✔ How To Choose Led Resistor

How To Choose Led Resistor

- May 01, 2018

If you have ever taken a basic electronics course in the past then they likely drilled ohms law into your head. It mitigates most of the unpredictable properties of leds.

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Ohms law the one formula to rule them all when it comes.

How to choose led resistor. Proper parallel led circuits have a series resistor for each led. If the leds voltage is a bit less than 32 v like 31 v the voltage can vary by much more than that the current will rise to 225 ma and the voltage drop across the resistor to 54 v. It is very important to select right series resistor before using a led in a circuit.

You would get about 170 ma through a normal white led and waste about 60 of your power over the resistor which would have to handle an absolute minimum of 1 watt of power so a normal 14w resistor would just not do. In this video i have explained how to calculate the resistance value for leds for different input voltage. This is why we use an series resistor with leds when current is not constant.

How to choose a resistor for an led shortcut formula. To ensure you have the correct resistor you will need to know three values from your circuit. You will use ohms law time and time again when dealing with resistors.

Vf forward voltage for your led. Then the power will be 120 mw so the 100 mw wont do. If forward current for your led.

Vs supply voltage this is the power supply that you are using to power your circuit. I would give the resistor somewhat headroom power wise. This is the voltage required to turn on your led.

The simplest way to determine what resistor to use with an led is to subtract the forward voltage rating of the led v f from the voltage of the power supply v s and divide by the forward current rating of the led i f. The value of a resistor is its resistance measured in ohms.