LONG RANGE FM TRANSMITTER

Long range FM transmitterThe power output of most of these circuits are very low because no power amplifier stages were incorporated.The transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance...

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Light-sensitive Alarm

INTRODUCTION The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery running flat. Normal lighting can be used, but the circuit will work best if a beam of light is arranged to fall on the light-sensor. Breaking this beam will then cause the bleeper to...

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Tester

INTRODUCTIONthis is responsible for testing components as well as checking circuit board tracks, wires and connections for continuity (conduction). It tries to pass a small current through the item being tested and the LED will light brightly, dimly or not at all according to the resistance of the item: LED bright means the resistance is low, less than about 1k LED dim means the resistance is medium, a few k LED off means the resistance is high,...

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Simple Electronic Lock

INTRODUCTION There are six (or more) push switches. To 'unlock' you must press all the correct ones at the same time, but not press any of the cancel switches. Pressing just one cancel switch will prevent the circuit unlocking. When the circuit unlocks it actually just turns on an LED for about one second, but it is intended to be adapted to turn on a relay which could be used to switch on another circuit. Please Note:This circuit just turns on...

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Automatic Headlight Brightness Switch

INTRODuCTIONDriving the highway with your high-beam headlights can really increase your visibility, but can be a blinding hazard for other drivers. This simple circuit can be wired into your headlight switch to provide automatic switching between high and low beam headlights when there is oncoming traffic. It does this by sensing the lights of that traffic. In this way, you can drive safely with your high-beams on without blinding other drivers....

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LED Thermometer

INTRODUCTIONThis LED thermometer is designed for in home use, to read temperatures between about 60 and 78 degrees Fahrenheit. It is based around a precision temperature sensor IC, the LM34DZ. This sensor require no calibration and can measure temperatures of between -50F and +300F. While the circuit shown here does not use the full range of that sensor, it can be modified to do so by simply changing the voltage reference to U2 at the sacrifice of...

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Wireless Switch

Wireless SwitchNormally, home appliances are controlled by means of switches, sensors, etc. However, physical contact with switches may be dangerous if there is any shorting. The circuit described here requires no physical contact for operating the appliance. You just need to move your hand between the infrared LED (IR LED1) and the photo transistor (T1).WorkingThe infrared rays transmitted by IR LED1 is detected by the photo transistor to activate...

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Long Range IR Transimmiter

Long Range IR TransimmiterMost of the IR remotes work reliably within a range of 5 metres The circuit complexityincreases if you design the IR transmitter for reliable operation over a longer range, say, 10 metres. To double the range from 5 metres to 10 metres, you need to increase the transmitted power four times. Here is a simple circuit that will give you a pretty long range. It usesthree infrared transmitting LEDs (IR1 through IR3) in series...

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Automatic Emergency Light

AUTOMATIC LOW-POWER EMERGENCY LIGHTHere is a white-LED-based emergency lightAdvantages1. It is highly bright due to the use of white LED s.2. The light turns on automatically when mains supply fails, and turns off when mains power resumes.3. It has its own battery charger.When the battery is fully charged, charging stops automatically.The circuit comprises two sections charger power supply and LED driver.The charger power supply sectionIt is built...

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Drinking Water Alarm

Drinking Water AlarmThe many States supply water for limited duration in a day. Time of water supply is decided by the management and the public does not know the same. In such a situation, this water alarm circuit will save the people from long wait as it will inform them as soon as the water supply starts.ConstructionAt the heart of this circuit is a small water sensor. For fabricating this water sensor, you need two foils—an aluminium foil and...

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IR Bug

Infra Red BugThis circuit can be used to detect the presence of modulated infrared signals in its vicinity from any electronic source, for instance, an IR handheld remote controller. It can also be used for testing IR burglar alarm systems.WorkingBesides the power supply (one 9V PP3/6F22 compact batterypack), it consists of an infrared signal detector-cum-preamplifier followed by a melody generatorand a tiny audio amplifier. The amplified signal...

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IR REMOTE

REMOTE CONTROL FOR HOME APPLIANCESConnect this circuit to any of your home appliances (lamp,fan, radio, etc) to make the appliance turn on/off from a TV, VCD or DVD remote control. The circuit can be activated from up to 10 metres.WorkingThe 38kHz infrared (IR) rays generated by the remote control are received by IR receiver module TSOP1738 of the circuit. Pin 1 of TSOP1738 is connected to ground, pin 2 is connected to the power supply through resistor...

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Rheostat

In real this is how an rheostat like..A rheostat is an electrical component that has an adjustable resistanceIntroduction:It is a type of potentiometer that has two terminals instead of three. The two main types of rheostat are the rotary and slider. The symbol for a rheostat is a resistor symbol with an arrow diagonally across it. They are used in many different applications, from light dimmers to the motor controllers in large industrial machines.Rheostat...

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