1. Temperature Increases On The LED Light. The main purpose of fixing resistors in an LED circuit is to control the amount of voltage that goes into your light, so if you don't fix a resistor then it will be difficult for the LEDs as they could receive too much current and power. For instance, let's say we fixed our 2 volts through a 1-ohm Simple Blinking LED Circuit: A very simple circuit that you can build to blink or flash LEDs. The circuit is built using transistors, resistors, capacitors, and LEDs. Of course you will need a breadboard, wire jumpers, and a power source. The parts list includes: PNP… Yes buying "12v" leds will not need any resistors because they should have them inline. You should also have no problems seeing them since most of the time they are under shrink. 5 volt ones would need resistors, but if you can get 12 why use the other ones. If you get bare leds with no resistor then a resistor is needed for sure. Step 1: 3 Volt Basic LED Circuit With 10 Ohms Resistor. The above diagram shows a 3V LED circuit, in this circuit there are two AA cells are used. When you are operating an LED with 3V you have to use minimum 10 ohms resistor . For more details visit Simple Basic LED Circuit. LED Resistor Calculator. To calculate the resistor needed for a simple LED circuit, simply take the voltage drop away from the source voltage then apply Ohm's Law. In other words where: V S is the source voltage, measured in volts (V), V LED is the voltage drop across the LED, measured in volts (V), Dimming an LED light is, add a resistors to the connection or even several resistors, to ensure you get the right brightness, this is called analog dimming. There is probably already a resistor in the line to drop the 12V, so the actual value you need is probably less than 10K. Now, we get to the tricky part: some LEDs will begin to dim .

do 12v leds need resistors