What Resistor Should I Use in an LED Circuit

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What Resistor Should I Use in an LED Circuit

While some may think using LED lights is just a matter of plug and play, for more complicated LED circuits, it's not so simple. An LED is a semiconductor, which means there are several ways to power and stabilise it. A resistor is great way stabilise the LED current, but choosing the right one can be complicated. There are different types of resistors, each with a its owns pros and cons.


Series Resistor

Without a resistor, an LED light can draw too much power from a battery and cause it to short, which is why a resistor is necessary. One of the easiest ways to add an LED resistor to any system is to place it in a series. By adding a resistor in a series, the current and voltage can stabilise. While the current can still increase, it won't spike too much, which can cause shorts. However, the series resistor is one of the least efficient methods, with a maximum efficiency of about 75 per cent. The power used by the resistor is practically wasted. Some might think that using a supply voltage that's the same or similar to the LED voltage is the solution, because that way, one could use a smaller resistor, which reduces wastage. The problem with that solution is that a small LED light resistor might not be able to perform well, and might not regulate the system at all.

 

Linear Current Source Resistor

A linear current source is a great way to provide constant current to an LED. This LED bulb resistor absorbs and delivers the current without having to depend on the voltage running through it. The brightness of the LEDs remain constant even with different power supplies.While a series resistor can reach 75 per cent efficiency, the linear current source can reach up to 93 per cent efficiency.

 

Switched Mode Current Sources

The most efficient way to power an LED circuit is to use the switched mode current sources or switched mode power supply method. This LED system could reach up to 100 per cent efficiency, with little to no power wasted. This requires an additional part, an inductor, to convert all the voltage into the exact specifications to power all the LEDs. It's a very complicated circuit and the 100 per cent values are most likely only in theory. However, it is much more efficient than the linear current source and it's possible to sustain the right type of current even if the input voltages vary across the board. Another advantage is that it is possible to put many LEDs in the system without any problem, even if the forward voltage of the LEDs exceeds the supply voltage.

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