homemade LED's

[Malabooboo]

...and what it looks like with the light on:

nothing special, but I've got plans :D

[Maxpowers]

ah LEDs i u should always have a resistor plugged with an LED just cause it will protect the LED from being Burnt and it will give u the best Brightness if u are using a proper resistor i think for 5v we used a 150ohm or 300ohm and that worked well. if u need some formulas for getting what u need Power=Voltage x Current and Voltage = Current x Resistance.

What u Have
5mm, 5 volt, 30mA, 300mcd

this is what u do R=5v/30mA
R=166.66Ohms

so use a resistor that is the closest to 167 Ohms so 150Ohms Resistor should do the job, But check the spec sheet that u got with the LEDs and see what is the voltage and current for nominal brightness.

O also i noticed that u already got some resistors... if u are unable to retrun thouse u can plug them in parallel to get the same effect of a single resistor here is a crappy diagram


Gah i think the format is a bit messy so i did a pic of it

[Malabooboo]

that's an idea, although I don't mind buying the right resistor, since they're really cheap.

ok, now what resistor do I need? when I run the numbers through this site Mr. C posted:

http://www.bit-tech.net/article/68/

...I get 233.3 ohms

[Maxpowers]

hmm ok the 1st question u should ask your self is what Voltage do u want to use??? the 5v or the 12v comming off the psu (i suggest use the 5v), and what is the diode forward voltage on the spec sheet of the LED. also there is a small problem with that calculator its idiot proof and it does not take in Real life situations for example when the Supply voltage = Diode forward voltage u get a R value of 0 this is NEVER used in real life as voltages spikes do occur and a voltage increase over a period of time will break the diode i guess it does not matter if u use cheap red or green or yellow LEDs but if u get into the Rare white or blue ones its a diff story. the reason for the Resisitor is so that the Diode only takes the voltage it needs and the rest is used up in the resistor if the voltage is way too high then u will see smoke come out of the resisitor but the LED will survive. so my final words are if u want to use the calculator online do its not that bad just make sure u have all the right values. :thumb:


hmm i should not answer things too early in the day there is a mistake the formual i gave u

its suposed ot be (Supply-Diode voltage)/current
sorry about that

and Diode voltage is usually 2.7v just in case u cant find it but i would try to find it somewhere cause it is important

also going back to my formula its the same thing as the page if Diode forward voltage = supply then R =0 rule that i use if thats the case then stick in a low R value

[lucas]

I'd start with a 390 ohm 1/2 watt resistor and see if that gave me the brightness I wanted. The 233 ohm value assumes that the forward drop across the led is 5 volts, which I think is a shakey assumption.

[Maxpowers]

ya i dont think it goes that high i would use 2.7v as voltage forward

[Malabooboo]

cool, thanks guys--it just says on the box the led came in "5 volt" so I assumed that's what it was

[dryadsoul]

The blues can be got here so someone would have to have them there as well ya'd think. :?:
<center>:cheers:</center>

Wiggo thinks correctly again: Radio Shack, being a
franchise outlet, may/nought have/be willing to stock needed LED's/resistors; however there are many other type's of stores
that always have them in stock. And i guess best resource for
Malabooboo, given your location, would be Fry's Electronic's-brick & mortar/outpost.com -click & mortar.
But, also found them yesterday, in Portland Hobby shop
at killer price: bag of 5 incl. resistors @ $4.00 in White/Red/Green/
yes,even Blue.......several sizes too.:wave:

[Malabooboo]

these are the LEDs I got, and it says on there "Typical Voltage is 5.0, with a maximum voltage of 6.0V"

you guys were saying blue leds are usually 2.7--how come this one is so high?

if my LEDs are 5V, I can just use my 5V wire from the power supply with no resistors, right? (sorry, I'm new at this whole electrical thing)

[Maxpowers]

this means that the LEDs have a built in resistor... again when u buy LEDs ask ask ask for a spec sheet of the LEDs u are buying on the spec sheet you will know every thing about the LED, if u have gotten the info that 5v will work and 6v max then plug it in and try it i guess i mean the worst that can happen is u will hear a pop and some smoke come from the LED, (but dont hold my word for it just in case it does not) that is if u have hooked it up right make sure not to mess up the (-)'ve and (+)'ve terminals as pluggin in some LEDs the wrong way can kill them, but i have never had this happen to me all that happened is that if u plug it in the wrong way it will not work :omg:

[Malabooboo]

built in resistor? nice!

how can you tell which is the positive?

[Maxpowers]

ok here is a site that came across me http://www.ledreps.com/faq/default.htm
it should solve any questions u have about polarity and so on

[man42871]

Re: homemade LED's

I bought some blue LED's (5mm, 5 volt, 30mA, 300mcd) at radio shack. And i need to know what kind of resistors i need to make them work right? I have a 12 volt power supply. I can make the lights come on but than are not bright.

[Lsdmeasap]

Re: homemade LED's

Depends on how many you use at once, here is a few calculators

Single
LED calculator for single LEDs

Multiple
LED series parallel array wizard