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!
Tonight I wanted to see just how close most of the popular COBs are in terms of lumen output at various wattages, so I punched some numbers into the manufacturer product selection tools and compiled a list. All results are calculated at a case temperature of 55 degrees Celcius (except for the Luminus CXM-22, for which I estimated Tj to be 85 degrees in order to have a case temperature as close to 55 C as possible). A color temperature of 3500K and 80CRI was used for every COB.
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.
Here are my results:
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.
- Select a COB from the dropdown
- Enter the quantity of COBs
- Select a drive current.
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.
UPDATE 05/30/2017: HLG-480H-C Drivers added.
UPDATE 06/16/2017: 72V Cree CXB3590 added.