Karaoke machine circuit based in transistors+ graphic equalizer Essay

Karaoke machine circuit based in transistors+ graphic equalizer - Essay Example The circuit will include following essential elements 1. Two inputs, 1 for microphone and a second for Line input, which could be mixed and boosted with a common emitter amplifier stage. 2. A six-band graphic equalizers stage. 3. A common emitter voltage boost amplifier stage. 4. A common collector power amplifier. 5. Circuit works from mains power supply. Circuit Operation Detailed circuit operation is given as under:- Power Supply The power supply is connected to pre amplifier and power amplifier blocks. The Transformer T1 is a simple step-down transformer which takes 240 V Ac current and gives out 9.5 V Ac at current rating of 1.3 amps approximately. The circuit requires steady DC current therefore output of transformer is applied to rectifiers. Transformer works on the principle of mutual induction of two coils. When current in the primary coil is changed, the flux linked to the secondary coil also changes. Consequently, an EMF is induced in the secondary coil. The transformer T1 consists of a rectangular core of soft iron in the form of sheets insulated from one another. Two separate coils of insulated wires, a primary coil and a secondary coil are wound on the core. These coils are well insulated from one another and from the core. The coil on the input side is called Primary coil and the coil on the output side is called Secondary coil. According to Faradays law EMF induced in a coil depends upon the rate of change of magnetic flux in the coil. If resistance of the coil is small then the induced EMF will be equal to voltage applied. A transformer in which Number of turns in primary coil are greater than Number of turns in secondary coil (Np>Ns) is called a step down transformer which is T1 in this case. In this way the Step down transformer T1 converts high alternate voltage of 240V to low alternate voltage of 9.5 V with current rating of 1.3 amps approximately. This voltage is next passed on to a rectifier to obtain a steady DC voltage. Rectifier D1 con sists of four diodes which are meant to convert Ac into DC. During each half of current cycle the diodes block reverse current and allow forward current. Rectifier D1 is a full wave rectifier which works during both positive and negative cycle of AC. Rectification is the conversion of alternating current (AC) to direct current (DC). This involves a device that only allows one-way flow of electrons and it is built around a four-diode bridge configuration therefore called a full-wave bridge or rectifier .Regardless of the polarity of the input, the current flows in the same direction through the load. That is, the negative half-cycle of source is a positive half-cycle at the load. The current flow is through two diodes in series for both polarities. Rectifier bridge works half time during positive sinosidal wave and half time during negative sinosidal wave. The result is a steady DC current measuring 9.5 V. This current is applied to Capacitor C18 with value 2500 uf, which charges the in put to around 13.5-14V peak voltage. This voltage is passed to a standard 12 V regulator IC1 that gives steady DC output of 12 V to run the complete circuit. In the power supply, heat is dissipated during transformer and voltage regulation stages. The capability of a capacitor to store electricity is known as capacitance of that capacitor. It is denoted by C. The measuring unit of capacitance is Farad, but Farad is very large unit. Its smaller units are Kilo Micro Farad (KMFD), Micro