This is submitted in the Make to Learn Youth Contest, and it requires me to add questions and answers.
Here are the questions:
1 - What did you make?
2 - How did you make it?
3 - Where did you make it?
4 - What did you learn?
Answer to all four questions:
I like using LEDs to light up things, but powering them isn't near as fun as making them. I usually end up having to use batteries, and it can be annoying to have to replace the batteries all the time. I eventually discovered that I could use a wall-wart to power LEDs, but the wall-warts were bulky and usually provided way more power than I needed. After further working with computers and electronics, I discovered USB power is usually rated at 5V and 500mA, perfect for powering a few LEDs. I made this LED logo lamp at home with some cheap stuff I had laying around. The logo is actually left over from a failed LED project, and it is the reason I ended up making this. I wanted to use it for something. Beyond the logo, the project was an experiment to see if USB power was easy enough to use for powering LEDs. It turns out that it is. From the research I did to make sure I didn't mess up my computer's USB ports, I discovered several things to be aware of before using USB for power. These are noted below in case someone skips over this part of the intro.
Here is how to make an LED logo light powered by USB.
NOTE! Be careful when plugging hand-made devices into a USB port on a computer, as a short may end up killing the computer. I recommend using a powered hub or a wall-to-USB phone charger; however, be careful as some chargers provide more than 5V.
Now, with that out of the way, let's get started!
Step 1: Gather the materials and tools
In order to create a USB powered custom logo light, you will need:
- An LED (I suggest a bright "true" color LED, not one that has a colored cover)
- A resistor (more on it in a moment)
- A junk USB cable
- Something to cut your logo out of (like construction paper)
- Tissue paper / tracing paper
- Soldering Iron
- Wire cutter / wire stripper
The resistor value should follow this equation: R = (V1 - V2) / I
R is resistance in ohms, V1 is source voltage in volts (5V for USB), V2 is the LED forward voltage in volts, and I is the LED current in amps. More than likely, your LED will have a current draw of 0.02A (or 20mA), but the forward voltage can range from 1V to 3.5V. I ended up using a resistor with a value slightly less than the equation gave me in order to make the LED a little brighter, but beware, having too low of a resistor may fry your LED.