Any electronic wizs out there?

[StrangeRanger]

I've got a 6v battery source and 2 little light bulbs that I need to power. Each light bulb, according to specs, runs at 2.4v and draws 500mA. Can you help me figure out what kind of voltage divider (ie: resistor) I need to step down from 6v to ~ 2.4v?
I tried using the Ohm's law calcualtion of R = E / I and got 2.4v / .5A = 4.8 ohm. But is that right? I can't seem to find a resistor with that low a rating. Thanks,
j

 

[nwfsnake]

You can probably just run them in series without a resistor.

 

[dighn]

put everything in series eg

(+)---bulb---bulb---vvvvv---(-) (vvvv = resistor)

so you have 2.4 + 2.4 + ? = 6 where ? is 1.2v

so just go R = V/I = 1.2/.5 = 2.4 ohm... you can find some 1 ohm resistors but it might work without a resistor too

 

[Demon-Xanth]

Light bulb, or LED?

Edit:
The reason why I ask, is that if they are light bulbs, you can just put them in series and run them as is. If they are LEDs, you MUST have a current limiting resistor. In this case, about half an ohm, and half a watt.

 

[dullard]

<- Dullard, not trained for this, but learned the hard way on his own.

Take Demon-Xanth's advice. If it is an LED, they don't run with a constant voltage - the voltage changes over time (resistance changes to near zero as it stays on). Instead, an LED runs off of constant current. You need a resistor to make certain the LEDs get a constant current (without it they burn themselves out by taking too much current). If they are just standard bulbs, a little extra voltage probably won't hurt.

Most 6V batteries aren't 6V, they are often a bit less (especially as they get used). So if you want a resistor, I'd go slightly under 2.4 ohms if you just want it in series (but there are possibly better circuits than that which would need different resistors). That is good, since I've never seen a 2.4 ohm resistor. 2 ohm and 2.2 ohm resistors are very easy to find (or a pair of 1 ohm resistors).

I like to take the worst case senerio. Low ohm resistors have a heat problem - low resistance means high current which overheats them. Most standard resistors people commonly think of are only 0.125 W, 0.25 W, or 0.5 W. None of those would be acceptable as they would burn up. I'd go for at least a 1 W resistor if I were you. Or maybe two 1 ohm (0.5 W) resistors in series.

 

[StrangeRanger]

Yes, I realize the battery is prolly more like 5.65v or so but even still you guys think i could just go:
+bat -->switch --> bulb 1 --> bulb 2 --> grnd
Guess I could try it...
j