The old mobile phone was changed to monitor. Redmi Note5 was actually tested for a month. Three kinds of people first persuaded them to quit.

When the home monitoring system is installed to the sixth head (how to plan the POE and network? I have written an article ), I set my sights on the storage room. There are tools and miscellaneous food piled in that corner, and the cat always sneaks in, trying to take pictures of its crime scenes. It costs more than 100 yuan to buy a serious camera. Is it worth it to watch cats? There happened to be a Redmi Note 5 lying in the drawer that had been gathering dust for three years. The screen was broken at one corner, but the camera was good. Use it to hold a seat without spending a penny.

After hanging it up for a month, it works, but there are so many pitfalls. Lay out the account first, and then decide whether to take action or not after reading it.

Let’s first make it clear which positions are worth filling with old mobile phones.

The correct way to change the old mobile phone to monitor is to "fill the gap", not to "support the backbone". There are six serious cameras in my house that monitor important locations such as the entrance, yard, and living room. Only places like the storage room where you can take a look at the presence of cats can get old mobile phones. If you don’t have any surveillance at home and want to use your old mobile phone as your main phone, give up the idea as soon as possible.

I will directly persuade these three types of people to quit. Don't even think about it if you want night vision. I'll go into details later and give the conclusion first.: My cell phone is blinding me at night. Don’t even think about installing it outdoors or in the garage. Mobile phones are not waterproof or sun-proof. In the summer, the temperature is 60 to 70 degrees in the car. I don’t dare to think about the environment of lithium batteries. Don’t even think about watching back video recordings in the cloud around the clock. The storage and upload logic of old mobile phones cannot support it. I don’t have a serious recording account. I calculated it in the storage article , a 2T disc of continuous recording can only be stored for a week, let alone an old 32G mobile phone.

On the contrary, indoors, places where you can see clearly during the day and occasionally glance at it, storage rooms, balcony corners, nurseries during the day, cat kennels and kennels - the old mobile phone is perfect for it, and it also has a two-way shouting function, so it can hear a few curses at the cat.

How to choose an app? I have installed all three.

The routines of these apps are the same: Install the "camera terminal" on your old phone and the "viewing terminal" on your portable phone, scan the QR code to pair, and you're done.

I tried all three for half a month. Pocket Viewer is the easiest to use. The servers are in China and pairing is fast. The free version provides real-time images, motion detection alarms and two-way voice. For video playback, you need to be a member, which costs more than 100 yuan a year. Alfred is the most popular overseas, and the interface is nice, but the server is overseas, and the remote connection sometimes spins in circles - that's it I can’t read that article through remote monitoring The manufacturer written in it says it's taunting you, and there's nothing you can do about it when it's its turn to taunt you. IP Webcam is for geeks. It is free and has no ads. The screen is opened directly in the browser on the LAN, and the traffic does not go through any third-party cloud. But if you want to watch it when you leave home, you have to go through the intranet yourself, which is not friendly to novices.

I ended up staying with IP Webcam. I only thought of checking out the storage room when I was at home. Just click on it next to the NAS in the LAN. It doesn’t cost you money and you don’t see ads. If you want to install a dog watcher for your parents' house, choose a mobile phone watcher and don't let the elderly have trouble.

My hands were hot on the first night, and the battery was the biggest problem.

The camera side has to keep working: The screen is always on, the camera is always on, and WiFi is always connected. The Redmi Note5 was plugged into the original charger and hung up all night. The next morning I took a temperature gun and hit the back, and it was 42 degrees.

What is the concept of 42 degrees? The article about router heating I wrote the scale: It is considered normal within 45 degrees. The number of mobile phones does not mean that they are fried. The problem is that they are kept at this temperature 24 hours a day. If the lithium battery is fully charged for a long time and the temperature is high, it will bulge sooner or later. This is not to scare people. A friend who repairs mobile phones told me that he has seven or eight bulging batteries lying in his cabinet, half of which are from old mobile phones that have been plugged in for a long time.

I divide the countermeasures into three levels according to the degree of convenience. First level, limited recharge: Look for "charging limit" or "overcharge protection" in the settings, and it will stop charging when it reaches 80%. The iPhone has an 80% upper limit in settings, battery, and charging. Samsung calls it battery protection, and Motorola calls it overcharge protection. It’s a pity that this old device like Redmi doesn’t have this function, so I’ll skip it.

The second gear, physical cooling: Replace with an old 5V/1A charger, which has less power and less heat. ； Spend another dozen yuan to buy an aluminum heat sink to put underneath. ； Turn the screen brightness to the minimum, as the screen consumes most of the power and generates heat. After changing the three-piece suit, I measured it again. It was 38 degrees and it was pressed down.

The third level, removing the battery and supplying it directly, is the most thorough and scary.: Some mobile phones cannot be turned on at all if the battery is removed. You have to leave a cable or connect a dummy load. If you have not removed the machine, don't force it. I thought it was troublesome, so I stopped in second gear.

There is a red line to remember: Touch the back cover every two weeks. If it becomes warped or becomes soft when pressed, stop using it and send it for repair immediately. Don't pierce the bulging battery yourself, don't bite it to remove it, and don't throw it directly into the trash can.

For network distribution and positioning, look at the sockets first and then the framing.

Pass the distribution network first: The cameras of many such apps only recognize 2.4G WiFi, as is the case with Alfred. When the router dual-band is integrated, the mobile phone secretly connects to 5G, and the pairing goes in an endless loop - the same root cause as the failure of the sweeping robot to connect to the network. That article I've written it thoroughly, and I'll fix the 2.4G first and then come back.

Besides software, there is another step that is easy to reverse: It's not "where to place the phone to take a better view", but "where the socket is, the best place to place the phone." The length of the charging cable is the radius of the camera position. The socket in the storage room is 1.2 meters above the door frame, so I took a mobile phone holder and put it on an old shoe box, diagonally facing the door. It doesn’t matter if the framing is a little bit rough, it’s about looking at the cat, not the license plate.

Also take a look at the signal in advance. My mobile phone measured -68dBm at the door of the storage room, which is enough. If your corner is lower than -70, the phone will be disconnected and reconnected repeatedly. Each time it is reconnected, it consumes extra power and generates heat. It is a vicious circle. This location is not suitable for it. Don’t force it. How to check the signal blind spot yourself? Wrote .

Clean up the phone itself before putting it on the shelf: Restore factory settings, turn off automatic screen lock, turn off system updates, and uninstall all apps that can be uninstalled. The screen freezes as soon as I open the lock screen. This is the root cause of the black screen on my first night. I spent half an hour troubleshooting.

Night vision and storage, these two shortcomings must be recognized

I had some illusions about night vision at first, so I tried it one night.: As soon as the sensor light in the corridor went out, the screen became completely black. When the sensitivity was raised to the highest level, only a shaking figure could be seen amid the noise on the screen. The reason is that there is an infrared cut-off filter in front of the mobile phone camera module, and the infrared fill light shines through it and pretends to be invisible. There is a method on the Internet of disassembling the camera and removing the filters. It is irreversible. After removing the filter, everything you take during the day will have a color cast. I don’t recommend it.

If you really want to watch it at night, there are two ways: Keep a nightlight that costs a few dollars and keep it on to feed the lens, or accept your fate in this position and replace it with a serious camera. The entry-level model with dual filter switching costs dozens of dollars, and the night vision is better than any mobile phone.

Storage is more realistic than night vision. The videos of Pocket Viewer and Alfred are stored in the App cloud. The free quota is basically for watching back on the same day. If you want to watch it 7 days and 30 days, you can subscribe, which is enough to buy half a camera in one year. IP Webcam can record locally on the mobile phone, but the 32G machine will be full after two or three days of recording at the highest quality. Once the loop coverage is turned on, the old video will be lost, which is just right. Connect to the NAS monitoring set Unified existence? It doesn't work, most of these apps can't spit out RTSP streams, and the NAS monitoring suite can't recognize it, so don't bother.

So think clearly about the positioning of old mobile phones: A small independent monitor, the video recording is a bonus, don’t expect it to be used as a video recorder.

Take your seat and take an electricity bill with you

Let’s calculate the electricity bill by the way.: The camera end is plugged in 24/7. I saw on the socket meter that it is just over 3 watts, which is around 30 kilowatt hours per year. The electricity bill is less than a pack of cigarettes. Inventory of home equipment and electricity bills If you can't get a number, don't worry about it.

Give an order at the end: Confirm the location (indoors, there is a socket, and the signal should not be lower than -70) → Put away the phone (restore to factory settings, turn off the lock screen, turn off updates) → Install the App for pairing → Three-piece charging and heating set (small charger, heat sink, low brightness) → Try it for a day during the day and then officially hang it up. Don’t throw away your old digital products in a hurry, I’ll take them away The old optical modem that was replaced was converted into a switch It’s the same idea—hardware picked up for free becomes money if you put it in the right place.