LED Pants

Step 2 Planning the circuit and the placement of the LED strip

Measure the length of the pants from the top of the front hip pocket to the bottom of the pants leg. Determine where you would like the LEDs and how closely spaced you would like them. For my pants, I wanted a strip with 13 LEDs evenly spaced. It turns out that the circuit is easier if you choose an even number of LEDs, but I didn't know that then!

Pick the specific LEDs you want. Go to the on-line circuit calculator of your choice. You will need to know the voltage of the LEDs, otherwise known as the "diode forward voltage". You will also need to know the voltage of the battery(ies) you'd like to use (the source voltage). I chose a 9 volt battery because it's compact and easy to slip into the pants pocket. I didn't need all 9 volts for the circuit and could have used four 1.5 volt AA batteries - but I didn't want the bulk of four batteries. Most LEDs have a "diode forward current" of 20 milliamps and that's the value I used.

Because I chose an odd number of LEDs, the circuit that dissipated the lowest wattage was a combined series/parallel circuit. I thought it was worth it to have the circuit generate as little heat as possible, so I chose that circuit rather than an easier parallel circuit. I had no idea how to actually wire the circuit and that caused the most difficulty I encountered in this project. So choose an even number of LEDs!

Review the pdf of the circuit diagram I used - the first circuit diagram is my complex circuit with both parallel and series components. The second circuit diagram shows the easier parallel circuit. If this is all Greek to you, look at the Instructable on parallel and series circuits.