Transistor Led Flasher

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This circuit has only two transistors, two capacitors and four resistors. That also means it consumes very little power

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You can control the flash rate by changing the size of the 47k resistors. You can also control the duty cycle by using resistors of different values on the two sides. The 330 ohm resistors control the current through the LEDs. Normally you want to limit this to 20mA, but to conserve battery power, you may need to limit it even further. You can also connect several LEDs in series, instead of using only one for each side. With red LEDs (1 per side) and the values shown, the circuit draws about 11mA. 

Part List

c828         = 2

330 Ohm  = 2

47k           = 2

47uF         = 2 

LED          =2

Spy Bug Fm Transmitter

Spy Bug Fm Transmitter

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This fm wireless transmitter should only be used for educational purposes.

Regular transmission using such a transmitter without a licence is illegal.

I would like to tell you not to use this for illegal things

This transmitter can deliver signals up to 50 meters. The transistor 2N2222 serves as the modulator 

as well as oscillator. Capacitor 33pf and inductor L1 forms the necessary tank circuit for making 

oscillation. Adjustments in the transmission frequency can be made by compressing or relaxing

the coil. The voice to be transmitted is coupled to the base of Q1 using an electret microphone. 

The FM signal available at the collector of Q1 is radiated using the antenna.

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Notes.

    Use a 3V battery for powering the circuit.

    The circuit can be assembled on a Vero board.

    Coil L1 can be made by making 5 turns of 24AWG wire on a 1cm plastic former.

    Antenna can be a 25cm long 18AWG wire.

5V Power Supply

5V Power Supply

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A voltage regulator is used to produce a constant linear output voltage. It’s generally used with AC to DC power supply. And also it can be used as well as a DC to DC voltage converter . 

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The LM78XX series typically has the ability to drive current up to 1A. For application requirements up to 150mA, 78LXX can be used. LM7805 has three legs: Input leg which can hold up to 36VDC Common leg (GND) and an output leg with the regulator's voltage. For maximum voltage regulation, adding a capacitor in parallel between the common leg and the output is usually recommended. Typically a 10uF & 100nF capacitor is used. This eliminates any high frequency AC voltage that could otherwise combine with the output voltage. See below circuit diagram which represents a typical use of a voltage regulator. 

Its output voltage is +5V DC that we need. You can supply any voltage in input; the output voltage will be always regulated +5V. But my recommendation is, don’t supply more than 18V or less than 8V in input. There used three capacitors in this voltage regulator circuit, they aren’t mandatory to use. But it will be best if you use them. They helped to produce a smooth regulated voltage at output. Use electrolyte capacitor instead of ceramic capacitor.

One limitation of 7805 I have found that is its output current 1A maximum. Otherwise it is a good voltage regulator if you are happy with 1A. But if   you need over 400mA current in output then you should use a Heat Sink with IC LM7805. Otherwise it may fall damage for overheating.

Part list

LM7805

1000uF

10uF

100nF