For the bag movement alarm project, I wanted to be able to monitor the battery level so I can warn the user when they need to change the battery.  A simple way to do this is just to monitor the voltage of the battery, as batteries have a pretty well articulate discharge curve:  with more…

When I integrated the TrinketPro into the bag movement alarm prototype project, the power circuit did not work.  So I needed to redesign the power circuit. I had posted a question about this in the Arduino.cc forum, where forum user dlloyd had helpfully pointed me to an excellent explanation of using MOSFETs as power switches.…

Now that I have the TrinketPro working fine, and have the sketch and prototyped circuit for the bag movement alarm project using an Uno, I wanted to replace the Uno with the TrinketPro. There were a few small changes, as there are two pins on the TrinketPro that are not available:  #2 and #7.  Since…

As part of the hackaday.io Everyday Carry contest that I am (in part) building the bag movement alarm for, I need to utilize a Trinket Pro.  Which is fine, because the product itself is a pretty affordable ~$10, and it packs pretty much to same punch as an Arduino Uno. I ordered one from the…

I had previously developed the power circuit, then added the 4 buttons and the speaker to build a button based secret code system, but I had developed the algorithm to use the accelerometer to determine if the device had moved enough to be considered stolen as a separate element. So I needed to integrate them together.…

I managed to get the accelerometer to work and put in a sensitivity so it prints when the chip has been moved (i.e. does not print the raw data, just the statement “MOVED” when there has been movement. However, for the bag movement alarm project I need it to tell for how long there has been…

For the bag movement alarm project, I got myself a cheap postage sized accelerometer.  The breakout board I purchased online is labeled GY-521, which I found out afterwards is just one of the many boards for the MPU-6050 chip.  The MPU-6050 is actually both an accelerometer as well as a gyro.  Pretty cool for such…

For the bag movement alarm system, I need to have a secret security code that can shut off the alarm. I wanted to have this be very simple, so just use a multi button interface.  For the project, I decided to chose 4 buttons (largely as this gives a good number for simple security, and…

So one of my new projects is to create a movement alarm for preventing bag theft. The motivation for creating this is threefold: 1) When I go to a happy-hour or a cocktail party, I often have my computer bag with me. But I do not want to carry it around with me, so I…