Simple LED Circuit
Updated 5/27/2009: The schematic will look very complicated, but once
you get used to some of the electronic component notations it will get
easier. For those that are new to schematics, I have created a pictural
representations of what the schematic is saying. I hope this helps
everyone that is new to electronic diagrams.
When building the circuit just make certain that you have the LED
oriented properly (anode to cathode) as in the schematic since LEDs are
polarity-sensitve. Resistors are not polarity-sensitve (you can place
them either direction) and as long as they are in series with the
circuit they can be placed anywhere. Technically it's probably more
correct to place the resistor between the negative (ground) of the
battery terminal and the negative (cathode) of the LED since that's the
way current flows, but since it's in series the resistor will drop the
voltage either way. You can use a different voltage power source, just
substitute the voltage in the equation above to find the resistor value
you'll need.
Here's another helpful tool that will help you hook up one or many LEDs -- LED Calculator
For example, if you had a 12v PC Power Supply, 3.2v voltage drop, 20mA LED and 1 LED, here's the design
Summary
As I mentioned previously, this was just a very basic circuit so that I
could begin putting my breadboard to good use. It doesn't get much
simpler than this =) Still, it was nice to see the LED light up in all
its glory and I now know I didn't buy dud LEDs a few months ago. Good
luck!
Where To Go From Here?
How to Use Solderless Breadboards - Learn how to use solderless breadboards by building the simple LED circuit from this tutorial.
Wiring Multiple LEDs - Building off the simple LED circuit, learn how to wire up additional LEDs
Comments:
| info on LED |
| Posted 05/12/10 5:24AM by mmkkhh |
|
i feel much happy to read the comment as above which have give me much info. thanks more info , , i will welcome ,, ,khurshid |
| Converting av to dc to be used to power LED's |
| Posted 03/15/10 9:00PM by Anonymous Techdoser |
| Is there a 'simple' way to convert 24vac to dc voltage to drive a LED? I fully understand the need to use the correct resistor value to reduce 24 volts to the required 2.2 volts. But how to change the darn voltage to dc???The whole package must fit inside a door bell button. |
| Re: without a resistor |
| Posted 11/20/09 5:53AM by AceBHound |
| Yes, that's correct -- you can hook 2 leds up without a resistor since the voltage drop will be greater than the power source voltage. You could even try 3 leds in series and as long as the LEDs can still operate around 2v they'll light (though dimmer than if they were getting the full 3-3.2v each). If you add too many LEDs though, you won't meet minimum voltage requirements and they won't light. Have fun! |
| without a resistor |
| Posted 11/18/09 1:31PM by spaceshipman |
| so am I right that if I hook up 2X 3V LEDs in series to a 6V battery I wont need a resistor? I'm also a beginner! |
| To Math Confusion |
| Posted 09/01/09 1:48PM by Anonymous Techdoser |
|
The 18A that the PSU puts out is not the component in the calculation that you should be using. What you are looking for is the consumption of the LED which is typically 20mA or .02A. Thus your calculation should be (12V-3.2V)/.02A = 440ohms. The resistor that you would need is a 470 ohms resistor. They are color coded as : Yellow, Violet, Brown, Gold. Note you should verify the voltage of the LED as every color has its' own voltage. Also verify the mA used by the LED. |
| Try this One |
| Posted 08/30/09 7:45AM by Anonymous Techdoser |
| use the same circuit with a lemon or two. Stick a piece of copper wire in one end and a galvanized nail in the other. You should have enough current to light the led. Trick add more lemons(batteries)to make it brighter. Then try other foods around the house. Why do some work and others don't. What even works better as a load is one of those little digital clocks from the dollar store. It takes very little current to make one of those start working and it is useful also. McGuyver will be proud of you. |
| Math Confusion |
| Posted 07/27/09 10:39AM by Anonymous Techdoser |
| Okay, going back to the simple circuit above... 6V - 3.2V / .02A = 140ohms. So, if, for some reason, I wanted to power an LED off of a PSU at 12V/18A... 12V-3.2V / 18A = 0.5ohms. That can't possibly be right! What have I done wrong, please? |
| larger batterys and several LEDs |
| Posted 06/12/09 9:08AM by Anonymous Techdoser |
| i would like to set up a string of some where around 200 leds and have them chase 4 or 5 light up at a time down the string i'm assuming ill have to use a car battery to get the voltage and ampreage that i need to do this successfully but am un sure of how to sequence them to work properly. i would like to see 5 on 5 off 5 on 5 off and so forth down the string |
| Power rating |
| Posted 05/25/09 7:02PM by Anonymous Techdoser |
|
These are the two most basic equations to electricity (they are useful to anyone and everyone, not just engineers and electricians): Power/watts(P) = Volts(V) * Current/Amps(I) Volts(V) = Amps(I) * Ohms(R) Typically written as: P=V*I V=I*R In the example a 6V bat is being used with a 3.2V LED, and a 330 ohm resister. This is all you need to know. To get the resister power, we need the resister voltage and current. ResisterV = BatV - LoadV = 6 - 3.2 = 2.8V ResisterI = (I=V/R) = 2.8V / 330ohms = 0.0085 or 8.5mA Now Resister Power = 0.0085A * 2.8V = 0.0238W Less than a tenth of a Watt is required. What if you choose the max rated power of 20mA with the 140ohm resister what is the power then? |
| To extend to 10LED with 9V |
| Posted 05/25/09 6:30PM by Anonymous Techdoser |
|
I assume you've identified that your led's forward voltage is 3.2V (they are not all the same, i'm working with IR LEDs right now that are 1.2V). If you have 3.2V LEDs then you can put two in series with the resister (for 1.2V LEDs, you could use 5-6 in series). However, for more you must make a parallel path with another resister and two LEDs. But you are right, for the resister look at the total series chain for voltage drop. (9 - 3.2 - 3.2) / 20mA --> 2.6V / 0.02A = 130 ohms (plus some margin for life time if needed). You may not use a common resister for two parallel pairs of LEDs. If one pair has a slightly smaller forward voltage total, then one side or the other will take more amperage and could keep one side off, and possibly blow out the other side. |
| Ok... help me extend this. |
| Posted 03/13/09 6:15PM by Anonymous Techdoser |
|
I have a 9v battery and want to light a series of LEDs (up to 10). 9v-3.2v = 5.8 5.8/20mA = 5.8/.02A = 290 ohms? But how does a series of LEDs affect it? If I hooked up 3 LEDs... you can't just keep subtracting. (9 - 3.2 - 3.2 - 3.2). Yes, I'm an idiot. I got a D in physics electromagnetism 20 years ago. |
| question about power rating on resistor? |
| Posted 02/25/09 10:12AM by Anonymous Techdoser |
| How do you know what power resistor to use? I mean 1/4 watt, 1/8 watt, 1/2 watt, etc.? I just bought a breadboard myself and this question has come up several times already. Any help would be greatly appreciated. |
| I can't get it! |
| Posted 01/05/09 9:36AM by Anonymous Techdoser |
| The title says it all. |
| Doesn't matter. |
| Posted 05/23/08 2:02PM by Anonymous Techdoser |
| The resistor can be on either end... The only thing that matters is that the polarity is right on the LED. Put the resistor anywhere you want. If the LED lights up voilla, if it doesn't reverse the pins and it will. |
| Simple LED Circuit |
| Posted 04/15/07 4:34AM by deltaboy12000 |
|
LED's cathode is identified by: 1. the short lead of the LED 2. the flat side of the case of the LED 3. the large internal metal side of the LED. If further understanding of LEDs is wanted look up N-type and P-type material. This is very advanced reading but it the science as to why LEDs only "work" when forward biased. Also in the digital world keep in mind its sometimes required to reverse bias a diode... |
| Just a small note. |
| Posted 10/21/06 2:42PM by TruthByDenial |
|
If your led doesn't light up. or you are confused. ∙Make sure your battery isn't dead ∙Flip the LED ( It only conducts current one way.) ∙You're resistor is fine, as long as its directly connected to positive wire. |
| I figured it out, before I found this site. |
| Posted 10/21/06 2:39PM by TruthByDenial |
|
One of the few things that I found Interesting is that, from negative to positive, You would have this {Wire (-) Connects to LED (-)} {The other leg of LED, LED (+) connects to one leg of resistor. (There is no way to put a resistor in backwards)} {The other leg of the resistor plugs into wire (+). So it goes. - wire, LED, Resistor, + wire. Hope this helps as I have just figured it out, and I'm just starting to learn about electricity and circuitry |
| Resistor Direction |
| Posted 10/12/06 8:28PM by PUREMUNY |
| Please help. I am trying to hook up a 2.4v LED light to a 2 AA battery pack. Which direction does the resistor go? Which end of the LED? Positive or negative on the battery pack. Thanks |
| lame |
| Posted 05/03/06 12:03AM by Anonymous Techdoser |
| I can't figure it out so I decided to maek a necklace out of all my resistors!!! It is so kewl LOL!!11! |
| URGENT |
| Posted 05/01/06 5:01PM by Anonymous Techdoser |
|
YOU MUST HAVE INSERTEED SUMTHING ELSE INSTEAD OF BATTERY CHEQUE YOUR PANTS |
| Diodes. |
| Posted 04/24/06 8:49AM by Anonymous Techdoser |
|
Two probably errors: -Battery polarity is backwards (fix: switch battery leads to circuit) -Diode is placed in reverse bias, backwards (fix: take out diode, flip it or turn 180 degrees, replace diode.) One possible error: -Something (breadboard, resistor, diode, battery) is broken or out of power. Note: Diodes require 0.7V to bias properly (light up). |
| help. |
| Posted 04/16/06 3:13PM by Anonymous Techdoser |
| maybe you've got your resistor in backwards? |
| I can't figure it out!! |
| Posted 04/16/06 3:12PM by Anonymous Techdoser |
| I've read the instructions like a millions times and I can't get it to work!!! LOL!! This schematic is too complicated. |