Digital & Analog Based Mini electronics Projects Page_10
91. Spy Ear:
What binoculars do to improve your vision, this
personal sound enhancer circuit does for listening. This lightweight gadget
produces an adjustable gain on sounds picked up from the built-in
high-sensitivity condenser microphone. So you can hear what you
have been
missing. With a 6V (4×1.5V) battery, it produces good results.
92. Stress Meter:
This stress monitor lets you assess
your emotional pain. If the stress is very high, it gives
visual
indication through a light-emitting diode (LED) display along with a warning
beep. The gadget is small enough to be worn around the wrist. The gadget is
based on the principle that the resistance of the skin varies in accordance
with your emotional states. If the stress level is high the skin offers less
resistance, and if the body is relaxed the skin resistance is high. The low
resistance of the skin during high stress is due to an increase in the blood
supply to the skin. This increases the permeability of the skin and hence the
conductivity for electric current.
93. Telephone Ring Tone Generator:
Here is a simple telephone ring tone generator
circuit designed using only a few components. It produces simulated telephone
ring tone and needs only DC voltage (4.5V DC to 12V DC). One may use this
circuit in ordinary intercom or phone-type intercom. The sound is quite loud
when this circuit is operated on +12V DC power supply. However, the volume of
ring sound is adjustable.
94. Three-Phase Appliance Protector:
Many of our costly appliances require
three-phase AC supply for operation. Failure
of any of the
phases makes the appliance prone to erratic functioning and may even lead to
failure. Hence it is of paramount importance to monitor the availability of the
three-phase supply and switch off the appliance in the event of failure of one
or two phases. The power to the appliance should resume with the availability
of all phases of the supply with certain time delay in order to avoid surges
and momentary fluctuations.
95. Touch Switch:
This simple circuit produces a warning beep
when somebody crosses a protected area in your home or office. The switch,
hidden below the floor mat, triggers the alarm when the person walks over it.
96. Traffic Controller:
This simple traffic controller can be used to
teach children rudiments of traffic rules The circuit use readily available
components. It mainl comprises rectifier diodes (1N4001), a 5V regulator 7805,
two timers IC 555, two relays (5V, single-changeover), three 15W, 230V bulbs
and some discrete components.
97. Transistorized Code Lock With Torch:
This electronic lock for domestic use opens
only when you connect the right combination of five switches. There are twelve switches
in total. If you connect a wrong combination, the lock remains closed. At
night, flip switch S3 to ‘on’ position in order to enable the torch. In the
daytime, flip it back to ‘off’ position.
98. Under Over Voltage Protector:
Manual stabilizers are still popular because of
their simple construction, low cost, and high reliability due to the absence of
any relays while covering a wide range of mains AC
voltages compared
to that handled by automatic voltage stabilizers. These are used mostly in
homes and in business centers for loads such as lighting, TV, and fridge, and
in certain areas where the mains AC voltage fluctuates between very low (during
peak hours) and abnormally high (during non-peak hours).
99. Variable Power Supply Using A
Fixed-Voltage Regulator Ic:
A voltage regulator (also called a ‘regulator’)
with only three terminals appears to be a
simple device,
but it is in fact a very complex integrated circuit. It converts a varying
input voltage into a constant ‘regulated’ output voltage. Voltage regulators
are available in a variety of outputs like 5V, 6V, 9V, 12V and 15V.
100.
Versatile
Power Supply:
Using this circuit, you can
obtain the following voltages (approx.) at a current limited to one ampere:
3.3V, 5V, 6V, 9V, 12V and 15V.
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