Timeline for How many ohms do you need before you need a resistor?
Current License: CC BY-SA 3.0
9 events
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| Mar 16, 2020 at 18:22 | comment | added | K H | I would just note that you need one resistor per series set of LEDs. In your first test, you could have put the two LEDs in series and they likely wouldn't have burned out. If the LEDs are in series the current through them must be the same as eachother, which means the LEDs will heat up roughly equally and share voltage roughly equally. Also note that what you need is that the resistor is providing is current regulation in the form of a PTC(Positive temperature coefficient). So the actual rule is that LEDs are very difficult to parallel and each series set requires current regulation. | |
| Jan 28, 2016 at 21:01 | vote | accept | eidylon | ||
| Jul 19, 2015 at 0:29 | comment | added | efox29 | @eidylon I should stated earlier in my original comment, that you shouldnt parrallel just leds together. My mistake, but glad you understand now. | |
| Jul 18, 2015 at 22:20 | comment | added | eidylon | I was wondering about how that worked... my very first project I did with some lighting, I used the LEDs out of Dollar Store flashlights, and there were zero resistors in the circuits... but they still worked. That kinda set me off on some false assumptions as I started out. LOL | |
| Jul 18, 2015 at 22:18 | comment | added | Peter Bennett | You ALWAYS require a resistor or other current-limiting device in series with an LED. Cheap LED flashlights often depend on the internal resistance of the battery to limit the current, but that's not recommended for most applications. | |
| Jul 18, 2015 at 22:15 | comment | added | Peter Bennett | A recommended practice for multiple LEDs is as I show above - a resistor in series with each LED. Any number of these resistor/LED combinations can be connected in parallel (subject to power supply limitations). Connecting multiple LEDs in parallel, with a single series resistor is not recommended. If you have a high enough power supply voltage, you can connect several LEDs in series, with a single resistor. | |
| Jul 18, 2015 at 22:13 | comment | added | eidylon | So the resistors also, while not apparently necessary in this particular circuit, would theoretically extend the lives of the LEDs, yes? | |
| Jul 18, 2015 at 22:10 | comment | added | eidylon | After efox29's comment above, I went and found this question and was wondering then what the proper way to resistorize the LEDs would be. Your diagram is what I was guessing... cool. So you actually can parallelize diodes, it is just better to give them all their own resistor instead of sharing, yes? Or even with individual resistors is parallelizing still frowned upon? | |
| Jul 18, 2015 at 21:31 | history | answered | Peter Bennett | CC BY-SA 3.0 |