Four Station Quiz
Here we have another Quiz circuit using a number of CMOS ICs. Now the number of contestants can be easily increased even though the present circuit shows only four. It uses a two input Quad AND gate (74HCT08), a four input Dual AND gate (74HCT21), a dual D flip flop (CD4013), and a 555. Truth [...]
Light Alarm (Sun Up Alarm)
This circuit designed to sound a loud alarm at the break of the dawn especially for those wh cannot wake up even with an alarm clock. Circuit can be modified as an intruder alarm or as a security alarm. Needless to say that 1.8 KHz astable multivibrator with 555 is used here again with a [...]
Basic Oscillator (Tone Generator) At 1.8 KHz -alarm circuits
Here we have an astable oscillator built around 555, which gives an alarm tone of 1.8 KHz directly driving a speaker. This is basic alarm circuit, which is later used in many other projects in the book. While the circuit shows only 1.8 KHz operation, it can be adapted to different applications by changing frequency [...]
IC555 Interal diagram and description
IC 555 has been one of the most popular ICs since Signetics introduced it in the early 70s. 555 is also called as a TIMER IC. This 8-pin chip is a versatile device suitable for astable, mono-stable and bi-stable operations. It is such a multipurpose device that hobbyists find clever uses of it everyday. It [...]
Water Low Level Alarm
Same buzzer, the same power supply but with a little ingenuity this gives an alarm when the water falls below a certain level.This circuit as shown in Schematic 7, which can be used to indicate when the level falls low in overhead tank, a sump or even in a bore well.Now you will find a [...]
Three Terminal Adjustable Regulator
Three terminal regulators are just right when we need a single fixed voltage. But they will be cumbersome as a hobbyist works with different voltages at different times and it becomes unwieldy to keep power supplies with a number of three terminal regulators. Wouldn’t it be better if we have an adjustable but regulated power [...]
Three Terminal Regulators- Unadjustable
These are simple, effective and interesting integrated circuits. They are short circuit protected, can stand up to 32V, have thermal protection and they can easily deliver regulated voltage with 1 amp of current. In these ICs, the last two digits give you the regulated voltage they deliver, 7806 gives you 6 volts and 7812 gives [...]
Resistors
Resistors are measured in ohms, and have a wattage rating. Resistance value is marked on the resistor in an internationally accepted color code. Normally quarter-watt resistors are used in the following circuits unless otherwise specified. Carbon film and metal film resistors are generally used. Wire wound resistors are used for higher wattage resistors.
Half Wave Power Supply
Half wave rectification is simplest, as it requires only one transformer, one diode and one capacitor, but we have added a LED to give power supply indication. A simple half wave rectifier for 12V is shown below 500mA transformers are generally used for these circuits. Connect the primary wires to the mains chord after carefully [...]
