OBJECTIVE
Here is a simple and very easy to build alarm siren producing gadget capable of producing five different types of siren tones. The gadget is built around a single IC 556 which is nothing but a dual IC timer 555.That is, it has two independent 555s within the same package. The type of siren can be selected from an appropriate combination of switches to be closed given in the accompanying table. The gadget could also be constructed using two 555s in place of one 556.
CIRCUIT DESCRIPTION
For a clear understanding of this circuit functioning, it is very important to identify those pins in IC556 that represent two independent 555’s. IC555 has eight terminals namely the COMMON (Pin-1), TRIGGER (Pin-2), OUTPUT (Pin-3), RESET (Pin-4), CONTROL (Pin-5), THRESHOLD read more
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OBJECTIVE
Wide fluctuations in the AC mains voltage is a very common problem in India. You should not be surprised if some one tells you that the voltage fluctuation could be as much as from 150 volts to 290 volts. Although, majority of our electrical and electronic appliances and gadgets have some kind of voltage stabilization internals built-in, yet more than 90 percent of the faults in these gadgets occur due to these power fluctuations. This simple test gadget can give you real time monitoring of the AC mains voltage in the form of glowing LEDS. It can give you the visible indication of AC mains voltage over a range of 170 volts to 280 volts in steps of 10 volts.
There are 12 LEDS numbered from LED-! to LED-12. For input AC mains voltage of less than 170 volts, all LEDs remain read more
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Objective
The objective here is to construct an emergency fluorescent light circuit that requires neither a choke nor a starter unlike conventional mains operable fluorescent light. Such emergency lighting units having different lighting power
capabilities are available in abundance in the market. The circuit given here is simple and highly| efficient. It operates from a 6V rechargeable battery (Lead-Acid type). The battery is trickle charged when the mains is present. The battery with a capacity of 6Ah (this is the battery used in this project) is capable of providing uninterrupted lighting for four hours in the absence of mains. The switch over is fully automatic i.e. When the mains goes OFF, the battery comes into the lighting circuit automatically and there is no requirement of read more
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Objective
It is an ideal project for those who want to build something that not only teaches them something but also gives them lot of fun. As the title suggests, this gadget can be used to measure quantitatively the reaction time of an individual. The reaction time can be measured in two different settings: In the first setting, the reactiontime can be measured upto a maximum of 99ms with a resolution of 1ms. In the second setting, the reaction time can be measured upto a maximum of 990ms with a resolution of toms. You can try this gadget with your friends and relatives and find out how quickly they react to a given situation.You can, try this with yourself too at different times and when you are In different states of mind and see the difference yourself.
Circuit description
The read more
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