Amazing Lightning Detector Project for Beginners

This new lightning detector circuit uses a single inductor tuned circuit to receive static pulses from lightning at a frequency near 200 kHz. The need for a tapped tuned circuit is eliminated by employing a very high input impedance RF amplifier, using a darlington transistor. The amplifier is micro-power, and the whole circuit draws only about 200 uA from two alkaline D cells, hardly denting the shelf life. The flasher portion of the circuit is similar to the earlier versions, only the polarity of the transistors is reversed. As a result, the output pulses momentarily go to ground from a normally-high state.

The schematic and close-up photos were made with the beginner in mind. Questions about the schematic can be answered by close-up examination of the photos. Try a magnifier utility for an even closer look.

The 150k resistor in the base of the 2N4401 may be replaced with a series combination of a 100k resistor and a 100k (or greater) potentiometer to add sensitivity control. Simply adjust the potentiometer until flashing just stops for maximum sensitivity. The fixed resistor is plenty sensitive for most users. But, the receiver will only work well outside or near a window. A few yards of wire could be used to run an antenna out a window, but connect a 47 pF capacitor in series with the wire at the detector end. Also, connecting a good ground will improve the sensitivity. Keep the unit away from electronic or electrical appliances and wiring for best performance.

Lightning Detector Circuit Diagram

A common mistake is to select a 10 uH choke instead of a 10 mH. The large green choke in the photo is typical of the size and markings to expect. Color bands are brown, black, orange. A wide silver band often indicates the beginning of the color code.

Some of the other parts in the prototype were chosen to make it easy for the beginner to see the values. For example, the large .1 uF "orange drop" can be a tiny ceramic type. Parts may be in odd positions, too. The orange 10 uF is twisted to make the markings visible and other parts are oriented to make viewing easy. 

The 100 uF shown across the battery is the blue part right below the MPSA63 in the photo below. Notice how it isn't right by the battery connections. Sometimes the position of a component relative to others is important but that information is often not on a schematic unless specifically stated. Schematics aren't usually physical representations; they just show which legs of the various parts are electrically connected. Schematics are usually accompanied by assembly drawings as part of a complete design especially when layout is critical. The point is to not take schematics to be mechanical layout instructions although they often are a fairly good start. On the other hand schematics generally aren't intentionally misleading about a good location for the part but a little electronics experience helps a great deal when there's only a schematic to go by.

The parts are not particularly critical. The darlington PNP transistor may be a different number, as may the other transistors. The diodes can be any silicon switching diode, like the 1N4448 (or probably any orange one you have). An amber LED with a 22 ohm resistor draws about 30 mA with fresh batteries. Vary the resistor to achieve the desired LED current for other colors (connect the LED and resistor to the battery through a current meter to select the value). The output transistor can sink several hundred mA, so several LEDs or other loads may be connected in parallel. The head from a cheap LED flahslight that uses two cells will be really bright! The pulse is pretty short to save power and for quick response, but for longer pulses, increase the 10 uF capacitor value. You might want a longer pulse to flash a 3 volt incandescent bulb (my favorite). Actually, I'm using a 1.5 volt bulb and it's really bright (not shown in the photos), even with this short pulse! I have lots of them and I'm sure I'll need to replace it fairly often.

Below is a "photo-shopped" close-up without the sensitivity adjustment option. The construction technique was chosen to make it easy to follow the wiring. Normally, the leads would be stuck through the holes and wired on the other side of the perf board. I used the perf board simply as a guide for copper nails driven into a pine board - strictly to make it easy to see all the connections.  The perf board serves no purpose beyond visibility, so one could also use nails and wood for the assembly. The copper nails from the home improvement store really solder easily, by the way.

The next photo shows the optional potentiometer and resistor for adjusting the sensitivity. Notice that the 150k resistor has been removed. The odd-looking color bands on the resistors were painted on to make them more visible after cleaning faded the original bands. The violet band looks a little dark on the 27k resistor between the two diodes; that should be red, violet, orange.

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Sourced By : techlib

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Simple Ghost Detector Circuit Diagram

This is the easy and Simple Ghost Detector Circuit Diagram. This is a changing charge detector. If a ghost disturbs the electric field in the vicinity of this gadget you will see the results on the LEDs. Don't hold your breath, unless you wish to become a ghost yourself. There's a pair 'a normal LEDs that display whether the charge at the antenna is changing in a positive or negative direction (green vs red).

Simple Ghost Detector Circuit Diagram

Here's how it works:
The electrometer JFET buffers the voltage on the telescoping antenna. Its gate is gently biased low by a neon lamp that contains a little thorium that makes it slightly conductive (most, if not all, neons have thorium inside to help them start). The 22 pF is optional and reduces the 60 Hz "hum" level a bit. Much bigger and the response to sudden changes starts to be impaired. The 1 megohm in the gate is there to protect the JFET from static discharge when the antenna is touched to something. The FET configuration is called a "voltage follower" and the source of the JFET follows the gate fairly closely with a positive offset of a volt or two. That voltage is coupled through the 22 uF and biased up to 2.25 volts by two 10 megohm resistors. That voltage is applied to two comparators, to the positive input of one and the negative input of the other. The other inputs of the comparators are biased to have a slight offset produced by to the 47k resistor. The 47k resistor determines the width of the detection "window." The voltage from the capacitor must exceed the additional voltage produced by the 47k to light either LED. Most homes are literally awash in 60 Hz "hum" from the wiring and both LEDs will light since the voltage easily exceeds the window "width." Increasing the 47k can prevent that behavior but also decrease the sensitivity. In my chicken wire enclosed garden (basically a Faraday shield) only the green LED glows, probably due to slight offsets. In the garden I can pull the antenna all the way out and I can detect my pocket comb dragged through my hair (to charge it) from several yards away. Wiggling it back and forth causes each LED to light brightly. It's pretty sensitive! In the house both LEDs glow but I can still detect a charged comb for quite a distance by observing variations in the brightness of the LEDs.

One point: to give the circuit good low frequency response the 22 uF is quite large. As a result the unit takes a couple of minutes to stabilize after power is applied. The red LED will come on for a minute or two. The capacitor should be a tantalum type or a very low leakage aluminum. It would be fine to use a 1 uF (or more) non-polar ceramic capacitor or a film capacitor, too, in order to achieve the needed low leakage.

I built my Ghost Detector into a peanut butter jar:

This was a rushed project and I made a few classic mistakes. The big one: I should have faced the battery pack outward to make it easy to change the batteries! Duh.

You will notice I didn't use the exact values in the schematic but they're close. I took these from my 2% drawer so they're a little "odd." That 51k is the 47k in the schematic .  I used 9.1 megohms for the 10 meghoms and 300 ohms for the 270 ohms in the schematic. Ignore these variations; they're insignificant. Notice that I covered the neon lamp with heat shrink tubing to keep out the light. Use heat shrink for this since the adhesive on black tape might be too conductive. Sourced By : .techlib

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Simple Lightning Detector Circuit Diagram

This is the Simple Lightning Detector Circuit Diagram. Built to make the wiring easy to follow. Read the text below!

This new lightning detector circuit uses a single inductor tuned circuit to receive static pulses from lightning at a frequency near 200 kHz. The need for a tapped tuned circuit is eliminated by employing a very high input impedance RF amplifier, using a darlington transistor. The amplifier is micro-power, and the whole circuit draws only about 200 uA from two alkaline D cells, hardly denting the shelf life. The flasher portion of the circuit is similar to the earlier versions, only the polarity of the transistors is reversed. As a result, the output pulses momentarily go to ground from a normally-high state.

The schematic and close-up photos were made with the beginner in mind. Questions about the schematic can be answered by close-up examination of the photos. Try a magnifier utility for an even closer look.

The 150k resistor in the base of the 2N4401 may be replaced with a series combination of a 100k resistor and a 100k (or greater) potentiometer to add sensitivity control. Simply adjust the potentiometer until flashing just stops for maximum sensitivity. The fixed resistor is plenty sensitive for most users. But, the receiver will only work well outside or near a window. A few yards of wire could be used to run an antenna out a window, but connect a 47 pF capacitor in series with the wire at the detector end. Also, connecting a good ground will improve the sensitivity. Keep the unit away from electronic or electrical appliances and wiring for best performance.

A common mistake is to select a 10 uH choke instead of a 10 mH. The large green choke in the photo is typical of the size and markings to expect. Color bands are brown, black, orange. A wide silver band often indicates the beginning of the color code.

Some of the other parts in the prototype were chosen to make it easy for the beginner to see the values. For example, the large .1 uF "orange drop" can be a tiny ceramic type. Parts may be in odd positions, too. The orange 10 uF is twisted to make the markings visible and other parts are oriented to make viewing easy.

The 100 uF shown across the battery is the blue part right below the MPSA63 in the photo below. Notice how it isn't right by the battery connections. Sometimes the position of a component relative to others is important, but that information is often not on a schematic, unless specifically stated. Schematics aren't usually physical representations; they just show which legs of the various parts are electrically connected. Schematics are usually accompanied by assembly drawings as part of a complete design, especially when layout is critical. The point is to not take schematics to be mechanical layout instructions, although they often are a fairly good start. On the other hand, schematics generally aren't intentionally misleading about a good location for the part, either, but a little electronics experience helps a great deal when there's only a schematic to go by.

The parts are not particularly critical. The darlington PNP transistor may be a different number, as may the other transistors. The diodes can be any silicon switching diode, like the 1N4448 (or probably any orange one you have). An amber LED with a 22 ohm resistor draws about 30 mA with fresh batteries. Vary the resistor to achieve the desired LED current for other colors (connect the LED and resistor to the battery through a current meter to select the value). The output transistor can sink several hundred mA, so several LEDs or other loads may be connected in parallel. The head from a cheap LED flahslight that uses two cells will be really bright! The pulse is pretty short to save power and for quick response, but for longer pulses, increase the 10 uF capacitor value. You might want a longer pulse to flash a 3 volt incandescent bulb (my favorite). Actually, I'm using a 1.5 volt bulb and it's really bright (not shown in the photos), even with this short pulse! I have lots of them and I'm sure I'll need to replace it fairly often.

Below is a "photoshopped" close-up without the sensitivity adjustment option. The construction technique was chosen to make it easy to follow the wiring. Normally, the leads would be stuck through the holes and wired on the other side of the perf board. I used the perf board simply as a guide for copper nails driven into a pine board - strictly to make it easy to see all the connections.  The perf board serves no purpose beyond visibility, so one could also use nails and wood for the assembly. The copper nails from the home improvement store really solder easily, by the way.

I made several image edits for clarity and to correct mistakes; they're not perfect but I think the connections are clear.

The next photo shows the optional potentiometer and resistor for adjusting the sensitivity. Notice that the 150k resistor has been removed. The odd-looking color bands on the resistors were painted on to make them more visible after cleaning faded the original bands. The violet band looks a little dark on the 27k resistor between the two diodes; that should be red, violet, orange.

Author:  Marcos in Brazil

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Using Laser Torch Intruder Detector Circuit Diagram

This is the Using Laser Torch Intruder Detector Circuit Diagram. intruder detector that uses an invisible laser beam to detect the intruder. The laser beam is produced using a 3V DC or 4.5V DC laser pointer or torch that is available in the market. The 3V DC or 4.5V DC power supply for the laser transmitter can also be given using a Bridger rectifier or full-wave rectifier.

Fig. 1 shows the block diagram of the complete unit comprising the transmitter and receiver sections. The laser beam from the transmitter after reflection from various mirrors (M1 through M6, as shown in Fig. 1) is made to fall on the photo detector in the receiver circuit.

 Fig. 1: Block diagram of intruder detector using laser torch

Once the laser beam is positioned, the receiver circuit is powered by closing switch S. An alarm unit operating on 230V AC is connected to the relay RL in the receiver circuit.

When an intruder interrupts the path of the beam or switches off the laser torch, the alarm unit becomes activated. The alarm unit remains activated until reset switch S is opened. To activate the alarm circuit again, reset switch S should be closed. The total distance traveled by the laser beam should be less than 800 m for 4.5V laser torch and 500 m for 3V laser torch.

The circuit of the receiver is shown in Fig. 2. When reset switch S is closed, the circuit is powered on. As the laser beam falls on the photo detector, transistor T (BC547) conducts, resulting in the collector being pulled down to ground potential. Thus no current flows to the gate of the SCR and it remains off.

Fig. 2: Receiver circuit

Once the path of the laser beam is interrupted, the base current of the transistor becomes very low and the transistor is driven to cut-off. Now the current starts to flow through resistor R1 and to the gate of SCR. Hence the SCR is fired and it begins to conduct. Thus relay RL connected to the anode of SCR is switched on and the alarm is activated. The alarm sounds until reset switch S is opened to turn off power to the circuit.

EFY Lab note:  We tested the circuit using only one mirror and found its range to be 25-30 metres. The range depends on the intensity of laser beam falling on the photodetector.
Author : G. Susinder Rajan

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Lie Detectors Circuit Diagram

LIE DETECTOR-1

This circuit detects the resistance between your fingers to provide an oscillation. The detection-points can detect resistances as high as 300k and because the resistance decreases, the frequency increases.

Separate the 2 bit pads and fasten them to the back of every hand. because the subject feels nervous, he can sweat and alter the frequency of the circuit.The photos show the circuit engineered on computer boards

with separate bit pads.

LIE DETECTOR-2

This circuit detects the resistance between your fingers to turn on the FALSE LED. The circuit sits with the TRUE LED illuminated. The 47k pot is adjusted to permit the LEDs to change state when touching the

probes. 

LIE DETECTOR-3

This circuit detects the resistance between your fingers to show the four LEDs. As you press tougher, more

LEDs are illuminated.

LIE DETECTOR-4

his circuit detects the resistance between your fingers to show the 3LEDs. As you press harder, a lot of LEDs are illuminated. Thecircuit is less complicated than Lie Detector-3. 

 

http://streampowers.blogspot.com/2012/07/sp-lie-detectors.html 

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Invisible Broken Wire Detector Circuit Diagram

Portable loads such as video cameras, halogen flood lights, electrical irons, hand drillers, grinders, and cutters are powered by connecting long 2- or 3-core cables to the mains plug. Due to prolonged usage, the power cord wires are subjected to mechanical strain and stress, which can lead to internal snapping of wires at any point. In such a case most people go for replacing the co e/cable, as finding the exact loca Portable loads such as video cameras, halogen flood lights, electrical irons, hand drillers, grinders, and cutters are powered by connecting long 2- or 3-core cables to the mains plug. Due to prolonged usage, the power cord wires are subjected to mechanical strain and stress, which can lead to internal snapping of wires at any point.

 In such a case most people go for replacing the core/cable, as finding the exact location of a broken wire is difficult. In 3-core cables, it appears almost impossible to detect a broken wire and the point of break without physically disturbing all the three wires that are concealed in a PVC jacket.  The circuit presented here can easily and quickly detect a broken/faulty wire and its breakage point in 1-core, 2-core, and 3-core cables without physically disturbing wires.  It is built using hex inverter CMOS CD4069. Gates N3 and N4 are used as a pulse generator that oscillates at around 1000 Hz in audio range.

The frequency is determined by timing components comprising resistors R3 and R4, and capacitor C1. Gates N1 and N2 are used to sense the presence of 230V AC field around the live wire and buffer weak AC voltage picked from the test probe. The voltage at output pin 10 of gate N2 can enable or inhibit the oscillator circuit. When the test probe is away from any high-voltage AC field, output pin 10 of gate N2 remains low. As a result, diode D3 conducts and inhibits the oscillator circuit from oscillating. Simultaneously, the output of gate N3 at pin 6 goes ‘low’ to cut off transistor T1. As a result, LED1 goes off. 

When the test probe is moved closer to 230V AC, 50Hz mains live wire, during every positive halfcycle, output pin 10 of gate N2 goes high. Thus during every positive half-cycle of the mains frequency, the oscillator circuit is allowed to oscillate at around 1 kHz, making red LED (LED1) to blink. (Due to the persistence of vision, the LED appears to be glowing continuously.) This type of blinking reduces consumption of the current from button cells used for power supply.  A 3V DC supply is sufficient for powering the whole circuit. AG13 or LR44 type button cells, which are also used inside laser pointers or in LED-based continuity testers, can be used for the circuit.

Circuit diagram :

 

Invisible Broken Wire Detector Circuit Diagram

The circuit consumes 3 mA during the sensing of AC mains voltage. For audio-visual indication, one may use a small buzzer (usually built inside quartz alarm time pieces) in parallel with one small (3mm) LCD in place of LED1 and resistor R5. In such a case, the current consumption of the circuit will be around 7 mA. Alternatively, one may use two 1.5V R6- or AA-type batteries. Using this gadget, one can also quickly detect fused small filament bulbs in serial loops powered by 230V AC mains. 

 The whole circuit can be accommodated in a small PVC pipe and used as a handy broken-wire detector. Before detecting broken faulty wires, take out any connected load and find out the faulty wire first by continuity method using any multimeter or continuity tester. 

Then connect 230V AC mains live wire at one end of the faulty wire, leaving the other end free. Connect neutral terminal of the mains AC to the remaining wires at one end. However, if any of the remaining wires is also found to be faulty, then both ends of these wires are connected to neutral. 

For single-wire testing, connecting neutral only to the live wire at one end is sufficient to detect the breakage point.  In this circuit, a 5cm (2-inch) long, thick, single-strand wire is used as the test probe. To detect the breakage point, turn on switch S1 and slowly move the test probe closer to the faulty wire, beginning with the input point of the live wire and proceeding towards its other end.LED1 starts glowing during the presence of AC voltage in faulty wire. When the breakage point is reached, LED1 immediately extinguishes due to the non-availability of mains AC voltage. The point where LED1 is turned off is the exact broken-wire point.  While testing a broken 3-core rounded cable wire, bend the probe’s edge in the form of ‘J’ to increase its sensitivity and move the bent edge of the test probe closer over the cable. During testing avoid any strong electric field close to the circuit to avoid false detection. 

Sourced by : Streampowers

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Water Level Controller Detector Circuit Diagram

In most houses, water is first stored in an underground tank (UGT) and from there it is pumped up to the overhead tank (OHT) located on the roof. People generally switch on the pump when their taps go dry and switch off the pump when the overhead tank starts overflowing. This results in the unnecessary wastage and sometimes non-availability of water in the case of emergency.  The simple circuit presented here makes this system automatic, i.e. it switches on the pump when the water level in the overhead tank goes low and switches it off as soon as the water level reaches a pre-determined level. It also prevents ‘dry run’ of the pump in case the level in the underground tank goes below the suction level. 

 

In the figure, the common probes connecting the underground tank and the overhead tank to +9V supply are marked ‘C’. The other probe in underground tank, which is slightly above the ‘dry run’ level, is marked ‘S’. The low-level and high-level probes in the overhead tank are marked ‘L’ and ‘H’, respectively.  When there is enough water in the underground tank, probes C and S are connected through water.As a result,transistor T1 gets forward biased and starts conducting. This, in turn, switches transistor T2 on. 

Initially, when the overhead tank is empty, transistors T3 and T5 are in cut-off state and hence pnp transistors T4 and T6 get forward biased via resistors R5 and R6, respectively.  As all series-connected transistors T2, T4, and T6 are forward biased, they conduct to energise relay RL1 (which is also connected in series with transistors T2, T4, and T6). Thus the supply to the pump motor gets completed via the lower set of relay contacts (assuming that switch S2 is on) and the pump starts filling the overhead tank. 

Once the relay has energised, transistor T6 is bypassed via the upper set of contacts of the relay. As soon as the water level touches probe L in the overhead tank, transistor T5 gets forward biased and starts conducting. This, in turn, reverse biases transistor T6, which then cuts off. But since transistor T6 is bypassed through the relay contacts, the pump continues to run. The level of water continues to rise.  When the water level touches probe H, transistor T3 gets forward biased and starts conducting. This causes reverse biasing of transistor T4 and it gets cut off. As a result, the relay de-energises and the pump stops. Transistors T4 and T6 will be turned on again only when the water level drops below the position of L probe. 

Presets VR1, VR2, and VR3 are to be adjusted in such a way that transistors T1, T3, and T5 are turned on when the water level touches probe pairs C-S, C-H, and C-L, respectively. Resistor R4 ensures that transistor T2 is ‘off’ in the absence of any base voltage. Similarly, resistors R5 and R6 ensure that transistors T4 and T6 are ‘on’ in the absence of any base voltage. Switches S1 and S2 can be used to switch on and switch off, respectively, the pump manually.  You can make and install probes on your own as per the requirement and facilities available. However, we are describing here how the probes were made for this prototype. 

The author used a piece of non-metallic conduit pipe (generally used for domestic wiring) slightly longer than the depth of the overhead tank. The common wire C goes up to the end of the pipe through the conduit. The wire for probes L and H goes along with the conduit from the outside and enters the conduit through two small holes bored into it as shown in Fig. 2. Care has to be taken to ensure that probes H and L do not touch wire C directly. Insulation of wires is to be removed from the points shown. The same arrangement can be followed for the underground tank also. To avoid any false triggering due to interference, a shielded wire may be used.

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Proximity Detector Circuit Diagram

This is the simple Proximity Detector Circuit Diagram. This proximity detector is constructed using an infrared diode detector. Infrared detector can be used in various equipment such as burglar alarms, touch free proximity switches for turning on a light, and solenoid-controlled valves for operating a water tap. Briefly, the circuit consists of an infrared transmitter and an infra-red receiver (such as Siemens SFH506-38 used in TV sets).

  The transmitter part consists of two 555 timers (IC1 and IC2) wired in astable mode, as shown in the figure, for driving an infrared LED. A burst output of 38 kHz, modulated at 100 Hz, is required for the infrared detector to sense the trans mission; hence the setup as shown is required.  To save power, the duty cycle of the 38kHz astable multivibrator is maintained at 10 per cent.  The receiver part has an infrared detector comprising IC 555 (IC3), wired for operation in monostable mode, followed by pnp transistor T1. Upon reception of infrared signals, the 555 timer (mono) is turned  ‘on’ and it re-mains  ‘on’ as long as the infrared signals are being received.  

Circuit Diagram :
 

Proximity Detector Circuit Diagram

 

When no more signals are received, the mono goes  ‘off’ after a few seconds (the delay depends on timing resistor-capacitor combination of R7-C5). The de-lay obtained using 470kilo-ohm resistor and 4.7µF capacitor is about 3 seconds. Unlike an ordinary mono, the capacitor in this mono is allowed to charge only when the reception of the signal has stopped, because of the pnp transistor T1 that shorts the charging capacitor as long as the output from IR receiver module is available (active low).  This setup can be used to detect proximity of an object moving by. Both transmitter and receiver can be mounted on a single breadboard/PCB, but care should be taken that infrared receiver is behind the infrared LED, so that the problem due to infrared leak-age is obviated.  

An object moving nearby actually reflects the infrared rays from the infrared LED. As the infrared receiver has a sensitivity angle of 60o, the IR rays are sensed within this lobe and the mono in the receiver section is triggered. This principle can be used to turn ‘on’ the light, using a relay, when a person comes nearby. The same automatically turns  ‘off’ after some time, as the person moves away. The sensitivity depends on the current limiting resistor in series with the infrared LED. It is ob-served that with in circuit resistance of preset VR1 set at 20 ohms, the object at a distance of about 25 cms can be sensed.  This circuit can be used for burglar alarms based on beam interruption, with the added advantage that the transmitter and receiver are housed in the same enclosure, avoiding any wiring problems.

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Room Noise Detector Schematic Circuit

This circuit is intended to signal, through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electret microphone to drive a LED. With SW1 in the first position the circuit is off. Second, third and fourth positions power the circuit and set the input sensitivity threshold to 85, 70 & 50 dB respectively. Current drawing is 1mA with LED off and 12-15mA when the LED is steady on.

Circuit diagram :

Room Noise Detector Circuit diagram

Parts List :

R1____________10K 1/4W Resistor
R2,R3_________22K 1/4W Resistors
R4___________100K 1/4W Resistor
R5,R9,R10_____56K 1/4W Resistors
R6_____________5K6 1/4W Resistor
R7___________560R 1/4W Resistor
R8_____________2K2 1/4W Resistor
R11____________1K 1/4W Resistor
R12___________33K 1/4W Resistor
R13__________330R 1/4W Resistor

C1___________100nF 63V Polyester Capacitor
C2____________10µF 25V Electrolytic Capacitor
C3___________470µF 25V Electrolytic Capacitor
C4____________47µF 25V Electrolytic Capacitor

D1_____________5mm. Red LED

IC1__________LM358 Low Power Dual Op-amp

Q1___________BC327 45V 800mA PNP Transistor

MIC1_________Miniature electret microphone

SW1__________2 poles 4 ways rotary switch

B1___________9V PP3 Battery

Clip for PP3 Battery

Use :

• Place the small box containing the circuit in the room where you intend to measure ambient noise.
• The 50 dB setting is provided to monitor the noise in the bedroom at night. If the LED is steady on, or flashes bright often, then your bedroom is inadequate and too noisy for sleep.
• The 70 dB setting is for living-rooms. If this level is often exceeded during the day, your apartment is rather uncomfortable.
• If noise level is constantly over 85 dB, 8 hours a day, then you are living in a dangerous environment.

Source by : Streampowers

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High-Performance Interruption Detector

The circuit presented here detects interruption in security systems. Its features include no false triggering by external factors (such as sun-light and rain), easy relative positioning of the sensors and alignment of the circuit, high sensitivity, and reliability. The circuit comprises three sections, namely, transmitter, receiver, and power supply. The transmitter generates modulated IR signals and the receiver detects the change in IR intensity. Power supply provides regulated +5V to the transmitter and the receiver. 

The power supply and the speaker are kept inside the premises while the transmitter and the receiver are placed oppo site to each other at the entrance where the detection is needed. Three connections (Vcc, GND, and SPKR) are needed from the power supply/speaker to the receiver section, while only two connections (Vcc and GND) are required to the transmitter. The transmitter is basically an astable multivibrator configured around NE555 (IC3). Its frequency should match the frequency of the detector/sensor module (36 kHz for the module shown in figure) in the receiver. The transmitter frequency is adjusted by preset VR2. For making the duty cycle less than 50 per cent, di-ode 1N4148 is connected in the charging path of capacitor C7. 

The output of astable multivibrator modulates the IR signal emitted from IR LEDs that are used in series to obtain a range of 7 metres (maximum). To increase the range any further, the transmitted power has to be raised by using more number of IR LEDs. In such a case, it is advisable to use another pair of IR LEDs and 33-ohm series resistor in parallel with the existing IR LEDs and resistor R5 across points X and Y. The receiver unit consists of a monostable multivibrator built around NE555 (IC2), a melody generator, and an IR sensor module. The output of the IR sensor module goes high in the standby mode or when there is continuous presence of modulated IR signal.

Circuit diagram :

High-Performance Interruption Detector Circuit Diagram

 

When the IR signal path is blocked, the output of the sensor module still re-mains high. However, when the block is removed, the output of the sensor module briefly goes low to trigger monostable IC3. This is due to the fact that the sensor module is meant for pulsed operation. Thus interruption of the IR path for a brief period gives rise to pulsed operation of the sensor module. Once monostable IC2 gets triggered, its output goes high and stays in that state for the duration of its pulse width that can be controlled by preset VR1. The high output at pin 3 of the monostable makes the musical IC to function. Voltage divider comprising R2 and R3 reduces the 555 output voltage to a safer value (around 3V) for UM66 operation. The du-ration of the musical notes is set by pre-set VR1 as stated earlier. 

For proper operation of the circuit, use 7.5V to 12V power supply. A battery backup can be provided so that the circuit works in the case of power failure also. Potmeter VR3 serves as a volume control. The transmitter, receiver, and power supply units should be assembled separately. The transmitter and the receiver should have proper coverings (booster) for protection against rain. The length of the wire used for connecting the IR sensor module and IR LEDs should be minimum. 

Streampowers

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Audio Peak Detector Circuit Diagram

This audio peak detector allows a pair of stereo channels to be monitored on a sin-gle LED. Identical circuitry is used in the left and right channels. Use is made of the switch-ing levels of Schmitt trigger NAND gates inside the familiar 4093 IC. The threshold level for gate IC1.A (IC1.B) is set with the aid of preset P1, which supplies a high-impedance bias level via R2 (R1). 

Circuit diagram :

Simple Audio Peak Detector Circuit Diagram 

When, owing to the instantaneous level of the audio signal superimposed on the bias voltage by C3 (C2), the dc level at pins 1 and 2 (5 and 6) of the Schmitt trigger gate drops below a certain level, the output of IC1.A (IC1.B) will go High. This level is copied to the input of IC1.C via D2 (D1) and due to the inverting action of IC1.C, LED D3 will light. Network R3-C1 provides some delay to enable very short audio peaks to be reliably indicated. Initially turn the wiper of P1 to the +12 V extreme — LED D3 should remain out. 

Then apply ‘line’ level audio to K1 and K3, preferably music with lots of peaks (for example, drum ‘n bass). Carefully adjust P1 until the peaks in the music are indicated by D3. The circuit has double RCA connectors for the left and right channels to obviate the use of those rare and expensive audio splitter (‘Y’) cables. 

Source by streampowers

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Snail Mail Detector Circuit Diagram

Since his letter-box is outdoors  and quite some way from the  house, the author was looking  for a simple means of knowing if  the postman had been without  having to go outside (contrary  to popular belief, the weather  isn’t always fine in the South of  France). Circuits for this kind of  ‘remote detection’ come up regularly, but always involve running cables between the letter- box and the detection circuit in  the house. Seeking to avoid running any extra cables, the author  had the idea of using the existing cables going to the doorbell,  conveniently located adjacent to  his letter-box.

 

The letter-box has two doors:  one  on  the  street  side  for  the  postman, and one on the gar-den side for collecting the post.  A  micro switch  is  fitted  to  the  street-side door, to light an indicator in the house showing that  the postman has been. A second  micro switch is fitted to the door  on the garden side, to turn off  the indicator once the post has  been collected. The only difficulty then remains to connect  these detectors to a remote circuit in the house that remembers  whether  the  postman’s  been or not.

 

The idea was to use the alternating half-cycles of the AC signal  on the cable going to the door-bell  to  transmit  the  information, according to the following logic:

• Both  half-cycles  present: no change in the status of the mail detector.
• An interruption (even brief) of one half-cycle: indicator lights permanently.
• An interruption (even brief) of the other half-cycle: the indicator goes out.

Note that the signal is tapped off  across the doorbell coil via R6  and the pair of diodes connected  in inverse-parallel (to limit the  signal,  par ticularly  when  the  bell is rung). The signal is then  filtered by R2/C1, before being  used by IC1, which is wired as a  comparator with hysteresis. The  trigger threshold is adjusted by  P1, using a pair of inverse parallel diodes as a voltage reference  (positive or negative according  to the output state):

 

For the detection to work, there  has to be continuity in the bell-push circuit this is generally  ensured by the little lamp illuminating the bell-push. Resistor R1  is added just in case the lamp is  blown or not present. To keep things simple, the circuit is powered directly from the  doorbell transformer itself (230 V  / 8 V). The author managed to fit  the little circuit within the door-bell unit, with the LED poking  through a hole in the casing so  it is readily visible in the hall of  his house. 

Source by Streampowers

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DTMF Proximity Detector Circuit Diagram

A DTMF-based IR transmitter and receiver pair can be used to realize a proximity detector. The circuit presented here enables you to detect any object capable of reflecting the IR beam and moving in front of the IR LED photo-detector pair up to a distance of about 12 cm from it. The circuit uses the commonly available telephony ICs such as dial-tone generator 91214B/91215B (IC1) and DTMF decoder CM8870 (IC2) in conjunction with infrared LED (IR LED1), photodiode D1, and other components as shown in the figure. A properly regulated 5V DC power supply is required for operation of the circuit.

The transmitter part is configured around dialer IC1. Its row 1 (pin 15) and column 1 (pin 12) get connected together via transistor T2 after a power-on delay (determined by capacitor C1 and resistors R1 and R16 in the base circuit of the transistor) to generate DTMF tone (combination of 697 Hz and 1209 Hz) corresponding to keypad digit “1” continuously. LED 2 is used to indicate the tone output from IC3. This tone output is amplified by Darlington transistor pair of T3 and T4 to drive IR LED1 via variable resistor VR1 in series with fixed 10-ohm resistor R14. Thus IR LED1 produces tone-modulated IR light.

Variable resistor VR1 controls the emission level to vary the transmission range. LED 3 indicates that transmission is taking place. A part of modulated IR light signal transmitted by IR LED1, after reflection from an object, falls on photodetector diode D1. (The photodetector is to be shielded from direct IR light transmission path of IR LED1 by using any opaque partition so that it receives only the reflected IR light.) On detection of the signal by photodetector, it is coupled to DTMF decoder IC2 through emitter-follower transistor T1.

When the valid tone pair is detected by the decoder, its StD pin 15 (shorted to TOE pin 10) goes ‘high’. The detection of the object in proximity of IR transmitter-receiver combination is indicated by LED1. The active-high logic output pulse (terminated at connector CON1, in the figure) can be used to switch on/off any device (such as a siren via a latch and relay driver) or it can be used to clock a counter, etc. This DTMF proximity detector finds applications in burglar alarms, object counter and tachometers, etc.

Sourced by : Streampowers

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Active ir Motion Detector Circuit Diagram

To explore how different motion detectors operate.To successfully build and test an ambient-light-ignoring active IR motion detector.

Background

 There are a wide variety of motion detectors available currently. To allow a better understanding of motion detectors,the following section provides a detailed description of a few different types.

Ultrasonic Motion Detectors

Ultrasonic transducers can be used to detect motion in an area where there are not supposed to be any moving objects.This type of motion detector is most commonly used in burglar alarm systems since they are very effective in this application.

 Figure 1 shows the operation of an ultrasonic motiondetector. There are tw1o transducers: one emits an ultrasonicwave and the other picks up reflections from the differentobjects in the area. The reflected waves arrive at the receiverin constant phase if none of the objects in the area are moving.If something moves, the received signal is shifted in phase. 

A phase comparator detects the shifted phase and sends a triggering pulse to the alarm.Ultrasonic motion detectors have certain advantages and disadvantages when compared with other types of motion detectors. The main advantages is that they are very sensitive and extremely fast acting. However, the largest problem with this type of motion detector is that it sometimes responds to normal environmental vibration that can be caused by a passing car or a plane overhead. Some types of motion detectors use infrared sensors to avoid this problem, but even these detectors have some problems.

 Passive Infrared Motion DetectorIn passive infrared motion detectors, a sensorcontaining an infrared-sensitive phototransistor is placed in thearea to be protected. Circuitry within the sensor detects theinfrared radiation emitted by the intruder`s body and triggersthe alarm. 

The problem with using this type of detector is that it can be falsely triggered by warm air movement or other disturbances that can alter the infrared radiation levels in an area. In order to prevent this problem, newer systems use tw1oinfrared sensors which monitor different zones within a protected area. Logic within system triggers the alarm only when the tw1o zones are activated in sequence, as would occur if a person walked through the protected area.

Active Infrared Motion Detector

Figure 2 shows the operation of an active infrared motion detector. In the active system each sensor consists oftw1o housings. One housing contains an infrared-emitting diode and an infrared-sensitive photo transistor. The other housing contains an infrared reflector.When positioned in front of an entrance to a protected area, the tw1o housings establish an invisible beam. A person entering the area interrupts the beam causing an alarm to be triggered. An active motion detector is much more reliable than a passive one, but it requires careful alignment when it is installed. The detector can be falsely triggered if one of the housings moves slightly and causes a discontinuous beam.

Project

 For our project, we decided to construct an activeinfrared motion detector. Originally, we wanted to build both anIR and an ultrasonic detector, but we decided that an ultrasonicdetector would require too much time for a three week project.However, we also decided that just building an IR motiondetector would probably be a trivial exercise. 

So, we decided to expand on the concept by building an ambient light ignoring motion detector.This type of motion detector uses the same basic concept as the active infrared motion detector. An interruption in a 5kHz modulated pulsating beam that is transmitted by an infrared diode and received by an infrared transistor sets off the alarm. A schematic of this motion detector is given in Figure 3.

 Figure 3. Ambient-Light-Ignoring Active Motion Detector

The circuit on the left is the transmitter circuit that establishes a 5 kHz modulated infrared beam. As you can see from the schematic of the receiver circuit, a resonance-handbarrow amplifier reduces the detector`s sensitivity to stray light. C1 and L1 in IC2A`s feedback loop cause the op amp to pass only those frequencies at or near the LED`s 5 kHz modulation rate. IC2B`s output increases when the received signal is sufficient to drop the negative voltage across C2 below the reference set by R2. The output of this circuit is then attached to some load resistance, which can be an alarm or, for demonstration purposes, an LED.

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