As promised, I'm starting to churn a new Mi Band 4 bracelet. However, I want to start not with opening the capsule itself, but with a more pressing topic – with the modernization of the charger, which many users complained about because of the need to remove the capsule from the strap for charging, which is negative affected the durability of this very strap.
And this concerned all generations of devices, starting with the very first. But Xiaomi stubbornly did not want to hear from their customers.
Well, the challenge is accepted.
Initially, two plans ripened in my head at once to resolve the issue with the charger.
The first option involved integrating the magnetic attachment of the capsule into the standard bath of the charger and getting rid of the mechanical attachment using plastic ears in this very charger. However, this seemed to me a half measure and modernization for the sake of modernization, since it did not solve the main problem – the need to remove the capsule from the strap.
The second option involved making a magnetic charger from scratch that did not require removing the capsule. The difficulty was in the need to create a master mold from a polymer, followed by the manufacture of the body of the charger itself and the integration of all the necessary contacts and connectors into it.
I even prepared everything I needed and tuned in to the modeling and construction, getting ready to enjoy the process and a numb back as a bonus.
As a result, congenital laziness won out, and an intermediate option was chosen as the final one. Which one? More on this below.
To begin with, I decided to implement the option with ear amputation.
Before that, having carefully examined the charger, I came to the conclusion that it, unlike the monolithic case in previous generations, is conditionally collapsible. This was understood by a careful look at the joint of the inner insert, which even outwardly differs from the main material of the bath.
So let's get started. To begin with, we push the knife into the joint and gently bend it out. At first it seems that everything is in vain, but if you continue to press gently, the inner tab gives in. And this happens best of all in places of curvature. It looks like this is where the fasteners are located.
We walk along the perimeter, and the hypothesis is confirmed. The tab snaps off, revealing to us … Exactly the same monolithic space under it. Hmm. I was hoping to see the wires and their locations so that I could better plan the operation.
Well, okay, the result obtained is also a result, since it gave us the knowledge that the inner tab itself has a fair amount of thickness, which means it will help us in placing the magnets.
Now you need to estimate the size of the magnets. Should fit.
To begin with, I will place one magnet, which, taking into account the design of the charger, should be enough to maintain contact, and then we'll see (remember about innate laziness).
So, it looks like it should work.
Now our task is to fix the magnet on the inner surface of the charger tray.
To do this, I use a soldering iron, with which I simply heat up the magnet and drown it a little in the softened plastic.
I am not afraid to damage the inner wires, as the external examination gave reason to believe that they are hidden deeper than I am going to immerse the magnet.
We heat the magnet and melt it into the base.
Now you need to fix it there, since the smooth metal of the magnet does not bond well with the plastic, alas. ?
We use good old superglue for this. We drip a little glue on the bottom of the resulting depression, put a magnet on top, press it all for a couple of minutes and put it aside to dry, and in the meantime we move on to the second stage.
Now we need to drill a hole in the middle, just above the magnet.
It is into this recess that the second magnet will go, which I plan to place on the capsule itself. Yes, just by this barbaric method. Subsequently, it is planned to open the capsule and place the magnet on the inside of the bottom of the capsule, but this is later, for now we will manage with a simple option.
We drill a hole, trying to fit into the dimensions, periodically applying the workpiece to the magnet at the bottom of the capsule.
The indescribable emotions of the cover from such bullying …
As a result, due to the fact that there was no drill of the required diameter in the house, no files (a nightmare, I handed everything out), the hole had to be cut with improvised means, and it turned out to be a little clumsy and unsightly. Well, okay, I don’t show it at exhibitions.
After the hole is ready, put the cover back in place, just pressing it down and additionally gluing it. It doesn't look too scary.
Now you need to glue the counter magnet to the capsule itself.
At first, putting a magnet on the capsule and trying on the capsule to the charger bath, I realized that the magnets are a little thicker than necessary, and I was upset to the point that I even decided to remove a little plastic from the capsule itself and practically realized my plan by removing a small layer.
But then he changed his mind in time and remembered that under these magnets there were two reciprocal metal patches made of a softer metal, which means that they can be grinded down to the desired thickness and put instead of the second magnet.
No sooner said than done. We take a patch, grind down the thickness and try on the resulting tandem. Now everything fits, and the capsule fits into the charger as it should.
We align the patch on the capsule and glue it to it with an additional layer, centering everything with tape and letting the patch dry on the capsule.
I am not allergic to metal, so a small metal piece on the inside is not a problem. If I had an allergy, I would simply cover the patch with a layer of varnish or paint, and that's it.
Then we try on the capsule to the resulting design and make sure that everything works.
It's time to get rid of your ears! We cut them mercilessly with a blunt knife and, pleased with ourselves, we look at the works of our hands.
Hurray, victory! Although stop, what a victory it is, if to charge the capsule you still have to remove it from the strap, thereby stretching it. Hmm.
It looks like we will have to proceed with option number 2.
Option number two
And I even started to implement plan number two, removing the magnet from the capsule and whipping up a master model with a glue gun, and was about to dive into the abyss of design when my eyes fell on the newly upgraded charger.
And then a crazy thought came to me – why not make the plan out of this, my own charger? Yes, there is a risk of screwing up and being left completely without a charger, but no one canceled two wires. And the operating time from one charge will allow you to find a new charger, if I still ruin this one.
Resolved, we will continue to collective farm.
Option number three
We try on the bath for the bracelet with a strap and estimate where and how much to cut off so that the contacts of the charger reach the contacts of the capsule.
You will have to cut quite a lot … And the wire gets in the way, which rests on the strap and does not allow the bath to lie tightly on the capsule.
Well, nothing, we'll come up with something along the way. We cut!
Something starts to emerge. But there is still too much unnecessary material.
And then I remembered that when I cut off my ears, I noticed that the bath consists of several layers, the outer one of which is dense silicone or rubber.
What if you remove the entire top layer?
No sooner said than done. We peel off all unnecessary, at the same time freeing the wire from the excess braid at the junction with the bath.
We cut more, mercilessly cutting off everything, in our opinion, superfluous. Just like Michelangelo, sculpting his David (yes, I know, I turned it over) …
We remove layer by layer and in the end we get just such a structure. Looks good. Or rather, not as bad as I expected.
Grind the edges a little and get the final result. It's time to check how all this will hold on the capsule, and whether it will be at all.
We apply. Holds, and quite confidently. And the wire, thanks to the removed excess material, does not even interfere. Wonderful.
Now we are testing the connection. And … Everything works as it should. This is a success.
Yes, in theory, you can put another magnet on the other side of the bracelet, but this is superfluous at the moment, since one magnet holds the entire structure quite confidently. Therefore, for now, let's dwell on this option.
Although the result can be called a 'collective farm', the experiment itself ended well, and in the end I now have what many bracelet users want Xiaomi – a magnetic charger that does not require removing the capsule from the bracelet.
I wanted to say that I am confident that the Chinese industry will respond to the aspirations of users and roll out magnetic chargers for the fourth generation Mi Band, but I doubt that they will bother with it. Although we will wait and see. This question worries me purely out of academic interest, since I personally already have such a magnetic charger, and it suits me completely.
The plans include making a convenient bedside stand for the charger in the form of an elegant docking station, on which the bracelet can be placed like on a holder. But this is still in theory, since, unlike smartwatches, most of which require charging almost every day, for a fitness bracelet such a station is more a matter of aesthetics than an urgent need. Therefore, if I do such a stand, then only with the ability to remove the charger itself from it if necessary. Go for it, but I went to continue to scoff at the bracelet.