Wiring Multiple LEDs
LEDs in Series
Wiring LEDs in series is pretty easy -- and a great way to learn how wiring in series affects the voltage and current on the circuit. In college, they taught us with actual light bulbs with sockets that we'd clip together in series with various leads -- ah, the good old days!
When wiring up any electrical circuit, the equation V=IR (otherwise known as Ohms Law) is imporant in figuring out the voltage and resistance at various points and the limits of the circuit. An interesting thing with series circuits is while the voltage drop will change based on the number of components you're hooking up, the current remains the same across the entire circuit.
Voltage = Current * Resistance
So V=IR can be rewritten V/I = R:
Voltage / Current = Resistance
So lets figure out how many resistors would be needed to connect two LEDs "in series":
(6v supply - 3v led - 3v led) / 0.02 Amps = Resistance
0v / 0.02 Amps = Resistance
Since 0 divided by anything is still 0, no resistors are needed.
Thus, the circuit would look something like this:
Why no resistors? When wiring in series, the current remains the same across the circuit, but the voltage still changes based on the number of components being hooked up. So since both LEDs need around 3v to light up, they're essentially using all of the 6v of the power supply in that circuit up and balancing some complex equations. If you had a 9v power supply, you could wire up 3 LEDs in series.. however with just a 6v power supply if you tried adding a 3rd LED the voltage drop of 9v would exceed the power supplies voltage enough that the LEDs wouldn't be getting the ~3v voltage they need to operate. This is probably why we used light bulbs in college, cause you would see the bulbs starting to dim as you hooked more and more bulbs in series, whereas an LED is more finicky about voltage requirements.
Below is a picture of two LEDs wired in series on my breadboard with a 6v battery supply as in the schematic. Notice that that (from left to right) the positive rail of the power supply connects to a jumper. The jumper connects to the anode of the first LED. The cathode of the first LED is then in the same row as the anode of the second LED. And the cathode of the second LED is in a totally different row that is then connected to the ground rail to complete the circuit.
Next lets take a look at wiring LEDs in parallel..
Comments:
| why is the resistor connected after the led |
| Posted 06/05/10 3:02AM by try.myx |
|
as in your circuit diagram in the wiring multple led , why is the resistor connected after the led . isnt it supposed to be in front. now im in doubt. From the way i think and understand the resistor is used to minimise the voltage. so that the led will not recieve excess of voltage from burning it. please clear me the doubt . thnx in advance |