Wiring Schematic Diagram

This circuit is to setup home-cinema set adjusting all the loudspeaker outputs to the same level when heard from the listening position.In practice this device is a simple (though linear and precise) 100µAac millivoltmeter.

The precision of the measure is entirely depending on the frequency response of the microphone used but, fortunately, for the main purpose of this circuit an absolutely flat response is not required. Therefore, a cheap miniature electret microphone can be used.

The circuit is based on non- inverting amplifier based on op-amp CA3140 (IC1).The sound picked by the condenser mic will be amplified by the IC1 and rectified by the bridge D1 to drive the meter M1.The deflection on the meter will be proportional to the pressure of the sound falling on the mic.The switch S1 can be used as an ON/OFF switch.

This is a volt meter circuit based on LM324 OpAmps chip. A bargraph generator is nothing more than a slack-handful of OpAmps, all thrown into a single chip. It is cheaper to use the LM324 and put in the few extra components needed.

R1 to R8 down the left all form a voltage divider from the 7.5v Zener diode. The resistors give me taps of 0.5v, 1.5v, 2.5v, 3.5v, 4,5v, 5.5v, and 6.5v. The top of the zener gives me the eighth voltage: 7.5v. These reference voltages are all connected to the negative-acting input of each OpAmp, and all the positive-acting inputs are gathered together for a common input. With 0v on the +ve inout, the output voltage of avery OpAmp is 0v.

If the input voltage lies between 0v and 0.5v then no LED lamps will light. If the input voltage rises to between 0.5v and 1.5v (1v +/-0.5v) then the first LED will light when the first OpAmp +ve input exceeds the -ve input threshold. In this way the LEDs all form a nice bar-graph display in 1v steps, +/- half a volt.

The A-B-C links should be in the A-B position for a normal bar-graph display, when each LED succesively lights as the voltage rises. With +4v input there will be four LEDs lit. If you fit the links in the A-C position then only one LED will light for each voltage step, to give a moving dot display. The top (last) link should always be in the A-B position for both modes.


This Op-Amp Voltmeter Circuit From www.sm0vpo.com:800

This is a signal injector circuit. Signal injector is important tool for troubleshooting your electronic circuits. As an example, this circuit can be used to test amplifier circuit. Here is the schematic diagram of the circuit:

This circuit also a lot of harmonics. By connecting the ground clip to the 0v rail and move through each stage, starting at the speaker, the fault in an amplifier can be found. At each preceding stage, the volume will increase. This circuit can inject FM sound sections in TV’s and the IF stages of radios.

When T1 conducts, its collector tension goes from high to low. Via C1, this is transmitted to the base of T2 making its collector tension drop from high to low as well. Via C2, this pulse blocks the base-current of T1, causing it to block up. As soon as the left side of C2 is charged enough by R3, T1 can conduct again and the cyclus is repeated.

This is simple 3-digits digital volt meter. The range is -99mV to +999mV. Two integrated circuits are used, the CA3161 and the CA3162.

IC1 converts the analogous signal to a digital signal and also produces the multiplex signal to drive T1-T3. The BCD-code from IC1 then goes to IC2, a BCD to 7-segment decoder/driver. From there the signal goes to the displays.

The timing for the CA3162 is supplied by a 786Hz ring oscillator, and the input at pin 6 determines the sampling rate. A 5V input provides a high speed sampling rate (96Hz), and grounding or floating pin 6 provides a low speed (4Hz) sampling rate. When pin 6 is fixed at +1.2V (by placing a 12K resistor between pin 6 and the +5V supply) a 'hold' feature is available. While the CA3162E is in the hold mode, sampling continues at 4Hz but the display data are latched to the last reading prior to the application of the 1.2V. Removal of the 1.2V restores continuous display changes. Note, however, that the sampling rate remains at 4Hz.

The 'EEE' or '---' displays indicate that the range of the system has been exceeded in the positive or negative direction, respectively. Negative voltages to -99mV are displayed with the minus sign in the MSD. The BCD code is 1010 for a negative overrange (---) and 1011 for a positive overrange (EEE).

To callibrate the circuit, connect HIGH and LOW to mass and adjust P1 to read '000'. Then connect a tension from 0 to 1V to HI and LOW with LOW connected to mass. Adjust P2 to read the tension in mV.

The measuring range can be raised, using tension dividers. To use the decimal points, connect DP1, DP2 and/or DP3 to mass.

This circuit is a digital frequency counter. It covers region 1HZ until 1MHZ. The IC1 schmitt trigger that it regulates the signal of entry and him changes in reasonable level suitable for the IC2-3-4. With the tenth pulse in the entry of IC2/1, is produced a pulse '' carry '' in the IC3/5. The same moment the IC2 causes the depiction in the display 1, The IC3 causes the display 2. When in the entry of IC3 it reaches and the tenth pulse, the display 2 and the display 3, (with total depiction 100, having the display in right order). The exit '' carry'' off IC4/5, can be used in order to it turns on the decimal point (comma) the display 1, in order to it shows a situation over the limits of measurement.

The timed begins with the one of half double timer (IC5A). Switch S1 select the interruption the time in 1sec or in 1ms. At the duration of this interruption, second half the (IC5B), it produces a interruption of depiction 2 or 3sec., at the duration which counter cut off by the entry and the displays remain OFF. In the end of depiction, a pulse RESET, begins the interruption of time/depiction.

The critical point is round the Q1-IC1, which should be placed as long as it becomes more near in the jack of entry, to reject of parasitic signals of high frequency. For the regulation, we can use a frequency counter good precision (if you do not have you are lented) and a generator of signal. We put switch S1, in place [HZ], we apply in the entry a low frequency and we regulate the trimmer TR2, so that we take the right clue, which should suit with source frequency counter We repeat also the regulation for the department of KHZ, with a higher frequency. The supply of circuit becomes with a battery +9V, if it is used as portable or from suitable power supply if it is incorporated in some unit that exists already.

List Component

R1     : 8.2Mohm          IC2-3-4 : 4026
R2-9   : 100Koh           IC5     : 556
R3     : 470Kohm          IC6     : 4007
R4     : 470 ohm          IC7     : 7805
R5-6-7 : 10Kohm           DS1-3   : Display 7segment Comm. Cath.
R8     : 3.3Mohm          TR1     : 1M ohm trimmer 
C1-2   : 1uF 63V Mylar    TR2     : 1Kohm trimmer 
C3     : 47uF 16V         Q1      : 2N930 
C4     : 100nF 63V        S1      : ON-OFF mini switch
C5     : 2.2uF 16V        S2      : 1X2 mini switch
C6     : 10uF 16V 
C7     : 10nF 63V Mylar
C8-10  : 1nF 63V Mylar 
C9     : 1uF 16V  

The circuit is formed by an input buffer and ac to dc voltage converter (IC1A) feeding a window comparator (IC2A, IC2B, IC2C) which illuminates one of three LEDs at a time. No setup is required: if correct values are used for resistors R3 to R7, LED D1 will illuminate at 0dB input (0.775V RMS), LED D2 at +5dB input (1.378V RMS) and LED D3 at +10dB (2.451V RMS).

R1       : 300K  1/4W Resistor
R2       : 1M2   1/4W Resistor
R3       : 510K  1/4W Resistor
R4       : 220K  1/4W Resistor
R5       : 91K   1/4W Resistor
R6       : 160K  1/4W Resistor
R7       : 56K   1/4W Resistor
R8,R9    : 100R  1/4W Resistors
R10      : 220R  1/4W Resistor
C1       : 100nF  
C2       : 1µF/63V
C3       : 10µF/25V
D1,D2,D3 : LEDs (Any coloring at will)
IC1      : LM393  
IC2      : LM324  
IC3      : 78L05  
SW1      : SPST  Toggle or Slider Switch