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ACKNOWLAGEMENT :-
In many cases, a doorbell that sounds off a musical tone is preferable over the common
buzz sound. This featured circuit is a musical doorbell. After the button S1 is pressed, a
short melody is played. When the button is pressed many times in rapid succession or
pressed longer, a different melody is generated and the melody plays longer.Our market
is flooded with cheap and cheerful AC/DC Multi-Tune Musical doorbells. Most of these
doorbells are built around customized microcontrollers from China, and usually run on
two penlight (1.5V AA type) cells. We can safely trigger these doorbells using the
existing AC 230V mains supply wiring of the doorbell switch.Did you know? With a
slight alteration, you can build your own security devices from these doorbells. For
example, recently I made-up a compact Shadow Sensor Alarm with the help of my
AC/DC Musical Doorbell for a school science fair project. One 5mm LDR is the one
and only additional component required for this simple yet wonderful task. Now I wish
to share the “hack” for the benefit of Electroschematics readers! Shadow sensor alarms
are usually used for protection against theft. A shadow alarm is a device that sounds an
alarm when a shadow falls on it. Our shadow sensor alarm unit is capable of sensing a
moving shadow in a restricted area, and can be easily installed on a wall, window or door
to protect our valuables from theft.
Note that constant lighting is required in the confined area to detect the moving shadow.
This shadow sensor alarm raises an alert in the form of a distinct musical tone (for a
finite duration) whenever a shadow is sensed by the photoresistor (LDR).It’s of no
concern about the microcontroller (melody generator chip) used inside the doorbell.
Just look into the inside electronics to find the AC trigger circuitry and take a note. If the
circuitry is similar/nearsimilar to he one shown here, you can hack your doorbell within
minutes. Otherwise, be prepared to do a serious homework before the actual “hacking”
process.This is the internal circuit diagram of the doorbell used by me. This unit is built
around a small microcontroller HL-06 (HLS5TA06), which is a low cost voice and
melody synthesizer with 4-bits CPU. Here, this 14-pin DIL microcontroller is
programmed as a 16-Tune English Melody Generator. A PNP transistor (BC557),
ofcourse with some supporting components, is connected in the trigger input circuit to
trigger the microcontroller HL-06.
INTRODUCTION
The RTS 993 is a CMOS LSI designed for use in
toys, doorbell, music boxed, melody clock /
timers and telephones. It is designed to play the
melody according to previously programmed
information and is capable of greeting songs with
piano effect . By pushing the sequence trigger
key, all songs can be sequenctially selected and
played with auto-stop function.
WORKING :-
Oscitlator Circuit :
The oscillator frequency is used as a time
base for which tone and tempo generators,
the accuracy of which aflects the quality of
the melody generator.
Tempo Generators :
There are 14 tempos available in this
embodiment 82,88,95,103,112,123,137,154,
176,205,246,308,410,and615 notes per min’s
Tone generator :
The Tone generator is a programmed divider.
The tone frequencies are created by
dividing the oscillator frequancies with M,
where M is an integer from 32 to 127 .There
are 27 tones selectable in this embodiment,
Including end code.
Rhythm Generator :
The rhythm generator is also a programmed
divider and is used to generate the beat for
each for each tone. In this embodiment, 15
beats are available as follows: ¼ , 1/2, ¾, 1,
5/4,3/2,7/4, 2,9/4, 5/2, 11/4, 3, 13/4,7/2,
and 15/4.
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ROM :
The mask ROM stores the tempo, tone and
rhytm Data. The ROM send sthese data to
respective generatores so as to control the
tempo of each song,the tone codes and the
rhythm codes.
RTS :
1. Home sweet home
2. Waltzing tell overture
3. William tell overture
4. Long long ago
5. America patrol
6. Amazing Grace
7. Battle ifymn of the Republic
8. Old folks at home
9. Toredors song
10. Oh, Susanna
11. Are you going run all night
12. Are you sleeping
13. O, sole Mio
14. Did you ever see a lassie
15. Oh ,my darling
16. I wish I was in Dixie
17. Santa lusia
18. Home on the range
19. America the Beautiful
20. The yellow roses of Taxes
21. Three blind mice
22. Love me thunder
23. Silver threads among the gold
24. My wild irish rose
25. she’ll be coming round the Mountain.