Category Archives: calculations

How to Switch a Transistor

In this video, I show how I solved my hourly hydration problem by wiring a transistor to a water pump behind my desk. I describe three different ways of switching: MOSFETs, BJTs and relays. I then skim over logic gates and show how I added lighting to my bedroom.

Music from http://goo.gl/NblLp

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Android Phone Battery Calculations

I recently received a new Samsung Galaxy S3. Coming to Android 4.1.1 from three years of iOS is quite liberating. The phone just gives you so many more customization options and control. Amongst all the new features though, I really like the power usage meter under Settings > Battery. It presents a nice graph that shows battery charge over time and the applications using the most power. I thought it would be fun to interpret the data a bit and calculate the “full charge time” and the charge rate in mA. My calculations are below:

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