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Why does an LED need a resistor in series?
The slightest difference in LED or supply voltage may cause the LED to light very dim, very bright, or even destroy. A series resistor will ensure that slight differences in voltage have only a minor effect on the LED’s current, provided that the voltage drop across the resistor is large enough.
Do you wire LEDs in series or parallel?
Since we don’t have enough voltage to wire any of them in series, the only option is to wire them in parallel. The voltage requirement for this setup is still 3.0v, however we need a power supply that can supply at least 100mA (5 LEDs x 20mA each LED).
What happens if there is no resistor in a led?
If you supply 3V to this LED without series resistor the LED will try to set for a voltage/current combination for this 3V. There’s no current that goes with this kind of voltage, theoretically it would be 10s, maybe 100s of amperes, which would destroy the LED. And that’s exactly what happens if your power supply can supply enough current.
Why is the resistance of LEDs so low?
The point is a LED is a diode anyway and diodes have very small internal resistance (in “forward” direction of course), so unless there’s something else in series the overall resistance is very low and the current is barely limited and this barely limited current can damage the LED and overload the circuit that powers it.
Can a 5 volt power supply destroy an led?
If you apply a voltage that results in a larger current, the LED may be destroyed. So it’s vital to stay within the limits of the LED. If you would attach an LED to a 5 Volt power supply directly, you would burn it instantly. The high current would destroy the pn-gate. That’s the point where the current limiting resistor comes in.
What kind of resistor do I need for 5 volt?
If we want to use it at 5 Volt, we have to use a resistor to dissipate the remaining 2.9 Volt. To compute the resitor, we use: R = V / I = (5 Volt – 2.1 Volt) / 25 mA = 116 Ohm. To be safe we use a 120, or better, 150 Ohm resistor.