A couple of updates:
1. Dimming capability. thee are a number of opportunities for 3in1 dimming. For the DIY person there is a few of what has been posted here. Most are what are called "High Side" dimming. if you google that term you will find many opportunities to build a dimming circuit. However if you are not so inclined to soldering and transistors, resistors, capacitors, etc, you m ight be interested in a pcb board already built for PLC or industrial controls and automation. Arduino's are being use used in much PLC now. Here is the link for the pwm driver. they range from $3 to $7 each channel.
http://www.ebay.com/itm/291855581114?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
2. Timers. Each light fixture needs to be timed for either 12/12, 18/6, 20/4, 3o min at lights out, etc. Each of those schedules requires timers. If you add up the costs of the timers to control each fixture, $30-50 each, the cost goes up quickly. Replacing all of those timers, 8-16 is a change event. never worrying about timers being on schedule or breaking down and requiring replacement, while it stayed on, when the rest of the lights went off. SAD face. I developed the GrowGreen Controller with this the top priority. When you consider the cost of 8 timers at even $20 each $160, is still more than one GrowGreen Controller alone. Dimming becomes the bonus.
3. I have shared all of the circuits I have developed for dimming Meanwell drivers and they all work, as well as those alluded to b y others. In order to build them you need the tools and components, ergo the board available on ebay for $5. Another approach is to use a optocoupler or light emitting diode and a light accepting diode to transfer signal from the 5v Arduino to the 10v Meanwell driver. A number of optocouplers are available for this purpose. You will need a 1k resistor on the pwn pin to the diode, and another 1k resistor, to create the high side switch, between 12v power and the Collector of the transistor, tying the emitter of the transistor to ground. The leads from the two ends of the 1k resistor go to the Meanwell driver. Positive from the power supply goes to the Dim+ and the Collector side of the resistor goes to Dim-, creating a 0-10v circuit driven by the Arduino 5v pwm signal. BTW, if you tap the signal coming out of the Arduino pin and ground, yopu also have a 5v pwm signal to use for on/off functionality of the Meanwell driver, while still having the ability to dim the drivers as well. Available optocouplers are the CYN75B, CYN75GB, 4N25, to name a few available.
4. If you also use supplemental lighting, Far Red, Deep Red, IR, or royal or all the above, you can also control these with an LDD driver board, 4up or 6up from rapid leds, coralux or ebay. you can build them yourself or buy them built, and populate them with various LDD drivers, 800ma, 1000ma, etc. for each supplemental light used. Each of these LDD drivers can also be controlled to dim, or on/off with just a 5v pwm signal. Any LEd controller can do that, but only the GrowGreen controller has 8 channels and flexible control over each channel independent of other channels.
More on the GrowGreen Controller can be found here.
https://growgreenled.wordpress.com/
Vegas