What type of battery or resistor should i use to light up 5mm LED ?

[TWE75]

Hi guys , may i know what type of battery should i use to power up LED for my truck ? I'm using those 5mm super bright type of LED . Or what value resistor should i use to lower the current ? Sorry i had to ask that cos i suck in my analogue electronics in school . I tried using CR2016 but it seem to lose its power pretty fast . I'm planning to power a total of 8 LED front and back .

I just had a small explosion ( sounds like a small firecracker going off , if you want to know the sound ) from one of the LED when i tried to use my 3s 35c 850mah lipo battery to power it . And the LED was blown to bits but luckily i was unscathed .

[nic]

http://www.kpsec.freeuk.com/components/led.htm

[TWE75]

Thanks for the link , but my maths suck , no matter how i calculate , the value doesn't make sense to me . I think i'll just get a 1k resistor to try with .

[Super-Hornet]

Try this?

http://www.ee.ucl.ac.uk/~amoss/java/calcled.htm

Or

http://www.electronics2000.co.uk/calc/led-series-resistor-calculator.php

[TWE75]

Ok this is really good , hands down lol . Got my resistor reading already . Thanks alot super hornet .

[yacsf]

Hi guys , may i know what type of battery should i use to power up LED for my truck ? I'm using those 5mm super bright type of LED . Or what value resistor should i use to lower the current ? Sorry i had to ask that cos i suck in my analogue electronics in school . I tried using CR2016 but it seem to lose its power pretty fast . I'm planning to power a total of 8 LED front and back .

I just had a small explosion ( sounds like a small firecracker going off , if you want to know the sound ) from one of the LED when i tried to use my 3s 35c 850mah lipo battery to power it . And the LED was blown to bits but luckily i was unscathed .

Single cell will do, or with you lipo 3S, connect at the balancer connector. There are 4 terminals, just connect next to each other, don't jump within the terminals or with voltmeter, measure and it should read 3.7V.

[Ezekiel Freshmen]

You want to provide no more than 26mA to each LED, White LED can go about 4V each. At 30mA they can get pretty hot, I prefer to hold them at 26mA.


I will tell you the simplest of methods ! No calculation required

You'll need an amp-meter and as many 10-50ohm variable resistor as you like.
Hook up as many LEDs in series, with the sum of forward voltages not overshooting the supply.

E.G.
3s 12.6v
Each of your 5mm White LED 3v min 4v max approx

Maximum 3 LEDs in series.
Maximum Rows of 3LEDs ? unlimited.

Now connect the amp-meter and variable resistor between the LED and battery.
Rotate the variable resistor to the maximum value, you will need the ohmmeter to check.

PLUG IN THE BATTERY WITH FINGERS CROSSED (:
Then turn the variable resistor to small till you a value of (26mA x No.Rows) reflected on the amp-meter.

2 rows = 52mA
10 rows = 0.26A

The resultant resistor value from my experience can get as low as 1ohm, which is almost rare in simlim tower (:

You can experiment between brightness and hotness of the LED with your fingers wrapped around one.
When it gets a little hot, you can just bring it down a notch with the VR without blowing up 50cent LEDs. (:


Benefits, even if you do not know the max or min forward voltages, maximum forward current that the LED can handle,
this method only requires your sense of touch and sight, don't need too much brain power. Don't even have to bother about the current too actually.
.
.
.
.
.

[Ezekiel Freshmen]

BTW, I get A for analogue electronics. And I do know how to calculate the resistor values using mathematics. I use the above mention method to test the max current I can go before the LED "KAputt".

.
.
.
.
.

[TWE75]

Thanks alot for all your invaluable help . I already got my 330ohm 1W resistor from sim lim tower today . I'll try the method as taught in the link super hornet provided and see how .

If it works , then i'll proceed to wire up Super bright LED for my plane too .

If anything goes wrong then i'll try the methods that you guys taught . By the way can i connect 4 super bright LED together in series ?

Freshmen , the explosion of the LED really shocked me cos i thought the most that can happen will be the LED failing to light up . But this particular LED head actually exploded into 3 pieces with a bang .

So , lesson learnt , LED CAN EXPLODE !!!

[Ezekiel Freshmen]

.....So , lesson learnt , LED CAN EXPLODE !!!

I have only ever pump in up to 5v to any LED, it was by mistake and at that voltage they pop and vent out.
You placed in an insane 12v ! lucky it just exploded, not vaporized haha

.
And yes you can put 4 LED in series, however....
- you will not achieve maximum brightness for long
- it will stop working once the battery goes below 12v, because the LED forward voltage is compromised if given ea LED FD min 3V.
- given the voltage vs charge curve of a lipo, going from 12.6v to 12v is pretty quick.

.

[aeronautical]

what i have done for past projects is put as many leds in parallel as you like and only use a 3 v power supply. it's not the brightest but it isn't hot and i didn't need a resister in any part of the circuit. (i didnt use 5 mm leds. i used 3 mm leds for my night kite)