INDEX

Above circuit shows how to produce +/-12V, 5V from 230V AC line. It basically consist of a bridge rectifier with a capacitor filter and a voltage regulator. If you invert polarity of the capacitors then sometimes it will burst because all the capacitor here are electrolytic capacitors. If you invert the polarity of the diodes then this circuit won't work. See the pins of voltage regulators.Here you can see that -12V is with respect to ground, remember that we measure all quantities with respect to ground. Suppose if you want -12V , don't say that you connect 0V to +ve and 12V to -ve lead because we say -12V with respect to ground and ground(0V) is a common terminal.
The main troubleshooting in circuit is to
1) check that your power supply, whether it will be able to provide the sufficient power to the circuit, controlling as well as motor driving circuit.
2) check the polarity of the power supply.
3) See the light of the adapter,
4) if it is OFF then you check whether your switch (power switch)is ON
5) If it is still OFF even though the power is ON then you check for the short circuits in the circuit.
6) If the light is DIM then you can infer that the adapter is not able to drive the circuit. When I connected a 3V DC motor from a toy car directly to adapter the light of the adapter becomes DIM. When I connected the output of adapter to input of 7805 and the output of 7805 directly to IR LED then the light of the LED DIM. Suppose if you connect the output of the adapter to 7805 and short the second and third pins of 7805(Vcc and gnd) then the light of the adapter will goes OFF