AT89C2051 Digital Visitor Counter Circuit

AT89C2051 Digital Visitor Counter Circuit

Digital visitor counter is a reliable circuit that takes over the task of counting Number of Persons/ Visitors in the Room very Accurately. When somebody enters into the Room then the Counter is Incremented by one and when any one leaves the room then the Counter is Decremented by One. The total number of Persons inside the Room is displayed on the seven segment displays. The microcontroller do the above job it receives the signals from the sensors, and this signals operated under the control of software which is stored in ROM

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AT89C2051 Digital Countdown Timer Schematic

A simple count-down LED timer that counts in minutes and seconds. Three buttons below the LED provide control of the unit, allowing you set the desired countdown time in minutes and seconds and a start/stop button. Completion of the countdown is indicated by an alarm that starts when the countdown has finished and the display reads zero.
The alarm is stopped by pressing the start/stop button.

Downloads:

Download the Source code from here:
Download the PCB from here:

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Simple Balanced Input with Gain Circuit Diagram

This circuit was created to provide a balance audio output from an electronic symmetrical input. You can set the regulation gain from potensiometer RV 1 and improve the signal level gain with potensiometer RV 2. This circuit needs a high quality material in order to annoying noises.

Parts list :
R1-2= 2.2Kohms metal film 1%
C1-2= 68pF ceramic OR milar
ICI= NE5532 -TL072
R3= 22Kohms metal film 1%
C3= 47uF 25V
RV1= 10Kohms Log.
R4= 6.8Kohmsmetal film 1%
C4= 10uF 25V
RV2= 47Kohms Log.
R5= 100ohms
C5-6= 100nF100V cer. OR mkt
J1= Female CANNON plug
R6-7= 47Kohms
C7= 10uF25V

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Symmetrical Class-A Amplifier Circuit

It’s very simple because this circuit using common components which easily found. This circuit diagram also provides a very good amplifier unit with low distortion. Similar with other audio circuit, the sound quality are depends on the quality of the component, including transistor, capacitor, resistor and the placement it self.

Part list:
R1= 100Kohm
R9= 100Kohm
C6-7= 47uF 40V
R2-3= 82Kohm
R10= 1Kohm
T1-2= BC 550C
R4-5= 22Kohm
C1-3= 10uF MKT
T3-4= BC 560C
R6-7= 100ohm
C2= 56pF ceramic
T5= BC 516
R8= 5.6Kohm
C4-5= 100nF 63V
T6= BC 517

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Low Impedance Simple Preamplifier Circuit

This is a simple low impedance preamplifier circuit diagram. It used to amplify an audio signal. This circuit use a 12Vdc sources and very simple because work with less components.
Part list:
R1= 47Kohm
R10= 820 ohm
C6-8= 47uF 25V
R2-5= 15Kohm
R13-14= 27 ohm
C7= 2.2uF 100V MKT
R3-4= 1.5Kohm
R15= 100Kohm
Q1-4-5= BC550C
R6-11= 1.5Kohm
R16-17= 22 ohm
Q2-3-6= BC560C
R7-12= 1.8Kohm
C1= 120pF
J1= 5pin connector
R8= 8.2 ohm
C2-5= 100nF 100V MKT
All R is metal film 1%
R9= 150 ohm
C3-4= 220uF 16V

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