Teardown of AC DC Chinese Adaptors from RC Toys and Chargers
Schematic of Unregulated AC-DC PSU
Unregulated Power AC-DC Adapters
I have a bunch of these AC-DC Adaptors from Remote Controlled Toy Chargers, some are from android chargers. Reusing these adapters will reduce electronic waste which are harmful for the environment. The adaptors from RC Toys are very heavy because of the Transformers.
I have this Jing Heng AC 220V 50Hz to DC 9.6V 800mA adaptor, this is what it looks like the casing is broken since I dropped it over ten times.
Inside, there is a thin wiring from the step down transformer which is connected to the Neutral and Live, it does not have any fuse so no protection in an event of a short circuit or over current. After the step down transformer, there is a 4x 1N4001 diode this is the bridge rectifier which converts AC to DC but I was surprised that is does not have any filtering capacitor to smooth out the ripples. Note that this is also a unregulated DC power supply which means it is susceptible to sudden surges/spikes in the AC input voltage, this is not recommended for sensitive digital IC circuits like microcontrollers and the Raspberry Pi. We need to use a Linear or Buck/Boost Voltage Regulators to power them.
Testing the adapter with a cheap multimeter, the 9.6V rated output is now -11.03V, oh. The polarity is inverted the wire with stripe is the positive and the black wire without white stripe is the negative. Trying again the multimeter now reads 10.52V, this could be my faulty multimeter or the unregulated voltage output of the adapter. Again it does not have any filtering capacitor so the values keeps floating.
The long wire of the output has thick insulation and thin copper wiring it maybe a 24AWG? chinese gauge standard. TODO for this thing is to add a Transient Suppressor and Buck converter to power the Wemos d1 mini.
Here is another one, it says AC/DC Adaptor, input 220V 50Hz output 3V 150mA. It weighs less than the previous one, opening it yields a thin wire no fuse to the neutral and live and a bridge rectifier PCB with a filtering 470uF 16V capacitor.
Powering it up, I used a 4-30V DC volt meter here and it reads 5.2 volts! But the output should be 3V! This is a mislabeled product! The wiring is the same as in the previous adapter and same polarity.
Here is another heavy AC DC no sticker label adapter, but upon plugging in it no longer works. Tearing it down there is a bridge rectifier and an LED with a resistor and no filtering capacitor.
Broken No label Adaptor
Switched-Mode Power Supplies
Here are my SMPS adapters from various devices such as chinese MP3 player, RC toy charger, android phone charger, and stun gun charger.
RC Toy adapter. Fenghui Electronic AC/DC Adaptor Model FH-2210572U AC 220-240V 50/60Hz and output of DC 6V at 250mA. Upon pluggin in, the voltage reading went to 15V then to 14.49V! Wow another mislabeled product. Tearing it down reveals a switch-mode power supply.
MP3 AC-DC Adapter. This is from a Chinese MP3 player. I tested the output and it appear to work fine. Specifications are as follows, YC-DC ADAPTER Model: 5V/5W Input: 100-240Vac 50/60Hz Output DC 5V 1A. The PCB is shown below, more tests are to be done and reverse engineering of the board and how safe it is.
Android Tablet Power Adaptor. This is from a Chinese Polaroid Android Tablet Charger. Specifications Model LA-520H Input: 100-240V ac 50/60 Hz 0.3A Output:5V 2A. The board is shown below, it has USB female socket but it is broken. I will solder a cable to the output.
Stun gun Adaptor
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Note: They are spelled as adaptors not adapters.
TODO:
Further Testing of SMPS
Modding of Unregulated Adapters
Reverse Engineering Schematics SMPS
Adding safety to unsafe adapters
