LED Circuit - How to wire 12 LEDs to 2 AA batteries?

sagor

Joined Mar 10, 2019
512
Certain LEDs will not run on 2 AA batteries if their forward voltage drop is over 3V, such as some blue LEDs (and some green LEDs).
You have to post what color LEDs these are, that will determine the voltage drop and any necessary resistor for the circuit.
 

Audioguru again

Joined Oct 21, 2019
3,853
You did not say the chemistry of the batteries or if they are brand new and unused or fully charged or if they are run down a little and produce only 2.4V.
Then a 3.4V blue or white LED will not work.
 

MisterBill2

Joined Jan 23, 2018
9,843
With that many LEDs and with AA cells, there is no need for a resistor in series, as the battery series resistance will limit the current. Of course it is most likely that the LEDs will have slightly different brightnesses. Now consider that if each LED only consumes 10 milliamps the load will be 120 milliamps, so the battery life will not be so very long.
 

MisterBill2

Joined Jan 23, 2018
9,843
You could actually using a joule thief circuit to power 12 LEDs or probably 24 LEDs...connect them in parallel to the joule thief and it will lights up. See this idea.

I watched that video and it never showed the actual circuit used. And when I paused to try to see the circuit some stupid still shot pops up. So as I see it the whole presentation is suspect and not very believable. Certainly a stepup switching regulator is possible, but with no circuit presented it smells rather fake.
 

DickCappels

Joined Aug 21, 2008
7,984
I believe it can be done like that. It is no big trick to get 100V from a simple blocking oscillator running from a 1.5 V battery provided the transistor will handle it.

1612447845958.png

This illustrates the circuit. I encourage you to use a better core than an old flooring nail -that was just to prove that you don't need to be scared of the inductor. Take note of the wire colors - there are two windings wound side-by-side as a twisted pair of wires but the phase of the two windings have them in series with a center tap. The circuit is a constant current source for diodes over 1.5 volts, so the output voltage is set by the forward bias voltage of the diode.
 

MisterBill2

Joined Jan 23, 2018
9,843
Yes, I forgot to mention that interesting fact about the video. And notice that the leads always go out of the picture as well. In addition, those LEDs are very bright. perhaps they are all in series , not parallel, and running from some single higher voltage supply. And I wonder how AG was able to see the layout long enough to see the resistors. Or does AG have a frame-grabber? When I paused the video immediately a different picture blocked my view. It seems that folks are supposed to buy the kit to get the circuit.
 

Audioguru again

Joined Oct 21, 2019
3,853
At the bottom left of the video screen is the pause/play button.
Also I could have pressed my keyboad Prtscrn key without pausing and pasted it into Microsoft Paste program.
I use Windows10Pro, do you use Win3.1?
 

MisterBill2

Joined Jan 23, 2018
9,843
At the bottom left of the video screen is the pause/play button.
Also I could have pressed my keyboad Prtscrn key without pausing and pasted it into Microsoft Paste program.
I use Windows10Pro, do you use Win3.1?
I am well aware of the pause/play button and I tried to stop it a number of times, each stop resulted in tyhe alternate image being displayed. And no I am using win7 because I do not like win10.
 
I watched that video and it never showed the actual circuit used. And when I paused to try to see the circuit some stupid still shot pops up. So as I see it the whole presentation is suspect and not very believable. Certainly a stepup switching regulator is possible, but with no circuit presented it smells rather fake.
You've never even tried how could you say it's fake...lol...its a very simple circuit anyway...that circuit cost a dollar with all the components except the LED more expensive than the circuit itself...nothing to lose to try and you already think its fake lololol....Typical overly smart wisdom.
 
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