Thyristor fast constant current charger circuit

It can quickly charge the nickel-cadmium battery with constant current, and can automatically cut off the power after being fully charged.
A constant current circuit composed of the AN7805 three-terminal fixed integrated voltage regulator and resistor R3 is used to charge the battery ( the constant current value is approximately equal to
the nominal voltage regulation value of the three-terminal fixed integrated voltage regulator divided by R3). When charging, press the button SB, the bidirectional thyristor V is turned on, and
the charging indicator light VL lights up. When the battery is fully charged (reaches 3V), by pre-setting the potentiometer RP, the transistor VT
is turned on, VL is turned off, the bidirectional thyristor V is turned off, the power supply is automatically cut off, and charging is stopped.