This intelligent electronic lock circuit is built using transistors
only. To open this electronic lock, one has to press tactile switches S1
through S4 sequentially. For deception you may annotate these switches
with different numbers on the control panel/keypad. For example, if you
want to use ten switches on the keypad marked ‘0’ through ‘9’, use any
four arbitrary numbers out of these for switches S1 through S4, and the
remaining six numbers...
"Develop Your Creations"
get a lot of electronic circuits
"Develop Your Creations"
get a lot of electronic circuits
"Develop Your Creations"
get a lot of electronic circuits
Luxurious Toilet Bathroom Facility
9:50 AM
Electronic Circuits
Aged persons in the house and guests often fumble while searching for
the toilet and bathroom switches at night. Also, very few of us take
care to switch off the lights of toilets/bathrooms after using them. The
circuit given here helps to overcome both the problems. The figure
shows two symmetrical circuits (one each for toilet and bathroom)
sharing common power supply and a melody generator-cum-audio warning
unit. The reed switches S1 and...
Automatic Heat Detector
9:48 AM
Electronic Circuits
This circuit uses a complementary pair comprising npn metallic
transistor T1 (BC109) and pnp germanium transistor T2 (AC188) to detect
heat (due to outbreak of fire, etc) in the vicinity and energise a
siren. The collector of transistor T1 is connected to the base of
transistor T2, while the collector of transistor T2 is connected to
relay RL1. The second part of the circuit comprises popular IC UM3561 (a
siren and machine-gun sound generator...
Musical Touch Bell
9:44 AM
Electronic Circuits
Here is a musical call bell that can be operated by just bridging the
gap between the touchplates with one’s fingertips. Thus there is no need
for a mechanical ‘on’/‘off’ switch because the touch-plates act as a
switch. Other features include low cost and low power consumption. The
bell can work on 1.5V or 3V, using one or two pencil cells, and can be
used in homes and offices. Two transistors are used for sensing the
finger touch and switching...
High Power Bicycle Horn
9:43 AM
Electronic Circuits
An interesting circuit of a bicycle horn based on a popular, low cost
telecom ringer chip is described here. This circuit can be powered using
the bicycle dynamo supply and does not require batteries, which need to
be replaced frequently. The section comprising diodes (D1 and D2) and
capacitors (C1 and C2) forms a half-wave voltage-doubler circuit. The
output of the voltage doubler is fed to capacitor C3 via resistor R1.
The maximum DC supply...
Overheat Detector Alarm/Switch
9:42 AM
Electronic Circuits
At the heart of this circuit is a precision integrated temperature
sensor type LM35 (IC1), which provides an accurately linear and directly
proportional output in mV, over the zero to +155 degrees C temperature
range. The LM35 develops an output voltage of 10 mV/K change in measured
temperature. Designed to draw a minimal current of its own, the LM35
has very low self heating in still air. Here the output of the LM35 is
applied to the non-inverting...
Test Beeper For Your Stereo
9:41 AM
Electronic Circuits
The test beeper generates a sinusoidal signal with a frequency of 1,000
Hz, a common test frequency for audio amplifiers. It consists of a
classical Wien-Bridge oscillator (also known as a Wien-Robinson
oscillator). The network that determines the frequency consists here of a
series connection of a resistor and capacitor (R1/C1) and a parallel
connection (R2/C2), where the values of the resistors and capacitors are
equal to each other. This...