Electronic Doorbell and Counter by HT-2811 and CMOS 4026

Description:

This circuit uses a synthesized sound chip from Holtek, the HT-2811. This reproduces the sound of a "ding-dong" chiming doorbell. Additionally, the circuit includes a CMOS 4026 counter display driver IC to count your visitors.

Circuit Notes:

The Holtek HT-2811 is available from Maplin electronics in the UK, order code BH69A. 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 IC pin out for the 4026 is shown in pin order below:

Pinouts of CMOS 4026:

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

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 debouncing 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.

Circuit Expansion:

The count may be expanded for up to 99 visits by cascading two CMOS 4026 IC's and using an additional 7 segment display. This is achieved by wiring pin 5 ( the 10's output ) of the first CMOS4026 to pin 1 (the clock input) of the second IC.

Please Note: The CMOS 4026 is availble from Elfa Electronics  part number 73-676-42. See my links page also.  

Designer: Anndy Collinson

Source: Anndy's page http://www.mitedu.freeserve.co.uk/Circuits/Switching/dbcounter.htm

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habibullahkhan said:

sir in ur sight the fm radio transmitter diagrams u have mention the range of this transmitter is 1-2 Km but its rang is only some feet.I m technical teacher and i want to build fm radio transmitter (frequency modulation range 3 Kilo meter and frequency 100MHZ) , it is requested to your that send me an fm radio transmitter schemetics circuit diagrams with full deatial and guidance IT IS FM TRANSMITTER VOICE TRANSMITTER FREQUENCY 100MHZ RANGE 3 KILOMETER my email is khu313@yahoo.com THANKS

January 27, 2008

Anshu said:

sir plese give me a digram for make FM trancemeter in 2 to 3 km range.i want to do broadcast in my town in FM recivers.

February 29, 2008