LED Boards and Resistors for 17 Volt Power Supply
I purchased 6 (21.6 X.05 X 0.031') circuit boards for LEDs and am having problem with wiring. All I want to do is hook up 18 LEDs in a row, that would be 3 sections of one of the boards, with one power soarce 17 volts. I figuerd out the wiring diagram on the bard and don't feel this is possible with this board. I've done blew $20 worth of bulbs and just gave up on it. Can I run 18 LEDs on this board from one power soarce?.
Selecting Resistors for LED Circuit Boards
Although possible, 17 volts might not be the best source voltage to be using. Something closer to 12 volts would be much more reasonable, considering the construction of the circuit on the LED board. However, if you are restricted to 17 volts, here is how you can do it. First, make sure the LEDs are inserted correctly. The cathode of the LED should be positioned with the square pad on the board. If you inserted your LEDs backwards, then you can simply reverse your power supply wire leads. Continue by populating every resistor pad on the board. To light all 18 LEDs within a three section span, you will need to make sure all resistors are populated. The resistor pads are setup to accept a standard 1206 surface mount chip resistor. However, you may want to solder on an axial leaded through-hole resistor if this is what you have access to. Both will do the same job, but the chip resistor just looks better. The resistor value will depend on two primary factors. What is the desired LED drive current, and what is the voltage drop across the LED? Since your source voltage is so high, you will have to be very conservative while selecting your drive current, to prevent over heating of the resistors. If you are using a standard 5mm red, orange or yellow LED, then you might try a resistor value around 1K ohms (1000 ohms). This will set your drive current around 10mA (0.01 amps), and your resistors will dissipate around 160mW. If you are using white, green, blue, or violet LEDs, then try a 680 ohm resistor or close to. This will drive your LEDs around 15mA and resistors will dissipate close to 150mW each. You can do these calculations also by using ohms law.