MAKE YOUR FIRST LIGHT DETECTOR

LIGHT DETECTOR Circuit

This circuit detects light falling on the Photo-cell (Light Dependent Resistor) to turn on the 555 and create a tone that is delivered to the speaker. Pin 4 must be held below 0.7v to turn the 555 off. Any voltage above 0.7v will activate the circuit. The adjustable sensitivity control is needed to set the level at which the circuit is activated.  When the sensitivity pot is turned so that it has the lowest resistance (as shown in red), a large amount of light must be detected by the LDR for its resistance to be low. This produces a voltage-divider made up of the LDR and 4k7 resistor. As the resistance of the LDR decreases, the voltage across the 4k7 increases and the circuit is activated. 

When the sensitivity control is taken to the 0v rail, its resistance increases and this effectively adds resistance to the 4k7. The lower-part of the voltage-divider now has a larger resistance and this is in series with the LDR. Less light is needed on the LDR for it to raise the voltage on pin 4 to turn the 555 on. 

 
SOURCE : http://www.555-timer-circuits.com/light-detector.html

MAKE YOUR FIRST AUTOMATIC CURTAIN CLOSER

AUTOMATIC CURTAIN CLOSER Circuit

This circuit uses a mixture of transistors, an IC and a relay and is used to automatically open and close a pair of curtains. Using switch S3 also allows manual control, allowing curtains to be left only partially open or closed. The circuit controls a motor that is attached to a simple pulley mechanism, to move the curtains. 

Automatic Operation
The circuit can be broken into three main parts; a bi-stable latch, a timer and a reversing circuit. Toggle switch S3 determines manual or automatic mode. The circuit as shown above is drawn in the automatic position and operation is as follows. The bi-stable is built around Q1 and Q2 and associated circuitry and controls relay A/2. S1 is used to open the curtains and S2 to close the curtains. At power on, a brief positive pulse is applied to the base of Q2 via C2. Q2 will be on, and activate relay A/2.
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MAKE YOUR OWN AMPLIFIER AT HOME

The 555 can be used as an amplifier. It operates very similar to pulse-width modulation. The component values cause the 555 to oscillate at approx 66kHz and the speaker does not respond to this high frequency.  Instead it responds to the average CD value of the modulated output and demonstrates the concept of pulse-width modulation. The chip gets very hot and is only for brief demonstrations. 

source : www.555-timer-circuits.com/

MAKE YOUR OWN WALKY - TALKY

MAKE YOUR OWN WALKY - TALKY

Walky talky is very interesting and attain grabbing project for electronics hobbyist. Communication is done without any physical connection and mobile network up range of 500 meter. Almost all communication devices utilize coil which is burden for electronics hobbyist. So, we design this circuit without using any coil.

Circuit Descriptions of walky-talky

The entire circuit of walky-talky is divided into two main section transmitter and receiver section.

Transmitter section:- Transmitter section utilize  IC NE566 (IC₄) as VCO (Voltage Control Oscillator) for generating frequency about 30 KHz. Resistor R₂₄ with Capacitor C₂₄ used as frequency components for frequencies determination. Voice is pick-up by mike (MIC₁) and changed it into equivalent electrical signal. Signal from microphone is amplified by transistor T₄ and given to pin no 5 0f IC₄. NAND gate N₁ with crystal oscillator XT₄ finalizes the output from pin 3 of IC₃. Lastly, signal from NAND N₂ through N₃ and N₄ given to antenna for transmission.

Receiver section: - Transmitted signal from another walky-talky is received from same antenna which is used for transmission. Field effect transistor T₁ boosts the received signal and make more powerful and send to amplifier section made from transistor T₂ and T₃ with crystal oscillator XT₁ through XT₃. Detector section is made from diode D₁, Capacitor C₆ and resistor R₁₂. 30 KHz frequency is obtained from detector section.

Frequency of Phase Locked Loop IC NE565 (IC₁) is adjusted by capacitor C₉, resistor R₁₇ and variable resistor VR₁. Amplifier IC LM386 (IC₂) is used to amplify the signal and given to speaker.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 47 KΩ

R₂ = 100 Ω

R₃, R₄, R₁₁, R₂₇ = 2.2 KΩ

R₅ = 330 KΩ

R₆, R₁₀ = 560 Ω

..Read more http://electronicsproject.org/walky-talky-without-using-inductor-or-coil/

Clap operated Remote Control for Fans

Clap operated Remote Control for Fans

Here is the circuit of clap-operated remote control fans is used to control not only switching properties but also control speed of fan. The main advantage of clap operated remote control for fan is, it can control up to ten-step speeds of fan where normally a fan has three to five step speeds.

Circuit description clap operated remote control for fan

This entire circuit clap operated remote control for fan is divided into four major section i.e. sound-operated trigger pulse generator, clock pulse generator, clock pulse counter and load operator.

Sound-operated trigger pulse: – The heart of this section is transistor T₁ BC148, configured as class-C amplifier mode. The MIC₁ is used to change voice signal into its corresponding electrical signal and is given to base of transistor T₁ in order to amplify and increase its intensity.

Clock pulse generator:- This section is build around timer IC NE555 and configured as monostable multivibrator. The trigger pulse generated by transistor T₁ is given to pin 2 of IC₁ and time period (T) for output high is calculated by formula.

T = 1.1RC

Clock Pulse counter:- This section is build around decade counter CD4017BC which counts the clock pulse generated by timer IC (IC₁). The output from IC₁ is given to pin 14 of IC₂. IC₂ has ten outputs, viz, o, 1, 2, 3, 4…..9. Here we use only three outputs i.e. output 1, 2 and 3 from pin 2, 4, and 7 respectively. Output 4 from pin 10 is directly connected to reset pin 15.

Load operator:- This section is build around three transistor as relay driver to operate three separate relay. Output from each pin of IC₂ is given to base of each transistor through 100Ω and LED as shown in circuit diagram. Output is taken from collector of transistor and is connected to relay. The three LEDs used to indicate gear or speed i.e. LED₁, LED₂ & LED₃ indicates gear 1, gear 2 & gear 3 respectively.

NOTE:-This circuit used to operate in 1^st speed similarly, 2^nd clap for 2^nd speed, 3^rd clap for 3^rd speed and 4^th clap to switch off the fan.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 10 KΩ

R₂ = 1.2 MΩ

R₃ = 2.2 KΩ

R₄ = 150 KΩ

..Read more http://electronicsproject.org/clap-operated-remote-control-for-fans/