Soldering Problem

[Scottzilla]

Okay, so here's what we know about your LEDs:
Forward Current - 20mA
Forward Voltage - 2.2

If you use a 9v power supply or battery and the LEDs are dropping 2.2v of that, then it means we need the resistor to drop 6.8v (9-2.2). We now know the voltage across the resistor and the current going through it (20ma or .02 amps, same as the LEDs), so we can use Ohm's law.

6.8v / .02A = 340 ohms

The next-highest standard value resistor is 390 ohms, so that's what you'd want to use (get 1/4 watt; 1/8 watt isn't big enough).

[Scottzilla]

BTW: technically you could power your 8 LEDs with fewer resistors, but this way you can have as few or as many LED/resistor pairs as you want without having to recalculate anything.

[mindtumor]

You could buy a power supply from minispotlight, that way you aren't draining batteries. It seems to me they were like $15.00 or so. That just covers your source though, you still need them resistors.

[Smiley]

Ha! Who needs night classes when I have you guys, eh?

Now that I've created something that works, I can start on the real thing.

[imax]

congrats, and good work!

[Infoamtek]

By George, I think he's got it.

[Scottzilla]

It's alive!

[Smiley]

O' Christmas tree, O' Christmas tree....



Almost done with my prop.

[Scottzilla]

Nice work. I can't wait to see your prop.

[icandrawem2]

Thats awesome man it looks just like a real workbench with real tools! sweet prop!