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power IR LED ? Answered

how can I power 30 IR leds comes from TV remote by a 3.6volt cell phone battery.
the LEDs are 1.5 volt.

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MDheliMech
MDheliMech

Best Answer 7 years ago

The answer depends on how they are wired. If wired in parallel yes, in series not. In a parallel circuit all of the LED's together draw 1.5v in your case. So 3.6v will work with a resistor. However the current, AKA amperage draw is added for each one. for example if one LED draws 30mA, that will be multiplied by the number of LED's 30mA x 30 LED's = 900mA this is important in determining battery life. It would be beneficial to do a search for LED parallel and LED serial circuits to better visualize this. I also included a couple of example images.


Now we come back to the question that steveastrouk asked, "How long for?" That comes down to capacity of your battery. For example a fully charged 1000mAh battery will release 1000 milliamps of current at a specific voltage for one hour before it is discharged. so for our example above. If your LED circuit draws 900mA, a fully charged, properly maintained 1000mAH battery should last a little over an hour. Check out this battery life calculator. It is meant for RC flight time but it works for any application. http://www.scoutuav.com/2011/05/12/calculate-flight-time/

circ2.jpgcirc1.jpg
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asifarifin
asifarifin

Answer 7 years ago

then what resistor should I use ?

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MDheliMech
MDheliMech

Answer 7 years ago

Check out Ledcalc.com You will need to know the battery voltage, and the LED voltage, and amperage draw for one LED. Put those numbers into the boxes on the website along with how many LED's you have and it will give you a resistor value and suggest a diagram for the circuit

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steveastrouk
steveastrouk

Answer 7 years ago

Which LED. How long for.

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MDheliMech
MDheliMech

Answer 7 years ago

If you wire them in parallel you will need a resistor. I use http://ledcalc.com/

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steveastrouk
steveastrouk

Answer 7 years ago

If he puts 30 in parallel with that battery, he's not going to get much current per LED. I don't know the output resistance of a coin cell, but its not especially low.

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asifarifin
asifarifin

Answer 7 years ago

I don't use a coin cell.It's a cell phone Li-Ion battery.

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tp.pa.12
tp.pa.12

5 years ago

I had a cheapo 29 led flash light with 3 AAA's in a holder. I went to a thrift store & wiped them out of TV remotes. I took out all the IR LED's from the remotes, then changed them out one by one until I had 29 IR LED's installed. Interesting because you don't know if it is off or on, and you have to hide it for people don't play with it & leave it on. I checked it out with my night vision, and it is not that bright, I am definitely going to have to increase the voltage, by adding a couple more batteries in series, so that is the tricky part, getting them nice & bright without over doing it & ruining the whole project.

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Josehf Murchison
Josehf Murchison

7 years ago

The next part 5 to 30 ma.

So for 30 IR LEDs in parallel you need 150 ma to 900 ma.

And for 30 IR LEDs in series you need 45 volts to 180 volts.

The .6 volts should not be a problem.

This is only if you are lucky and all your LEDs are 5 ma and 1.5 volts.

Two in series and 15 parallel the circuit would be would be 3 volts and 75 ma.

My LG cell phone battery is 3.7 and 800 mah it might work for 2hr before the battery didn’t have enough power to support the circuit.

See my Instructables:

https://www.instructables.com/id/Ghost-Busted/

https://www.instructables.com/id/Photo-Components-Testing/

https://www.instructables.com/id/Liner-Counter/

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MDheliMech
MDheliMech

Answer 7 years ago

Hey good call on the two serial circuits. No resistor required. I think your answer was more what the asker was looking for. I may have went overboard with info.

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MDheliMech
MDheliMech

Answer 7 years ago

It would be helpful to know the amperage draw of the LED though.

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Josehf Murchison
Josehf Murchison

Answer 7 years ago

It would be helpful to know the amperage of the LEDs as I said earlier 5 ma up and 1 volt up.

Salvaged IR LEDs are hard to get the data on simply because they don’t have part numbers.

Go to this page.

http://www.maxim4u.com/

Search these IR LEDs.

IR333
IR383
QED234
TSAL6400

This one I got from Radio Shack runs on 5 volts 150 ma.

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MDheliMech
MDheliMech

Answer 7 years ago

Wow 150mA. That's no joke there.

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Josehf Murchison
Josehf Murchison

Answer 7 years ago

Yea and on the battery he wants to use maybe 30 minutes on six LEDs.

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MDheliMech
MDheliMech

Answer 7 years ago

That being said. Another valid question would be will they be on continuously like a flashlite or in bursts like a TV remote control. If it were in bursts it might not be too bad depending on how long / how often the burst.

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Josehf Murchison
Josehf Murchison

Answer 7 years ago

He has to be doing ether one of two things night vision or light setting a resin.

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MDheliMech
MDheliMech

Answer 7 years ago

I thought about the NV thing. But I didn't know about the resin thing.

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Josehf Murchison
Josehf Murchison

Answer 7 years ago

Most are UV like the fillings in a dentist office but there are IR resins also.

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MDheliMech
MDheliMech

Answer 7 years ago

It depends on the current draw of the circuit compared to the mAH capacity of the battery.

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steveastrouk
steveastrouk

Answer 7 years ago

Precisely. That's why I ask the question.

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MDheliMech
MDheliMech

Answer 7 years ago

My guess would be that the author of the question would like them to last for as long as possible with the battery specs already given. It doesn't appear from this question that he wants to know what type of battery will last a given amount of time. Of course I only assume that because he states that he already has a battery in mind.