oreo57
Well-known member
Oddly enough the 1000mA and 1500mA series does have analog dimming.. See spec sheet.
http://www.meanwell.com/search/LDD-L/LDD-L-spec.pdf
Meanwell LDD driver: for those who want to dim to 0 using Arduino
- Thread starter pwreef
- Start date
Oddly enough the 1000mA and 1500mA series does have analog dimming.. See spec sheet.
http://www.meanwell.com/search/LDD-L/LDD-L-spec.pdf
Krazie4Acans
New member
The analog dimming on those LDDs uses the single dim pin. If you were to drive that pin with a PWM signal at 5 volts it would either over ride the analog dimming of less than 2.5 volts out cause a short between the high voltage VIN supply and the PWM controller.
It would be much safer and reliable to use only one method and limit the output with that method instead of trying to mesh two methods together. That's my thoughts and two cents. Krazie :jester:
It would be much safer and reliable to use only one method and limit the output with that method instead of trying to mesh two methods together. That's my thoughts and two cents. Krazie :jester:
Scuba_Steve
Premium Member
Besides if I did that I would still be driving my LEDs at 100%. (Not to assume you dont know how PWM modulation works) but just in case... PWM flickers the light on and off quickly to give the appearance of dimming. It is still driving the light at full force when it flickers it on, which is what I dont want to happen.
BTW I just figured out how to get my arduino to change its PWM output to a true analog output so I can control that dimming function effectively.
http://arduino-info.wikispaces.com/Analog-Output
Krazie4Acans
New member
I know how the PWM works. Which is why during the time that the PWM pulse is high, you would have 5 volts in on the dim pin which would override the analog input. So if you were to try it then what you would end up getting is the analog input would become the minimum brightness during the off pulse and then 100% during the on pulse. So the average current in that configuration would be higher than just running it PWM alone.
Using your arduino in analog mode will still be driving the dim pin with a 0-5 volt signal which would be double the voltage that is needed for the analog dim. Make sure you use a voltage divider or something else on that output to drop it by half. You will also only be able to dim to 20%with the analog in. Krazie :jester:
Using your arduino in analog mode will still be driving the dim pin with a 0-5 volt signal which would be double the voltage that is needed for the analog dim. Make sure you use a voltage divider or something else on that output to drop it by half. You will also only be able to dim to 20%with the analog in. Krazie :jester:
oreo57
Well-known member
Not exactly sure why you are worried about the pwm "flicker" The pulses effectivly are equiv to an amp drop..LED's can take it. Besides even though you have an analog dim doesn't necessarily mean the concurrent output is not pulsed. The 2 systems can be seperate and different. As to using an R/C circuit, you still have 0-5V out..
BTW most commercial have a global preset to limit max out. You can set them to 90% max and be done w/ it..I'm sure you can code that in.
Scuba_Steve
Premium Member
Im not worried about the amp drop from the flicker. I am worried about driving the LEDs at 100% power. Whether doing it in PWM mode or not.
I didnt read the data sheet thoroughly btw. I thought I could lower the analog dimmer to lets say 2.3V, then apply PWM to that 2.3V signal. Unfortunately the LDD views 2.6V and higher as a PWM high, whereas 2.5V is full power for analog. So it definitely is one or the other.
No need for a voltage divider. The link I posted is a method to turn the arduinos 5V signal into a variable 0-5V signal. Ive already tested it. I can control the voltage down to the 0.01V consistently. It only requires a 4.7k resistor and a .1uf capacitor.
As for the pulsed analog output, only a test with a multimeter will tell if thats the case or not. crosses fingers
I didnt read the data sheet thoroughly btw. I thought I could lower the analog dimmer to lets say 2.3V, then apply PWM to that 2.3V signal. Unfortunately the LDD views 2.6V and higher as a PWM high, whereas 2.5V is full power for analog. So it definitely is one or the other.
No need for a voltage divider. The link I posted is a method to turn the arduinos 5V signal into a variable 0-5V signal. Ive already tested it. I can control the voltage down to the 0.01V consistently. It only requires a 4.7k resistor and a .1uf capacitor.
As for the pulsed analog output, only a test with a multimeter will tell if thats the case or not. crosses fingers
Why not just use the 1200L and regular pwm dimming? A few hundred extra mA wont make a noticeable difference in light output especially when talking about whites over a reef. Very few people that set the xpg up running even 1000mA ever run at 100% duty cycle anyhow after they get them over the tank. The higher you drive the LED the less efficient it gets. better to use an extra couple LEDs at lower current in the long run...........
And if you really need the extra punch from a single LED then look to a more powerful model like the XML or Luxeon M.
Just my two cents.
:beer:
oreo57
Well-known member
Err yes an R/C circuit.. resistor capacitor..
No you'll need an ocilloscope.. most meters will average at that frequency..if the output is "pulsed" regardless of level.
I'm not exactly sure how the "output" is handled when dimmed. I don't believe, in most cases, it is simply an amp reduction. That causes color shifts in LED's..Pulsing does not.
jedimasterben
LED world domination!
Just an FYI for anyone wanting to use SCW, there are now several wattages available - 3w, 5w, 8w, and 12w, marked by their model SCW03, SCW05, etc. I have three fans on my LED array for my tank, and the SCW05 can only power two of them so I needed to have two SCW, when I could have used one SCW08 to do the job 
Krazie4Acans
New member
Also don't forget that you have to pay attention to the input voltage. SCW08B's will only handle 36V in. While SCW08C's will handle upto 52V in. That one bit me and I made some smoke. Krazie :jester:
jedimasterben
LED world domination!
Actually, the A models are 9-18v, B models are 18-36v, and C models are 36-72v for all of the SCW wattages.
But yeah, it can be easy to let the smoke out! Do they manage to pack the same amount of smoke as they do in the LDD? Cause good lord, I blew ONE LDD and it filled a room with a nice haze! :smokin:
oreo57
Well-known member
We actually this shows you have no choice. Re: of "dimming type" output is just pulsed full current..as it should be:
http://www.ultimatereef.net/forums/showthread.php?p=6535081
Scuba_Steve
Premium Member
That is during PWM mode though, correct? That is exactly how it is suppose to behave in PWM mode. I didnt see anywhere in that thread where he tested it in analog. He is just concluding that while using PWM you are not actually dimming the LED as some might hope you would be.
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Krazie4Acans
New member
Dimming LED's by reducing current changes the produced color spectrum of the LED. It is not desirable to do it that way for aquarium lighting.
PWM pulses the light on and off to appear dimmed but is producing the same color spectrum at all PWM values because the the current is the same. There have been many studies on this and the color shift is noted in the spec sheets for every LED die out there. The only way to guarantee the true spectrum of the LED produced light is to keep the current constant.
I ran analog dimmed LEDs for years and never got good results in coral response from analog dimmed LEDs. This has not been an issue since I switched to PWM dimming on my LEDs and the color response from the corals is the same regardless of the PWM level. Krazie :jester:
PWM pulses the light on and off to appear dimmed but is producing the same color spectrum at all PWM values because the the current is the same. There have been many studies on this and the color shift is noted in the spec sheets for every LED die out there. The only way to guarantee the true spectrum of the LED produced light is to keep the current constant.
I ran analog dimmed LEDs for years and never got good results in coral response from analog dimmed LEDs. This has not been an issue since I switched to PWM dimming on my LEDs and the color response from the corals is the same regardless of the PWM level. Krazie :jester:
oreo57
Well-known member
As I mentioned, I'm "assuming" the same output regardless of source..PWM or analog. I have no official confirmation. I also assume it "pulses" up till full out, then it "may" default to full on.. based on current/voltage needs....but that could be an error also..
Technically, whether pulsed of amp decrease.. it is still "dimmed"..
Krazie4Acans
New member
True they are both "dimmed". However, dimmed in spectrum and dimmed out of spectrum are not the same thing.
When colors are so critical in our hobby it does matter (well at least to me and my corals). You have the data so you can choose to do whichever way works for you and see if you get the same results I did.
The data sheet for the 1000L and 1500L strangely doesn't show any output graphs or even mention the method used for analog dimming. That is pretty strange for a data sheet. Maybe I'll do some more digging and see if I can find the full data sheet with all the details instead of the retail data sheet. Krazie :jester:
When colors are so critical in our hobby it does matter (well at least to me and my corals). You have the data so you can choose to do whichever way works for you and see if you get the same results I did.
The data sheet for the 1000L and 1500L strangely doesn't show any output graphs or even mention the method used for analog dimming. That is pretty strange for a data sheet. Maybe I'll do some more digging and see if I can find the full data sheet with all the details instead of the retail data sheet. Krazie :jester:
Krazie4Acans
New member
oreo57
Well-known member
I have been agreeing w/ you all along on this..
As I said I suspect a PWM output regardless of "input"..
any significance that the analog Voltage (2.5) top is 1/2 of the 5V pwm......... ???
Krazie4Acans
New member
That wasn't for you as much as for others reading the thread that might not know there IS a difference.
So you are thinking that they snuck an A to PWM chip inside there with all that other stuff? And that the PWM in is TTL level trigger and the analog is 3.3V triggered? That would be interesting. I know when Der Wille Zer Macht, O2Surplus and others were doing research on the LDD's, way back when, that they came up with a chip that would do analog or PWM in but that you had to choose which one in the layout. You couldn't change it just by lowering the input signal max.
I wonder if they worked with the supplier to change that with the newer 1000L and 1500L parts? Seams like the part was a 6239 or something like that. I'll have to check the old thread and see. It was the same level input for analog as the new LDD is. still a bit disappointing that the analog input causes a reduction in the dimming capability. From 0 to 20% on is generally a pretty significant jump with LEDs. Quite interesting. Krazie :jester:
