Simple Solar Power System. Design Note 18

Solar based power system is now becoming popular to save energy and money. It is easy to install a simple 100 Watts Solar lighting system for outdoor lighting. No need for constructing the circuits and all necessary units are readily available and anybody can install this. It runs on a 12 volt Car battery and no switching is needed. It turns on the outdoor lamps around 6 p.m and turns off at 6.a.m. The car battery can power the system for minimum 3 years so it is very cost effective. Another advantage is that, the outdoor lights will automatically turns on / off even if the inmates are not in home giving some security. Cost of the system is around Rs.5000 including battery.
The system requires the following:

Continue reading “Simple Solar Power System. Design Note 18”


Earth Fault Indicator. Design Note 17


This is my circuit published in Electronics For You Magazine. I have designed this circuit for checking the Earth connection in the power sockets ,whether it is intact or not. Earth connection is a must in power sockets especially if the gadget connecting has a metal body. If there is any leakage from live wire, the earth connection will bleed the current to earth and protect us from shock. So this circuit can be used to check the power sockets before using gadgets like Heater, Electric Iron etc. It also indicates whether there is power in the socket and the polarity of Phase and Neutral is correct.
Continue reading “Earth Fault Indicator. Design Note 17”

LM 317 Voltage Regulator. Design Note 16

LM 317 is the popular adjustable voltage regulator IC commonly used to make variable power supply. It is a three terminal device with Input, Output and Adjustment pins. Actually, LM317 is an Op Amp with relatively high output current capacity. The Inverting input of the Om Amp is Adjustment pin, while the Non-inverting input is set by an internal band gap voltage reference which produces a stable reference voltage of 1.25 volts.
Continue reading “LM 317 Voltage Regulator. Design Note 16”

Solar Power Supply. Design Note 15

IMAGEYou can make this Solar Power supply as your work bench power supply for testing prototypes. It delivers variable voltage from 1.5 volt to 12 volts with a current up to 300 milli amperes. It can also be used to charge batteries during day time. By using the Pot, it is easy to set the output volt from 1.5 to 12 Volts.
Continue reading “Solar Power Supply. Design Note 15”

TDA 1554 Amplifier. Design Note 14


IC TDA 1554 Q is a class B output amplifier IC in a 17 lead single in line package. The IC contains 4 x 11 Watts single ended or 2 x 22 Watts Bridge amplifiers. IC TDA 1554Q is mainly used in Car Stereo Amplifiers and requires only a few components to make a good quality Stereo amplifier. It works off 12 to 18 volts DC which can be derived from a 12 volt 2 Amps power supply.
Continue reading “TDA 1554 Amplifier. Design Note 14”

How to remove noise from 433 MHz receiver. Design Note 13


The handy low cost 433 MHz Transmitter and Receiver pair is now widely used in Arduino based circuits. But one of the serious problems with the Receiver is its inherent property of accepting lot of noise from the background. This gives erratic output data which causes error reading. If the output is connected to an audio amplifier, hissing sound appears in the speaker when the receiver is in standby without receiving the signals from the transmitter. So careful designing of the power supply and a Glitch removing circuit will considerably reduce the noise from the data out of Receiver (Rx).

Continue reading “How to remove noise from 433 MHz receiver. Design Note 13”

Reducing Hiss in LM 386 Amplifier. Design Note 12


LM 386 is a popular 8 pin IC used as Audio Amplifier in hobby circuits. It is very handy and requires only a few components to make it as an Amplifier. Its output gives sufficient sound through an 8 Ohm speaker. But one problem during its working is unnecessary hissing sound through the speaker. This hissing sound becomes a nuisance in the standby state if the amplifier is gainy and the signal level is low. But we can eliminate this hissing noise by slightly modifying the circuit design.
Continue reading “Reducing Hiss in LM 386 Amplifier. Design Note 12”