using Arduino to dim multiple LED strings question

I have four strings of 3W LEDs. Each string has 10 LEDs and all LEDs are the same color, same make. All 40 LEDs need to be dimmed uniformly. I'll be using a Meanwell LDD 700 on each string (4 LDD700s). So...

Can all 4 strings be dimmed with a single output from the Arduino?

Reference this post found by using Google search: http://forum.arduino.cc/index.php?topic=155985.0

I have been unable to find a specific reference to Arduino PWM fanout for input to your specific controller. In general, you can find the specific Atmega sink or source pin capability in the specific microcontroller data sheet. Then, there is also a total microcontroller current limit.

Ray

If these LED strings are the normal common strips, they are rated to be fed from a 12 v source without the need to be current limited. Look at the LEDs on the strip. If you can see resistors between the LEDs, they are already current limited. They will probably be in groups of three with resistors between them.

If you want them all to be treated as one light, simply connect them all in parallel and switch using a relay or mosfet. Do not drive the relay direct from the Arduino without a driver transistor and fly back diode.

Weedpharma

Hi, LDD700? What are the rest of the model number, there are a variety of controllers that Meanwell make that start with LDD700.

Tom..... :)

Thanks guys. I have Meanwell LDD-700LS. They are surface mount and look like a pain to solder. Oh well, I have them so I'll get it done.

I did not find any mention of hooking up the dimming function of several LDD700 units in parallel to Arduiono in the linked thread. I did look at the datasheets-sorry to say I did not understand enough to find the answer.

I soldered the LED strings in series with no resistors. Yes, all four strings need to be treated as a single light. I am interested in Arduino for the control that is possible.

I just thought maybe someone would know off the top of their head if connecting 4 LDD700s in parallel to Arduino for dimming is OK.

BTW, this is for a dual algae filter. There are really 8 strings of LEDs and 8 LDD700s, 4 strings at the blue peak for photosynthesis and four strings at the red peak. I could definitely make it work without the use of a microcontroller like Arduino, but I'd never be able to find what I'm looking for in the filter without one.

Joe

So you have the chip-like package at the bottom of page 3?
http://www.meanwell.com/search/LDD-L/LDD-L-spec.pdf
This block of data:
“PWM
DIMMING
&
ON/OFF
CONTROL”
makes it look like the input needs 1mA drive current. 8 LDD-700LS from 1 arduino pin should be okay.

Thanks Crossroads. Yeah, it looks like a water bug. Since each side will need to be dimmed independently, a set of four LDD-700 units will be used on each side.