led wiring help ?

[monica]

oh i see i have seen some like these that do come with resistor, that need to be added on some were,

what size are these onesas i like the 1.8 mm ones 3 mm i used before a little big to fit in light poles

as i said i know very little about this stuff, thus why , i need help, as with that one would not know were black and red on ,lol, :oops:

i will strip down the one i have and post it

 

[Deleted member 3568]

Hi moni its always the long one that's positive that's why it's longer these are 5mm which are the cheapest and for general use are ok but yes sometimes you need smaller ones

 

[monica]

oh i will remember that thank you,

see these are the ones I was going to get which are the same as the 3mm white ones i have at the moment,

http://www.ebay.com.au/itm/L1218DY-20pcs-Pre-Wired-1-8mm-Diffused-YELLOW-Led-Lamp-Light-Set-12V-18V-NEW-/170949297363?pt=AU_Toys_Hobbies_Model_Railways&hash=item27cd5f44d3

it do say that they are wired Pre-Wired(1000 Ohm resistor in series). if thats any help,

 

[monica]

got the pic for you and its a clear one, that is a resistors.?,

so i should be fine to run them off a 9v,or even 2 x AA ?

View attachment 83815

 

[Deleted member 3568]

Yes it's definitely a resistor. Resistors dissipate excess voltage they are rated in ohms the higher the ohms the more they dissipate. As an example 9v powering 1led would need 330 ohms resistor. 9v powering 2led would need 150ohms resistor. 12v powering 1led would need 470ohms and 12v powering 2 would need 330. If you were using 2AA batteries you would not need a resistor (depending on the forward voltage of your led mine is 3.2) so 2AA bats would light mine up. All of the above examples are based on my leds, not all leds have the same spec, the point I am making is this different power supplies require different resistors so you need to know what your resistor is and the forward voltage of your led. Sorry moni I am not an electrician this is just what I have picked up doing my rc ships and boats I am sure someone on here will give you a much better and more well informed explanation than I have, I mean I am sure resistors are much more complex than I make them out to be, but I only know what I need to know about them. Incidentally should you decide to use normal leds with no resistor when you use resistors you can attach them either way round they don't have a negative or positive.

 

[monica]

thank you so much for spending to time to help Ken and all, very nice off you all oh WOW, most off that went over the head lol,

but after reading it acouple of times, i do get what you are meaning, but its good they do have them on,so even with a 9vlt,or even 4x AA, i should be ok i think :oops:

you have explained it well, as its not just a matter off put in leds by the sounds off it, but ha, i try that way

your a better eletrician than I, we all ways manage to sort things out hear ,o_O

great help ta,

 

[Deleted member 3568]

Sorry moni I obviously didn't explain it very well if your led is the same specs as mine and runs on 3.2 volts 2AA batteries won't be enough if there is any resistor on them as it will reduce the voltage to a point where they won't light. Conversely if your resistor is say 150 ohms and you put 9volts through the led a 150 ohm resistor won't dissipate enough voltage and the led will blow so you need to know what resistor you have and what your led runs at. Sorry I am not trying to make things complicated just trying to save you wasting leds and time.

 

[monica]

your cool Ken, i know what your getting at and it is great help, and dont wont them to just blow, i understand that,much,

if im right dont resistor, have a standed color code for the ohm, i did hear or read that some were once, ?

and also dose it make a diffidence which way there run like looped or other ?

to how much power dose get to each led ?

4 x AA is still less than a 9vlt bat ?

sorry for the silly Q,s, but glad you spend the time to help,:rolleyes:

 

[Deleted member 3568]

Yes 4AA's= 6volts. And yes resistors do have standard colours but there are loads of them all I can tell you is yours aren't 150ohms or 330ohms or 470 as they are ones I use and none of those match your colours on your resistor, as I said I am no electrician and would not even know where to look for the colour coding I am sure someone on here must know. I would say the simple answer would be cut your resistor off and buy the one you need for your voltage, but even that's not that simple as I have no idea what your forward voltage is or what your forward current mA is 85%of leds run at 3.2 and 20mA but I don't know if yours are in the 15%which don't. Sorry I know that's no help.

 

[monica]

thank you Ken for all the time you have spent,explaining all off this, just go,s to show that some think is not as simple as one may think it is,

I think i have a model train shop some were around maybe ,they can run then and work out whats needed ,or have some one to help as well,

 

[Deleted member 3568]

Good idea sorry I couldn't be of more help

 

[monica]

you have been off great help Ken and i do real appreciate it, :D

i will look up that site, but themain problem is the ones i have did not have a bit of paper saying what all the specs are,so thats why you cannot work things out,:rolleyes:

 

[monica]

found some think interesting with this you tube ,

he said just to use a 1k resister, on each led, and that sorts out the hard maths,

and my head is hurting with all this oh my ,

so what do you think of that meth in doing them, ?

 

[Deleted member 3568]

Give it a go I don't know enough either way, maybe that is what you have on yours as I said it's not one I've used. Good luck anyway

 

[Deleted member 3568]

just checked it out and he seems to know what hes talking about (certainly more than me)go for it.

 

[Stevekir]

Search for:

resistor colour coding

This might help to show what the value of an LED resistor in (its measured in "ohms").

 

[monica]

sorry for the late reply,

you have done a great job of trying to get this stuff in my melon head Ken,im just a goof with some thing and you have done a good job,:rolleyes:

Hi Steve, yes i did look that up as well, was just trying cheats way not to mess with Ohms lore thats all,i did see some time ago

a chart for with this amount of this voltage leds use this resister, placed hear and hear, and so no,just wonted things to be easy :D