Parts needed photo - dloftus photos at pbase.com

dloftus | all galleries >> How to make a LED Flashlight bulb - for 2, 1.5 volt batteries (3 volts total) > Parts needed

Parts needed

The LED is a Jumbo Red, 5000 mcd from Radio Shack (Catalog 276-086). The long leg is the one connected to the positive side of the battery through the center of the flashlight bulb base, the short leg is connected to the side of the bulb base. The resistor is a 47 ohm
(Catalog 271-1342 for a 5 pack) and is used with a two battery flashlight. The large resistor is a 1/2 watt and the smaller one is a 1/4 watt. For this demonstration I used the larger one, because I got that size by mistake, but it still works. It's just that the smaller resister is easier to fit in the base. Also notice the hole in the base of the bulb now that the solder is removed.

other sizes: small medium large original

previous | next

post a comment

dloftus		06-Dec-2004 15:54
Kevin, The LED I used has a maximum forward voltage of 2.4 volts and the resister is used to lower the 3 volts to be no higher than that. The LED has a maximum REVERSE voltage of 3 volts, but I don't think that is the way the LED is suppose to run. If you are using an LED that is rated for 3 volts (I think some of the new white LED's might be rated for 3 volts) then a resistor would not be needed. You can go to the following web page and check the specifications for the LED I used: http://support.radioshack.com/support_supplies/doc14/14056.htm I hope this helps. Don Loftus Gainesville, FL

Kevin		06-Dec-2004 09:48
Why is the resistor needed? As the LED is to operate at 3volts and the current drain small I don't understand why the resistor is used. Would it work without the resistor?