Is it reliable to replace an old phone with a surveillance camera? I tried the Redmi Note 5, which had been gathering dust for three years, for a month, and three people were the first to give up

when the home surveillance reached the sixth end (how was that POE and network planned I wrote an article about ), I set my sights on the storage room. That corner was piled with tools and grains, and the cat kept sneaking inside, trying to film the crime scene. Buying a proper camera for over a hundred yuan to see if the cat is worth it. There was a Redmi Note 5 that had gathered dust for three years in the drawer; the screen was shattered in the corners, but the camera was still good. You can use it to fill a camera position, and you won't spend a cent.

hang it up for a month, it works, but there are really many pitfalls. First, lay out the bill, and after you read it, decide whether to act.

first clarify: which positions are worth replacing with an old phone

the correct way to upgrade an old phone to surveillance is to "fill the position," not "the top beam." My six proper cameras guard the doorway, yard, and living room—these are key spots. In the storage room, where you can check if the cat is there, you get to get an old phone. If you don't have any surveillance cameras at home and want to use your old phone as your main device, it's best to give up the idea early.

three types of people, I would immediately dissuade them. If you want night vision, don't even think about it. I'll explain more later, but to give you the conclusion: using a phone at night is just blind with your eyes open. If you want to install it outdoors or in a garage, don't even think about it. The phone isn't waterproof or sunproof, and in summer, the temperature in the car is 60 to 70 degrees. I can't imagine the lithium battery environment. If you want to record video in the cloud around the clock for playback, don't even think about it. The storage and upload logic of old phones can't hold up. I calculated a serious recording account in the storage section, and a 2TB drive only records continuously for a week, let alone a 32GB old phone.

conversely, indoors, spots you can see clearly during the day and occasionally glance at—storage rooms, balcony corners, daytime nurseries, cat and dog beds—old phones handle it perfectly, and it even offers a two-way call feature, so if you curse at a cat, it can hear it.

App how to choose, I've installed all three

the same trick for these apps: old phones install the "camera end," portable phones install the "viewing end," scan the code to pair, and it's done.

I tried all three for half a month. Palm Guard is the most convenient, with servers located domestically, fast pairing, free version provides real-time feed, motion detection alerts, and two-way voice control. Recording playback requires a membership, costing over 100 yuan per year. Alfred is the hottest overseas brand, with a nice interface, but the servers are overseas. Remote connections often spin around—it's just that you can't watch remotely the article about vendor cloud manipulation, and when it's their turn, there's nothing you can do. IP Webcam is gear-oriented, free and ad-free. The screen opens directly in your browser on the local network, and data doesn't go through any third-party clouds. But if you want to watch it outside your home, you have to manually tweak the internal network, which isn't user-friendly.

What does the free version of

App	server	offer	who is it suitable for
the home of the palm	real-time	domestic footage + motion detection alarms, replay requires members to	images for convenience, remote viewing
Alfred	overseas	Real-time footage + alarms, occasionally unable to connect to	overseas accounts
IP Webcam	but just browse freely on cloud	local area networks, remotely handling	geeks, Privacy Sensitive

I ended up keeping the IP webcam. I only remembered to check the storage room when I was home. Just click next to the NAS on the local network, and you won't spend money or watch ads. If you install a dog watch for your parents' home, choose a mobile home watch—don't let the elderly mess with it.

the first night is already hot to the touch, and the battery is the biggest flaw

camera has to keep working: screen always on, camera on, WiFi always connected. The Redmi Note 5 was left plugged in and left with the original charger all night, and the next morning I used a thermometer to check my back—42 degrees.

What does

42 mean by that? the article about router overheating I wrote about a speed splitter: 45 degrees is considered normal. The phone isn't exploding, but the problem is that it operates 24/7 at a temperature. Lithium batteries that have been fully charged and exposed to high temperatures for a long time will eventually become bulging. This is not just a scare. A phone repair friend told me that his cabinet had seven or eight bulging batteries, half of which came from old phones that had been plugged in for a long time.

I divide the strategies into three levels based on ease of convenience. Level 1, Charging Limit: In the settings, find "Charging Limit" or "Overcharge Protection" and stop charging at 80%. iPhone has an 80% limit in settings, battery, and charging. Samsung calls it battery protection, Motorola calls it overcharge protection. Unfortunately, Redmi's older phone doesn't have this feature, so I'll skip it.

Level 2, physical cooling: replace with an old 5V/1A charger, which has low power output and low heat generation; Then spend a dozen yuan or so to buy aluminum heatsinks underneath; Set the screen brightness to the lowest and the screen is the main source of power consumption and heat. After replacing the three-piece set, I tested again—38 degrees, pressed down.

third level, the battery is disassembled and supplied directly, which is the most thorough and scary: some phones can't turn on after removing the battery, so you have to leave a ribbon cable or connect a fake load. If you've never taken it apart, don't force it. I found it troublesome and stopped in second gear.

remember one red thread: touch the back cover every two weeks. If it peels off or feels soft when pressed, stop using it immediately and send it in for repair. Don't poke bulging batteries yourself, don't bite them to disassemble, and don't throw them directly in the trash.

grid layout and placement, first check the sockets, then the framing

network setup is a hurdle first: many of these apps only recognize 2.4G WiFi on their cameras, and Alfred is one of them. When the router is dual-band, the phone secretly connects to 5G, and pairing cycles in a loop—the same root cause as the robot vacuum's network failure — article thoroughly covered it, first stabilize 2.4G before coming back.

Besides

software, there's another easy mistake: it's not about 'where to place your phone for framing,' but 'where the socket is, so you can put your phone.' The length of the charging cable is the radius of the device's position. The storage room socket is 1.2 meters above the door frame, so I put a phone stand on an old shoebox, facing the doorway. It's fine to settle for the shots—after all, you're looking at the cat, not the license plate.

also took a sneak peek at the signal. At the storage room door, my phone measured -68dBm, which is sufficient. If your corner drops below -70, the phone will repeatedly disconnect and reconnect, and each reconnection consumes extra power and heats, creating a vicious cycle. This position is not suitable for it. Don't force it. How to self-check for signal blind spots written .

Before

release, clean up the phone itself: restore factory settings, turn off auto lock screen, disable system updates, and uninstall all apps that can be removed. The screen freezes as soon as I turn on the lock screen. This is the root cause of my first night's black screen, and I spent half an hour checking for nothing.

night vision and storage—these two shortcomings must be acknowledged

night vision, I had my own hopes at first and tried it all night: when the hallway sensor light went off, the image went completely black. When the sensitivity was set to maximum, I could only see a flickering figure amid the screen of noise. The reason is that the front of the phone's camera module has an infrared cutoff filter, and when the infrared fill light shines on it, it makes it invisible. There are online methods for removing filters after disassembly, which is irreversible. After removing the filter, everything you take during the day will be color cast, which I don't recommend.

really want to watch at night, there are two options: keep a small night light costing a few yuan on continuously to feed the lens light, or accept the fate at this spot and replace it with a proper camera. The entry-level model with dual filter switching costs only a few dozen yuan, and its night vision is better than any phone.

storage is more realistic than night vision. Videos from Palm Vision and Alfred are stored in the app cloud, and the free quota is basically for same-day playback. If you want to subscribe for 7 or 30 days, you can buy half a camera in a year. IP Webcam can record locally on the phone, but a 32G device can record at maximum quality for two or three days and then fill up. Once you turn on the loop override, the old footage disappears in no time. It just connect to the NAS surveillance system store it all together? If it doesn't work, most of these apps can't generate RTSP streams, and NAS monitoring suites won't recognize them, so don't bother.

think carefully about the positioning of your old phone: a standalone small monitor, recording is a gift, don't expect it to be a recorder.

took the opportunity to pay for electricity

quick quick calculation: the camera terminal is powered 7x24, and I see just over 3 watts on the socket meter, about 30 kWh per year. The electricity bill is less than the price of a pack of cigarettes. inventory of household appliances and electricity bills doesn't make the , so don't worry about it.

the final order: confirm the location (indoors, with outlets, signal not below -70%)→ pack up the phone (restore from factory, turn off lock screen, turn off updates), → pair apps→ charging and heating trio (small charger, heatsink, low brightness), try it out for a day during the day→ then officially hang it up. Don't rush to throw away old digital products. Earlier, I replaced my old optical modem with a switch the same idea—hardware you pick up for free, put it in the right place and it's money.