hello everyone, i am planning on wiring up some leds to light up a area inside of my case. I was going to try and keep it as simple as possible and was wondering if i would be able to wire each led separate from each other like this. http://www.putfile.com/pic.php?img=7075782 i was just wondering if you all thought this would work or not. im not connecting each led on the same series or in parallel so do you think this will work or not? thanks if you have any suggestions please tell me. im a noob when it comes to wiring up leds. thanks
You're basically wiring an LED and a resistor in series; then wiring all your LED/resistor sets in parallel across the +%V or +12V rail; and yes it does work.
ok thanks for your help. ive been wanting to put some leds in my case and got some off ebay so i figured why not. just was not sure how to wire them up. do you think ill have any problem setting it up like this? thanks
As long as you use the right size resistor for each LED you'll be fine. The resistor selection is based on 3 things; Supply voltage = Vs LED forward voltage = Vf LED current draw = If (mA) The necessary resistor size (ohms) is: R = (Vs - Vf) / If
ok heres the specs for the led forward voltage 3.2- 3.4v forward current 20mA and supply voltage is 12V so R= (12 - 3.2) / 20 = 0.44 or 440 ohms?
ok so when my leds and resistors come in how do i tell what resistors i have, i know that you use its color stripes to determine what it is but is there i guide that i can look at for these codes? thanks
I'd say save yourself some soldering & some heatshrink and just buy 1 x 430 ohm 1 watt resistor. This gets soldered to the +12v and then solder the four led power wires to it. The ground wiring would be the same: Don't use less than 1watt resistor or it will get hot. 1 watt won't get hot, maybe just the tiniest bit warm if anything at all. You can use 2 watt or higher if you want to ensure that no heat whatsoever is felt at all. edit: maybe future proof/upgrade proof it, and just use a 430 ohm 5 watt resistor, that way you can wire up to about 15 leds without heat being felt. I reckon about 10 blue leds, spaced out well, would light up that blue case nicely btw
Here's how I remember it: 0 Big Black 1 Brown Brown 2 Rabbits Red 3 Often Orange 4 Yield Yellow 5 Great Green 6 Big Blue 7 Vocal Violet 8 Groans Grey 9 When White 5% Gingerly Gold 10% Slapped Silver So red blue violet red gold is 267 x 102 = 26700 ohms, 5% tolerance
i think ill just stick with my way of doing it since i already have one resistor for each led that i have plust i should be able to run as many leds off the connector as i need to.
It would be if he'd used a 120R resistor, but two mistakes cancel out. With a single 430R to 4 parallel LEDs they'll roughly share out the 20.4mA available, ~5mA each.
Quick way to damage the leds??? +-5ma? In my limited experience i've seen a variance closer to +- .5ma, this is using a digital multimeter.... An extra .5ma can blow the crap out of an led, so it's best to solder a resistor for every led, after measuring the actual resistance of each resistor in the store before buying, to try get as close to the 20.4ma as possible. I think i better rewire the leds in every single pc, amp, speaker, car, router, anything else i've installed leds in?
the main reason that i want to put 1 resistor per led is because in case 1 resistor goes out it would only take out 1 led instead of 4 or more. that is my main reason for wanting to do it this way.
Problem here is that if one LED have a tiny, tiny production error (very common) it will draw more current. In some cases this could make one led draw all the current that can be passed trough the resistor. If the resistor is calculated for 4 x20mA that one LED will suddenly draw 80mA. At these currents most LEDs start to smell funny. I have seen it happen. When resistors burn out they very rarely short. They just stop conducting. However, i highly doubt that a resistor will burn out at those loads.
The ~5mA means 'about 5mA', not '+/-5mA'. Putting "similar" LEDs in parallel doesn't guarantee they'll share the current evenly if there's only 1 resistor to several LEDs; the one with the lowest forward voltage, even if only by a few mV, will take more than its fair share and get a bit warmer. Rising temperature lowers forward voltage, it takes an even bigger share, so it's easy to get runaway and burn out one LED and then put more load on the others and repeat. With the 430R resistor you suggested no harm would be done, as each LED will only get about a quarter of the safe current, but the common mistake is to aim for 80mA with four parallel LEDs using 110R (or the nearest value). Looks OK in theory but the LED tolerance may give bad results. But using 430R for 4 LEDs giving ~5mA isn't going to give as much light as 20mA per LED, and with multiple LEDs most users want maximum illumination. One resistor per string of series LEDs is the best way. True, but then each LED only gets 1.33mA and will be fairly dim. The resistor will only dissipate 0.18W so why use a 5W? See Kirchoff's Laws.
so ok, heres basically what im trying to do, i have a fan in the case that i want to light up with four leds, i ordered leds and 1 resistor for each led, which ever resistor that calculates out to 12v supply is what im getting, so 50 leds and 50 resistors so im thinking if i have the supplies why not use them. so is my way of wiring the safest way of doing it and the least complicated? or should i try another way.
MASSIVE BRAINFART I see what you mean by "two mistakes cancel out", but it's actually three mistakes i have often wired them in series with a single resistor, looking back, it's possible i haven't wired them in parrallel before I dunno why i drew a diagram for wiring them in parrallel that's really wierd, kirchov would be pissed! Sorry kirchov, i was listening in class all those years ago, first time i forgot, honest I have a theory, usually when i get a question of attaching devices to a molex, it's often about connecting fans = no resistor, just wire them up in parrallel When i brain-farted it's quite obvious which memories got mixed up Your way is fine morris, best to ignore me sometimes i guess
