You need some voltage drop across the resistor, however, so putting two LEDs in series is out. You need 4.5V across the resistor for 20mA so. R = 9V − 4.5V 20mA = 220Ω R = 9 V − 4.5 V 20 m A = 220 Ω. A 9V battery can't supply very much current, but without series resistor the current may still be too much for the LEDs. It is quicker to wire them in your scenario than any other way. As you add LEDs to your parallel array, the voltage requirements stay the same. As you add LEDs to your parallel array, the current requirements increases the amount that each LED requires (5 LEDs @ 20mA = 100mA requirement/draw). 100 Ohm 1/4 watt resistor. 470 ohms (1 piece) Start by hooking all four resistors in series (in a string). Resistance adds when you hook resistors in series, so you'll have an overall resistance of 910 ohms to start with. Hook the mess in series with your LED, and hook it all up to 24 volts. Now take your voltmeter and measure the voltage across the LED lamp. Obviously, replace 'x' with the Ohm rating shown on the LED Calculator website. Now all that remains is to solder wires from the power source to the resistors and then to the LED (remembering to solder the wires to the positive and negative connections of the LED) as shown in the diagram and try them out. Step 4: Ensure the Load Equalizer Wires can Reach. Once you've found your turn signal bulb wires, make sure your load equalizer can reach an internal metal surface of your vehicle and that the wiring can reach the turn signal wires. If not, the load equalizer wires can be extended to reach from the mounting location to the turn signal wiring. A quick explanation of the resistors chosen: Assuming a nominal 12V supply, the 15Ohm resistor will allow a current of 0.8A. The power dissipated by the resistor will therefore = V*A = 12*0.8 = 9.6W, thus making the 10W rated resistor sufficient (particularly when installed with a means to transfer heat away). For example, I know the "12 volt" power supply to my old slot-car track put out considerably more than 12V, especially with a capacitor across the terminals. A 12 volt car battery charges on something like 14 volts, so in a car it might need to withstand that voltage, but by itself it's 12.6 volts fully charged, which I'm sure is close enough. At a basic level, load resistors are purpose-designed for installation in vehicles where problems result from L.E.D replacement of standard incandescent globes. Suitable for indicator and brake light circuits, LED load resistors are designed to draw the same current as a 21-watt incandescent globe, correcting any problems with low current draw With the LED characteristics as shown above you could break into two strings, each with a separate current defining series resistor. If the operating current you want is about 20mA, then for two LEDs you would expect approximately 3.3V per LED Vf. If your supply is 12V, then you will need a series resistor that drops 5.4V at 20mA. OK, let's do the calculation. A simplified model for a LED is a fixed voltage source in series with a small resistor. Let's pick this LED from Kingbright. The slope is 20mA/100mV, so the internal resistance is 5\$\Omega\$. The the intrinsic LED voltage is 1.9V. Let's assume that the LEDs need 20mA and that our power supply is 5V. In this case if you're changing 2x filament light bulbs you will need 2x load resistors). Video: Install a Load Resistor for LED Lights. Topics: Precautions: LED Resistor Wiring Diagrams: LED Load Resistors & LED Lights. LED Light Prices; Item: Location: Load Resistors: US Prices: AU Prices: UK Prices: CA Prices: IE Prices: FR Prices: LED The current limiting resistor is a protective resistor connected in series to avoid excessive current burning of the appliance. The principle is to reduce the current by increasing the total resistance of the load. Generally, it can also play a role of partial pressure. Usually, in a local circuit, a resistor that has no other function in The main reason LEDs need resistors is to protect the LED from excessive current which can permanently damage the LED. LEDs have current ratings which indicate the optimal current at which the LED operates effectively. The resistor would get 0.6 volts at 12 mA. So at 12 mA since the graph for brightness looks linear with respect to current, they'll be at 60% brightness. 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 MNv9Op.

do 12v leds need resistors