Another home video surveillance

One fine day, the idea arose of putting a small camera in the stairwell and controlling the front door of the apartment.
The main requirement for the system was a budget solution. The final version came out not quite the way I wanted, due to some mistakes made during the design and implementation of the system.

• Camera.
After reviewing the market offers, the choice was made in favor of analog CCTV cameras. Unlike digital ip cameras, the analog price tag starts at $ 10, if vandals tear off such a camera, the loss will be small. You can immediately buy a couple of pieces in reserve and not particularly worry about safety.
In Chinese for $ 12, a color camera was purchased, with a resolution of 420 TV lines of miniature performance.




The shape of the camera is offered in various versions, approximately the size of a matchbox. Now I would stop on a camera with a protective dome, simply due to simple maintenance, it is easier and faster to wipe the dome with a rag.
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Advice1: do not take, as I am a color camera, take black and white. Lighting in the stairwell leaves much to be desired, the color rendition as a result is none, and the sensitivity is lower than in ch.b. Chroma for access conditions is a useless feature.
Tip2: take the camera immediately with IR illumination, often there is just poor lighting in the stairwell, the lamps often burn out and sometimes break. Backlight improves the performance of the entire system.

Testing the camera, slightly disappointed. The actual resolution in terms of digit turned out to be slightly more than 320x240. Confident identification of human features with a standard camera lens with a viewing angle of 90 degrees was 2 meters. Beyond this distance, the facial features blurred and it was possible to judge only the general physical characteristics of the subject (height, gait, clothes, etc.).
However, to control 1 specific entrance door, these parameters were enough.

Tip3: If you want to uniquely identify people across the entire area of ​​the staircase, take a higher resolution camera 600-700 TV lines.

Some camera insides.





• Lens and camera location.
A lens with a viewing angle of 170 degrees was ordered to the camera for testing. In the photo above is a "shirk", below is a regular lens with a viewing angle of 90 degrees.


However, in the future shirik not useful. My staircase shape is a narrow elongated rectangle, setting the width only led to more capture of the dead useless space in the form of the side walls of the staircase corridor, plus the facial recognition feature distance dropped to 1 meter (the wider the captured image, the smaller the "pixels" the objects get in the frame at the same distance).
As a result, I left the regular lens, turned the camera 90 degrees and got a portrait image of my narrow corridor, capturing a large area of ​​the informative space of the corridor floor and the dead side walls.

Tip1: Look at once what lens you need to screw on the camera, do not be afraid to experiment with portrait positioning. As a guide, it is convenient to use any soap box with a zoom, lean it against the point of potential camera attachment and play zoom and lens position while taking pictures in parallel. Choose the most informative option, with a minimum amount of "dead" space. The resulting zoom can be converted to the required focal length of the lens according to the specification for the soap box.

As the primary installation option, at first the plane of the wall opposite the door was chosen, the camera hung almost under the ceiling. However, this had to be abandoned due to the fact that there was a large dead zone, which the camera did not see, it was possible to quietly approach and break the camera; then nothing would be left on the recording. Plus, watching the back of the head is not informative. As a result, the camera was hung in the corner on the side of the door and lowered below.

Council2. Hang the camera so that you cannot get close to it unnoticed. If the camera is torn off, at least someone will be seen. Do not chase the high position of the camera, but it is more vandal resistant, but less informative. You will only see the tops and caps.

Example from YouTube, with non-informative image.


• Communication line.
The camera requires 3 power wires, 1 - common, 2 - +12 volts, 3 - video. In the case of a microphone using 4 wire - sound.
For connection it is convenient to use a regular twisted pair, there is a sufficient amount of wires, even with a margin. For lines that are a couple of tens of meters long, this option is quite acceptable.
I have already been laid twisted pair to the corridor panel under the Internet. And since for 100 m / b only 4 wires are used, the remaining ones were quite enough for my needs.
No mutual negative influence of Ethernet on video and vice versa was observed.
From the shield to the installation point of the camera, a separate twisted pair was laid, the total length of the entire line was about 30 meters.

• Recorder.
Simply, the camera is of little use without the possibility of fixing what it sees. Therefore, DVR recorders come to the rescue.
Of course, the cheapest and most flexible option is to purchase a capture board and plug it into a computer. Further linux + for example motion. However, I wanted something small, budget and silent. Put and forget.
It is ideal if the recorder would have the ability to connect to the Internet to synchronize video data with external storage. If something happens to the recorder, you can always access the data via the Internet.
With these thoughts, was ordered for $ 40 mini recorder with the ability to record on an SD card, with a usb connector.



Office site.
en.readerme.com/html/products/WIFIshexiangji/3.html

The recorder has the function of a motion detector and writes video only when something happens to the camera lens. Consumes a scant amount of electricity. It supports a resolution of 640x480, which even more than the camera could give out, was enough for a staircase. Has the size of a pack of cigarettes.
It was supposed to connect the device via usb to the zuksel-kinetics and synchronize the video with external ftp-storage.

Stuffing device.


Built on SAA7111 video processor and anyka Chinese microcontroller.


The recording logic is as follows: all movement in front of the camera is written + 1 minute after. One minute of 640x480 video takes 30 MB. An 8GB SD card is inserted into the recorder. Enough for a week. Naturally, this indicator depends on the traffic intensity of people in front of the camera. I have it low.

Alas, this recorder did not meet all expectations. When connected via usb to a computer, the device stops writing video, switching to the “flash drive” mode. Real-time synchronization with the Internet storage turned out to be impossible.

Tip: If you want this feature, look at the more advanced devices, with support for network data transfer protocols. As a rule, such devices support already from 4 cameras, they write to the hard disk and most likely represent something like a PC with linux on board. In Chinese shops, the price tag starts at about $ 70.
An overview of such a device can be viewed, for example, here.
habrahabr.ru/post/170287

• Monitor
In fact, the monitor is not needed, although I have a small screen, next to my workplace. It is used only to see who is ringing the door when it is too lazy to go immediately to open. And so hangs dead weight. I wouldn't buy a monitor specifically now.

• Nutrition.
To power the camera and recorder, there is enough of a small low-power power supply unit for 12 volts. Included with the recorder, the good Chinese have put such a block, it is used to power the entire system. In case of power failure in the socket, a regular computer bespereboynik is used. Since the camera + recorder consumes a little energy, if you wish, you can assemble a simple circuit on diodes and batteries. (found on the Internet).


• Legal aspect.
Since the staircase is a common area, in theory it is necessary to collect the consent of the neighbors to place the camera and hang a sign - “Video surveillance is being conducted”. However, as a rule, neighbors do not care what it is, and why, so decide how to deal with the legal aspect. The only thing I do not recommend, contact with cameras hidden installation, it is illegal.