MULTI-SWITCH DOORBELL WITH INDICATORS

Here’s the circuit of a multi-switch input musical doorbell (shown in Fig.1). The circuit is built around the popular and less expensive quad D-latch CD4042B (IC1). When switch S6 is pushed to...

KNOCK ALARM

This circuit (Fig. 1), used in conjunction with a thin piezoelectric plate,senses the vibration generated on knocking a surface (such as a door or a table) to activate the alarm. It...

Night Lamps

Here are two night lamp circuits using LEDs. One could be used as a night-vision clock and the other as a TV lamp. Both the circuits are AC operated and consume...

Musical Water Shower

Won’t it be nice to have music playing in the background all the while when you take a shower? This simple circuit does the same. It plays different tunes repeatedly for...

TRAFFIC BATON

In small towns, there are no traffic lights and the police regulates the traffic with hand signals. Since their hand signals may not be visible at night, it is necessary to...

TRAFFIC CONTROLLER

This simple traffic controller can be used to teach children rudiments of traffic rules. The circuit (shown in Fig. 1) uses readily available components. It mainly comprises rectifier diodes (1N4001), a 5V...

Hot-Water-Ready Alarm

Electric kettles turn off automatically when water has boiled. What if the boiler beeps to alert you when your water has boiled? The tripping sound of the thermal switch may not...

Peak Hour Timer

Electrical appliances like refrigerators and air-conditioners consume heavy current if the line voltage drops during the peak hours between 6 pm and 9 pm. If there is no low-voltage cut-off in...

Touch Alarm

This is a new type of touch alarm that uses an RF oscillator at its input. One special feature of this touch alarm is that it can use a big-size touch...

Heat Control Unit

This circuit will turn the heater ‘on’ when the temperature of water falls below the lower limit set by you and turn it ‘off’ when the temperature increases above the higher...