Audible Continuity Tester
Here is a pretty simple, low-cost audible continuity tester that makes use of just one quad comparator IC LM339, some resistors and a piezobuzzer. The circuit including the comparator works off a single 9V battery.
Audible IR Proximity Detector
This circuit gives an audible indication when any object comes in front of the infrared reflecting sensor (containing IR LED and phototransistor). The sound generated by the sensor will be louder if the object close to the reflecting sensor is opaque.
White LED Based Emergency Lamp and Turning Indicator
White LEDs are replacing the conventional incandescent and fluorescent bulbs due to their high power efficiency and low operating voltage. These can be utilised...
IR Receiver Module Tester
Here is an IR receiver module tester for on-board testing of IR modules used for remote control of TV sets and VCD players. The...
IR Music Transmitter and Receiver
This IR music transmitter and receiver contains two circuits - one transmitter and one receiver. The transmitter transmits musical tones through an IR LED and the receiver receives those signals through a photo transistor.
Safety Guard: Time Delay Circuit
When voltages suddenly changes, the change is not smooth, it may go on fluctuating for a short while. This may not be a good...
House Security System
This is a circuit for a home security system that sets off an alarm when someone interrupts a laser beam that continuously falls on LDR of the circuit. A combination of 6 plain mirrors is used to direct the laser beam around the house to form a net.
Shock Warning Circuit
Electrical leakage can cause lethal shocks. But such an unfortunate situation can be avoided with this shock warning system. It uses minimal number of...
DC Changeover System with Battery Protection unit
Emergency lights commonly available in the market come with battery over-charging protection but no discharging protection. Here is a DC changeover system that protects...
Numeric Display Digital Dice
This is a circuit for a digital dice with numeric display that generates random numbers from 1 to 6 and displays them on a 7-segment LCD. The circuit can be modified to increase the range from 1 to 9.
