DIY experts teach you how to build a mobile phone wireless charger for just 100 yuan [Photos and text]

　　Many mobile phone users envy Palm's wireless charging magic device "Philosopher's Stone". Now, if we modify the Philosopher's Stone, we can have a mobile phone wireless charging power bank at a cost of less than 100 yuan . Such a cool device, don't you consider equipping your small phone with one? This is definitely a huge asset for you to show off to your friends!

　　The original intention of making this work was that my Veer's battery life was so long that it was impossible to read e-books for 8 hours straight . In fact, it was not just Xiaowei. Now, almost all smart phones, including the iPhone , have poor battery life, so mobile power supplies have become popular. However, Xiaowei's data cable is very special. It is large in size and expensive. Frequent plugging and unplugging can easily cause the contacts to loosen. Xiaowei's use of a mobile power supply also involves the modification of the line. What's more, it is quite troublesome to carry a mobile power supply and a data cable at the same time. You should know that Xiaowei was born to charge with a touchstone. Do you know the touchstone? It is a killer for palm/hp mobile phones. Just put the mobile phone on the touchstone and you can charge the mobile phone wirelessly. Forget about plugging and unplugging. But the touchstone must be connected to a wire. At best, you can buy two touchstones, one at home and one in the office. What if you encounter a short business trip or a meeting? How great it would be if you could carry the touchstone with you!

　　1 Materials

　　〇DC5v 1.5A or above lithium battery boost circuit 1 piece 33 yuan

　　〇DC5v lithium battery charging circuit 1 piece 7 yuan

　　〇Palm Touchstone 2pcs 24 Yuan

　　〇Dianjinshi charging back cover 1 piece 14 yuan

　　〇Polymer lithium battery (with protection circuit) 1 piece 19 yuan

　　〇DC 5v 1A double throw electromagnetic relay 1 piece 3 yuan

　　０Plastic box 1 piece 5 yuan

　　〇 Prepare a DV5V 1.5A power supply, a mic ro interface cable (good quality), some cables, and some tools. If you want to use a non-palm mobile phone to realize wireless mobile power, you need to prepare a touchstone charging back cover to transform an ordinary mobile phone into a mobile phone that can use touchstone. For modification, please refer to http://t.cn/zOy otN p, which will not be listed here.

　　Here I chose the 2A version of YZX for the boost board, which is a bit more expensive, but at least it is made of real materials. The charging board is directly disassembled from a charger.

　　2 Remove the required parts

　　Disassemble the parts.

　　This step is actually still the preparation of materials, disassembling the finished product and taking out the required parts.

　　How to remove the back cover of the Touchstone: Use a hair dryer to blow evenly on the back of the back cover (the side with PLAM written on it) until the side with the contacts is hot to the touch, then quickly peel off the black sticker. Note that there is a metal sheet under the sticker that needs to be peeled off as well. If it takes too much effort to peel it off, it means that your hair dryer is not hot enough. After removing the black paper, you can see a brass coil that looks like an induction cooker and a green circuit board. Well, I suggest that you stop here. You can consider sticking the back cover directly onto the shell of the mobile power bank (I will explain this below). If you must remove the coil (for example, to modify it into the back cover of other mobile phones), be sure to carefully cut off the glue below the coil and circuit board with a thin blade, and then lift it off bit by bit. Because the part circled in red in the picture is as fragile as a fly's leg, it will break if you are not careful.

　　Then we take out the charging board. This is not challenging, so I won’t go into details.

　　Here comes the key point, dismantling the Touchstone. There are three screws at the bottom of the Touchstone, which can be seen by tearing off the rubber pad. After removing the screws, you can easily pry open the bottom cover from the square port where the charging cable is plugged in with a hard object. Then there is the circuit board. The circuit board is glued to the metal block below at the micro interface end. It is still the old way, use a hair dryer to heat it up, and then carefully lift it off. It should be noted that when lifting the circuit board, be careful not to break the two hair-thin coils in the corner. In fact, to be on the safe side, it is better not to use a soldering iron to solder these two wires before removing the circuit board. When the circuit board is removed, you can see a piece of metal with several screws on it. Remove it. After removing the metal block, you will find that there is a magnetic block with an artistic shape stuck on the back of the metal block. Use a blade to cut the glue and you can get it off.

　　Finally, connect the wires to the charging board, boost board, and battery contacts. At this point, the preparations are basically complete.

　　3 Upper cover

　　Since the surface of the Philosopher's Stone is concave, it fits the back cover of the Palm very well, but this concave is difficult to process. In addition, the very thin coil in the Philosopher's Stone is also glued to the outer shell, which is difficult to remove. And the metal word "plam" on the Philosopher's Stone is also cool, so I decided to embed the Philosopher's Stone into the mobile power bank.

　　First, cut off the top of the outer shell of the Philosopher's Stone, leaving a section about 1.2cm high, which can actually be used as a reference for the height of the four magnets inside. Then turn the cut section over, and you can see a number of raised, slightly flattened square dots near the edge. Use a blade to cut off these dots, and you can easily remove the plastic ring on the top edge of the Philosopher's Stone.

　　At this time, the side view of the touchstone looks like a "convex" shape. Looking down at the touchstone, according to the diameter of the inner circle, dig a hole on the upper cover of the mobile power bank so that the protruding inner circle of the touchstone can just pass through the hole. Pay attention to thinning the area on the back cover of the mobile power bank where the four magnets of the touchstone are supported, so that the touchstone can be perfectly embedded in the upper cover of the mobile power bank.

　　Then, secure it with glue.

　　Next, lead out the wires on the Golden Stone circuit board and short-circuit the three pins in the middle. I forgot to take a photo here, so I quoted the picture from the great god Segara. Or you can also follow Segara's method to short-circuit R62, R63 and the third pin D+, see http://t.cn/h1u7J1 for details

　　Put the circuit board upside down in the upper cover of the mobile power bank, displace the coil on the circuit board from the touchstone, and then weld the thin coil that was removed from the touchstone. Note that the screw columns between the circuit board and the upper cover should leave space for the screw columns of the lower cover to pass through, to prevent the lower cover from not closing.

　　Next, install the charging board and boost board into the upper cover and secure them.

　　Here I also drilled two small holes on the top cover to make indicator lights. I found a ballpoint pen with a hard and transparent PE material. I used an electric grinder to grind out a thin strip that just passed through the small hole, and carefully bent it with a lighter. I put the other end of the thin strip against the LED on the circuit board to lead the light of the indicator to the outside of the top cover. Then I used oil (plasticine) or electrical tape to wrap the LED and the thin strip to prevent light interference. Finally, I used a nail file to file the pen protruding from the top cover flat, and polished it with a piece of wood. Everything was perfect. It's a pity that I forgot to take a photo of the production process, but fortunately you can see the finished effect below.

　　In addition, I used hot melt glue to fix all the parts. It is easier to place the parts in the space as you like with hot melt glue, and when you need to modify or recycle the parts in the future, you can disassemble them by heating them with a hair dryer. Even when the welding level is not high enough, hot melt glue can be used as an auxiliary means to reduce cold solder joints. The most important thing is that hot melt glue is cheap enough and can be wasted at will.

　　4 Lower cover

　　The lower cover is relatively easy to remove, mainly by combining the back cover of the Touchstone with the lower cover of the power bank. There are three solutions:

　　Solution 1 is to stick the back cover of the Touchstone to the bottom cover of the mobile power bank, and then drill holes for leads. The advantage is that it is easy to make, but the disadvantage is that it is not beautiful.

　　The second solution is to take out the circuit board, coil and four steel sheets from the back cover of the Touchstone, dig out the corresponding grooves in the lower cover of the mobile power bank, and embed the coil, circuit board and iron sheet into the lower cover. The advantage is that it looks good, but the disadvantage is that it is difficult to make. You can also refer to my previous article http://t.cn/zOyotNp for this solution

　　Plan three is a compromise, which is between the first two plans in terms of aesthetics and ease of production. It is to cut the back cover of the Touchstone into small pieces, dig a hole of the same shape on the lower cover of the mobile power bank, and finally embed it and fix it.

　　5. Fusion

　　At this point, the upper and lower covers are done, and the final step is to connect the wires and close the upper and lower covers. A simple solution is that the back cover of the Touchstone supplies power to the charging board, the charging board charges the battery, the battery discharges to the boost board, and the boost board supplies power to the Touchstone, like this:

　　By the way, I chose 705462 polymer lithium battery because it has 2700mah. In fact, 606168 is enough, and there is no need to worry about the 100mah. In short, the battery should be as large as possible to fill the remaining space of the shell, but pay attention to the connection column, the bump of the solder point, the wire and other inconspicuous things that take up space. If the battery is even one millimeter larger, it may not be able to cover the lid in the end.

　　6. Achievements Display

　　This is the back of the power bank.

　　When placed on the philosopher's stone, the red light will come on, indicating that it is charging.

　　The front of the power bank, with the phone on top.

　　Put your phone on the power bank like a sandwich.

　　Take the power bank off the Philosopher's Stone and simulate charging your phone on the street. The blue discharge light comes on, indicating that the battery is discharging. Look at the phone screen and a small black plug lights up next to the battery icon.

　　7 A Failed Attempt

　　After two days of trial use, I found that the above wireless mobile power bank is not perfect and has fatal functional defects. First, the battery can never be fully charged in the "sandwich" state. It is always charging while charging and discharging. Even if the phone is fully charged , the mobile power bank will always light up red. But if you take the phone away, the mobile power bank will quickly light up green (fully charged). The second problem is the problem of power loss. The idle mobile power bank will slowly lose power by itself, and a fully charged mobile power bank will be completely discharged after being left for two days and two nights.

　　Jobs said that imperfect products are garbage, so he began to try to upgrade garbage. First, the battery cannot be discharged while charging. Second, the charging circuit should be disconnected when the mobile power bank is removed from the philosopher's stone. Based on this idea, he began to try to design a solution.

　　The easiest solution is to use a bunch of switches , so I started trying to use analog switches, selected the most commonly used 4053, and started designing the circuit.

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　　I quickly built the circuit using a breadboard. Do you see my finger in the lower left corner? It's cool to use a "seesaw" to control the on and off of the battery.

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　　This is the 4053 analog switch. I bought one with a pin package specifically for the price of 1 dollar.

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　　The actual test was successful as expected.

　　A new problem soon emerged. In order to automatically disconnect the charging circuit when fully charged, a fully charged control signal is required. The red LED indicator is a good signal source, but the output voltage of this product is only 1.5v (only 1.2v in actual measurement), which is not enough to activate the analog switch. So I searched all over the world for the charging circuit and finally found that R5 outputs 4.2v when charging and 0v when fully charged.

　　So I connected the wires to a breadboard for actual testing, and everything worked as expected. I was ecstatic.

　　　Finally, I assembled all the parts, stuffed them into the box, and placed the power bank on the philosopher's stone with a smile on my face... Not charging??? I put my phone on the power bank, but there was no response???

　　I had no choice but to disassemble the power bank to find the cause. After countless measurements and experiments, it took more than a week to finally find the problem. I forgot to take photos during this period, sorry.

　　It turns out that when the back cover of the Touchstone is placed on the Touchstone, it may be affected by the magnetic field, and the 4053 analog switch no longer follows the rule that the Sn pin controls Zn to close Ynx. Instead, Zn and Yn0 are always disconnected, and the resistance between Zn and Yn1 changes randomly from tens of K to tens of M. Everything is messed up. IC, 4053 can't work normally. Analog things are really unreliable.

　　8 Another failed attempt

　　Since analog switches are unreliable, I decided to use physical switches. This time I decided to use electromagnetic relays, and the HK19f with a DC5v double-pole double-throw is a good choice. It has 8 pins and costs 3 yuan each.

　　The circuit is designed to achieve two functions. First, the charging circuit is disconnected when the power bank is not placed on the touchstone to prevent power leakage. Second, when the power bank is placed on the touchstone, the back cover of the touchstone is used to directly power the discharge circuit, while at the same time disconnecting the discharge circuit from the battery.

　　After connecting the circuit and listening to the clicking sound of the relay, I felt so happy.

　　I quickly installed the parts, closed the casing, and tested it. I put the power bank on the touchstone, and it made a "pop" sound. I picked up the power bank, and it made another "pop" sound. I had a lot of fun playing with it, which was even more stupid than watching the status bar move at a snail's pace when I installed Windows.

　　Tragedy often occurs at the climax of comedy. After I put my mobile phone on the power bank, the power bank no longer made a popping sound.

　　We disassembled it and looked for the fault. It turned out that the back cover of the Philosopher's Stone was burned.

　　I guess the power of the back cover of the Philosopher's Stone is not enough to drive the full power output of the Philosopher's Stone. I started to try to stack two back covers of the Philosopher's Stone on top of each other and connect them in parallel to power the Philosopher's Stone. But I soon found that no matter how close the two back covers of the Philosopher's Stone were to the Philosopher's Stone, even if the coils were removed and tightly stacked on the surface of the Philosopher's Stone, the coil farthest from the Philosopher's Stone would not work.

　　9 Improved

　　Since there is no way to use the back cover of the Touchstone to directly power the Touchstone, then just connect the charging and discharging together. It is nothing more than charging and discharging at the same time, which causes the battery to be always undercharged. In fact, at this time, the battery can basically maintain 85%~90% of the power, which is enough. As for the problem that may affect the battery life, it is not considered. If the battery of ten yuan is broken, just replace it with a new one.

　　The redesigned circuit is really simple this time.

　　Weld the parts and assemble into the box.

　　This time, for the convenience of frequent debugging, the back cover and the battery connector were plugged in. By the way, the boost board was also replaced with a 3A boost board from QSKJ, which is cheap, only 20 yuan. I also replaced it with a dual TP4057 charging board, which outputs 1A and can charge faster, and only 6.5 yuan per piece.

　　Also, because the new boost board has a large coil, it can only be placed vertically, which causes the position of the indicator light to be changed and has to be redone.

　　It is also worth mentioning that in order to solve the problem of power leakage, I strung a reed on the positive electrode of the battery. There is a pin on the reed, which protrudes a little bit from the side of the upper cover. When the mobile phone is placed on the upper cover of the mobile power bank, the pin will be pressed down, the reed will be closed, and the battery will output to the boost board. When the mobile phone is removed, the pin will pop up, the reed will be disconnected, and the power will not leak.

　　After finishing everything, I put the mobile power bank on the touchstone and it made a familiar and pleasant sound, even more pleasant than the Intel light. The red light was on, indicating charging.

　　Stack the phone on the power bank, the phone screen lights up and displays "Charging".

　　I Ca~ finally succeeded.

　　10 Conclusion

　　After putting away the tools, it is time to take stock as usual.

　　First of all, the YZX board is not protected, and the 61030 chip it uses is also very easy to burn, and it may also burn the Philosopher's Stone. Therefore, if you use the YZX board, the lithium battery must be equipped with a protection board, the boost board must be shielded, and it is best to add a fuse between the output and the Philosopher's Stone. When the back cover of the Philosopher's Stone was removed, the metal sheet removed was a good shielding material.

　　Secondly, the power of the Golden Stone must be above 1A to work, otherwise it will not light up at all. If the power is slightly worse, it is easy to cause a cycle of lighting up and then breaking, then lighting up and breaking again. This phenomenon is also closely related to the wire material. You should choose a good wire material and keep it as short as possible. Moreover, this phenomenon is also related to the Golden Stone itself. I was once angry about this problem. In a fit of anger, I bought 3 stones and 5 back covers, plus the original two stones. I found that when the wire material was poor, only one stone was normal, and the other 4 stones were in a cycle of lighting up and breaking. When I changed to a good wire but the wire was very long, three stones were normal, and two stones were in a cycle of lighting up and breaking. Finally, when I used a good wire but it was very short, the five modified 8700s were normal, but only four stones were normal when charging Xiaowei, and one stone was in a cycle of lighting up and breaking. And this damn stone can only charge Xiaowei normally with the original charging head + original charging cable, so I had to put it on the desk.

　　Again, the final solution only uses a single-pole double-throw electromagnetic relay, so there is no need to use 19F. A 5-pin one will do. The size can be half as small, so it can be placed horizontally to save space.

　　Also, if you travel between home and work, you can remove the back cover of the Touchstone on the mobile power bank and add a USB port. If you use Xiaowei's data cable, you can also make a magnetic interface. That way it becomes a mobile enhanced version of the Touchstone.

　　Finally, you can use the back cover of the Philosopher's Stone to transform other things. I also transformed a mifi, which automatically turns on the wireless network and charges when placed on the Philosopher's Stone. It is very convenient to take it with you at any time, and you no longer have to plug and unplug the damn plug.

　　The Touchstone is just a starting point. I believe that the future of life will be wireless and unlimited, so plugs and sockets can go to hell.