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:
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
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