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One type of metal detector is a type of beat frequency oscillator (BFO). The methods used in metal detectors in general are changing the characteristics of the oscillator when there are close to the metal sensor. The detector works based on the resonant frequency that has been set change when there is a metal object is located quite close to the search coil sensors. Tuning circuit (tuned circuit) should be a part of our oscillator circuit so that if approached by a metal coil sensor specific hence the output frequency of the oscillation circuit is about to change. Variation changes the output frequency depends on the frequency chosen. The selection of the higher frequency will cause the circuit sensitivity increases because the greater the frequency change. Stay if the selection frequency is too high then the practice will produce a system that is not sensitive. This is because the high frequency of most will not be reflected back but will be absorbed by the soil, building materials. M...

This metal detector circuit diagram is designed using on a transistor radio as an detector. L1 search coil of the metal detector must have 18 turns from a 0.65 mm enameled wire scrambled on a 4 inch diameter support . The C1 capacitor is a variable capacitor with a value of 365 pF, C2 is a 100pF silver mica capacitor , C3 is a 0.05 uF disc capacitor and the C4 is a 4.7 uF capacitor . Radio Metal Detector Circuit diagram The Q1 transistor can be RCA SK3011 npn transistor or equivalent type and all resistors need to be ½ watts . With the radio tuned to a weak station you must adjust the variable capacitor C1 until the locator oscillator beats against the received signal. If a metal is detected the inductance of the L1 coil is changed, changing the frequency of the locator oscillator’s, resulting a change in the beat tone radio .

SIMPLE HEAT SWITCH CIRCUIT Hello everyone, Here we are discussing about a Simple Heat sensing or detecting circuit. This circuit indicates you whenever it senses Temperature. The sensing is done by using a THERMISTOR of 110 ohms. The resistance of Thermistor reduces on increase in Temperature which makes the LED glow. The circuit is powered by a 6V battery. CIRCUIT DIAGRAM FOR HEAT DETECTOR Components used:- R1 THERMISTOR 110Ω R2 100Ω R3 3.3KΩ Q1 Bc548 NPN You can also Try Smoke Detector using 555 Timer

This proximity detector using an infrared detector (Fig. 1) can be used in various equipment like automatic door openers and burglar alarms. The circuit primarily consists of an infrared transmitter and an infrared receiver. Fig. 1: IR proximity detector The transmitter section consists of a 555 timer IC functioning in astable mode. It is wired as shown in the figure. The output from astable is fed to an infrared LED via resistor R4, which limits its operating current. This circuit provides a frequency output of 38 kHz at 50 per cent duty cycle, which is required for the infrared detector /receiver module. Siemens SFH5110-38 is a much better choice than SFH506-38. Siemens SFH5110-38 is turned on by a continuous frequency of 38 kHz with 50 per cent duty cycle, whereas SFH506 requires a burst frequency of 38k to sense. Hence, SFH5110-38 is used. The receiver section comprises an infrared receiver module, a 555 monostable multivibrator, and an LED indicator. Upon reception of infrared s...

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 m...

NE567  tone decoder / PLL IC. NE567 is a tone decoder IC from Philips. The IC has a built in PLL circuit with AM lock detection and an output driver circuit. The main function of NE567 is to drive a load (usually LED) when a frequency with in its detection band is available at the IC’s input. Center frequency of the input frequency band, output delay etc can be programmed using external components. The features of NE567 IC includes 0.01Hz to 500KHz frequency range, highly stable centre frequency, programmable bandwidth, high noise rejection, can sink 100mA at the output, highly immune to false triggering, externally adjustable VCO frequency etc. The common applications of NE567 are touch tone decoding, remote controls, ultrasonic controls, frequency monitoring etc. NE567 proximity detector circuit.   A simple proximity detector circuit using NE567 is shown here. Pin 8 is the output terminal of the internal output driver circuit inside the IC. This pin goes low when the input f...

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 F...

How to Build a High-Performance Interruption Detector Circuit Diagram . 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 ast...

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 ...

This Room Noise Detector Schematic circuit diagram 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,R1 _____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_____...

Having been affected by earth fault accidents,  the author put together this little circuit. It  consist of just three elements: the neon with its  original resistor for example, salvaged from  the switch on an AC power bar and a small  capacitor (class Y) salvaged from the electronics of a low-consumption lamp. A larger capacitance makes the neon glow brighter. All this  for no money at all. The neon lights only when there is an efficient Earth present. This works  well at the author’s home, with Live or Neutral either way round. In the Elektor laboratory based in The Netherlands, some concerns  were expressed as described in the June 2011  issue [1], as the circuit was sensitive to the relative positions of the Live and Neutral. So the  Earth fault detector can also be used as a Phase  detector, but probably in Belgium only. . The whole thing can easily be incorporated into a power socket; the author used a small transparent cove...

This circuit is based on a passive infrared (PIR) sensor, which automatically switches on a device when someone comes close to it. It can be used for detection of theft or an unauthorised person entering a restricted area or building. It can also turn on lights when someone approaches the area where it is installed. Applications of this circuit include security systems, corridor lights and bathroom lights, among others. Fig. 1: Circuit diagram of the motion detector Circuit and working The circuit diagram of the motion detector using NE555 timer is shown in Fig. 1. It is built around 230V AC primary to 9V, 300mA secondary transformer X1, bridge rectifier DB107 (BR1), 6V voltage regulator 7806 (IC1), timer NE555 (IC2) and a few other components. The 230V AC mains is stepped down to 9V, 300mA through step-down transformer X1. Secondary output of X1 goes to bridge rectifier BR1. Capacitor C1 filters the ripples and the rectified output is given to regulator 7806 (IC1). IC1 provides 6V reg...

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).  Simple Audio Peak Detector 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...

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. Bed Room Noise Detector Circuit Schematic  Room Noise Detector Circuit Diagram Parts: R1 = 10K R2 = 22K R3 = 22K R4 = 100K R5 = 56K R6 = 5.6K R7 = 560R R8 = 2.2K R9 = 56K R10 = 56K R11 = 1K R12 = 33K R13 = 330R C1 = 100nF-63V C2 = 10µF-25V C3 = 470µF-25V C4 = 47µF-25V D1 = 5mm. Red LED Q1 = BC327 B1 = 9V PP3 Battery SW1 = 2 poles 4 ways rotary switch IC1 = LM358 Low Power Dual Op-amp MIC1 = Miniature electret microphone Use: Place the small box cont...

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 c...

Description Egor! Come quick! A storm approaches! Here is a VLF receiver tuned to 300 kHz designed to detect the crackle of approaching lightning. A bright lamp flashes in sychrony with the lightning bolts indicating the proximity and intensity of the storm. Figure 1 shows the simple receiver which consists of a tuned amplifier driving a modified flasher circuit. The flasher is biased to not flash until a burst of RF energy, amplified by the 2N3904, is applied to the base of the 2N4403. The receiver standby current is about 350 microamps which is nothing at all to a couple of D cells, hardly denting the shelf life. Of course, the stormier it gets, the shorter the battery life.  Circuit Diagram For best effect, mount the lamp in an old-fashioned holder with an extra-large colored glass lense. Or construct your own fixture with a plate of textured colored glass behind a panel painted with black-crackle paint. Watch a few old science fiction movies for other ideas. A totally different...