Regulating voltage.


This is a cheap 5V regulator from Radio Shack. The LEDs are designed to be driven at a maximum of 4.5V so we will need a resistor to drop the voltage. I’m too lazy to remember and apply ohm’s law here, so I used an LED resistor calculator. To drop 5V down to 4.5V I’ll need a 56 ohm resistor. All the sources I’ve checked recommend putting a resistor in series with each LED. For asthetic and weight reasons I don’t want 4 resistors on the head so I’m going to go with a single resistor and hope the 4 LEDs have a similar enough resistance.

For the next project I’ll use a variable regulator and add a pot to the case for brightness control. I suspect the LEDs could be driven at 5V for some time, but it would certainly reduce their lifetime.



Here’s everything wrapped in heat shrink and tucked into the case. I didn’t have a 56 ohm resistor so I had to settle with a 1/4 watt 100 ohm resistor I found in my junk bin. The resistor is attached to the right lead of the regulator and covered in heat shrink. I may remove the tubing if it gets too hot. This should drop the voltage down to 3.3V and doesn’t appear to affect brightness much if any. The calculator says this array should draw 80 mA, but my meter measured just 43 mA. Not sure why the difference, but it’s producing light and not overheating so I won’t complain.

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