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During the COVID-19 pandemic, an engineer created a device to maintain a safe social distance—
Of course, even without COVID, this is a great item to cure “laziness”. When friends visit at home, you don’t need to open the door in person; you can directly control the system to open the door with your phone; it can also become a smart intercom, allowing you to talk to colleagues or family at the office or home.
As a smart doorbell, when a visitor presses the button, the Raspberry Pi-powered smart doorbell opens a virtual meeting room for the visitor. At this time, the system will send a notification to your phone, which includes a link to enter the same meeting room to chat with the guest. When you create two such smart doorbells, they can join the same meeting room, serving as a visual intercom system.
Today, we will share some of the production processes and coding ideas with you, which are definitely worth a try!
Hardware Components
The smart doorbell mainly consists of five parts: Raspberry Pi 3+, button + camera + LCD screen + speaker + microphone. The Raspberry Pi 3 needs no introduction; it is the most popular, but if you don’t have a 3, 3B and 4 can completely replace it. If you are a Raspberry Pi novice, click here to view the recommended learning path.Next, let’s talk about the other components:For aesthetic purposes, the on/off button uses a LED button.
Compared to ordinary buttons, this switch button has four pins, and the wiring method is different from traditional push-button switches:Choose any wiring method according to your design idea, but note that if the purchased LED button does not have a built-in resistor, you need to solder a resistor onto it. This is because the LED typically operates at a voltage between 1.8-2.8V, while the Raspberry Pi operates at 3.3V.The camera is a Raspberry Pi dedicated camera, which can be directly installed using a soft ribbon cable:The display uses a 3.5-inch LCD screen, and usually, when purchased, it will come with an integrated operating system driver. Even if you don’t know how to configure it, the seller will provide technical support, so you don’t have to worry too much in this regard.
Regarding the case, many manufacturers in China are making them and they look very nice, which can be directly purchased on Taobao. Of course, you can also DIY your own case; to refer to this project’s case, you can reply in “Darwin Says”: smart doorbell to obtain CAD designs.
The microphone used is a mini USB microphone, very convenient and compact, and the configuration difficulty is low.The speaker needs to connect the output end of the Raspberry Pi’s built-in 3.5mm audio jack to the audio output of the LCD screen. (Please note to choose an LCD screen with audio output function when purchasing, otherwise you need to add an external speaker)
Different Raspberry Pi models may use different audio jacks; here we take the PJ322 audio jack as an example:
The outer ring of the socket (large exposed area) is the ground part of pin 1, pins 2 and 3 are the left and right channels of the headphone, and pin 4 is the microphone interface of the headphone. You only need to connect the left and right channels of the audio jack on the Raspberry Pi to the audio output of the LCD screen with wires. Different audio jacks have different wiring methods; if you are unsure, you can use a multimeter to measure it yourself.
Software Configuration
After the hardware installation is complete, it’s time for software code configuration:Enter the raspi-config command in the terminal and navigate to InterfacingOptions-cameraUse the following command in the terminal to save the image locally to test if the camera is working properly:
sudo raspistill -o test.jpg
Open the sound input settings:
alsamixer -c l
Press F4 to open the capture settings and raise the level to 100. Use the following command to test the audio capture function:
arecord --device=hw:1,0 --format S16_LE --rate44100 -c1 test.wav -V mono
Press control-c to stop, and an audio file named test.wav will be generated in the local directory.
Use the following command to play and test if the microphone function is working properly
aplay test.wav
Save settings to make them effective after reboot:
sudo alsactl store
The video call function requires the use of a third-party platform https://jitsi.org/jitsi-meet/.
It is easy to operate, and there are many tutorials online. Here’s a brief introduction to the configuration steps:
# Ensure support is available for apt repositories served via HTTPS
apt-get install apt-transport-https
# Retrieve the latest package versions across all repositories
apt-get update
# Perform jitsi-meet installation
apt-get -y install jitsi-meet
During the installation process, you will be asked to enter the hostname for the Jitsi Meet instance. If you have already set the FQDN of the instance in DNS, enter this instance name. If you do not have a resolvable hostname, you can enter the static IP address of the computer. This hostname (or IP address) will be used for virtual host configuration inside Jitsi Meet, and others will use it to access the online meeting.4. Test if the installation was successfulAfter the installation and configuration are complete, you can enter the Raspberry Pi’s instance name or IP address in your computer’s browser to enter the video conference.
Note: The actual configuration process will be more complicated than described above. If you are interested, you can reply in “Darwin Says” on WeChat for the official configuration instructions.
Lock Design and Configuration
With a smart doorbell, shouldn’t we pair it with a smart lock? This way, you can directly control the door remotely. Due to the different door-opening methods in each household, here we only provide inspiration and ideas for the lock setup.
The principle of the lock’s production is not difficult; it sends control signals from the Raspberry Pi to the servo, and the servo twists the bolt to lock or unlock. The real challenge is how to match the servo with your home’s bolt (lever lock, push-pull lock, spherical lock).Using the MG996R servo (cheap and powerful) to twist the spherical lock, to ensure that the servo system fits tightly with the lock, you can create a matching case through 3D printing, allowing it to perfectly twist the lock (which is very unfriendly for those without a 3D printer).
Adjust the servo’s twisting center so that it is at the center of the case shown in the right image, and then put the case from the left image on the servo, as shown below:To enhance the interactive experience, add a red LED in the case to indicate the lock’s on/off status:
This simple smart lock is complete and perfectly matches the smart doorbell! Friends who want to do this project can reply in “Darwin Says” on WeChat: smart doorbell to obtain the overall project code.Seeing others do projects so well, are you not tempted? Follow the Darwin project practical training: Linux video surveillance system project in progress, Teacher Wei Dongshan’s first lesson is available for viewing immediately:
Add WeChat zm857827273, and join the project group chat
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Darwin Project Sharing Series—— Focusing on popular application technologies such as IoT, Embedded Systems, AI, FPGA, etc., open source sharing schematics, code, and project solutions, making you a knowledge base at hand.
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