Engineering

Automated door system

Earlier this year we moved from Berlin to Lisbon and found a nice apartment not too far from the city center.

Our apartment building door, like most around Lisbon, is old and doesn’t work very well. And with many friends coming to visit this summer, I decided to automate the door so that me and my friends can open the door using our mobile phones instead of spending 5 minutes trying to jiggle the key in the lock to get it open.

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Roll your own secure Dropbox alternative

Dropbox is a great software that I have been using for almost 10 years. It has helped me a lot during university, sharing project files, backing up my thesis and much more. It is a great service, but it also comes with a lot of problems regarding security and transparency (I will not get in-depth here). You can check for example, this article, or this one (there are many more if you look for it).

With this security issue in my mind, I decided to roll my own Dropbox-like service. The main difference is that I will know where all files are and that I am the only one with access to the unencrypted files. After building my own simple infrastructure, I decided to write a quick tutorial showing my solution and how you can create your own! Let’s get started…

The main software that we are going to use is called Resilio Sync (previously BitTorrent Sync). It takes care of all the syncronization between computer, mobile and server, just like Dropbox.

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NeoPixel 24 & HC-RS04 Sonar Support


sonar neopixel 01

I am currently working on a project that involve using a HC-SR04 Sonar sensor to control the lights of a Adafruit NeoPixel 24 Leds Ring. Yesterday I quickly designed a 3D model with DesignSpark Mechanical that I am using to center the sensor inside the led ring. I have also added a few spaces where the cable can pass though without disturbing the flat surface.

You can download it from GitHub, and there will probably be updates on the design in a near future.

What do you think?

Check this cool 3D preview by GitHub:

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Altium Tip: Smooth edges with Teardrops

Teardrops is a really nice feature present in Altium, where it analyzes all the traces and try to smoothen the edges of the connections. Most users don’t know that this feature exists, and even if doesn’t add a major change on the design it can certainly improve the quality of your project, especially if you are working on high-speed or high-power electronics.

altium teardrops

To access the menu, while editing your PCB, go to Tools >> Teardrops… (or simply press t + e).

Bellow you can check a random PCB design with and without Teardrops:

altium teardrops before

altium teardrops after

Interfacing two Adafruit MMA8451 via I2C

This week I had to interface two accelerometers (adafruit MMA8451 breakout boards) into one Arduino board.

On Adafruits website, they write that you can address the sensors with 0x1C by adding a pull-down resistor on the “A” pin, or 0x1D by connecting the
“3Vo” to a 3V3 source. What they don’t tell is how to use them both at the same time, which gets clear once you take a look at the Adafruit_MMA8451 class within the library file Adafruit_MMA8451.h.

bool begin(uint8_t addr = MMA8451_DEFAULT_ADDRESS);

metronome

Here you have a simple code based on the library example, but adding the two sensors: