Detector and Sensor

Fire Alarm Using NE555

noreply@blogger.com (Quick Zone) — Fri, 09 Oct 2009 18:02:00 +0000

The following circuit is an fire alarm that is quite nice and simple. This alarm function to provide early warning of fires. This alarm provides warning of fire to the user so it can be prevented early.

This fire alarm circuit should be placed in places prone to fire. Fire will cause a fire which caused enough smoke that will reduce the intensity of light to the LDR, which can pass light to the surrounding environment.

With decreasing light intensity will increase resistor value of the LDR and the voltage on PIN2 of IC 555 will drop to be 1-3V. This will trigger the use of bistable mode of IC 555 that cause increased voltage on pin 3 to 9V, which provides voltage to activate the Chip on Board (COB). The signal output from the COB will give sound then be amplified by an audio amplifier IC.

In this circuit, the audio amplifier-wired around IC TDA 2002. The sensitivity of the circuit depends on the distance between the lamp and LDR and the creation of preset VR1. So, by placing the lamp and LDR at appropriate distances, can be varied preset VR1 to obtain optimum sensitivity. S1 reset switch is provided in the circuit to turn off the fire alarm after the fire was noticed by the user.

2-Zone Alarm

noreply@blogger.com (Quick Zone) — Fri, 09 Oct 2009 17:01:00 +0000

This is a really small alarm that could easily fit inside a pocket. However, I also demanded reliable operation, simple construction and very low power consumption. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) takes.

Then I suddenly realized that a simple transistor switch might do the job and I was right. As you can clearly see from the schematics, the circuit is utterly primitive and consists of two identical transistor switches. Each has its own alarm LED and they're coupled to a neat 82dB buzzer. The two 1N4148 diodes are used to prevent a signal from one sensor from triggering both LEDs. The sensors are connected to the jumpers. Use either loops of very thin (like 0.1mm) enamel coated wire or normally closed reed switches or even a combination of both.

Since this little alarm is intended to be kept in arms reach at all times, there aren't any provisions for automatic shutdown after a certain period of time. The buzzer will sound until you turn the whole circuit off or connect the wire loop back to the jumpers. The same goes for the two LEDs, each indicating its own zone. Construction is not critical and there aren't any traps for the novice. The two 100n capacitors aren't really necessary, I just included them to make sure that there is no noise interference coming from the long wire loops.

For transistors, you can use any NPN general-purpose audio amplifiers/switches (BC 107/108/109, BC 237/238, 2N2222, 2N3904...). Assemble the circuit on perf board. Together with the buzzer and a 9V battery, it should easily fit in a pocket-sized plastic box smaller than a pack of cigarettes. A fresh battery should suffice for months of continuous operation.

Possible uses:
Tie a wire loop to your suitcase and place a reed switch to the door of your hotel room. If sleeping outside, place the wire loop all around your tent or sleeping bag ten centimeters above ground. Any intruder will tear the loop, thus triggering the alarm.

Source: Tiny 2-Zone Alarm

Rain Alarm using Water Sensor

noreply@blogger.com (Quick Zone) — Tue, 22 Sep 2009 02:00:00 +0000

Rain alarm is a simple circuit using water sensor (transducer) that produces an audible alarm whenever rain falls. The circuit can be based on two transistors and or a NE555 IC.

The two transistors are wired as a switch which goes on when the base of Q1 is shorted to the positive of the supply by the rainwater falling on the sensor. When the transistors are ON power supply is available to the IC1 which is wired as an astable multivibrator .The out put of IC1 drives the speaker to produce a alarm.

A 555 astable multivibrator is used here which gives a tone of about 1 KHz upon detecting water. The sensor when wetted by water completes the circuit and makes the 555 oscillate at about 1kHz.

The Circuits of Rain Alarm

Water Sensor (Transducer)-Rain Sensing Grid Schematic

It has to placed making an angle of about 30 - 45 degrees to the ground. This makes the rain water to flow through it to the ground and prevents the alarm from going on due to the stored water on the sensor.

The metal used to make the sensor has to be aluminium and not copper. This is because copper forms a blue oxide on its layer on prolonged exposure to moisture and has to be cleaned regularly.

The aluminium foils may be secured to the wooden / plastic board via epoxy adhesive or small screws.
The contact X and Y from the sensor may be obtained by small crocodile clips or you may use screws.

Source : Rain Alarm Circuit - Rain Alarm

Radios Clock Time Signals

noreply@blogger.com (Quick Zone) — Mon, 06 Apr 2009 19:14:00 +0000

Radio Clock listens to radio time signals from your radio and corrects the time on your PC clock. Radio Clock enables you to decode the time signals sent by various LF and HF radio stations in the standard frequency and time service. Radio Clock uses your PC to display the time code received from the radio station, using a suitable receiver, and compares it with the local time on your PC.

At present Radio Clock can decode the following time signals.

If you register Radio Clock, you can set it to correct your PC clock time automatically. To enjoy this extra feature, you can register Radio Clock here.

Radio Controlled Clock
On these pages, I will introduce a Radio Controlled Clock. But this clock works with Japanese radio clock system so the country out of Japan can not use this equipment just as it is. Please arrange in the system in your country by yourself referring to the contents to carry on these pages.

Pictures Radio Controlled Clock and Schematic

See more: Infrared Light Photo-Detector - Dynamic Metal Detector

Simple Metal Detector

noreply@blogger.com (Quick Zone) — Sun, 05 Apr 2009 22:40:00 +0000

It's a simple metal detector design that has the quite good characteristics. the principle of operation which one differs from the classic schemes (BFO, transmit-receive known as "two-boxes" metal detector, inductive).

The dynamic mode is used to find targets in interference environment. There is known from theory of signal filtration that if signal shape is determined we can construct optimal filter - the best one for extracting the signal with maximum signal/noise ratio. This filter is known as optimal matched filter. In our device we realized digital optimal matched filter as part of microcontroller software. The filter parameters are optimized for effective ferro- and nonferro targets detection on 0.5-1.0 m/s velocity of sensor.

Features of the Metal Detector:
Power supply .............................4.5-6V;
DC consumption .......................15 mA;
Indication ...................................sound + 8 LEDs;
Modes ........................................static or dynamic;
Discrimination.............................ferro/non-ferro.

Metal Detector Schematic, Layout and PCB

Switches controled (versions V1.9 and V2.0 of firmware):
S0: reset device;
S1: reserved;
S2: on - threshold hight, off - threshold low;
S3: measuring time on - 30ms, off - 120ms;
S4: selftuning on/off (in dynamic mode only);
S5: mode on - static, off - dynamic.

Metal Detector Coil Design

Approx. 100 curls 200 mm in diameter. Cupper wire in isolation 0,35 mm diameter

Source : Metal Detector
See More: Infrared Light Photo-Detector

Car Parking Aid Sensor

noreply@blogger.com (Quick Zone) — Sat, 22 Nov 2008 11:04:00 +0000

This Sensor circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when approaching too close to the wall.

All distances of the sensor mentioned before can vary in this operation , depending on infra-red transmitting and receiving LEDs used and are mostly affected by the color of the reflecting surface. Black surfaces lower greatly the device sensitivity. Obviously, you can use this circuit in other applications like liquids level detection, proximity devices etc.

Source: Car Parking Aid Sensor

See more : Photocell Detector

Smoke Detector for Fire Alarm

noreply@blogger.com (Quick Zone) — Thu, 20 Nov 2008 16:29:00 +0000

Smoke detector is typically used in advanced alarm systems. Most of these devices for professional use gas-detectors, ionization chambers or radioactive elements as sensors. In this circuit, we are not using any component of this complex. Instead, we use two LDR and a LED.

LM1801 special purpose IC, which is specially designed for smoke detector, gives us build this circuit using the minimum number of components. It includes an internal Zener block, two outputs reference voltage, a voltage comparator, fixing the diodes and a transistor output 500mA.

The smoke detector circuit is connected to the network directly. D1 rectifies the source, and R7 is reduced to the level that the circuit can operate. Capacitor C2 and zener diode voltage stabilizes within the IC regulates it.

Two identical LDRs are connected in bridge type for this connection prevents the circuit from temperature changes and the effects of aging.

R13 LDR and LED should be positioned so that the smoke particles to reduce the fall of light on the LDR and change its resistance. On the other hand, R12 LDR and LED must be placed next to and no air movement occurs. The best way to do this, place R12 and LED in a separate box. Thus, the smoke will not affect R12, and its resistance will remain the same.

When the comparator detects the voltage difference between two LDRs it triggers transistor Th1 and following the start of the alarm. P1 is the calibration potentiometer. Hp1 generates an alarm sounds. Circuit includes an alarm output to drive additional external alarm system.

PIC Controlled Alarm Clock

noreply@blogger.com (Quick Zone) — Tue, 18 Nov 2008 07:47:00 +0000

Here's a alarm clock circuit based on PIC Controlled. Two circuit boards put together a simple PIC based design comprising of two interlinked vero-board cards. The larger of the two circuit boards holds the 5V power regulator, the display processor (a PIC 16F74), the real time clock (Dallas DS1307), 3V backup battery and buzzer. See the schematic below for detail.

The PIC board looked like this before fitting the ICs and LED/switch wire connections. It is also missing the 1Hz signal, I2C clock and I2C data connections between the PIC and RTC chips. I used a 4MHz resonator with built in load capacitors instead of the crystal and separate capacitors shown on the schematic. Also I added one more link wire after taking this photo to connect GND to -ve terminal of the backup battery. (The copper tracks run left-to-right on this board with cuts between the IC pins and in a couple of other strategic places.

The PIC microcontroller is programmed to read the real-time clock using I2C serial communication several times a second and update the display. It does no time keeping itself. Even the pulsing central pair of LEDs are driven by the real time clock (by means of a 1Hz output signal) and which is read by the PIC.

The PIC performs two other functions; it compares the time against the alarm settings to determine when it should go off and also handles time, date and alarm setting. The 16F74 has no EEPROM of its own so all the settings are stored in the DS1307 and read at power-on-reset. I was planning to mount connectors on the board for all the switch and display wires but in the end there wasn't enough room so I soldered the wires directly

I ordered a 16F74 microcontroller from Farnell because it had more than enough I/O pins and supported I2C on chip. After I received the chip and read the small print in the data sheet I discovered that the SSP module was only really suitable for an I2C slave. What I really needed was a MSSP module. So my code disables the SSP module and generates the I2C master clock and data signals (on the RC3/SCL and RC4/SDA pins) using a 'bit-banged' approach.

A smaller circuit board holds all the display LEDs and sits above the base board on plastic spacers.

The following ZIP contains all the PIC assembler need to program the alarm clock. The code is in two pieces: one project builds a library of PIC routines (including start power up modules) and another contains the clock specific code. Build the library first.

Source Code ZIP (30.6Kb)

Source: PIC Controlled Alarm Clock

See more : CdS Photocell Detector

Simple Home Alarm Circuit

noreply@blogger.com (Quick Zone) — Sat, 15 Nov 2008 04:43:00 +0000

Here's a simple home alarm circuit is for those who are eager to know the concept of home security system. It consists of three 555 timers gets the input from a contact that could be connected to a motion detector or any momentary contact that monitors a certain process. Once the contact is momentarily closed, the first timer which is configured as a monostable output will output a high pulse with a duration up to a maximum of 220 seconds.

This output is fed into the second timer which is configured as an astable 1Hz square wave generator. The output of this second timer is then fed into the third timer to control its frequency modulation. This frequency modulation will then power a speaker and generate a siren tone similar to the police siren.

The first timer U1 is configured as a monostable timer with a variable timing of up to a maximum of 220 seconds. The timing can be changed by adjusting the VR1 1M ohm potentiometer. If you need to further increase the timing, the electrolytic capacitor E1 can be changed to a larger value. Once the contact CT is momentarily closed, a pulse will be generated at the output pin 3 of U1.

U1 is then feed into pin 4 RESET of both U2 and U3 timers causing both timers to start their astable mode operations. U2 is configured as a square wave close to 1 Hz astable oscillator by fixing the values of E3, R2 and R3.

f = 1.44/[(R2 + 2R3)(E3)]

= 1.44/[(10 + 2*82)(10)] Hz

= 0.8 Hz

The output of U2 timer is used to feed the control voltage of the U3 timer through resistor R6 where it is subjected to frequency modulation. This frequency modulation will generate a tone similar to the police siren. The frequency of this tone generator can be varied by changing the value of potentiometer VR2. When set to its maximum value of 220k ohm, it will have a tone frequency of approximately 320 Hz. The output of U2 is used to drive a power transistor which in turn drive an 8 ohm speaker. Diode D2 is used to prevent the damage of transistor Q1 due to the back emf generated by the speaker during the ON/OFF driving of the speaker.

Parts List of the home alarm circuit

See more: Photo Transistor Detector

Automatic Intruder Burglar Alarm

noreply@blogger.com (Quick Zone) — Fri, 14 Nov 2008 02:10:00 +0000

This is a burglar alarm circuit written by Ron J. Its features include automatic Exit and Entry delays and a timed Bell/Siren Cut-Off. It's designed to be used with the usual types of normally-closed input devices such as - magnetic reed contacts - micro switches - foil tape - and PIRs. But it can be Easily Modified to accept normally-open triggering devices - such as pressure mats.

Hot It works
This intruder burglar alarm is easy to use. First check that the building is secure and that the green LED is lit. Then move SW1 to the "set" position. The red LED will light. You now have about 30 seconds to leave the building. When you return and open the door - the Buzzer will sound. You then have about 30 seconds to move SW1 to the "off" position. If you fail to do so - the relay will energize and the Siren will sound.

While at least one of the switches in the normally-closed loop remains open - the Siren will continue to sound. However, about 15-minutes after the loop has been restored - the relay will de-energize - the Siren will Cut-Off - and the alarm will Reset. Of course, you can turn the Siren off at any time by moving SW1 to the "off" position.

Source:Automatic Intruder Burglar Alarm

See more: Phototransistor Detector

Xenon Lamp Flash Detector

noreply@blogger.com (Quick Zone) — Fri, 26 Sep 2008 20:31:00 +0000

This circuit is xenon lamp flash detector. It has a very low standby current requirement yet has very high sensitivity toward the light flashes from a xenon lamp. When connected to a flip/flop it can serve as an on on/off controller.

Souce: Xenon Lamp Flash Detector

See more: Phototransistor Detector

Infrared Gate Sensor

noreply@blogger.com (Quick Zone) — Fri, 26 Sep 2008 20:30:00 +0000

Circuit is Infrared gate sensor. It's an infrared gate with two sensors planned to use in the wall in the way behind a door. It can be applied in a toilet to keep track of that someone is inside exceeding a certain amount of time. After that time elapsed, the circuit triggers the digital output wich can turn on a ventillator. The time period the output is turned on can be separately controlled by a second timer.

If you plan to build this gate sensor circuit, beware that you may have lots of difficulties though the schematic may seem simple. The construction of the circuit requires some amount of equipment like an oscilloscope and a DVM, too. Without them, the device will do weird things you wouldn't expect, and even if it is correctly put together, you must adjust it with care both mechanically in its final place and electronically with the help of an oscilloscope. Only if you want to span about less than 20-30 inches with the infra diodes can forget about this calibration. Alternatively you can take ideas from this construction.

Source: Infrared Gate Sensor
See More : Audio Detector Circuit

Biscuit Tin Alarm

noreply@blogger.com (Quick Zone) — Tue, 23 Sep 2008 17:56:00 +0000

Someone is stealing the biscuits! Your mission, should you choose to accept it, is to design a circuit which will give an audible alarm as soon as the biscuit tin is opened. The circuit provides a delay of around 10 seconds when the power supply is first connected during which the circuit can be placed in the tin. After this, if the LDR is exposed to light the alarm is triggered and remains ON, producing a penetrating high pitched sound until the power is disconnected.

Prototype board testing leads eventually to a complete circuit for the device being developed. You can continue to make small alterations until the circuit behaves in the way you want.

The sensor detects the opening of the tin. The output of the sensor triggers the latch so that its output goes HIGH. The reset subsystem provides some way of silencing the alarm.

Source : Biscuit Tin alarm
See More : Audio Detector Circuit

UltraSonic Radar

noreply@blogger.com (Quick Zone) — Tue, 12 Aug 2008 06:08:00 +0000

This is a ultrasonic radar project with many practical applications in security and alarm systems for homes, shops and cars. It consists of a set of ultrasonic receiver and transmitter which operate at the same frequency. When something moves in the area covered by the circuit the circuit’s fine balance is disturbed and the alarm is triggered. The circuit is very sensitive and can be adjusted to reset itself automatically or to stay triggered till it is reset manually after an alarm.

Adjustments
This kit does not need any adjustments, if you follow the building instructions.

Warning
If they are used as part of a larger assembly and any damage is caused, our company bears no responsibility.

While using electrical parts, handle power supply and equipment with great care, following safety standards as described by international specs and regulations.

If it does not work
Check your work for possible dry joints, bridges across adjacent tracks or soldering flux residues that usually cause problems. Check again all the external connections to and from the circuit to see if there is a mistake there.

See that there are no components missing or inserted in the wrong places.
Make sure that all the polarised components have been soldered the right way round. Make sure that the supply has the correct voltage and is connected the right way round to your circuit. Check your project for faulty or damaged components.

If everything checks and your project still fails to work, please contact your retailer and the Smart Kit Service will repair it for you.

Parts List
R1 = 180 KOhm C1, 6 = 10uF/16V TR1, 2, 3 = BC547 , BC548
R2 = 12 KOhm C2 = 47uF/16V P1 = 10 KOhm trimmer
R3, 8 = 47 KOhm C3 = 4,7 pF P2 = 47 KOhm trimmer
R4 = 3,9 KOhm C4, 7 = 1 nF IC1, 2 = 741 OP-AMP
R5, 6, 16 = 10 KOhm C5 = 10nF IC3 = 4093 C-MOS
R7, 10, 12, 14, 17 = 100 KΩ C8, 11 = 4,7 uF/16V R = TRANSDUCER 40KHz
R9, 11 = 1 MOhm C9 = 22uF/16V T = TRANSDUCER 40KHz
R13, 15 = 3,3 KOhm C10 = 100 nF D1, 2, 3, 4 = 1N4148
C12 = 2,2 uF/16V
C13 = 3,3nF
C14 = 47nF

Source: UltraSonic Radar
See More : Audio Detector

Bat Detector Circuit

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 22:51:00 +0000

This Bat Detector Circuit is authored by Chris Eve. Basic tests with a variety of salvaged electret microphones all showed good response to 50kHz and beyond, the smaller the unit the better the response. My tests indicate that a small electret microphone has at least some response to 100kHz and that this response is reasonably "flat" to at least 50kHz.

The microphone I use is approximately 6mm in diameter and can be mounted within the body of a 3.5mm jack plug. Having the microphone socketed rather than fixed within the detector case is optional, but gives further opportunity to experiment with uni-directional or "Pressure Zone" modules (see below), or other microphones mounted remotely from the electronics.

This bat detector circuit to have better sensitivity, both in distance to a visible bat and in audio frequency, than some other published circuits using a 40kHz transducer with 4000x gain amplification, though the 40kHz transducer I used for the comparison may have a bearing on these results.

The high-pass filter is included purely to help eliminate the circuit being triggered by ambient noise. The filter is a 4-pole Chebychev with a very steep roll-off below 15kHz. There is virtually zero response at 10kHz and below. This type of circuit relies on the wanted signal being loud enough to trigger the CMOS counter, so the less unwanted signal that reaches the circuit the better. Whilst any of the basic circuits based around a 40kHz transducer will perform adequately for the detection of bats calling within that frequency range, which includes many of the more common species, this circuit will give much better indication of the presence of less-common bats that call at lower frequencies, around 20kHz, as well, hopefully, those at somewhat higher frequencies.

When used at dusk, when individual bats are still visible, pointing a unidirectional microphone at a solitary bat indicates a usable range of at least 100ft (30m). Bats actually call very loudly indeed ... it's probably a good job we cannot hear them, else they would keep us awake!

This circuit was built in a metal box, because that was what I had to hand, using point-to-point wiring on a ground-plane. Perforated strip-board should be perfectly adequate and probably a lot easier to fault-find should you make a mistake. I do not have nor intend to produce a pcb layout, so please do not ask for one, though if you should feel the need to produce one and have the inclination to share it I would be only too willing to include it (or a link to it) on this page. The circuit may be more susceptable to interference from electronic sources if built in a plastic container. Current consumption is around 15mA with no audio output, so a PP3 battery should last for several evenings unless you have got a lot of bats in your area. For regular or extended use, rechargeable batteries or an external power source would make sense. Note that the LM386 has an absolute maximum voltage of 15v (12v recommended), but the rest of the circuit is OK to 15v. Also be aware, if tempted to use a regulated supply incorporating a 78xx series regulator, that these do generate a lot of noise, so extra filtering could be necessary, especially on the microphone supply. Component choice for the high-pass filter section is critical for good results, close-tolerance low-noise resistors and capacitors should be used to achieve the expected performance. Similar low-noise components should also be used in the rest of the circuit, (no carbon resistors!), though the tolerances are less critical elsewhere.

Having the microphone and loudspeaker both mounted on/in the detector itself can result in unwanted feedback limiting the volume the speaker can be used at. With the microphone mounted on the detector, simply handling the unit can cause audio output, though this can be reduced to a minimum if the unit is held firmly and moved gently. Remote mounting of the speaker and/or microphone, the use of a uni-directional microphone module (also helpful to determine where the bat is or for listening to an individual bat), or at least having the speaker facing away from the microphone, all help reduce/eliminate feedback, making it easier to share the experience with others.

Source: Bat Detector Circuit
See more : Oxygen Sensor

Lie Detector Circuit #2

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 22:23:00 +0000

This lie detector circuit can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as the ones the professionals use, but it works. It works by measuring skin resistance, which goes down when you lie.

Parts List:

R1 - 33K 1/4W Resistor
R2 - 5K Pot
R3 - 1.5K 1/4W Resistor
C1 - 1uF 16V Electrolytic Capacitor
Q1 - 2N3565 NPN Transistor
M1 - 0-1 mA Analog Meter
MISC - Case, Wire, Electrodes (See Notes)

Notes:

The electrodes can be alligator clips (although they can be painful), electrode pads (like the type they use in the hospital), or just wires and tape.
To use the circuit, attach the electrodes to the back of the subjects hand, about 1 inch apart. Then, adjust the meter for a reading of 0. Ask the questions. You know the subject is lying when the meter changes.

Source: Lie Detector circuit
See more : Oxygen Sensor Simulator

Lie Detector Circuit

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 22:17:00 +0000

This detector circuit is for detecting a Lie. The lie detector circuit diagram consists of three transistors, a capacitor, two lights or LEDs, five resistors, and a variable resistor.

This Lie Detector circuit is based on the fact that a person's skin resistance changes when they sweat (sweating because they're lying). Dry skin has a resistance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more.

Resistors R1 and R2 form a voltage divider. They have resistances of 1 000 000 ohms (1 mega ohms) and, because their values are equal, the voltage at the upper probe wire is half the battery voltage (about 4.5 volts).

A person holding the probe wires will change the voltage at the upper probe wire depending on their skin resistance. The skin resistance is in parallel with R2 and, because it is likely to be similar to or smaller than R2, the voltage at the probe wire will fall as skin resistance falls.

Capacitor C1 functions as a smoothing capacitor and removes the 50Hz induced mains hum that is found on a person's body.

TR1 and R3 form a buffer circuit (called an emitter-follower). The voltage at the emitter of TR1 follows the voltage at the probe wire and is now able to drive transistor TR2.

Transistors TR1 and TR2 act as a voltage comparator. If the voltage at the base of TR2 is higher than at the base of TR3 then the green LED (L1) will come on. If the reverse is true then the red LED (L2) will light.

To test the Lie Detector hold the probe wires. Adjust VR1 until the green LED is just on and the red LED is just off. This is the point at which the voltage at the base of TR2 is just greater than at the base of TR3. Now use moist fingers to hold the probes. This lowers the skin resistance and causes the voltage at the base of TR2 to fall. The voltage at the base of TR3 is now greater and the red LED comes on.

How to Use the Lie Detector

The Lie Detector needs tuning before it can be used, and it needs tuning for every person that uses it as everyone has slightly different skin.

Touch the two probe wires against the palm of your (dry) hand, such that the metal ends are a couple of centimeters apart (the metal ends must not touch each other). Adjust the tuning control (VR1) until the red light (FALSE) just goes out. The Lie Detector is now tuned for your skin. If you lick your palm and touch the wires against it again, the red light should come on brightly.

You should now understand how to use the Lie Detector to detect a real lie. Touch the two probe wires against the palm of the subject's hand and adjust the tuning control as before until the red light just goes out. When the subject tells a lie, and begins to sweat, the red light will get brighter.

It must be emphasized that the Lie Detector won't detect every lie, as it is really only a sweat detector. It only detects lies that have consequences to being told, lies that cause the subject to sweat (with fear). Pretend or 'joke' lies won't have any effect.

The Lie Detector has a number of other uses, detailed below, and it could perhaps more accurately be described as an 'Experiment Machine'.

Use lie detector to test the conductivity of the human body. Get a group of people to hold hands in a circle with the two probes of the Lie Detector as part of the circle. See how many bodies the current will flow through to make the red LED light.
Testing the conductivity of objects. For example, metals, plastics, wood, hair, the lead of a pencil. If a material is conductive then touching the lie detector probe wires against it will make the red LED light.
Determining whether a houseplant needs watering. Touch the lie detector probe wires against the soil. If the green LED stays on, the plant needs watering. If the red LED comes on, the soil is sufficiently moist.
Determining whether a cake is cooked. Press the lie detector probe wires into the surface of the cake. If the red LED comes on then the cake is still moist and needs further cooking

Source: Lie Detector Circuit
See more : Oxygen Sensor Simulator

Infrared Light Photo-Detector Circuit

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 22:07:00 +0000

This is a basic infrared light photo detector circuit. In this circuit the light falling on the phototransistor will be from an Infrared Light Emitting Diode (IrLED) but otherwise it is the same as the phototransistor circuit shown above.

When the light falling on the phototransistor (Q1) is blocked, its conductance will decrease and the voltage across Q1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit.

Source: Infrared Light Photo-Detector
See More : Pressure Sensor

Basic CdS Photocell Detector

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 22:01:00 +0000

This is a Basic Cadmium Sulfide (Cds) Photocell Detector circuit. In this circuit, when the light falling on the photocell (PC 1) is blocked, its resistance will increase and the voltage across PC 1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit.

Due to wide variations in CdS photocells it is usually best to install the cell and then measure its resistance under normal lighting conditions. A resistor with a value that is approximately 3 to 5 times the measured resistance of the cell is then selected for R1. For example; If the cell resistance is measured at 400 ohms then a 1200 to 2200 ohms resistor would be used.

Increasing the value of R1 will cause the sensitivity of the sensor to decrease. This may be necessary when the light falling on the cell is not very strong or shadows can affect the photocell.

This Photocell Detector circuit can be adapted for use in dark areas by placing a small light above the photocell.

Source: Basic CdS Phocell Detector
See More : Tire Pressure Sensor

Basic Phototransistor Detector

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 21:55:00 +0000

This is a Phototransistor Detector circuit. In this circuit, when the light falling on the phototransistor (Q1) is blocked, its conductance will decrease and the voltage across Q1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit.

The only critical part of this circuit is the value of resistor R1 which in most cases can be 470K ohms but may have to be increase if the room is dark or decreased if the room is well lit.

Increasing the value of R1 will cause the sensitivity of the sensor to decrease. This may be necessary when the light falling on the cell is not very strong or shadows can affect the phototransistor.

There are a number of phototransistors sizes and case styles. The smaller cases will be easier to hide but connecting wires may be more difficult.

Visit Basic Phototransistor Detector See More : Tire Pressure Sensor

Audio Detector Circuit

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 21:43:00 +0000

This electronic detector circuit is to do audio detection. The circuit is for detecting one of those 3.6khz (approx) beepers from Radio Shack. The component used is a single IC (LM324 quad op amp) and a handful of parts.

Notes:

The capacitor and resistor on the output of the peak detector are selected to give a reasonable decay time. I.e. so a single pulse doesn't stretch out and be miss-interpreted as an audio signal. I think I sample the output at 100ms intervals and signal a valid sound if three consecutive samples are true.
The only critical parts are the trimmer, capacitors and the 560 ohm resistor in the band pass filter. The diode is not critical: any small diode will do fine.
The trimmer is used to set the center frequency. I just run the beeper and adjust for the strongest output signal.
It uses a condenser mic, surplus. Probably any computer microphone will do. The 4.7K resistor is a typical load for those things.

Authorized by: Larry Barello, See more: Pressure Monitoring.

Oxygen Sensor Simulator

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 21:26:00 +0000

This circuit is an oxygen sensor for car. The oxygen sensor simulator as built on a protoboard. Note the cigarette lighter plug used for power source. The adjustment knob is at the left, and the switch is on the right. The red indicator LED is in the middle. Only use red, because the voltage drop of the LED is part of the circuit!

The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate. The big "V" is a digital voltmeter (not shown in the pictures). Using a smaller value for C1, perhaps 4.7 uF, will make the circuit oscillate faster and might be more like a real oxygen sensor (a new sensor switches more often than an old one).

The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate. The big "V" is a digital voltmeter (not shown in the pictures). Using a smaller value for C1, perhaps 4.7 uF, will make the circuit oscillate faster and might be more like a real oxygen sensor (a new sensor switches more often than an old one).

The schematic diagram of the adapter cable and oxygen sensor. Note the heater is shown as a resistor, mine measured about 7 ohms.

Source: Oxygen Sensor Simulator
See more: Tire Pressure Monitoring.

Infineon SP35 Tire Pressure Sensor

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 18:38:00 +0000

The SP35 is a highly integrated device which performs all necessary functions of a TPM module in the wheel for high-volume applications. The device contains the sensing element, the micro controller, the LF receiver and the transmitter in one package.

The Sensor design is based upon Infineon’s patented bulk micro-machined sensing technology which allows highly reliable measurements in harsh environments. The SP35 measures pressure, temperature, supply voltage and radial acceleration. The device is offered with a pressure range of 100–450 kPa.

The Infineon SP35 Tire Pressure Sensor incorporates all the major active functions of wheel-mounted TPMS in a single package. The integrated device, mounted on a printed circuit board with a battery and antenna, enables tier-one suppliers to meet the requirements of the new regulations. Its single package integrates an MEMS pressure sensor, acceleration sensor and temperature sensor with an 8-bit controller and wireless communication module. It eliminates the need for separate communication chips, thus reducing complexity and reportedly cutting costs by about 10 percent.

Major Functional Blocks of SP35 Tyre Pressure Sensor

Pressure sensor
Radial acceleration sensor
Temperature sensor
Battery voltage sensor
8051 compatible microcontroller
6 kByte onchip FLASH memory
256 byte RAM
Advanced power control/wake-up system to minimize battery consumption
RF transmitter for 315 and 434 MHz
Selectable output power 5 or 8 dBm
LF receiver for 125 kHz
P-DSOSP-14-6 Package

Download Infineon SP35 Tire Pressure Sensor Application Note

Source: Infineon SP35 Tire Pressure Sensor See more: Tire Pressure Monitoring.

Tire Pressure Monitoring (TPM) System from Microchip

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 17:35:00 +0000

This document explains a typical tire pressure monitoring (TPM) system specifically intended for automotive use. It serves as a reference to design a real-world system based on various Microchip products. A TPM system primarily monitors the internal temperature and pressure of an automobile's tire. There is a variety of system approaches to follow; although this one is a rather comprehensive auto-location system.

An auto-location system can dynamically detect the position of a specific sensor, which is useful when tires are rotated. The heart of the TPM system is the Sensor/Transmitter (S/TX) device and it is based on Microchip's rfPIC12F675.

SYSTEM COMPONENTS
The TPM system consists of the following major component.
• Sensor/Transmitter Device
• RF Receiver Module
• Low Frequency (LF) Commander Device
• Control Unit
• Pressure Vessel (Tire)

Download Tire Pressure Monitoring System (TPMS) Application Note from Microchip

Authors:
Ruan Lourens, Microchip Technology Inc.
Curtis Kell, Kell Laboratories

Privacy Policy

noreply@blogger.com (Quick Zone) — Mon, 11 Aug 2008 17:30:00 +0000

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