What’s worth recovering from your old smartphone — from an engineering student perspective

How much time do you use a smartphone before you change it for a new model? On average, the useful life of a smartphone is around two years; it could be more or less depending on how you take care of it, though. The reason why the average life of a phone is just a couple of years is the battery. Lithium-Ion batteries are used in cellphones because they offer high energy density, i.e., they last longer, low maintenance, and they keep their capacity for much more time compared to other batteries.

Nevertheless, Li-ion batteries have a limited life and require protection circuits to prevent severe damage if charged improperly. Also, the highly competitive cellphone-market make smartphone companies release new models every year, regardless of the improvement, and previous year’s models. Thus, there are those who replace their phone after twelve months, despite the status of their old smartphone.

You can imagine the tons of e-waste that we get from our old phones. That’s why it’s useful to know whether we can recover some electronic components from them, and where we can throw away old electronic devices.

Smartphone surgery

If you open your old smartphone, you will encounter the battery, PCBs, cameras, several connectors, and microphones. Looking at those tiny pieces is incredible. You have decades of technological improvement in the palm of your hand, and rarely you ever get to see it. The electronics professor of the department is always making emphasis on the fact that modern phones contain billions of transistors on one PCB. Even if you are not an engineer or an electronics fan, that number should tell you a couple of things about how far we have gone.

What you can’t recover

When I say that some components cannot be used again, I mean that they are not useful for electronic projects. However, they can be recycled in the appropriate places or used as spare parts for other phones. First, let’s talk about the front and back covers of your phone, and the metal shield in between.

As you can imagine, these parts are just for protecting your phone, and to keep the inner components in place. Since they are made of plastic and metal, you could potentially recycle them or sell them as parts. Nevertheless, we’re talking about an old smartphone, so finding a buyer can be unlikely.
Attached to the inner metal cover, you will see the main PCB board. This PCB contains the microprocessor, the DRAM Memory, and many other micro-components. You’ll also find the main camera and the bottom PCB, but more about that later.

Unless you have the appropriate equipment, you won’t be able to use the resistors, capacitors, diodes, and transistors. But what about the microchips? In this case, I found a DRAM memory and a Qualcomm processor fabricated by Samsung. Both components could be worth some money, but they are antiquated compared to what recent smartphones have. Furthermore, for a regular person, it would be troublesome to detach these components from the PCB without damage. Also, utilizing these processors in a project could be complicated because there is little to no information on the Internet about their functioning. Other small chips found on the PCB are cheap, but as explained before, without the correct tools, it is almost impossible to work with them.

What you might be able to recover

The main camera, speakers, bottom PCB, and the screen deserve an in-between section. The main camera, for example, has seventeen pins to operate it, and there’s no datasheet to explain how to work with them. Furthermore, I assume it will require programming, which could be a challenge without any document for assistance. Therefore, some might be able to implement it in a project or use it as a replacement. The same happens with the microphones: they still work, but I don’t find any use in them.

The screen is another story. Smartphone screens do not come with an HDMI micro-connector, but rather with a complex set of pins. Of course, you might discover how to use them, but finding the right input for the connector could be a problem. However, I have seen videos of some people who were able to use an old smartphone screen, so there could be more information about it than, for example, the camera.

The bottom PCB contains the sensors for the home buttons and some other components. However, as explained before, it is impracticable to recover those elements. The only part that could be desoldered and used again is the micro-USB port.

What you can recover

I know it looks discouraging, but two pieces are better than nothing at all. As I mentioned at the beginning, the Lithium battery is the component that limits the most a smartphone’s useful life. But it does not mean that it can’t be re-utilized. If the battery has no damage, you can use it for projects such as small robots, drones, or to power something that draws current for a long period of time.

As you can see, the battery still works.

For example, the battery of this smartphone specifies 7.4-Wh of power. If you have a project that uses 3.3-V and 200-mA, you could use the battery to power it for about 11 hours. Just remember that you need to be extremely careful when manipulating a Li-ion battery. Improper handling of it could result in an explosion.

Lastly, we will talk about the motor. All cellphones have one of these, and we use it when our smartphone is in vibration mode. Even though it does not look as powerful, with 5-V and 200-mA from an Arduino, you can make it vibrate significantly. Thus, the vibrator motor can be applied to projects that require an alarm or some kind of warning buzzer.

Bonus: you can always keep all the screws from the phone. You never know when you’ll need to use them for a project.

The verdict

Although, there’s not much you can save from an old smartphone, you should be responsible for how you throw it away. Some components can contaminate the soil and water if you don’t dump it properly. Therefore, be aware of the electronic-waste centers around your neighbor, or you can handle it to someone who knows how to recycle a phone. Also, if you are an engineering student like me, who wants to get some components from an old smartphone, be careful not to damage the battery, and also when desoldering and disarming the parts.



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