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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 rating of 3.6V, 650 mAh. For increasing the...
The range of this FM transmitter is around 100 metres at 9V DC supply. The circuit comprises three stages. The first stage is a microphone preamplifier built around BC548 transistor. The next stage is a VHF oscillator wired around another...
With this micro-power flasher you can baffle the intruders trying to break into your home. The unit continuously emits flashing light both during day and night giving the impression that the occupants of the house are present inside. The...
Human speech generally occupies an audio spectrum of 300 to 3400 Hz. There is a requirement, especially in telephone circuits, to limit the frequency response to this range. The ‘Digital Speech Security System’ published in EFY Electronics Projects Vol....
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 the condenser microphone and converted into corresponding electrical...
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 circuit is powered by regulated 9V. The AC...
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 a corner inside the briefcase. The circuit uses...
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 IC. It is used in telephones and a...
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 of operation: flasher mode and dimmer mode. The...
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 is connected to the first inverter (N1) through...