Simple 6 Input Alarm

This simple alarm circuit was designed for use in a combined garage and rumpus room. It can be assembled on Veroboard and uses just one IC plus a handful of cheap components. The circuit is based on a straightforward 555 timer circuit (IC1). This is wired as a monostable and sets the siren period which is adjustable up to about three minutes using potentiometer VR1. In operation, IC1s pin 2 input monitors the detector circuit for negative-going signals. When a switch is closed, a brief negative-going pulse is applied to pin 2 via a 10µF capacitor and its corresponding series diode (D2-D7). This triggers IC1 which switches its pin 3 output high and switches off relay RLY1 (ie, RLY1 is normally on).

As a result, the piezo siren sounds for the duration of the monostable period. In addition, relay RLY2 is turned on via diode D9 and latches on via D10. This means that the strobe light (which is wired to the normally open contact) will continue to flash until the alarm is switched off (via the keyswitch). At the end of the monostable period, RLY1 turns off and this turns off the piezo siren. The circuit can then be retriggered by any further trigger inputs from the switches. A variety of detectors with normally open contacts can be used for the switches, including reed switches, pressure mats, IR detectors and glass breakage detectors. All switches must be open before the alarm is switched on.

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The Differential Input and Differential Output

For getting balanced differential output 
we use this circuit. In this circuit  two source is present, so the
superposition theory is applied to get the output. In this circuit both
the inverting and non-inverting terminal is working.It rejects the
common-mode voltages, so  it is very useful in noisy environments.

A  differential input and differential output amplifier using two identical Op amp. It is     most commonly used as a preamplifier and driving push-pull  arrangement. The differential input and output  are inphase or the same polarity provided  V_in  =V_x – V_y and

V_o  =V_ox – V_oy

When we want to find out the 1^st op-amps output V_OX , we will use the  superposition theory.

When we get  V_X  is active , V_Y  is  inactive then ,

In non inverting terminal 

V₁= (1+ )V_X

When we get  V_y   is  active,  V_x   is  inactive then,

In  inverting terminal,

V₁ = - V_y

 So, V_ox = V₁+V₁

                =(1+ )V_X  -  V_y

 

Fig: The circuit diagram of the differential input and output amplifier. 

When we want to find out the 2^nd  op-amps output V_Oy ,we will use superposition theory.

                      When we get  V_X  is active , V_Y  is  inactive then

                      In  inverting terminal ,

                      V₂= - V_x

        

      Again, when  we get  V_y  is  active ,  V_x  is  inactive then

        In non inverting terminal we get, 

V₂= (1+ )V_y

So, V_oy = V₂+V₂

                                      =(1+ )V_y - V_x

So the output result   

V_o = V_ox  –  V_oy 

= (1+ )V_X  -  V_y  –[(1+ )V_y - V_x ]

                                      = (1+ ) ( V_X - V_y ) +( V_X - V_y )

                                       = ( V_X - V_y ) (1+ )

Design

To design a input and differential output amplifier,  taking a  differential output of at least 3.7V and the  differential  input V_in  =10V.

                        We know,

 V_o = ( V_X - V_y ) (1+ )

            Or, 3.7 = (0.1) (1+ )

 Or, 37 = (1+ )

            Or, 36 = 

            Or, R_f  = 18 R₁

                                    Let, R₁ = 100Ώ, then R_f  = 1.8 KΏ . 

                   Fig: The designing circuit diagram of the differential input and output amplifier. 

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Dual Input Far Field Noise Suppression Microphone Amplifier Circuit

This is a circuit diagram for microphone amplifier. This circuit is using LMV1090 as based op amp signal in the circuit. This is the figure of the circuit;

The LMV1090 is a fully analog dual differential input, differential output, microphone array amplifier designed to reduce background acoustic noise, while delivering superb speech clarity in voice communication applications. The LMV1090 preserves near-field voice signals within 4cm of the microphones while rejecting far-field acoustic noise greater than 50cm from the microphones. Up to 20dB of far-field rejection is possible in a properly configured and using ±0.5dB matched microphones. [Schematic circuit source: National Semiconductor Notes].

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