 # Question: Do LED Lights Need A Resistor?

## Should I put a resistor before or after the LED?

It doesn’t matter.

The resistor can go before – or after – the LED, and it will still protect it.

the current that flows out of a battery is always equal to the current that flows back into the battery..

## Can I connect a LED directly to a battery?

Five-volt LEDs can be connected to a nine-volt battery, but an external resistor is also needed in order to drop the voltage to the five volts required.

## Why do you need a 330 ohm resistor for an LED?

Detail: 330 ohms may be used by some people as a “get you going” value that works “well enough” in many cases. The purpose of the resistor is to “drop” voltage that is not required to operate the LED, when the LED is operating at the desired current.

## What resistor do I need to reduce voltage?

To reduce voltage in half, we simply form a voltage divider circuit between 2 resistors of equal value (for example, 2 10KΩ) resistors. To divide voltage in half, all you must do is place any 2 resistors of equal value in series and then place a jumper wire in between the resistors.

## What happens if you don’t use a resistor with an LED?

When hooking up an LED, you are always supposed to use a current-limiting resistor to protect the LED from the full voltage. If you hook the LED up directly to the 5 volts without a resistor, the LED will be over-driven, it will be very bright for a while, and then it will burn out.

## Why is it necessary to use a resistor in series with an LED?

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.

## How do I know what resistor to use with LED?

We’ll use the following formula to determine the resistor value: Resistor = (Battery Voltage – LED voltage) / desired LED current. For a typical white LED that requires 10mA, powered by 12V the values are: (12-3.4)/. 010=860 ohms. To use several LEDs in parallel, sum the current values.

## How do you connect a led to a 12v battery?

Connect one end of the resistor to the positive terminal of the battery. Connect the other end of the resistor to the positive (anode) terminal of the LED. Connect the cathode of the LED to the negative terminal of the battery. The LED should illuminate.

## Can you use an LED as a diode?

Yes, an LED works as a photo diode (as do most diodes) but are always packaged so as to admit light. So if you need a rather poor photo-diode, you can use an LED, and if it is good enough for the application, then it will likely be cheaper than a “real” photo diode that is made in much lower quantities.

## Do LEDs need constant current?

Since there’s no current regulation the brightness of the LED cannot be maintained at a constant level and overdriving LEDs can occur. That’s why all LEDs need to be current driven. Constant current (CC) LED drivers are often compared with constant voltage (CV) LED drivers.

## Do I need a resistor for a 12v LED?

1 Answer. AFAIK there is no, or at least no common, led diode that is typically 12V forward voltage by it self. 12V led are modules that consist of some combination of diodes and resistors to make them suitable for 12V power applications without needing extra current limiting.

## How many LEDs can be connected in parallel?

Wiring LEDs in parallel allows many LEDs to share just one low voltage power supply. We could take those same four 3V LEDs and wire them in parallel to a smaller power supply, say two AA batteries putting out a total of 3V and each of the LEDs would get the 3V they need.

## What happen if you connect a LED directly to a 12v DC?

If the voltage exceeds the voltage required by the LED it will probably burn out. If the voltage is lower then the the LED might not light or be much dimmer. Two identical resistors are connected in parallel to a battery.