July 18, 2009

SOLAR BUG

Solar Bug
This is a fun circuit, hide this solar-powered circuit suitably and see the reaction of your friends to the chirpy sound produced by it every few minutes. In all probability, it will coax them to find out where the sound is coming from. The circuit runs off a miniature solar power panel, which can be taken out from an old calculator such as Citizen CT-500. A panel giving 1.5V to 2.5V is required. Note that the circuit can work properly from a panel as small as 3 cm(square).

Working
If a digital voltmeter is connected across capacitor C2, a slow build-up of voltage can be observed when the panel is exposed to light. Transistors T1 and T2 form a relaxation oscillator.When C1 charges to 0.6V, transistor T1 conducts and the charge built up in C2 is discharged through the
piezobuzzer to produce a short beep. While testing the circuit, the value of resistor R1 can be reduced to, say, 1 kilo-ohm. Use a good-quality buzzer to ensure that the sound produced is
loud enough.

Circuit Diagram


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July 17, 2009

EPE December 2008

EPE December 2008


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EPE November 2008

EPE November 2008


Size : 13.9 MB





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EPE October 2008

EPE October 2008


Size : 13.3 MB





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EPE September 2008

EPE September 2008


Size : 14.4 MB





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FORMULAE

July 16, 2009

Laser Activated Switch

Laser Activated Switch

This circuit is built around a 555 timer using very few components. Since the circuit is very simple, even a novice can easily build it and use it as a controlling device. A laser pointer, now easily available in the market, can be used to operate this device. This circuit has been tested in operational conditions from a distance of 500 metres and was found to work satisfactorily, though it can be controlled from still longer distances. Aiming the laser beam exactly on to the LDR is a practical problem. The circuit is very useful in switching on/off a fan at night without getting off the bed. It can also be used for controlling a variety of other devices like radio or music system. The limitation is that the circuit is operational only in dark or dull-lit environments. By focusing the laser beam on LDR1 the connected gadget can be activated through the relay, whereas by focusing laser beam on LDR2 we can switch off the gadget. The timer is configured to operate in bistable mode. The laser pointers are available for less than Rs 30 in the market. The cost of the actual circuit is less than Rs 25.

Circuit Diagram


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July 15, 2009

EPE August 2008

EPE August 2008



Size : 15.8 MB





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EPE July 2008

EPE July 2008



Size : 10.7 MB





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EPE June 2008

EPE June 2008



Size : 11.6 MB





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EPE May 2008

EPE May 2008



Size : 13.6 MB





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EPE April 2008

EPE April 2008





Size : 10.5 MB

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EPE March 2008

EPE March 2008



Size : 11.2 MB




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EPE February 2008

EPE February 2008



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EPE January 2008

EPE January 2008


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July 13, 2009

Mobile Cellphone Charger

MOBILE CELLPHONE CHARGER

Charging of the cellphone battery is a big problem while travelling as power supply source is not generally accessible. If you keep your cellphone switched on continuously, its battery will go flat within five to six hours, making the cellphone useless. A fully charged battery becomes necessary especially when your distance from the nearest relay station increases. Here’s a simple charger that replenishes the cellphone battery within two to three hours. Basically, the charger is a current-limited voltage source. Generally, cellphone battery packs require 3.6-6V DC and 180-200mA current for charging. These usually contain three NiCd cells, each having 1.2V rating. Current of 100mA is sufficient for charging the cellphone battery at a slow rate. A 12V battery containing eight pen gives sufficient current (1.8A) to charge the battery connected
across the output terminals. The circuit also monitors the voltage level of the battery. It automatically cuts off the charging process when its output terminal voltage increases above the
predetermined voltage level.

Working
Timer IC NE555 is used to charge and monitor the voltage level in the battery. Control voltage pin 5 of IC1 is provided with a reference voltage of 5.6V by zener
diode ZD1. Threshold pin 6 is supplied with a voltage set by VR1 and trigger pin 2 is supplied with a voltage set by VR2. When the discharged cellphone battery is connected to the circuit, the voltage given to trigger pin 2 of IC1 is below 1/3Vcc and hence the flip-flop in the IC is switched on to take output pin 3 high. When the battery is fully charged, the output terminal voltage
increases the voltage at pin 2 of IC1 above the trigger point threshold. This switches off
the flip-flop and the output goes low to terminate the charging process. Threshold pin 6 of IC1 is referenced at 2/3Vcc set by VR1. Transistor T1 is used to enhance the charging current. Value of R3 is critical in providing the required current for charging. With the given value of 39-ohm the charging current is around 180 mA. The circuit can be constructed on a small general-purpose PCB. For calibration of cut-off voltage level, use a variable DC power source. Connect the output terminals of the circuit to the variable power supply set at 7V. Adjust VR1 in the middle
position and slowly adjust VR2 until LED1 goes off, indicating low output. LED1 should turn on when the voltage of the variable power supply reduces below 5V. Enclose the circuit in a small plastic case and use suitable connector for connecting to the cellphone battery.

Circuit Diagram


NOTE : Click the image for better Quality

Secret Bell

Secret Bell
Many people move through the corridors and steps in multi storied buildings. As most of them are strangers for the inhabitants of the flats, it becomes necessary to verify the identity of the visitor before opening the door as he can be a burglar. This circuit helps you identify the members of your family. It is basically a switch less musical bell that activates with a single puff of breath. The condenser mic fitted inside the existing door-bell switch box will trigger the bell on detecting air-pressure changes following the breath. As only the members of your family know the secret of the bell and hence puff out before the hole for the switch box, the door can
be opened without fear.

Working
The front end of the circuit is a condenser mic amplifier with fixed sensitivity. Transistor T1 amplifies the signal received from the condenser mic through capacitor C1. When transistor T1 conducts, a short negative pulse triggers the monostable wired around IC1. The monostable time is decided by resistor R7 and capacitor C5. Reset pin 4 of IC1 is made stable by R6 and C3. Resistor R5 acts as a pull-up resistor for trigger pin 2 of IC1 to keep the trigger pin high in the standby mode. The high output from IC1 is used to power IC UM66 (IC2). IC2 generates a soft melody on receiving 3 volts at pin 2. Transistor T2 amplifies the music
notes. A zener diode maintains the power for IC2 at a safer level of 3 volts. The condenser mic
should be connected to the circuit using a single-core shielded wire to reduce noise interference

Circuit Diagram


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July 12, 2009

Abbreviations from N-Zt

Abbreviations used in Electronics

N to TWT


N
Number of turns in an inductor

N
Revolutions per minute

n
Nano (10-9)

N
Negative

nA
Nanoampere

NC
Normally closed

NC
No connection

NEG, neg
Negative

nF
Nanofarad

nH
Nanohenry

nm
Nanometer

NO
Normally open

NPN
Negative-positive-negative

ns
Nanosecond

nW
Nanowatt

OP AMP
Operational amplifier

P
Pico (10-12)

P
Power

p
Instantaneous power

P
Positive, also peak

PA
Public address or power amplifier

pA
Picoampere

PAL
Programmable Array Logic

PAM, pam
Pulse amplitude modulation

Pap

Apparent power

Pav

Average power

PCB
Printed circuit board

PCM, pcm
Pulse-code modulation

PDM
Pulse-duration modulation

pF
Picofarad

PLD
Programmable Logic Device

PLL
Phase locked loop

PM
Phase modulation, also Permanent magnet

PNP
Positive-negative-positive

POT, pot
Potentiometer

P-P
Peak to peak

PPM
Pulse-position modulation

PRF
Pulse repetition frequency

PRT
Pulse repetition time

pw
Pulse width

PWM, pwm
Pulse width modulation

Q
Charge, also quality

q
Instantaneous charge

R
Potentiometer

R
Resistance

RAM
Random access memory

RC
Resistance-capacitance, also Radio controlled

rcvr
Receiver

rect
Rectifier

ref
Reference

rf
Radio frequencies

RF
Radio frequencies

RFI
Radio frequency interference

RL

Load resistor

RLC
Resistance-capacitance-inductance

RMS, rms
Root mean square

ROM
Read only memory

rpm
Revolutions per minute

SCR
Silicon controlled rectifier

SHF
Super high frequency

SIP
Single in-line package

SNR
Signal-to-noise ratio

SPDT
Single pole double throw

sq cm
Square centimeter

SSB
Single sideband

SW
Short wave

SWR
Standing-wave ratio

SYNC, sync
Synchronous

T
Tera (1012)

T
Torque

T
Transformer

t
Time in seconds

TC
Time constant, also temperature coefficient

TE
Transverse electric

temp
Temperature

THz
Terahertz

TM
Transverse magnetic

TR
Transmit-receive

TTL
Transistor-transistor logic

TV
Television

TWT
Travelling wave tube
UHF
Ultra high frequency

UHV
Ultra high voltage

UJT
Unijunction transistor

UV
Ultraviolet

V
Vacuum tube

V, v
Volt

v
Instantaneous voltage

VA
Volt ampere

Vav

Voltage (average value)

VBE

DC voltage base to emitter

Vc

Capacitive voltage

VCE

DC voltage collector to emitter

VCO
Voltage controlled oscillator

VHF
Very high frequency

Vin

Input voltage

VL

Inductive voltage

VLF
Very low frequency

Vm, Vmax
Maximum voltage

VOM
Volt ohm milliameter

Vout

Output voltage

Vp

Primary voltage

VS

Source voltage

VSWR
Voltage standing wave ratio

VT

Total voltage

W
Watt

XC
Capacitive reactance

XL
Inductive reactance

Y
Admittance

Z
Impedance

Zin
Input impedance

Zo
Output impedance

Zp
Primary impedance

Zs
Secondary impedance

ZT
Total impedance


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Electronics is the study and use of electrical that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves. and semiconductors. The pure study of such devices is considered as a branch of physics, while the design and construction electronic circuits to solve practical problems is called electronic engineering.

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