APPLIANCE TIMER-CUM-CLAP SWITCH

When planning for a week-end outing to return late in the evening, we are often in an ambivalence whether to leave the staircase/outside light ‘on’ or ‘off.’ We sometimes miss our...

Optical Smoke Detector

This optical smoke detector uses a low-cost, readily-available, slotted, through-scan, infrared photo-switch. When smoke is detected, the relay energises to activate the audio/visual warning alarm. Fig. 1 shows the circuit of the...

INFRARED ELECTRONIC SHOOTING GAME

Just trigger an infrared electronic gun and there goes one invisible bullet hitting the bull’s eye, if timed properly. The circuit is very simple, inexpensive and easy to construct. The game...

Optical Remote on/off Switch

First published on: 1-10-2006 Using this optical remote control, you can switch on/off any electrical or electronic load. Like any remote control system, it has a mini transmitter unit (Fig. 1) and...

Smart Battery Protector Using a Shunt Regulator

The life expectancy of a battery dramatically reduces when it is discharged below the minimum recommended battery voltage. You must disconnect the load before discharging is complete. Otherwise, it can damage...

Telephone Operated Calling System

Dual-tone multiple-frequency (DTMF) receiver IC is commonly used in telephone equipment. One common DTMF receiver is Holtek HT9170 used in electronic communication circuits. The Holtek HT9170 series comprises DTMF receivers integrated...

Bodmas Rule

The term ‘BODMAS’ is an acronym for ‘bracket,’ ‘of’, ‘division,’ ‘multiplication,’ ‘addition’ and ‘subtraction’ and the ‘BODMAS rule’ is a mnemonic for the hierarchy of various arithmetical operators. A mathematical expression...

Infrared Toggle Switch

This infrared toggle switch can be controlled by any TV/VCR remote operating at 38kHz frequency. The circuit uses readily available, low-cost components and can be assembled on a small veroboard.Fig. 1...

WASHING MACHINE MOTOR CONTROLLER

Washing machines usually employ a single-phase motor. In semi-automatic washing machines, a purely mechanical switch controls the timing and direction of the motor. These switches are costly and wear out easily. Here’s...

FRIENDLY CHARGER FOR MOBILE PHONES

Most mobile chargers do not have current/voltage regulation or short-circuit protection. These chargers provide raw 6-12V DC for charging the battery pack. Most of the mobile phone battery packs have a...