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Content:
0:00 Intro
0:15 PCB and stencil unboxing
0:30 Solder paste and placing SMD components
2:15 Soldering the PCB top side with the hotplate
2:42 Soldering through-hole components
3:08 Soldering the 3.7 V LiPo battery
3:40 Fixing the USB-C connector mistake
4:22 3D printing the base plate
4:43 Coding
4:52 Installation
5:21 5 V power module
6:44 Tuning the radar sensor
7:10 NextPCB sponsor video
7:37 Testing and operation explanation
This is the second part of an electronic system I designed to try to catch the burglars. In the previous video, I showed you how I designed and built the receiver module. This time, it is all about the Long Range transmitter, and how the whole system works. Although it may seem overkill and unnecessary, I chose an ESP32 again as the microcontroller. The reason being is that I want to leave a door open for future expansion. Having Bluetooth and WiFi connectivity at my disposal is always a good thing. Nevertheless, this could have been done with a simpler and cheaper ATmega328P.
As you will see, I made a PCB design that features less components, since I did not need some of the peripherals that I used in the receiver module (0,96’’ oled display, 3.3 V passive buzzer, etc.). However, the most important thing to accomplish was to be able to install the device in a way that nobody could tell it was there. So I did not want to drill any holes in the walls, add visible sensors or any other element that could let anyone know that something new had been added there.
I tried infrared sensors or “PIR”, magnetic reed switches, and some others in order to detect the event of an intrusion. In the end, I decided to go with the RCWL-0516 radar sensor, which is based on the infamous Doppler effect. It is surprisingly sensible even when placed inside a plastic enclosure like the one here shown. It was capable to detect a slight movement of my body from a couple of meters away. In fact, I had to add a resistor in order to reduce its sensitivity, avoiding false alarms.
Again, this module uses the same LoRa 868 MHz module, as a transmitter, to communicate with the receiver. It keeps sending data every couple of seconds to inform that there is no intruder inside the storage unit, and its own battery level. Talking about battery, this module is also equipped with a 1-cell 3.7 V LiPo battery plus an onboard charger IC (MCP73831). This is to ensure that, no matter if a mains power brownout occurs, the transmitter will always be able to send packages to the receiver and alert the owner to the critical situation.
I hope you enjoy the video! Stay tuned for the next one.
Links:
Instagram: / elite_worm
GitHub: github.com/eliteworm