Electronics (renamed thread) HELP! lOOK AT MY WORK, WILL IT EXPLODE?

Alrighty, in my project log which is in my sig, i wan't to solder some LEDS but im 15 yeras old and know hardly anything about electricity(really like nothing)
SO i foudn a good webisht, http://shop.sickmods.net/shop/Resistors/1.4_Watt/ but im still confused. So what do i need besides the LED? the resistor, wire, anything else? and how can i give it power without doing any sever mods to my 330$ psu? or do i have to get a cheapo- second psu? and if i do that, how do i go about having my power switch turn on both psu's?

thanks for help, and guys i mean im a total noob anything, ANYTHING i should know would be appreciated

 

hi

yeah thats about it + a stripboard to solder everything together(not important)
electricity is all about V= I x R, there is alot of info how to calculate the resistor just hit google

this is good : http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator

 

thanks, but then how do i connect 2 psu's to one power switch?

 

How about some basics about LEDs:

linear 1 led center.

Everybody uses a LED calculator, so use the wizard.

Next some basics about electronics. Most computer LED modding is going to require 1/2w resistors, so spend the extra few pennies.
Next you have your elements (LED, resistor, etc), you need a way to connect them. Best method: soldering wires between them (or you could use bread boards, but they're a little inconvenient to mount).

So to work with wires, you'll need some wires (20 AWG is fine), you'll should get a stripper/crimper tool, you'll need a wire cutter (all available at radioshack or sears). To connect the wires, your best bet is to solder them, so you'll need a soldering iron and solder, and super useful a Helping Hands kit. To cover over your joints, its best to use heatshrink tubing and a lighter. Alternatively, you can ghetto your connections by twisting the bare wires together and taping with electrical tape.

The easiest way to start to psus simultaneously is to buy it from performance-pcs.

Alternatively, you can do a little research and build your own for a few bucks.

Next, you need a power source for your LEDs. 3 common voltages are available to you from any 4 pin molex termination from the psu. 12v, 5v, and 7v. To get 12v, you connect across the yellow line and a black ground. To get 5v, you bridge across a red line and a ground. To get 7v, you bridge across yellow to the red (12-5=7 get it?).

To access these lines, the simplest method is purchase some 4pin molex extension cables (again available at performance-pcs) and cut them up.

Alternatively, you can buy the housings, the pins, wire, and a crimping tool and build your own cables from scratch.


My recommended basic tools:

Basic stripper crimper tool
Wire (performance-pcs)
soldering iron and solder
Heatshrink tubing and lighter
Electrical tape

 

You'll only need the 5v if your running LEDs, and its dead simple to set them up. It is however highly important (like super super important) that you put them in facing the correct direction, because they will only work if put in forward-bias. The long leg of the LED is the positive side, and the shorter one is the negative. If you cannot tell or if the legs are the same length because they've been cut, take a look inside the actual bulb of the LED and look for the "flag." The flag is the negative side of the LED, so the leg connected to it is the negative lead, or cathode.

To string LEDs together, connect the positive leg of LED 1 to the negative leg of LED 2 and so on.

To know the difference between anode and cathode, which are the positive and negative legs on the LED, think of the rule A+ C-. Okay, its not really a rule, but just remember it.

Use Linear's resistor calculator to find the perfect resistor for your setup of LEDs. Resistors are very important or else your LEDs will burn and smell horrible.

 

thanks.
So, this is estimate but, if im goign to run 4 led's, then i should go:
12v from molex->soldered to 12 gauge wire or 20awg wire-> resistor that matches exactly the led setup i have, usign calculator->led negative side-> next LED's negative side-> yada yada yadda finish chain of led's->wire that goes to where? to the negative 12v back to the molex? thats where im a little lost here...

 

1) You need to figure out how to build your circuit. Do you want your LEDs in a series or parallel. The linear 1 wizard is going to give you some suggetions, but its best to figure it out. For example, if you have exactly 3v LEDs, and you want 4 of them. Then you could roughly string all 4 of them in series off the 12v line. +12v source (yellow wire) - 1st LED (will roughly drop the voltage to 9v) - 2nd LED (roughly drop to 6v) - 3rd LED (roughly 3v) - 4th LED (roughly back to ground) - Ground (black wire).

On the other hand you may wish to wish to go parallel. Again, the hypothetical 3v LED. Then the nearest voltage line would be the 5v. So you would go +5v source (red wire) - resistor (exact ohms can be calculated by the calculator) - LED - Ground (black wire). To get 4 LEDs lit in this fashion, you would need to make 4 parallels of this circuit.

So, make sure to draw lots of diagrams first.

If you want, I am getting set to wire up some LEDs in my current project. See post #56. If you want, I'll post some explicit diagrams and drawings and pics, so you can get a good idea of how to work things. Unfortunately, I won't get to it for a few days.

navig

 

just to remind everybody there is another method to find out the negative lead of a LED: there is a flat side on the plastic casing of the diode you can just turn the led and feel it or see it whatever you prefer.

 

http://www.metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng

i find this site works alot better and the guru feature is useful for noobs

 

im still not understanding the difference between parrallel and series, does one have a resistor for each one?

 

have a look at the site a linked above

series : voltages add up

so if you have 3 leds in series and they are each 3 volts then they need 9 volts
if you have 12 volts and you only need 9 volts then you have to remove 3 volts using a resistor
the resistor needed can be calculated useing V =I x R (say the leds are 20ma)
3 = 0.02 x R , R = 150 ohms ( nearest is 180 ohms)

parallel : Amps add up
if you have 3 leds in parallel and each leds is 3 volts then you only need 3 volts
if you have 12 volts and you only need 3 volts then you have to remove 9 volts using a resistor
you can also run groups of leds in series running in parallel , so you could run 9 leds in 3 groups of 3
when running leds in parallel you can use 2 different setups for the resistor/s
1. you can use 1 resistor for each line ( 3 resistors in the above example )
if you wanted to drop the voltage buy 9 volts for each line then you would use 9 = 0.02 x R , R = 450ohms ( 470 ohms nearest) you need 3 of then one for each led
2. you can use 1 resistor before the wires split (this way is easier but not as safe)
if you wanted to drop the voltage buy 9 volts then you would have to add the amps from each line 9 = 0.06 x R , R = 150ohm (nearest 180ohm)

 

thanks! you have been so helpfull. So series/parallel sounds the best to me, but is the only disadvantgage of number 2( 3 resistors) that you have to buy 2 more of them?

And just out of curiosity, if you wan'ted more, its not possible for that 12v line? you need to to go on to another line, right? line being another molex

 

if you wanted you could have up to 4 3volt leds in each line 4x3=12 and then use a very small resistor if any at all or you could use lower voltage leds (reds are 2volts ) so you could have up to 6 of those

and yes the only problem with 2 is that you need are resistors , with 2 you can also have diferent amounts of leds in each line as long as the resistors for each line make the total voltage up to 12v

you can also use different volt lines yellow wire is 12v and red line is 5v

 

alright! i bought everything.
got some soldering stuff!
40 watt soldering gun
22 gauge wire
electical tape
.032" solder
3 blue led's
tons of various resisters
And i got my test done. tell me if this is going to explode:

Shot with COOLPIX P4 at 2007-07-10
anything i missed? can i plug it in? i think its a 1/4 watt 120 or 220 ohm(whatever is what you need) its not perfect, and i know the led's willl burn to br i ghtly/ not bir ghtly enough, but this was just to see if i could do it before gettign it perfect and ordering it online. So does this look safe to test?

 

if you did the calculations correctly i don't see how its going to explode. Just remember Ohm's law V=IR with the correct units (voltage in Volts, current in Amps, and Resistance in Ohms) and you should be good. good luck

PS. should take high school physics if they offer it at your school, you can learn the basics of electronics, pretty useful IMO, i took it last year when i was your age ;D

 

damn. it didn't work. Im gunna try a different resistor.

I don't have a SATA take off thing, so i cut the cables off of the sata head, could that have done it? i

 

.

 

GODDAMN!

with a new resister(different watt/ohm) and only 2 led's it still doesn't work.

Next im goign to try 1 5v led straight up to 5v(yellow) wire...

 

If you run a parallel, you can basically run as many led's as you want.

 

guys i need your help! ill make a diagram of what im doing to see if we can see whats wrong,

but i CANT GET IT TO WORK!!!!

ive tried every combination, yada yada yada...

your supposed to but electrical tape at the jonts, right?