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Step 7Wiring up multiple LEDs in series
Now that I knew how to wire one LED with various combinations of LED voltages and power supplies, it was time to explore how to light up multiple LEDs. When it comes to wiring more than one LED to a power supply there are two options. The first option is to wire them in series and the second is to wire them in parallel.
To see an in depth explanation about the difference between series and parallel check out this page. I'm going to cover wiring LEDs in series first.
LEDs wired in series are connected end to end (the negative electrode of the first LED connects to the positive electrode of the second LED and the negative electrode of the second LED connects to the positive electrode of the third LED and so on and so on...). The main advantage of wiring things in series is that it distributes the total voltage of the power source between all of the LEDs. What that means is that if I had a 12V car battery, I could power 4, 3V LEDs (attaching a resistor to each of them). Hypothetically this could also work to power 12, 1V LEDs; 6, 2V LEDs; or even 1 12V LED if such a thing existed.
Ok, let's try wiring 2, 2.6V LEDs in series to the 9V power supply and run through the math.
R = (9V - 5.2V) / .02A
R = 190 Ohms
Next higher resistance value - 200 Ohms
Now the variety package of resistors didn't come with a 190 or 200 Ohm resistor, but it did come with other resistors which I could use to make a 200 Ohm resistor. Just like LEDs, resistors can be wired together in either series or parallel (see next step for an explanation on wiring things together in parallel).
When same value resistors are wired together in series you add their resistance. When same value resistors are wired together in parallel you divide the value of the resistor by the number of resistors wired together.
So, in the most simplified sense, two 100 Ohm resistors wired together in series will equal 1 200 Ohm resistor (100 + 100 = 200). Two 100 Ohm resistors wired together in parallel will equal one 50 Ohm resistor (100 / 2 = 50).
Unfortunately, I learned this key point after I wired my resistors together for the experiment. I had originally wanted to wire two 100 Ohm resistors together to equal the 200 Ohms of resistance I needed to protect my LEDs. Instead of wiring them in series, as it should have been, I wired my resistors in parallel (did I mention I am beginner with resistors?) So my resistors were only providing 50 Ohms of resistance - which apparently worked out OK on my LEDs in the short duration of the experiment. Having too much power getting to the LEDs would probably burn them out in the long term. (Thanks beanwaur and shark500 for pointing this out.)
I took my resistors and placed them in front of the positive lead of the first LED that was wired in series and hooked them up to the battery and once again, there was LED light!
With three different combinations of LEDs and battery power supplies and no puffs of plastic smoke yet things were looking good - aside from my little confusion between wiring resistors in series and in parallel.
To see an in depth explanation about the difference between series and parallel check out this page. I'm going to cover wiring LEDs in series first.
LEDs wired in series are connected end to end (the negative electrode of the first LED connects to the positive electrode of the second LED and the negative electrode of the second LED connects to the positive electrode of the third LED and so on and so on...). The main advantage of wiring things in series is that it distributes the total voltage of the power source between all of the LEDs. What that means is that if I had a 12V car battery, I could power 4, 3V LEDs (attaching a resistor to each of them). Hypothetically this could also work to power 12, 1V LEDs; 6, 2V LEDs; or even 1 12V LED if such a thing existed.
Ok, let's try wiring 2, 2.6V LEDs in series to the 9V power supply and run through the math.
R = (9V - 5.2V) / .02A
R = 190 Ohms
Next higher resistance value - 200 Ohms
Now the variety package of resistors didn't come with a 190 or 200 Ohm resistor, but it did come with other resistors which I could use to make a 200 Ohm resistor. Just like LEDs, resistors can be wired together in either series or parallel (see next step for an explanation on wiring things together in parallel).
When same value resistors are wired together in series you add their resistance. When same value resistors are wired together in parallel you divide the value of the resistor by the number of resistors wired together.
So, in the most simplified sense, two 100 Ohm resistors wired together in series will equal 1 200 Ohm resistor (100 + 100 = 200). Two 100 Ohm resistors wired together in parallel will equal one 50 Ohm resistor (100 / 2 = 50).
Unfortunately, I learned this key point after I wired my resistors together for the experiment. I had originally wanted to wire two 100 Ohm resistors together to equal the 200 Ohms of resistance I needed to protect my LEDs. Instead of wiring them in series, as it should have been, I wired my resistors in parallel (did I mention I am beginner with resistors?) So my resistors were only providing 50 Ohms of resistance - which apparently worked out OK on my LEDs in the short duration of the experiment. Having too much power getting to the LEDs would probably burn them out in the long term. (Thanks beanwaur and shark500 for pointing this out.)
I took my resistors and placed them in front of the positive lead of the first LED that was wired in series and hooked them up to the battery and once again, there was LED light!
With three different combinations of LEDs and battery power supplies and no puffs of plastic smoke yet things were looking good - aside from my little confusion between wiring resistors in series and in parallel.
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I have a question but btw, you have an awesome website for ppl like me who's interested in learning to light up some LEDs!!!
Forward voltage: 3.0-3.2
Current: 20ma
Battery: 6V
1. Following your instruction, I first tested my 2 of my LED, in a series without any resistors to my 6V and baam! it lit up! thanks!
but after about 20 secs, the LEDs started to get hot. Is that normal? I don't think I'd need any resistors or I wouldn't even know how since I would get 0 ohm resistor value
2. My project is to light up 8 LEDs. 4 pararell LED each side, then 2 of 4 pararell LEDs in series. so like. (1+1+1+1) + (1+1+1+1).
so I'm thinking (3V, .08ohm) + (3V, .08ohm) so it would be 6V with .08ohm right?
then it would require no resistor since 6v-6v=0 right?
Or would that get too hot and require resistors?
any help is appreciated!!!
Thanks!!
So if your LED requires Forward Voltage of 3.0-3.2Vf, and 20mA, and you want to run it off 6V. If you were just trying to power one LED it would be (6V-3.2V)/.02mA. Meaning you'd need a 140 ohm resistor before attaching the LED to power.
As far as hooking them up in series/parallel, you should be able to do it with one resistor at the beginning of each series of 4 of 140 ohms. Which would make each series 20mA and 3.2 Volts after the resistor. Hope this helps.
I have two 5 Volt LEDs from radio shack. What would be the best way to hook them up and with what ohm of resistor?
Thanks
Actually ... such a thing now does exist!!!
http://led.linear1.org/12vdc-leds-from-best-hong-kong/
Insane!!!
Thanks.
That is no different at all from you buying a regular LED that runs at 1v to 3.5v and adding resistors to allow them to run off of a 12v power source.
A 12v LED would not need any resistor to run directly off of a 12v power source (but what color it would be, I have no idea, as the voltage of the LED is tied in directly to the LED color...)
While that is not strictly true, as the emitted colour is dependant on the particular semiconductor material used, one finds in practice that various colours of LEDs have different forward voltages.
OK, how about these: www.elexp.com/opt_3330.htm
i changed the lights on my dash using LED's , if you are going to use series calculate your circuit for 14V so your resistance should be R=(14V - (Nleds*Vleds))/0.02Amp where Nleds is the number of leds you are using and Vleds is the voltage they consume, if you dont have testing equipment or the datasheet for your LED's you could use 1.7V to do the math, id also reccomend u look for an instructable here on LED diffussion
It only makes sense to construct a circuit with a single LED per current limiting resistor if the source voltage is 5 volts (for white LEDs) or about 3 volts (for red LEDs). Otherwise, if the circuit operates from 12 volts DC, and contains 3 white LEDs, it would only make sense to place them is a series configuration with one resistor. This is only one circuit example.
Placing all three LEDs in parallel with a resistor for each string would draw 3 times total current, making the circuit much less efficient. This results from all the excess heat disipation from the resistors. However, placing the LEDs in series will only draw 20mA (as opposed to 60mA or whatever drive current was chosen). A high quality LED (such as Nichia Brand) should not fail unless exceeding the data sheet ratings.
I found lots more information like this on the Lunar Accents site: http://www.LunarAccents.com