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This is the simple circuit of white LED lamp that can be directly powered from AC Supply. Full Wave rectifier method used to convert AC to DC. In this, the 220ohm 1/2W resistor limits the current, 470K ohm 1/4W resistor, 470nF 400V capacitor and 1N4007 diodes are used to step down and rectification and it gives 40mA.
The circuit has two stable states that change alternatively. It is implemented by the coupling capacitors that instantly transfer voltage changes because the voltage across a capacitor cannot suddenly change. In each state, one transistor is switched on and the other is switched off. Accordingly, one fully charged capacitor discharges slowly thus converting the time into an exponentially changing voltage. At the same time, the other empty capacitor quickly charges thus restoring its charge. The circuit operation is based on the fact that the forward-biased base-emitter junction of the switched-on bipolar transistor can provide a path for the capacitor restoration.
We could know the water level in the tank by showing L(low), H(half), and F(full) on a 7-segment-display. This water level indicator circuit is designed by using the 7408 (U2) quad two-input AND gate IC (that contains four independent gates) and a 7404 (U1) hex inverting gate IC. When the tank is full a buzzer gives sound to alert and a Switch(SW) is used to turn off the buzzer.
This rain detector alarm circuit project is an very simple circuit , that will start an audio warning , if the liquid is present on the sense pad . This rain detector alarm circuit diagram is based on two transistors BC547 and BC557 . When the sense pads conducts , Tr1 and Tr2 will generate a pitch sound .
This Simple Siren circuit will generate siren sound when SW pressed and increate sound frequency becuase capacitor C1 charged when switch SW released the frequency will decreated(C1 discharged).
The simplest rectifier circuit is nothing more than a diode connected in series with the ac input. Since a diode passes current in only one direction, only half of the incoming ac wave will reach the rectifier output. Thus, this is a basic half-wave rectifier. The orientation of the diode matters; as shown, it passes only the positive half-cycle of the ac input, so the output voltage contains a positive dc component. If the diode were to be reversed, the negative half-cycle would be passed instead, and the dc component of the output would have a negative polarity.