By aRie eMDee
This equaliser uses low-cost op-amps. Good-quality opamps powered by a single voltage supply are readily available in the market. The op-amp should have a noise density of less than 24nV/√Hz, slew rate of more than 5V/µs and gainbandwidth product greater than 3MHz. The NE5532 or LM833 used in this circuit meets these requirements. Equaliser circuits typically divide the audio spectrum into separate frequency bands and have independent gain control for each band.
A Cmos 4060 Burglar Alarm
Circuit: Aryanto
Description:
This is a single zone alarm - with automatic exit, entry and siren cut-off timers. It will accommodate all the usual types of normally-closed input devices - such as magnetic-reed contacts - foil tape - PIRs etc.
Description:
This is a single zone alarm - with automatic exit, entry and siren cut-off timers. It will accommodate all the usual types of normally-closed input devices - such as magnetic-reed contacts - foil tape - PIRs etc.
Direct-to-Home TV: All channels without a cable
DTH services will bring an era of competition for cable TV operators and force them to improve quality. Users will have access to high quality programming on pay channels while persons in far-flung areas where cable operators are yet to reach will be able to use the dish antennas for receiving channels.
Direct to home tv Enjoy more channels with better quality!
The recently approved direct-to-home (DTH) TV obviates the requirement of cable-wallahs and enables viewers to access error-free programmes with better picture- and audio-quality
Security Monitor
Circuit : Aryanto
Email : arie.emdee@yahoo.com
Description:
A remote listening circuit. The area to be monitored is connected via a cable and allows remote audio listening.
Email : arie.emdee@yahoo.com
Description:
A remote listening circuit. The area to be monitored is connected via a cable and allows remote audio listening.
AUTOMATIC SCHOOL BELL
Consider that a school has a total of eight periods with a lunch break after the fourth period. Each period is 45 minutes long, while the duration of the lunch break is 30 minutes. To ring this automatic school bell to start the first period, the peon needs to momentarily press switch S1. Thereafter, the bell sounds every 45 minutes to indicate the end of consecutive periods, except
immediately after the fourth period,when it sounds after 30 minutes to indicate that the lunch break is over.
immediately after the fourth period,when it sounds after 30 minutes to indicate that the lunch break is over.
QUALITY FM TRANSMITTER
This FM transmitter for your stereo or any other amplifier provides a good signal strength up to a distance of 500 metres with a power output of about 200 mW. It works off a 9V battery. The audio-frequency modulation stage is built around transistor BF494 (T1), which is wired as a VHF oscillator and modulates the audio signal present at the base. Using preset VR1, you can adjust the audio signal level.The VHF frequency is decided by
Mobil Cell Phone Charger
Charging of the cellphone battery is a big problem while travelling as power supply source is not generally accessible. If you keep your cellphone switched on continuously, its battery will go flat within five to six hours, making the cellphone useless. A fully charged battery becomes necessary especially when your distance from the nearest relay station increases. Here’s a simple charger that replenishes the cellphone battery within two to three hours.
Long Range IR Transmitter
Most of the IR remotes work reliably within a range of 5 metres. The circuit complexity increases if you design the IR transmitter
Medium Power FM Transmitter
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 BC548. (BC series transistors are generally used in low-frequency stages. But these also work fine
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 BC548. (BC series transistors are generally used in low-frequency stages. But these also work fine
Laptop Protector
Protect your valuable laptop against theft using this miniature alarm generator. Fixed inside the laptop case, it will sound a loud alarm when someone tries to take the laptop. This highly sensitive circuit uses a homemade tilt switch to activate the alarm through tilting of the laptop case. The circuit uses readily available components and can be assembled on a small piece of Vero board or a general purpose PCB. It is powered by a 12V miniature battery used in remote
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