If the lamps that Ed wants to use are designed for 4.5 to 6V operation, they already have current-limiting built in. Heck, running them right off 12V might not even overcurrent them, but there's no way to know for sure without knowing more of what's in the package. -- Mike "Rocket J Squirrel" Elliott 71 Type 2: the Wonderbus 84 Westfalia: Mellow Yellow ("The Electrical Banana") 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano KG6RCR On 9/17/2007 12:37 PM Todd Last wrote: > I thought that current was the important factor in LEDs. > Does the LM7805 have a current range? > > I would guess that the battery device is limited by the current from the AAA batteries - which may not be so for the 12V car system. > > This may be a moot point, but as they say, a little knowledge is a dangerous thing. And my electronics knowledge is definately rusty. > > Todd > > -------------- Original message ---------------------- > From: vanagonvw <ac.vanagon@GMAIL.COM> >> Ed Duntz wrote: >>> Is there an easy way to run 4.5 or 6 volt LEDs on 12 volts? >> Yep. Piece o' cake. :-) >> >> LM7805 is the base number for the part at Radio Shack. It can deliver up >> to 1 amp out, so depending on what you are doing, you need more than >> one, or a different device with more output capability. >> >> An LM317 is much the same, only it allows you to adjust the voltage out >> with a few resistors, if you want to be dead on 4.5V or 6V, but 5V will >> work fine in most cases. >> >> digikey.com or mouser.com have online data sheets that will show how to >> wire it up if you search for the part number. Calculate the max current, >> and make sure you use a heat sink if necessary, by the data sheet. >> >> Basically, you will just wire 12V to one pin, ground the gnd pin, and >> take the 5V off the third pin. May want to use filter caps on the input >> and the output, but its all in the data sheet. >> >> Lots of people around who can help. If you need more, just ask. >> >> John > |
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