Electronics help

[sinkoman]

Well, i'm a newb at electronics, but every so often I like to just muss around with stuff and try to make stuff.

So today I was going to go buy a few blue LED's, a couple of 9v batteries, and some pvc and make a flashlight

The LED's I plan on getting run on 5-6v's and have a 30mA current.

Now I want to make sure I don't blow any LED's, seeing as they are a tad expensive, and was wondering if I got this right.

If I was to run 3 6v 30mA current LED's on 3 9v batteries, I would need 200 ohms of ressistance, yes?

I was also wondering, would it be best to buy half volt ressistors or forth volt ressistors. They're both same price but I was wondering which would be best.

 

[sinkoman]

Oh cmon! Don't tell me nobody knows.

God, I gotta go get the stuff already.

:angry:

 

[duffers20]

Can't really remember that much about electronics from physics at school, but I do remember that if you connect up an led the wrong way round then you will blow it, best check that out. there will be one side of the led that has a small flat edge to it and thats how you tell the polarity of the led, not sure how though. Also this is the only formula that i can remember that i think will help you, V (in volts) = I (current in amps) * R (resistance in ohms). Good luck!

 

[psyno]

Yeah, no, I got it.

Depends how you're hooking it up, whether you put your components in serial or parallel. You won't want the current thru an LED to exceed 30 mA. For the simplest circuit you could imagine on these lines, a single 9 v battery in series with a resistor and an LED, you'd need to make sure that i < .03 A.

v = ir
i < .03 A
v/r < .03 A
v = 9
9/r < .03 A
9 < .03 * r
r > 300 ohms

Of course, your LEDs have a not-at-all-insignificant internal resistance, but that would only lower the current, so it won't blow up.

I can't say about your 3 battery, 3 LED setup without knowing how you intend to put it together. Feel free to attach a circuit diagram, like this: .

Of course, you'd want to figure out what that resistance is so you can make an accurate model of your circuit.

 

[sinkoman]

I got the stuff yesterday and soldered it all together yesterday.

I ended up using 4 AA's in a 4 AA holder, and 300 ohms of ressistance on a single, uber bright white LED.

YAY! IT WORKS! Hehe, don't you just love that satisfaction you get from doing something on your own, and then it WORKS!!!

Well, at the moment it's just a block of batteries with some wires comming out of it, some ressistors soldered onto it (I couldn't afford a cb) and a big mettal ball at the end (I got an LED holder too, just for kicks).

So today, I might run down to City Mill and grab some PVC, and it'll REALLY look like a flashlight!

:thumbs:

EDIT: BTW, It's a 3.6v 20mA 1100mcd white LED.

 

[Tyguy]

i made a house outta popsicle sticks........and it was great