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LED LightsLED Lights
Auto LED Lights In automobiles, LED lights are usually used as indicators to alert the driver of activated circuits. An activated LED light may mean that the fog light is on; a door is unlocked or not closed properly, etc. A car’s power supply however is 12 volts strong while the voltage requirement is an LED light is usually only 2 volts. This means that LED lights cannot be connected directly to the car’s power supply and needs a resistor to lower the voltage to the needed level. The typical resistors used in this application are the 560 or 470 ohm resistor. These types of resistors are commonly available in electronic stores. How to Wire LED Lights A LED light is composed of two leads which are the anode and the cathode. The cathode is the shorted lead and the one connected to the larger electrode. As always keep in mind that the LED light must not be connected directly to the car’s power supply as this will literally fry the LEDs and make them useless. When wiring LED lights, it is best to test the circuit first using alligator clips, temporary connections to the resistors and temporary wires to the battery before making it permanent. This way, you will be able to make changes on the connections if the number of resistors is not enough or if the wires are connected to the wrong terminals. The resistor should be connected to the cathode of the LED light on one end and the negative terminal of the battery on the other. The anode of the LED, on the other hand, should be connected directly to the positive terminal of the battery. Upon determining that the connections and the circuit are working, you can then solder the connections together to make it permanent. Note however that LED lights can be damaged by excessive heat so make sure that you proceed with this step quickly and accurately. Connecting Devices to the LED Light Connecting a LED light to auto devices to act as an indicator that it is activated involves pretty much the same steps as those mentioned above. First, connect the longer side of the LED light or the anode into the positive output power side of the switch that activates the device. Secondly connect the appropriate resistor on the other end of the LED light or the cathode and lastly, connect the end of the resistor to ground. This way, the power then flows from the switch, into the LED light, into the resistor and lastly into ground. Calculations for the Resistor To calculate what value you would need for the resistor when wiring a LED circuit, calculations must be made. First, remember that since both the LED light and the resistor are in series, the current flowing through the LED is the same as the current flowing through the resistor. Secondly, the required voltage across the resistor will be the difference between the voltage of the battery and the needed voltage of the LED light Thus for the usual LED light using only 2 volts, this means that the resistor should be capable of handling 12-2= 10 volts. For the white and blue LED lights that use 4 volts, this means that the resistor in series should be capable of handling 12-4 = 8 volts. Using Ohm’s Law then, the required resistance is the voltage value of the resistor divided by the amps or R=V/I. this means that for 0.02 amps running through a standard LED light the resistance of the attached resistor should be (voltage) 12-2=10 divided by 0.02 or 10/0.02 = 500 ohms. We can then use the resistors nearest to this value for the LED light (470 or 560 ohm resistors). For blue or white LEDs on the other hand, the voltage would be 12-4 = 8 volts divided by 0.02 amps or 8/0.02= 400 ohms. The 390 ohm or 470 ohm resistor can be used in this case.
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