#Meet friends by disassembling#Power converter disassembly comparison

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I made a water level meter with a single-chip microcomputer. I needed a power converter, but I didn't want to make it myself. So I found a 5V power converter used in a switch from a pile of old power converters and mobile phone chargers. The power supply shell was complete, as shown below:

To be on the safe side, I powered on the power and measured the no-load output voltage. I was shocked to find that the no-load output voltage of this nominally 5V power converter exceeded 10V. Even if the voltage would drop after connecting a load, the microcontroller may not be able to withstand this voltage shock.

So I decided to take it apart and see what it was:

This heavy thing has only four rectifier diodes and a filter capacitor, besides a large transformer, and no voltage regulator. I really don't know how it was used on the switch back then. Maybe there was a voltage regulator inside the switch.
This power converter was unusable, so I found a 5V mobile phone charger and disassembled it for inspection, as shown below:

The following figure is the specific

This charger is obviously smaller! There are four rectifier diodes printed on the screen, but only one is installed, and there is no corresponding line or hole on the circuit board. See the picture below

Obviously, such a converter cannot be used on a single-chip microcomputer, so I found a 5.3V charger for a Panda mobile phone, as shown below:

With the previous experience, let’s take it apart and see.
This charger is made of much more durable materials, worthy of being a product from a big manufacturer (this phone was bought around 2003). Here is the back of the circuit board:
I didn't expect that I used a lot of SMD components at that time, and the SMD full bridge in the upper left corner was particularly eye-catching.
I trusted the products of big manufacturers, so I decided to use this as a power converter.
I soldered off the original output line and replaced it with a universal standard plug line, as shown below:

Install the shell

When the power is on, the output voltage is 5.29V.

After connecting the water level meter, although the voltage is slightly higher than 5V, it can be used normally.

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