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 Electronics LED question

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Electronics LED question
« on: Mar 12, 2013, 12:05 PM »
I want to use some of the Alpena LED strips like Autozone sells.  Says they are 12w and something about .8 amps. Can I hook a 9 volt up to them the same way I am doing for my helmet fan which is 12w as well?  Different batteries for each, just wasn't sure I could put a 9v on the LEDs without it causing a problem somewhere.

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Re: Electronics LED question
« Reply #1 on: Mar 12, 2013, 05:08 PM »
So long as the forward voltage of your power source doesn't exceed the max forward voltage of your lights you should be ok.

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Re: Electronics LED question
« Reply #2 on: Jul 29, 2013, 03:03 AM »
Yes they can run a 9V, they won't be as bright but the 9V will last longer than a tiny 12V camera battery.

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Re: Electronics LED question
« Reply #3 on: Sep 29, 2013, 11:17 PM »
I actually had to use two AA batteries for my LED.  The 9v battery kept burning it out even with a resistor.  It's best to know what voltage they can take use Ohms Law then figure out what battery you need to use.  Trust me you don't want to burn out perfectly good LEDs.

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Re: Electronics LED question
« Reply #4 on: Sep 30, 2013, 01:42 AM »
I have more of those light strips on my kit than a Christmas tree, every one of them runs off a 9v batt. Never had one single issue.

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Re: Electronics LED question
« Reply #5 on: Sep 30, 2013, 04:19 PM »
Most common LED's are going to be rated at 3.5-4v max.  When you connect LED's in series, you have to double the minimum voltage to power them sufficiently for minimal illumination. 

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Re: Electronics LED question
« Reply #6 on: Sep 30, 2013, 05:46 PM »
Most common LED's are going to be rated at 3.5-4v max.  When you connect LED's in series, you have to double the minimum voltage to power them sufficiently for minimal illumination.

Uhh, not quite boss.

If you're talking LEDs in series then the voltage required to power them all depends on how many LEDs are in series.
If each LED is rated for 1.5V, then you would need 3V for two, 4.5V for three, 6V for four, etc.
Evidently there comes a number of LEDs in a row that would require very high voltages, so instead you would place X number of LEDs in series, and then have several sets of series all in parallel.

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Re: Electronics LED question
« Reply #7 on: Oct 01, 2013, 08:02 AM »
I don't know why I said doubled, lol.  I think I was searching for a way to say *add* and it came out as *doubled*.    Basically you have to increase minimum voltage by x1 (not x2). 

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Re: Electronics LED question
« Reply #8 on: Oct 01, 2013, 11:34 AM »
Well, to get past the very high voltage you can just make a Cascade Multiplyer from a 9V battery or two to power 20 or so LEDs if need-be.

Im not certain if you'd need 1.5V for each LEDs, the amount of power drawn from 3 1.5V LEDs should run on a pair of AAAs without much issue-though if you used a pair of AAAs with 1.5V LEDs to lower the voltage to about 1.5-1.7 a 100 Ohm resistor would do the trick.

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Re: Electronics LED question
« Reply #9 on: Oct 01, 2013, 11:51 AM »
Well, to get past the very high voltage you can just make a Cascade Multiplyer from a 9V battery or two to power 20 or so LEDs if need-be.

Im not certain if you'd need 1.5V for each LEDs, the amount of power drawn from 3 1.5V LEDs should run on a pair of AAAs without much issue-though if you used a pair of AAAs with 1.5V LEDs to lower the voltage to about 1.5-1.7 a 100 Ohm resistor would do the trick.

A switched capacitor circuit is typically more complex than just using a higher voltage battery or splitting the LEDs into several parallel branches. Though yes, you could do that.


You're mixing voltage with power, two distinct things.
That all depends if you're running them in series or parallel, if you're talking in parallel yes, for two AAAs, you want a resistor that will provide a voltage drop of 1.5V and will act as your current limiter.
If you have three LEDs in series, two AAAs may power them, but they will be dimmer as they're not getting a proper 1.5V each.


The standard forward voltage drop is 1.5V for a diode, standard LEDs are actually closer to 1.7V each but for simplicity's sake, 1.5V works.


That said, it varies by colour and brightness. Red LEDs consume the least, so always check the specs on the LEDs you've purchased.

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Re: Electronics LED question
« Reply #10 on: Oct 01, 2013, 03:12 PM »
If you have three LEDs in series, two AAAs may power them, but they will be dimmer as they're not getting a proper 1.5V each.

Not to mention that they will eat through those batteries pretty quickly just trying to stay illuminated.

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