Convert Old Electric Toothbrush to Plug-in - top electric toothbrush

The electric toothbrush is very good, but after a few years of use, the rechargeable NiCad battery inside will wear out.
After my Sonicare toothbrush stopped charging, I bought a new toothbrush for Christmas (thanks, Santa! )
Decided to try and fix my old one.
I decided to convert the battery to use the wall instead of just replacing the battery with a new onewart-
Style socket plug-in.
The two sides of the box are well sealed (
Waterproof, or at least waterproof/toothpaste)
So it may take some effort to open it.
I recommend using a slotted screwdriver to carefully pry open the shell at the seams.
You can also get a lot of leverage at the top, and the toothbrush head is screwed down at the bottom.
Try not to break the whole case or break it because we will stick it together at the end.
You should see some coils, circuit boards and some batteries once you turn it on.
This toothbrush has done such a simple thing, it has some strange technology!
As long as we open the case, we might as well do some exploration.
This special toothbrush handle is fully sealed, charging the battery using a magnetic coil and moving the toothbrush head.
The coil at the bottom is used to charge the battery and there are similar coils in the charger base station.
Removing the board allows us to do some experiments on the coil.
When the coil is not in the base station, if we measure the current in the coil, we naturally do not see the current.
When I put it in the charging base station, my multimeter shows about 30 mA.
It may be more useful to measure it using an oscilloscope, as it may be an AC signal.
Maybe I will do that one day.
Very interesting!
Since the batteries are actually dead, I removed them from the board and welded them on some of my own wires.
I connect the wire to the LM317 adjustable voltage regulator so that I can experiment with the voltage running the toothbrush.
I had to add some power capacitors to keep the output voltage stable and decided to try 2. 4 volts output.
I calculated the appropriate resistor value to be added to the regulator and was very close to 2. 4 volts.
When I pressed the toothbrush button it started buzzing as usual.
It looks like I can power the toothbrush from a constant DC voltage source. Hurray!
I found the smallest voltage wall.
I have the Thunderbolt adapter in the zerobars, that's 5. 0 volts.
Everything was fine after testing on the toothbrush, so I decided to use this.
I was a little worried that the extra voltage would make it wear out faster or heat the coil.
However, it only runs twice a day for two minutes, so it may be fine.
I pop the bottom carefully with a slotted screwdriver (charging)
Coils and two batteries so I have room to drill holes for the power cord.
Try not to break the outer shell when prying into these parts!
Next, I drilled a small hole at the bottom of the box, just enough rope to pass through.
I stripped the end of the wire and welded the wire to the circuit board that previously connected the battery.
Make sure to pass the wire through the shell before soldering the wire to the circuit board!
After welding, be sure to test the circuit again to make sure the toothbrush is still working.
The original waterproof on the toothbrush handle is very good because I can put it next to the bathroom sink and let the toothpaste drop on it, all without worrying about destroying anything inside.
I wanted to be as waterproof as possible, so I applied strong glue to the contact area between the two pieces of the case.
I looked at it to make sure I could see a little glue seeping out of the edges.
I used several woodworking fixtures to put pressure on the case.
The next day I was unable to pull the case open with my hand and I was pretty sure it was waterproof.
The boxes are stuck together and it's time to brush your teeth!
Be sure to use the appropriate amount of toothpaste and brush your teeth.
Don't forget those on the way back, or the inside of your teeth!
Hope you like this Instructable and I hope it helps some toothbrushes stay away from landfill when their batteries run out!