My first Intro to Fabrication assignment was to make a flashlight, where a “flashlight” could be anything that was portable, battery-powered, and created light. I chose to make a simple light out of a 9V battery clip, a tactile switch, and a large white LED in a holder that I scavenged from the junk shelf.
To make sure that the LED still worked, I used some jumper cables to connect the LED to the battery clip, with a resistor in between. I read that most white LEDs work well at 3.3V and 25mA, and if you plugg those numbers into Ohm’s Law (V / I = R), you get a resistance of (9V - 3.3V) / 0.025A = 228Ω, so a 220Ω resistor seemed like a reasonable choice.
First, I cut off some excess plastic from the LED holder using a pair of wire cutters.
Next, I soldered the anode of the LED to a resistor, which was in turn soldered to one leg of the tactile switch. Then, I soldered the other leg of the switch to the battery clip’s power wire, and the battery clip’s ground wire to the LED’s cathode. I also cut off the two unused legs of the switch.
Finally, I hot glued the switch and the LED holder to the top of the battery clip.