Hearing Aid

This low-cost, general-purpose electronic hearing aid works off 3V DC (2x1.5V battery). In this circuit, transistor T1 and associated components form the audio signal preamplifier for the acoustic signals picked up by...

Remote-Controlled Fan Regulator

Using this circuit, you can change the speed of the fan from your couch or bed. Infrared receiver module TSOP1738 is used to receive the infrared signal transmitted by remote control. The...

Briefcase Alarm

This miniature alarm unit protects your valuables from theft by sounding an alarm when somebody attempts to pick up your briefcase. It is a battery-operated gadget that can be hidden in...

DTMF Receiver IC MT8870 Tester

Today, most telephone equipment use a DTMF receiver IC. One common DTMF receiver IC is the Motorola MT8870 that is widely used in electronic communications circuits. The MT8870 is an 18-pin...

Farmhouse Lantern-Cum-Flasher

This circuit uses a dual op-amp IC LM358 and two transistors. It can be powered by a 6V maintenance-free rechargeable battery or a lead-acid accumulator type battery. It has two modes...

Logic ‘high’/’low’ Indicator

This logic 'high'/'low' indicator circuit comprises two ICs. One is hex inverter IC 7404 (IC1) and the other is a bistable multivibrator built around timer IC 555 (IC2). A logic probe...

Simple Short-Wave Transmitter

This low-cost short-wave transmitter is tunable from 10 to 15 MHz with the help of ½ Jgang condenser VC1, which determines the carrier frequency of the transmitter in conjunction with inductor...

Simple Transistor Type and Lead Identifier

A bipolar junction transistor (BJT) has three regions, of which the emitter and the collector are made of the same type of semiconductor (‘n’ for npn and ‘p’ for pnp) but...

Twinkle Twinkle X’mas Star

Christmas just would not be Christmas if you do not put a flashing star on your Christmas tree. Here is the circuit of such a flashing star. Fig. 1 shows the circuit...

Picnic Lamp

You can take this white LED based night lamp on your picnic outings. The lamp has sound trigger and push-to-on facilities and gives ample light during a walk at night. It...