B Blueprint New Member Jun 28, 2005 #1 Hi, i'm pretty new to circutry... anyway, im using a simple breadboard system, simply making an LED light up. I'm using 3xAA batteries (4.5v), i have a LED, but just need to know what strength resistor to use. Can anyone help? Thanks.
Hi, i'm pretty new to circutry... anyway, im using a simple breadboard system, simply making an LED light up. I'm using 3xAA batteries (4.5v), i have a LED, but just need to know what strength resistor to use. Can anyone help? Thanks.
Someone Electro New Member Jun 28, 2005 #2 It depends on what kind of LED.We need to know the LEDs voltage and curent. This is caculated this way: (Vb-Vfw) / I = R Vb = batery voltage Vfw = LEDs voltage I = curent R = resistor you nead. Easy as pie.
It depends on what kind of LED.We need to know the LEDs voltage and curent. This is caculated this way: (Vb-Vfw) / I = R Vb = batery voltage Vfw = LEDs voltage I = curent R = resistor you nead. Easy as pie.
J Jay.slovak Active Member Jun 28, 2005 #3 I think Microcontrolers is not a got section for resistor-for-LED problem :lol:
Someone Electro New Member Jun 28, 2005 #4 yea that too. unles he is trying to controll it from an mcu but i dont think he is doing that
B Blueprint New Member Jun 28, 2005 #5 Ok thanks guys... It's a bog standard 2mm LED, think its a 2v LED. how do i work out the current? (i'm not controlling it from a MCU yet...)
Ok thanks guys... It's a bog standard 2mm LED, think its a 2v LED. how do i work out the current? (i'm not controlling it from a MCU yet...)
J Jay.slovak Active Member Jun 28, 2005 #6 Blueprint said: Ok thanks guys... It's a bog standard 2mm LED, think its a 2v LED. how do i work out the current? (i'm not controlling it from a MCU yet...) Click to expand... OK, say you power it with 5V, then resistor needed (for LED U=2V, I=0.02A) is (5-2)/0.02=R, Therefore R= 150Ohms Usually LEDs require 20mA (0.02A) current to function It's that simple :lol:
Blueprint said: Ok thanks guys... It's a bog standard 2mm LED, think its a 2v LED. how do i work out the current? (i'm not controlling it from a MCU yet...) Click to expand... OK, say you power it with 5V, then resistor needed (for LED U=2V, I=0.02A) is (5-2)/0.02=R, Therefore R= 150Ohms Usually LEDs require 20mA (0.02A) current to function It's that simple :lol:
Someone Electro New Member Jun 28, 2005 #8 (4,5 - 2) / 0,01 = 250 so that wod be an 220 Ohm resistor(it wod let 10mA in the LED) This is Ohoms law whith a litle tweak to caculate this (Ohoms law wod be V / I = R).
(4,5 - 2) / 0,01 = 250 so that wod be an 220 Ohm resistor(it wod let 10mA in the LED) This is Ohoms law whith a litle tweak to caculate this (Ohoms law wod be V / I = R).
J Jay.slovak Active Member Jun 28, 2005 #9 Blueprint said: You're a genuis thanks v much . Click to expand... I wouldn't consider anybody as genius only because he/she can calculate proper resistor for LED. :lol:
Blueprint said: You're a genuis thanks v much . Click to expand... I wouldn't consider anybody as genius only because he/she can calculate proper resistor for LED. :lol:
B Blueprint New Member Jun 28, 2005 #10 Yeah true, but I found it pretty hard to work out the current of a 2mm LED from Maplin. Most of their stuff is German for a start, so it takes me a little longer to read their kinda 2-lined instruction leaflets that comes with the shizzle. Anyway thanks for your help, you're all Ledges.
Yeah true, but I found it pretty hard to work out the current of a 2mm LED from Maplin. Most of their stuff is German for a start, so it takes me a little longer to read their kinda 2-lined instruction leaflets that comes with the shizzle. Anyway thanks for your help, you're all Ledges.