16 TUNE MUSICAL DOOR-BELL
This simple circuit finds application as a doorbell as well as telephone intruder music player, toy or attention call bell.
The heart of the circuit is an APM993D named as IC1. IC APM993D is a programmed 1024 note ROM memory, which generates 16 musical tunes when it gets triggered. The main feature of this IC is that it has inbuilt tone generator, rhythm generator, modulator, oscillator, frequency divider and preamplifier. So a very few number of components have to be connected externally to set up timing and to build an external AF amplifier/driver circuit.
AUTO ON/OFF TIMER
Widely used to switch ON/OFF devices with settable timing from 3 to 30min
This is a simple and inexpensive timer, widely used to switch on/off devices. It has a settable timing between 3min to 30min. The circuit is build around counter IC4060 (IC1) and inverter IC4049 (IC2).
The circuit switches on autometically when power is on, and it switches off when the settable time is over.
COOLER TIMER
Timer with ON time and OFF time setting for cooler/pump.
During summer seasons, we all us knows the need of coolers. If cooler is on for long time, then the requirement of water is also very large. To minimize this problem to a large extent cooler timer is designed. This circuit control the on and off time of cooler water pump according to the user requirement. The minimum and maximum time setting are fraction of second and one-and-a-half minute respectively.
ELECTRONIC HARMONIUM
The modern electronics presents this Electronic Harmonium as a hobby kit or people who are interested to have hands on experience in this field.
This harmonium can generate 15 different notes of music (one at a time). It has a PCB with 15 parallel copper strips. Each strip corresponds to one note. So as you put the probe on a strip, the instrument plays a corresponding note.
The circuit is build around IC1, which is used as a astable multivibrator. The frequency produced depend on the note selected by the probe. When we put the probe on different strips, we are effectively changing the frequency by changing the resistance between pin7 and pin2 of IC1.
