The project is made by two elements:
- the hardware device, that receives commands and switch the output on and off;
- the application, running on a smartphone, that sends commands and display output status.
These two elements communicate using a bluetooth link; on the hardware side I chose the Bluegiga WT11 module, already described in other blog posts..
Here’s electronic switch’s block diagram:
All the logic is implemented in an Arduino Pro Mini, connected to Bluegiga module via serial link. I decided to use a software serial on PIN 2-3 to keep the main serial port (hardware) available for debugging.
A power supply with two linear regulators supplies the correct voltage outputs (5V e 3.3V) for both the modules.
The output is switched using a 5V relay, controlled by an Arduino PIN through a NPN transistor.
Schematics e PCB
I designed the PCB to fit a standard electric box, with an internal space of 68x68mm.
The PCB was designed using Eagle’s free version: in GitHub’s repository you can find .sch and .brd files (all the files are licensed ).
In the same repository you can find the BOM (bill of materials).
The first prototype…
… and some photos about the first complete model: