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| When current limiting resistors are needed with LED? |
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| Youkai:
I'm trying to understand when/how current limiting resistors are needed. Specifically I'm using a segment of this https://www.superbrightleds.com/moreinfo/flexible-led-strip-lights-color-changing/rgb-led-strip-light-flexible-custom-length-led-tape-light-with-9-smds-per-ft-3-chip-smd-led-5050/3502/ I got a wall plug from the thrift store that outputs 12v. Since the output is 12v and the LED is rated for 12v is a current limiting resistor needed? If I add a resistor in series with the LED strip that would reduce the voltage that is available to the LED strip correct? If a current limiting resistor is needed I would want to put it in the DC12+ line so I only have to use one resistor instead of 3 correct? |
| jm_araujo:
That strip already has the current limiting resistors. It's those small black SMD components on the strip, so in your case you don't need any additional ones when using a 12V power supply as specified by the manufacturer. |
| ovnr:
The LED strip already has current limiting resistors; you don't need any. Yes, adding more resistors will reduce the current - and voltage. If you do add one to the V+ line, you will have issues where adjusting the brightness of one color will impact the brightness of the other colors, therefore it's recommended to use separate resistors per color. |
| Youkai:
Ok good to know about it already having the resistors. Thank you for that. What if I get a single red LED that is rated for 5v and I power it from a 5v power supply? Is a current limiting resistor needed then? I'm trying to understand conceptually when/why you need a "current limiting resistor". Wherever I have used resistors in the past I have used them for Voltage reducing. E.g. I have a 5v power supply and the LED is rated for 3v. Are Voltage limiting and Current limiting basically the same due to Ohms law? |
| Jwillis:
LEDs will take as much current as they can get until they burn out .Most LEDs need to be limited to under 75mA current .So you select your resistor according to the voltage to only supply Under 75ma using Ohms law. R=V/ Less than 75mA . Some LEDs may require more ,some may require less .So it's important to know what the LED is rated for. |
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