[TC] Home Made Movie Maker

Like real movies, this circuit makes use of a characteristic of the human eye and brain known as the persistence of vision. A sequence of still pictures is projected onto a screen in rapid succession. The pictures differ slightly from one another and the brain interprets the succession of still pictures as continuous motion.

Here the pictures are shadows cast by low-voltage lamps. There are four Lamps in all, which glow in sequence cyclically. This gives the illusion of a simple but realistic movie.

Fig. 1 shows the circuit for the movie maker. It is driven by clock pulses provided by NAND gates N1 and N2. The flickering frequency is adjustable through preset VR1. A suitable rate for perceiving continuous motion is 16 Hz. The clock pulses are fed to counter IC CD4022 (IC2). IC2 has eight outputs, but only the first four (0-3) are used in this circuit. The outputs go high one at a time, in sequence. The fifth output (output 4) is connected to the reset input so that the counter is immediately reset at the fifth count and the first output (output 0) goes high.

The counter outputs are fed to CD4049 hex buffer (IC3). The buffer outputs drive transistors T1 through T4 in a sequence. As each transistor conducts, the lamp connected to it glows. The lamps are rated at 0.3A so these provide enough light to operate the movie show in a dimly-lit room.

Fig. 1: Circuit for movie maker

Assemble the circuit on a general-purpose PCB. Power-on the circuitusing switch S1 and make sure that the outputs of IC2 (0 through 3) are normally low but briefly go high three-four times within a second. Also ensure that the lamps flash one at a time in a repeating sequence. If the sequence appears to be wrong or any of the lamps fails to glow, check the wiring. The light shield and film holder can be made of a thin card, sheet metal or plywood. Strictly adhere to the various dimensions as shown in Fig. 2. Otherwise, the shadow images may fail to register properly when projected.

Use a plastic cabinet as shown in Fig. 3 to hold the circuit board and battery. Owing to the power requirements of the lamps, it is more economical to use four 1.5V cells in a battery box. Else, you can use a 6V power adaptor. 

Fig. 2: Assembly arrangement

There are two ways of mounting the lamps. The more satisfactory but more expensive method is to bolt the four lamps. Alternatively, drill four 1cm dia. holes on the front of the cabinet, wedge the base of the lamps in these holes and solder wire to the bases.

Fig. 3: Plastic case with assembled circuit 

The easiest way to prepare the film frames is to photocopy the desired drawings onto transparent films. Alternatively, trace them on a transparent acetate film or draughtsman's film, using a fine marker pen. Align all the drawings on the frames and project onto the screen. 

  

Fig. 3: Flim making

Working of the circuit is simple. First of all, fix the clock frequency at about 16 Hz. Place the film on the holder. Ensure a distance of 12 cm between the screen and the assembled unit and power-on the circuit using switch S1. Now you can see your drawings as a short movie clip on the screen.

EFY note. We have tested this circuit without the mechanical arrangement.

Source: 
  http://electronicsforu.com/

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[TC] Automatic Street Light

Introduction:

Needs no manual operation for switching ON and OFF. When there is need of light it automatically switches ON. When darkness rises to a certain value then sensor circuit gets activated and switches ON and when there is other source of light i.e. day time, the street light gets OFF. The sensitiveness of the street light can also be adjusted. In our project we have used four L.E.D for indication of bulb but for high power switching one can connect Relay (electromagnetic switch) at the output of pin 3 of I.C 555. Then it will be possible to turn ON/OFF any electrical appliances connected all the way through relay.

                        Automatic Street Light

Principle :

This circuit uses a popular timer I.C 555. I.C 555 is connected as comparator with pin-6 connected with positive rail, the output goes high(1) when the trigger pin 2 is at lower then 1/3rd level of the supply voltage. Conversely the output goes low (0) when it is above 1/3rd level. So small change in the voltage of pin-2 is enough to change the level of output (pin-3) from 1 to 0 and 0 to 1. The output has only two states high and low and can not remain in any intermediate stage. It is powered by a 6V battery for portable use. The circuit is economic in power consumption. Pin 4, 6 and 8 is connected to the positive supply and pin 1 is grounded. To detect the present of an object we have used LDR and a source of light. LDR is a special type of resistance whose value depends on the brightness of the light which is falling on it. It has resistance of about 1 mega ohm when in total darkness, but a resistance of only about 5k ohms when brightness illuminated. It responds to a large part of light spectrum. We have made a potential divider circuit with LDR and 100K variable resistance connected in series. We know that voltage is directly proportional to conductance so more voltage we will get from this divider when LDR is getting light and low voltage in darkness. This divided voltage is given to pin 2 of IC 555. Variable resistance is so adjusted that it crosses potential of 1/3rd in brightness and fall below 1/3rd in darkness.
Sensitiveness can be adjusted by this variable resistance. As soon as LDR gets dark the voltage of pin 2 drops1/3rd of the supply voltage and pin 3 gets high and LED or buzzer which is connected to the output gets activated.

                        Circuit Diagram of Automatic Street Light

Component used :

9v Battery with strip
Switch
L.D.R (Light Depending Resistance)
I.C NE555 with Base
L.E.D (Light Emitting Diode) 3 to 6 pieces.
Variable Resistance of 47 Kilo ohms
P.C.B (Printed Circuit Board of 555 or Vero board.

COMPONENTS :

a) Battery: For 9v power supply we can use 6pcs dry cell or 6F22 9v single piece battery.
b)Switch:Any general purpose switch can be used. Switch is used as circuit breaker.
c) L.D.R: (Light Depending Resistance)
it is a special type of resistance whose value depends on the brightness of light which is falling on it. It has resistance of about 1mega ohm when in total darkness, but a resistance of only about 5k ohms when brightness illuminated. It responds to a large part of light spectrum.
d) L.E.D: (Light Emitting Diode)
A diode is a component that only allows electricity to flow one way. It can be 
thought as a sort of one way street for electrons. Because of this characteristic, diode are used to transform or rectify AC voltage into a DC voltage. Diodes have two connections, an 
anode and a cathode. The cathode is the end on the schematic with the point of the triangle pointing towards a line. In other words, the triangle points toward
that cathode. The anode is, of course, the opposite end. Current flows from the anode to the cathode. Light emitting diodes, or LEDs, differ from regular diodes in that when a voltage is applied, they emit light. This light can be red (most common), green, yellow, orange, blue (not very common), or infa red. LEDs are used as indicators, transmitters, etc. Most likely, a LED will never burn out like a regular lamp will and requires many times less current. Because LEDs act like regular diodes 
and will form a short if connected between + and -, a current limiting resistor is used to prevent that very thing. LEDs may or may not be drawn with the circle surrounding them.

e) Variable resistance: (Potentiometer)

Resistors are one of the most common electronic components. A resistor is a device that limits, or resists current. The current limiting ability or resistance is measured in ohms, represented by the Greek symbol Omega. Variable resistors (also called potentiometers or just "pots") are resistors that have a variable resistance. You adjust the resistance by turning a shaft. This shaft moves a wiper across the actual resistor element. By changing the amounts of resistor between the wiper connection and the connection (s) to the resistor element, you can change the resistance. You will often see the resistance of resistors written with K (kilohms) after the number value. This means that there are that many thousands of ohms. For example, 1K is 1000 ohm,2K is 2000 ohm, 3.3K is 3300 ohm, etc. You may also see the suffix M (mega ohms). This simply means million. Resistors are also rated by their power handling capability. This is the amount of heat the resistor can take before it is destroyed. The power capability is measured in W (watts) Common wattages for variable
resistors are 1/8W, 1/4W, 1/2W and 1W. Anything of a higher wattage is referred to as a rheostat
f) PCB (Printed Circuit Board)
with the help of P.C.B it is easy to assemble circuit with neat and clean end products. P.C.B is made of Bakelite with surface pasted with copper track-layout. For each components leg, hole is made.
Connection pin is passed through the hole and is soldered.
WORKING:
When light falls on the LDR then its resistance decreases which results in increase of the voltage at pin 2 of the IC 555. IC 555 has got comparator inbuilt, which compares between the input voltage from pin2 and 1/3rd of the power supply voltage. When input falls below 1/3rd then output is set high otherwise it is set low. Since in
brightness, input voltage rises so we 
obtain no positive voltage at output of pin 3 to drive relay or LED, besides in poor light condition we get output to energize.
Precautions:
a) Use a Sensitive LDR. Before using it should be tested with multimeter.
b) I.C should not be heated too much while soldering, can destroy the I.C. For safety and easy to replace, use of I.C base is suggested. While placing the I.C pin no 1 should be made sure at right hole.
c) Opposite polarity of battery can destroy I.C so please check the polarity before switching ON the circuit. One should use diode in series with switch for safety since diode allows flowing current in one direction only.
d) L.E.D glows in forward bias only so incorrect polarity of L.E.D will not glow. Out put voltage of our project is 7.3 volt therefore 4 LED in series can be easily used with out resistance.
e) Each component should be soldered neat and clean. We should check for any dry soldered.
f) LDR should be so adjusted that it should not get light from streetlight itself.

Source :http://www.circuiteasy.com/

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[Tc] Google To Use 'Wireless Balloons' To Deliver Wi-Fi

Google will reportedly use Air balloons and satellites to provide Internet access to under-served countries.  It is interesting that Google is planning to build wireless networks around the world in emerging markets such as Africa and Asia, but what’s more interesting is how the web giant plans to deploy this plan. The company is actually planning to offer Wi-Fi in these areas by using balloons. Yes, you heard us right! Not through the conventional cable strings but rather via flying balloons.

As reported by the Wall Street Journal, Google is also supposedly planning to explore experimental methods to provide wireless connection to previously under served areas. These methods will include satellite Internet and the all new balloons plan, which will allegedly use high-altitude devices to blast wireless signals across hundreds of square miles.

This means that these aren’t just the conventional Wi-Fi routers tied on to the weather balloons. The devices will use different frequencies than those of television broadcasts.

So why is Google investing so much in hardware and engineering for underdeveloped areas? The Wall Street Journal in its report says that Google is just interested in increasing the user base into the Google sphere of apps and devices. This will in turn help Google to achieve considerable success in online advertising.

Way to go Google, you are doing some philanthropy too!

Source: http://www.efytimes.com/

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