Automatic Street Light

Automatic Street light
An introduction:
Needs no manual operation for switching ON and OFF. When there is need of light. It detects itself weather there is need for light or not. When darkness rises to a certain value then automatically street light is switched 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.
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:
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) LDR used should be sensitive.
Before using in the circuit 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.
Components:-
1) 9V battery with snap
2)LDR
3)Variable resistance 100K
ohms
4)Resistance 470 ohms
5)LED
6)IC 555
7)Switch

12V Latch Circuit Diagram

This circuit controls a solenoid by the operation of a single push-button switch. The circuit will supply loads of over 1 A and can be operated up to a maximum speed of once every 0.6 second. When power is first applied to the circuit, the solenoid will always start in its off position. Other features of the circuit are its automatic turn-off, if the load is shorted, and its virtually zero-power consumption when off.

12V Latch Circuit Diagram

Time Switch

This circuit is especially designed for those who often need to wake up early in the morning. Ordinary alarms in electronic watches are not loud enough and very often they fail to wake up. The switch circuit described here will come handy; it can be used to switch on a TV, radio or tape recorder etc, which will not allow even the laziest amongst us to ignore their sound for too long. Besides, this time switch can also be used to switch on/off any other electric or electronic gadget at any time.

What you need is a simple analogue electronic clock with alarm facility and a small circuit to implement the time switch. This time switch has two modes. One is ‘time-on’ mode and the other is ‘time-off ’ mode. In time-on mode, you set up the alarm in your clock as per normal procedure and at the set time this switch turns on the gadget connected at the output socket-1. In time-off mode, it turns your gadget off at the set time.

The optional output socket-2 is wired in such a way that when you use this socket, the mode changes without having to flip the mode switch (i.e.mode switch can be omitted). Please refer to the back panel diagram of a typical analogue clock and the audio jack, to see how the existing buzzer of the clock is required to be wired to the audio output from the clock.

This will ensure that when plug is inserted in the audio jack, the clock’s buzzer will remain off and not consume any power unnecessarily. The audio alarm output from the clock is coupled to the AF detector built around low-power switching transistor T1. During alarm, the collector of transistor T1 will fluctuate around ground level and Vcc.

During absence of audio alarm input, the collector of transistor T1 is held at Vcc potential. The next stage consists of an S-R latch built around NAND gates N1 and N2. Capacitor C2 and resistor R4 are used for power-on-reset. On switching the power supply, gate N2 output will acquire logic 1 and that of gate N1 logic 0. This is the initial state, irrespective of the position of mode switch. At the time of alarm, when point A connected to collector of transistor T1 passes through logic 0 state, the output logic state of both the gates will toggle.

Assuming that mode switch is flipped to ‘Mode Off’ position at power-on-reset (when point D is at logic 1), initially diode D1 would be in blocking state and transistor T2 would be forward biased via resistor R5 and diodes D2 and D3. As a result, the relay is in energised state, which makes output power available at output socket1 and cuts it off from socket-2. At alarm time, the audio signal toggles logic output states of both gates N1 and N2. As a result, point D goes to logic 0 state. Diode D1 conducts, taking the voltage at junction of diodes D1 and D2 to near about 1 volt.

Diode D3 ensures that its series combination with diode D2 puts them in blocking mode. Capacitor C3 meanwhile discharges via resistor R6 and the voltage at base of transistor T2 approaches towards ground level, cutting off transistor T2 and de-energising relay RL1. Now the power at output socket-1 would be cut off while it becomes available in socket-2. If the above operation is repeated with switch S1 in ‘Mode On,’ the power would initially not be available in socket-1 (but available in socket-2). But after the alarm, the power would become available in socket-1 and not in socket-2.

Simple Op Amp Radio

This is basically a crystal radio with an audio amplifier which is fairly sensitive and receives several strong stations in the Los Angeles area with a minimal 15 foot antenna. Longer antennas will provide a stronger signal but the selectivity will be worse and strong stations may be heard in the background of weaker ones.

Using a long wire antenna, the selectivity can be improved by connecting it to one of the taps on the coil instead of the junction of the capacitor and coil. Some connection to ground is required but I found that standing outside on a concrete slab and just allowing the long headphone leads to lay on the concrete was sufficient to listen to the local news station (KNX 1070).

Simple Op-Amp Radio Circuit Diagram

 The inductor was wound with 200 turns of #28 enameled copper wire on a 7/8 diameter, 4 inch length of PVC pipe, which yields about 220 uH. The inductor was wound with taps every 20 turns so the diode and antenna connections could be selected for best results which turned out to be 60 turns from the antenna end for the diode.

The diode should be a germanium (1N34A type) for best results, but silicon diodes will also work if the signal is strong enough. The carrier frequency is removed from the rectified signal at the cathode of the diode by the 300 pF cap and the audio frequency is passed by the 0.1uF capacitor to the non-inverting input of the first op-amp which functions as a high impedance buffer stage.

The second op-amp stage increases the voltage level about 50 times and is DC coupled to the first through the 10K resistor. If the pairs of 100K and 1 Meg resistors are not close in value (1%) you may need to either use closer matched values or add a capacitor in series with the 10K resistor to keep the DC voltage at the transistor emitter between 3 and 6 volts.

Another approach would be to reduce the overall gain with a smaller feedback resistor (470K). High impedance headphones will probably work best, but walkman stereo type headphones will also work. Circuit draws about 10 mA from a 9 volt source. Germanium diodes (1N34A) types are available from Radio Shack, #276-1123.

Infrared Remote Control

This circuit will allow you to turn on any piece of equipment that operates on 115 volts ac. The receiver circuit is based on the Radio Shack infrared receiver module (MOD), part number 276-137. It is also available from some of the other sources listed on my Links page. The MOD accepts a 40khz IR signal that is modulated at 4 khz. When a signal is received the MOD will go low. The sensitivity of the MOD is set by different values for R1 and C1.

Infrared Remote Control Circuit Diagram

The values for R1 may need to be as high as 10,000 ohms and for C1 40uf. This will prevent the unit from turning on under normal lighting conditions. You will need to experiment with the values that work best for you. The output of the 4013 chip a flip flop toggles on and off with the reception of a IR pulse. The output of the 4013 turns on the MOC optical coupler which in turn switches on the triac and supplies power to the AC load.