Q & A

How to drive a LED (module)?

Light Emitting Diode (LED) is semiconductor diode. The brightness of the LED depends on the current that it will draw. The current that an LED will draw depends on the voltage that is applied; and its voltage/current chart is not linear. Typically LED starts conduct minimum current from its low working voltage, and within half of volt to its high working voltage and with maximum current.

Therefore, it's common to control a LED with controlling current rather than voltage. Most people use constant current power supply or driver, which output a constant current by adjusting its voltage, within a range of course.

To select a suitable driver, first decide how much current you want to flow through LED. If LEDs are connected in series, same current will flow through all LED in that line. You may also set identical circuit side by side and connect them in parallel, that way, they will divide the current evenly (almost).

With the working current set, and working voltage fall into a narrow range, you can calculate this circuit's rough wattage by multiply current and voltage. Most LED driver vendors list their driver using wattage for indexing, just make sure you driver has a suitable current and voltage range.

Can I use a constant voltage driver?

For cost consensus projects, one may want to use constant voltage driver, which is more popular and typically cost less, from 10 to 20% less. However, LED work load current is sensitive to voltage, so that requires more tuning to find a best working setting; and it's hard to set a precise current, you are more or less rely on LED module's tolerance. The good news is: Our module has a lot of tolerance.

The way to use one is as such: Find a CV driver with output voltage slightly higher than your module set, and use its maximum current as your working current. Or course, we can use resistor to drop a few volts.

Use resistor to drop voltage:

Using resistor to drop voltage need some calculation: We know Easy LED module has voltage around 10.5 Volt (up and down depend on temperature, too) when driven at 1500mA. Since we are designing a circuit at about 1.5~2A of current here, so for every Ohm can drop 1.5 ~ 2 Volts. For one blade with 12V voltage driver, use 1 ohm to drop 1.5V; For two blades with 24V driver, just use 2 ohm to drop 3 volts, and current should come up from 1.4A and climb to 1.5~1.6A pretty stable. Do choice resister has enough wattage rating. (2W for 1 ohm and 5W for 2 ohm) The advantage of use resistor is: when current increased, the voltage drop also increased. It's easy get balance with LEDs

How do you dim your LED modules?

Many constant current power supply provide dimming function.

However, many require micro-processor to issue adjust instructions, rest just can be adjusted via a VR by hand.

Easy LED lighting use two smaller constant current power supply, each provide half of maximum current, that way use two switches to control two PS, you can select 0, 50% or full current output from combine output of both drivers. This method is in fact, cheaper than using one big adjustable PS plus micro-controller.