are actually only running 2.4 watts. I still think you can do away with some LEDs though, but really there is a big diff between 1000 ma and 700ma :)


Yes, will be running at 700ma. The tank is 2m long 1m wide and water lever at 700mm.
The reason for all the sections with a dimmer circuit on each is because I'm building a controller that can simulate sunrise/sunset/lightning and clouds.
The more sections you have the better you can simulate sunset/sunrise. I know Vertex use 12 sections on their 1.8m unit. The thing that puzzles me is that they use 3 mean well drivers to power the unit.
That is where my question came in.

Quote

The problem is that I will need 14 individual Mean Well drivers, 2 per 300mm x 300mm section.
So I think this is not the best way to do it. I would rather run 3 big drivers, one for white, one for blue and one for royal blue.
Now I need a circuit to dimm each block of LEDs.


Quote
Well, your choices are limited, due to the fact that high power LEDs gobble voltage, you are pretty much stuck unless you want to go into heavy duty commercial power supplies and have some specialty divers made. However, Thomas Reseach has a 120w driver out that tops out at 114volts and runs at just over 1000ma. It has a 10v dimmer circuit. Feasibly, you can run 32 3watters. The only place I know that has them, is Nanotuners, I believe they have exclusive distro rights in NA. They are also substantially more expensive that the 48v mean wells. They are between 80 and 130 dollars.


Thanks will have a look at Nanotuners!

Quote
Driver at 700mA 3.2 volt
Driver at 1000mA 3.3 volt

The CREE model numers:

Neutral White Cree XP-G LED (XPGWHT-L1-0000-00FE4)
Blue Cree XP-E LED (XPEBLU-L1-0000-00201)
Royal Blue Cree XP-E LED (XPEROY-L1-0000-00B01)


Quote
If I were you, I'd consider using a cool white LED instead like XPGWHT-L1-0000-00H51. It will push you to between 5000k-8000k. Also, you get better lumen output from that chip


Thanks will keep that in mind.

Quote
That being said, I have a question while I am here,

Can you daisy chain all the blue or white drivers together into one PWM channel or does each driver need it's own channel?


You can only daisy chain as much LED's together as the Driver can support.
So you can put 14 blue on 1 driver and 12  white on 1 driver.

If you only control white and blue in one big section, you would not be able to simulate sunset/sunrist

bmcmvox

Quote
You can only daisy chain as much LED's together as the Driver can support.
So you can put 14 blue on 1 driver and 12  white on 1 driver.

If you only control white and blue in one big section, you would not be able to simulate sunset/sunrist


What I mean is, can you daisy chain the dimming circuits of multiple drivers together into one pwm channel of the arduino. So if you have 4 drivers running blue and 4 drivers running white, can you put the dimming circuits in a series for each colour group, and into one channel for the Arduino (thus using 2 channels total). Currently, as I understand it, you would need 8 channels, one for each driver. It doesn't matter If I need to add components to make it work, just want to know if it is possible.

Hope that clears up the question.

lcornelius


Quote
You can only daisy chain as much LED's together as the Driver can support.
So you can put 14 blue on 1 driver and 12  white on 1 driver.

If you only control white and blue in one big section, you would not be able to simulate sunset/sunrist


What I mean is, can you daisy chain the dimming circuits of multiple drivers together into one pwm channel of the arduino. So if you have 4 drivers running blue and 4 drivers running white, can you put the dimming circuits in a series for each colour group, and into one channel for the Arduino (thus using 2 channels total). Currently, as I understand it, you would need 8 channels, one for each driver. It doesn't matter If I need to add components to make it work, just want to know if it is possible.

Hope that clears up the question.


Yes it is possible to control multiple drivers with a singe pwm channel. I have not tested this, but have read that you can do this.

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