Driver FAQ’s There are two primary types of LED Drivers, Constant Current and Constant Voltage. They both preform a similar function as a MH or T5 Ballast. The Constant Current Driver and Dimmable drivers normally have a variable voltage range and a constant current output. This allows the driver to automatically output the voltage based on how many LEDs on the string. Drivers have a minimum and maximum voltage to function. For our applications the Constant Current Driver works best. We normally have 3-15 LEDs wired in series and want them to operate at a given current. . One question we always get is “how many LEDs can I drive?”. The short answer is it depends on the forward voltage of the LEDs and voltage range of the Driver. In this example we will use the Meanwell LPC 35-700 and the Cree XT-E 5 watt LED. According to the PDF Data Sheet the LPC 35-700 has a forward voltage range between 9 and 48VDC. The Cree XT-E PDF Data Sheet shows a forward voltage range of 2.85 to 3.4. The forward voltage range of the LED is based on current and heat. Generally the higher the current and heat the more the forward voltage drop. For the Drivers the forward voltage range is based on the individual components. The published forward voltage range may be slightly off which is why we recommend to pad the book answer by 1 LED. Now for the book answer…For the LPC-35-700 with a minimum forward voltage range of 9 you would simply divide this by the minimum forward voltage of the LED. 9/2.85=3.15 or 4 LEDs because you must round up on the minimum side. For the maximum number of LEDs you would take the maximum forward voltage of the LED (3.4 VDC) and divide the maximum forward voltage rating of the driver (48 VDC). 48/3.4=14.11 or 14 LEDs maximum. In our experience and field analysis these numbers do work for the Mean well LPC 35-700. Now for the dimmable drivers. We currently recommend both the Mean Well ELN60-48D and the Inventronics 700mA 40 w. There are many other drivers out there but we have had the greatest reliability and success with these two brands. The Mean Well 48D driver is without a doubt is the most recognized dimmable driver and is the standard for most DIY Kits. It can receive an input AC voltage from almost any country in the world except for North Korea which upon our last check does not offer residential electrical service. Its out put is rated at 24-48Vf at 1.2A and its adjustable. Overall we like and use the ELN60-48D in our own personal reefs however it does have some issues we will document. For starters its output current is adjustable which is a huge plus. The Driver is Rated at 1.2A, however we have measured it at up to 1.8A output current. This can be a good thing or a bad thing. Do not run it over 1.2A or you risk overheating it. If you are well versed in electrical DIY this is a popular driver. The Inventronics 700mA Driver is pre adjusted and has a voltage range of 18-54 Vf. We prefer this driver over all others as its proven reliability and the fact it includes a 10VDC output wire on the control side. This allows for a potentiometer to be directly connected to the driver. Both the Meanwell or the Inventronics can be controlled automatically with an APEX or manually with our DimBox. Simply adjust it to the three most common settings, 700mA for XPE, 1050mA for XPG/XTE or 1.2A for two parallel strings of XPE. If you are simply too busy we offer this adjustment and you will not have to open up the Driver, hook up a Volt Ohm Meter and adjust the internal pot. Dimming the ELN60-48D is done by a 1-10VDC input. Consider this the control and the driver will not work without a control. The Blue+ and White- wires need to be attached to a 1-10VDC source. We really like the APEX Controller to control the drivers but you could us a simple Radio Shack Enercell #273-315 to control your driver. Simply cut the plug off, test polarity and hook it up. If everything is soldered properly and you turn on your driver and nothing happens, then when you unplugg it you get a quick blink you might have the polarity backwards on the blue and whit wires. Please do not use the 12VDC setting as the Driver is only rated for 10VDC. Per the PDF Data Sheet,the ELN60-48D will dim down to 5% with 1VDC input. With no Input the driver will turn off or not turn on. The Inventronics Driver is dimmable via a 1-10VDC input just like the Mean Well ELN60-48D, however the Hyperon offers a few advantages. It has an extra 10VDC wire. This can be used with a potientiometer to manually dim the driver. The Inventronics driver is dimmable down to 10% with a 1VDC input this is the drivers lowest setting. From here the increase in intensity is linear with an increase in control voltage with 10VDC being 100%. Unlike the Mean Well the Inventronics can be configured to run in a nondimmable mode. To do this you would simply connect the yellow wire to the purple wire. We highly recommend this driver for anyone who is planning to add a quality controller like an APEX or Profilux in the future. The question of driver harmonics has come up may times. Both the Mean Well and Hyperon have a start up current draw which can be as high 30 or even 60 Amps. This happens for a micro second. If you consider 10 or 20 Mean Well ELN60-48D drivers all turned on at exactly the same micro second the max Cold Start Inrush Current of 60A x 10 or 20 is capable of overwhelming standard household circuits. We have yet to see a documented case of this happening and the engineers at Mean Well dismiss this as a safety issue. We agree as in today’s overly litigious society we would see warning labels saying do dot turn on more than one at a time. This said its not a bad idea to have your drivers plugged into fused surge protected powerstrips. This is more to protect your investment from outside electrical surges but the protection works both ways. If you are still concerned, staggering the on times eliminates the extremely remote chance of this phenomena occurring. Driver Number Of LEDs mA Constant/Dimmable ELN 35-700 4-14 XT-E LEDs 700mA Constant EUC40DS700 7-15 XT-E LEDs 700mA Dimmable EUC40DS1050 4-10 XT-E LEDs 1050mA Dimmable ELN 30-48D 4-14 XT-E LEDs 630 mA Dimmable ELN 60-48D 9-14 XT-E LEDs Adjustable to 1.2mA Dimmable All these drivers can be set to do Parallel strings. This will result in the current (mA) being divided by two if there are 2 strings or divided by 3 if there are 3 strings. Learn more about parallel strings here. [warning_box]The Meanwell 60-48d Must be tuned before use to avoid damaging your LEDs[/warning_box] Larger Drivers: There are two common types of large drivers. The Mean Well CLG and HLG series and the Higher Wattage Inventronics drivers. Both drivers we only recommend for advanced professional use. The Mean Well are Class II and are engineered for the end user to configure their LED array in Parallel Strings. Whenever you use parallel strings we highly recommend the use of resistors and fuses. The up side of these large drivers with multiple parallel strings is you still have a Class II fixture and can use the BJB Solderless Connectors . Our most popular large driver is the CLG 150-48. Its rated at 3.2 A and is perfect for driving 48 LEDS in four parallel strings of twelve. This will drive each string at 800mA. The main drawback to parallel strings is sometimes you have more current running through one string and less through another. A 50-150 mA difference between strings is common and generally is not a big deal. The Higher Wattage Inventronics Drivers can drive up to 79 LEDs in series. This is done via a constant 700mA current and a forward voltage of up to 285VDC. This high voltage renders this driver for professional use only. We have used them on our systems and they work quite well however any soldering errors will be exasperated with the higher voltage. These recommendations are based on a forward voltage range of 3.2 to 3.5 . Our SolderLess BJB Connectors are designed for a max voltage of 60VDC and max current of 2000mA. Thus the BJB Connectors will not work with the 150-200Watt Inventronics drivers. Driver Number Of LEDs mA 200 Watt Dimmable 44-79 700mA 150 Watt Dimmable 33-60 700mA If you have any Driver or LED questions please contact us through our Sponsor Forum at Reef2Reef or Reef Central or simply contact us.