Since a lot of people have been looking for help on their strip builds, I figured it’d probably be helpful to have a calculator just for this. Now that we’re seeing more and more of these systems being built, it has become apparent that running all strips in parallel is the way to go – it’s expandable, the math is easier for large numbers of strips, and wiring is less confusing, so I’m only doing this for parallel builds. Check out the parallel strip build tool below!
This is a subject I touched on in an earlier video where I tried to run about 175 volts worth of LED (5 COBs) off of a driver only rated for 143 volts max. The result in that test was that the driver maintained its full voltage (~143v), but put out next to nothing for current. What I set out to test this time was what would happen if you were trying to pull just a handful of volts more than the driver was rated for, as opposed to trying to pull 30+ more than rated. By adding resistors in series with my 4 COB lights, I was able to slowly increase the voltage drop of my circuit to meet and exceed the max rating of my driver and see how it reacted.
In this video, we’ll have a look at what happens when the sum of your COB voltage drop in a circuit is below the minimum constant current region voltage of your driver, as well as what happens when it’s above the maximum constant current region voltage of your driver.
I’ve had a number of requests to put up a constant voltage version of my COB LED Driver Selection Tool so I drafted one up today. Please see the notes at the bottom of this post for some important additional info. Also, if you’d like to see any COBs added, let me know which ones and I’ll see if I can include them.
Constant voltage drivers are becoming more popular lately. They’re safer, flexible, and often cheaper than their constant current counterparts, but it can be a little more difficult to pick the right CV driver for your system than it would be for a CC build. Don’t sweat though, it’s really not very hard. All you need is an understanding of how parallel wiring works and to know how to manipulate forward voltage and current numbers using data sheets or product simulators.
Below are the steps to take to find a suitable constant voltage driver. Continue reading
In my previous test, I ran a couple of Vero 18 COBs at their typical rated current to see if I could get either of them to go into thermal runaway. Over the 4 hours I tested them, each of the COBs ended up pulling an additional ~50mA each than what they started at, but stabilized at this level. Curious to see if I could get one of my COBs to go thermal, I decided to take another stab at this and hit a couple different chips with considerably higher currents than they’d normally be run at.
After playing with my new HLG-100H-36A constant voltage driver for awhile, I conducted a little experiment this weekend to see if I could get either of my Vero 18 COBs to go into thermal runaway. Thermal runaway can happen in constant voltage systems where the current is allowed to vary, while the voltage is held steady. As the COB LEDs heat up, their properties change, and this causes them to draw more current, thereby heating them up further and drawing even more current. Eventually, the LED can destroy itself due to this cycle of drawing more current and heating.
Quite often, you’ll see recommendations to add a resistor in series with your LED if you’re using a constant voltage driver. I wanted to see if I could get away with skipping these resistors and simply running my COBs hooked up directly to the driver.
There’s a ton of information out there about finding drivers for your 4+ COB systems, but not a whole lot regarding drivers for setups with only 1 COB. The main problem is that most of the popular drivers for bigger systems have constant current ranges that are too high for a single COB, so they won’t work. We’ll need to find smaller drivers with similar characteristics in order to properly power your single COB grow light.
This post will examine a few different constant current drivers that will work for single COBs of different voltages. Note that these models are chosen with 120V AC power in mind, and may not work if your mains are 230V or whatever else. Always check the input voltage rating in the data sheet to be sure.
The spreadsheet will calculate your total forward voltage and highlight all of the Mean Well HLG-C drivers that are compatible with the parameters you entered. All data is pulled from manufacturer product simulator tools. If the total forward voltage (Vf Total) of your system falls within the rated constant current range of a driver (between V_min and V_max), that driver will turn green, indicating it is a match. I welcome any and all feedback on how to improve this tool – if you notice an error, have a suggestion, or would like to see other COBs or drivers, leave a comment.
Please note that even though big drivers may be capable of driving tons of COBs in series at low current, the high voltage generated by wiring the COBs in series may exceed the rating of your COB holders or connectors (a number of common holders are rated for a maximum of 250V – this would equate to a max of about 7x 36V COBs in series per driver). Always check your equipment specs to verify it can handle the total voltage.
UPDATE 04/17/2017: Citizen CLU COBs updated to Version 6 (F1), Quantum Board 288 and 304 models added.
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