Simple Electronic Doorbell Circuit Using Counter

This is a simple design circuit for a door alarm circuit, but in this design using electronic system. This circuit uses a synthesized sound chip from Holtek, the HT-2811. This circuit reproduces the sound of a "ding-dong" chiming doorbell. Additionally, the circuit includes a CMOS 4026 counter display driver IC to count your visitors. This is the figure of the circuit.


The operating voltage must remain within 2.4 to 3.3 VDC and standby current is minimal. The reset switch zeroes the count, and the 7 segment display is a common cathode type. To save power consumption the display can be enabled or disabled with a switch as shown in the above diagram. The count will still be held in memory.

The envelope of the chime is set by the 220k, 330k, 3u3 and 4u7 resistors and capacitors. These values are the manufactures default values, but may be adjusted to alter the length and delay of the chime. The combination of the 2k2, 22k and 47u resistor capacitor network has a double function. It provides a de-bouncing circuit for the bell press and at the same time has a sufficiently long time constant. This ensures that anyone rapidly pressing the doorbell switch, only advances the count once. The 47u capacitor may be increased in size, if needed.

Pin IC CMOS can look for the list below.
Pin 1 is the clock input
Pin 2 is the clock enable
Pin 3 is display enable
Pin 4 enables the carry output
Pin 5 is the carry output
Pin 6 is display segment f Pin 7 is display segment g
Pin 8 is 0 V.
Pin 9 is display segment d Pin 10 is display segment a
Pin 11 is display segment e Pin 12 is display segment b
Pin 13 is display segment c Pin 14 is the2 output
Pin 15 is reset
Pin 16 is +Vcc

Simple Cascaded Timer Circuit

This is a simple design circuit that uses a CMOS dual re-trigger mono stable IC 4528 in a cascade timer circuit. The CMOS timer can be easily cascaded with other similar 4528 circuits to lengthen the timing needed. This is the figure of the circuit.


The timing of the project is determined by VR3 and C1 for the first stage and VR4 and C2 for the second stage. Once button S1 is pressed, the 1st stage output pin 6 logic level will go high and output pin 7 will go low for the preset time which is determined by VR3 and C1. When the time is up, the output pin 6 will go low and pin 7 high. At this moment of time, pin 7 will positive trigger the 2nd stage of the timer at pin 12. Output pin 10 will go high and pin 9 will go low for a time determine by VR4 and C2 before the cycle end with pin 10 back to low and pin 9 to high.

Simple 10 Minute Timer Circuit Using 555 IC

This is a design for simple timer circuit. This circuit can giving 10 minute of the timer. This circuit is based on 555 IC for the operation. This circuit can connect with microcontroller for practicing the programming. This is the figure of the circuit.


When ever you need to get an alarm or intimation after ten minutes, the circuit shown below can be used. The circuit is nothing but a mono stable multi vibrator based on IC NE 555.When ever you press the reset push button the green LED D1 glows after 10 minutes. The time duration can be set by varying the POT R5. The switch S1 can be a push button switch. The IC1 must be mounted on an IC base.