Measuring AA Battery Life for LED Pixel Halloween Costume
Check out how Ryan Brown tests his power draw for his Halloween costume to make sure he has the battery life required:
As I mentioned in the LED Ring construction post, I wanted to make sure 4 AA batteries would power my 25 RGB LEDs through a good 3+ hours of trick-or-treating. The Adafruit doc provides a good battery life estimate, but I figured I might as well measure it.
Fortunately, I had a myDAQ handy, and hooked it up to measure battery current and voltage (above). (Note: the power consumed by the 1N4001 diode is not measured with this setup.)
I then wrote a quick LabVIEW VI to measure & log the battery voltage and current every second. This way I could see the voltage and current drop as the batteries discharged….
The pixels are connected by a 4-conductor cable. +5V (Red), Ground (Blue), Data (Yellow) and Clock (Green). Data is shifted down from one pixel to the next so that you can easily cut the strand or attach more onto the end.
Each dot is digitally controlled, with an internal 8-bit PWM LED driver (24-bit color for 16 million different shades). The pixels must be clocked by a microcontroller, we have an example code linked below that works on an Arduino, it should be simple to adapt it to any other microcontroller.
The pixels use 8mm diffused RGB LEDs, with a 120 degree beam width. The total max brightness of all LEDs is about 1600mcd but with the light more evenly distributed & mixed than a clear LED. (Please note: mcd ratings of LEDs are notoriously inflated by most LED sellers, so be extra-skeptical when reviewing LED ratings!)
Eink, E-paper, Think Ink – Collin shares six segments pondering the unusual low-power display technology that somehow still seems a bit sci-fi – http://adafruit.com/thinkink
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