Welcome to my build log for the Build Inside the Box Challenge! This is my first blog/writeup/build on here, so if you have any feedback, please leave a comment!
Here are the contents of The Box:
- Arduino MKR Zero – Neat little development board, uses a Cortex M0+ MCU, and has an SD card slot.
- USB Power Bank – 10Ah 5V power bank, should be able to power any project that doesn’t involve large motors
- WAGO Terminal Blocks – great way to connect cables together
- MCP604 – quad opamp, 6V max supply voltage, comes in a DIP package for ease of soldering
- Photointerrupter/Phototransistor – an infrared emitter and phototransistor, with a gap between them.
- 128x64 OLED Display – I2C/SPI monochrome display
- Analog Temp Sensor
- VL53L0X ToF Sensor
Ideas and planning
My first thought was that the ToF sensor could be used as a park assist on a car, so that was the first idea I started planning. My car radio is quite bad, so the MKR Zero could be used as a music player with an I2S DAC/AMP, put the OLED and some buttons on the steering wheel, power them somehow, and I’ve got a nice and handy music player controller as well. However, I had absolutely no idea what to do with the opamp, phototransistor, and power bank.
Time for another idea. The weather is starting to be good, so who doesn’t like to go on some bike trips? I hate having to mount my phone on the bike, the screen is barely visible outside, none of the tracker apps do exactly what I want, so let’s make something for my bike.
My first ideas were using the phototransistor for measuring rotational speed of the wheel. I wanted to put a small plastic circle thing on the axis of the wheel, cut part of it out, and mount the phototransistor on the side, something like this:
My second thought was using the ToF sensors for an anti-theft system. I’ve had bad experiences with off the shelf bike alarms, so this is the perfect opportunity to make my custom one. Mount the two ToF sensors on two sides, use one of them(user selectable at activation) to constantly measure the distance to the nearest object(wall, lamp post, etc.), and if the distance changes, the bike is being moved. I got some piezo buzzers to use as a mini siren, and the opamp can be used to amplify the Arduino’s 3.3V output to drive them.
User facing box
Adafruit has a great library for this device, with examples for using multiple sensors on one I2C bus.
The datasheet of the DHT11 says it needs 3.5V at least, so it can't run off of 3.3V, but let's try anyways.