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Monday, October 12, 2009

Intercom Circuit Using Fader

This is a complete circuit that is shown in the diagram below and is formed by a microphone amplifier built around IC1A, is a design for intercom circuit. In this circuit, there are 2 IC, LM358 that is used to low power dual op amp and 4016 or 4066 Quad bilateral for switch IC. This IC that is used to control the circuit. This is the figure of the circuit.

The two microphones (small electret types) are connected to J1 and J2 and the two headphone sets (usually 32 Ohms impedance) to J4 and J5. The iPod headphone output is connected to J3 by means of suitable stereo cable and 3mm jack plugs. R4 acts as a volume control for the microphones and also sets the threshold at which the music will be muted: it should be set once for all and then left alone. When speaking is stopped, the music will revert to full volume after some time-delay, set by R12 and C6. The value of these components can be varied to suit one's own needs. The headphone amplifiers, despite the high number of transistors used, are simple enough, efficient and, above all, setup-free. They are able to deliver a full 5V peak-to-peak sinewave into 16 Ohm (i.e. about 200mW into two 32 Ohm headphones wired in parallel) with less than 1% distortion @ 1KHz and 0.7% @ 10KHz. At the standard 40mW headphone power output capability, distortion figures are 0.6% @ 1KHz and 0.3% @ 10KHz.


R1,R2___________22K  1/4W Resistor R3,R20___________1K  1/4W Resistors R4______________50K  1/2W Trimmer Cermet or Carbon R5______________47K  1/4W Resistor R6,R7,R8_______100K  1/4W Resistors R9,R10__________68K  1/4W Resistors (See Comments) R11,R15,R16______1M  1/4W Resistors R12____________470K  1/4W Resistor (See Comments) R13,R14________220K  1/4W Resistors R17,R18________100K  1/4W Resistors R19____________470R  1/4W Resistor C1,C2,C5,C7,C8_100nF  63V Polyester or Ceramic Capacitors C3_____________100nF  63V Polyester or Ceramic Capacitor (See Notes) C4,C6___________10µF  25V Electrolytic Capacitors C9_____________100µF  25V Electrolytic Capacitor C10____________220µF  25V Electrolytic Capacitor C11____________470µF  25V Electrolytic Capacitor D1,D2________1N4148   75V 150mA Diodes Q1____________BC560C  45V 100mA Low noise High gain PNP Transistor Q2____________BC550C  45V 100mA Low noise High gain NPN Transistor Q3,Q6_________BC337   45V 800mA NPN Transistors Q4,Q5_________BC327   45V 800mA PNP Transistors IC1___________LM358   Low Power Dual Op-amp IC2____________4016 or 4066 Quad bilateral switch IC J1,J2___________3mm  Mono Jack sockets J3,J4,J5________3mm  Stereo Jack sockets SW1____________SPST  Toggle or Slider Switch B1_______________6V  Battery (4 x AA or AAA 1.5V Cells in series                               or any 6V rechargeable battery pack etc.)


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