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A very simple heat detector alarm electronic project can be designed using the UM3561 sound generator circuit and some other common electronic parts . This heat detector electronic circuit project uses a complementary pair comprising npn and pnp transistor to detect heat Collector of T1 transistor is connected to the base of the T2 transistor , while the collector of T2 transistor is connected to RL1 relay T3 and T4 transistors connected in darlington configuration are used to amplify the audio signal from the UM3561 ic. When the temperature close to the T1 transistor is hot , the resistance to the emitter –collector goes low and it starts conducting . In same time T2 transistor conducts , because its base is connected to the collector of T1 transistor and the RL1 relay energized and switches on the siren which produce a fire engine alarm sound. This electronic circuit project must be powered from a 6 volts DC power supply , but the UM3561 IC is powered using a 3 volt zener diode , bec...

This is the Simple Light Detector Circuit Diagram. Variable resistor R1 adjusts the light threshold at which the circuit triggers. R1's value is chosen to match the photocells resistance at darkness. The circuit uses a CMOS 4001 IC. Gate U1a acts as the trigger, U1b and c form a latch. S1 resets the circuit. The output device may be a low power piezo buzzer.  Simple Light Detector Circuit Diagram   Author:   Mick Devine, UK

This is a simple cell phone detector circuit diagram , this is a pocket-size mobile transmission detector or sniffer can sense the presence of an activated mobile cellphone from a distance of one and-a-half meters. So it can be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorized video transmission. Sourced: EFY  Simple Cell Phone Detector Circuit Diagram  

This is the Simple Resistance ratio Detector Circuit Diagram.  Photoelectric control, temperature detection and moisture sensing require a circuit that can accurately detect a given resistance ratio. A simple technique that uses an op amp as a sensing element can provide 0,5% accuracy with low parts cost. The reed-relay contacts close when the resistance of the sensor Rp equals 47% of the standard Rs.   Resistance ratio Detector Circuit Diagram:   Adjusting either Rl or R2 provides a variable threshold; the threshold is controlled by varying R3. For the most part, the type of resistors used for Rl and R2 determines the accuracy and stability of the circuit. With metal-film resistors, less than 0.5% change in ratio sensing occurs over the commercial temperature range (0 to 70 C) with ac input variations from 105 to 135 V.

It is a very simple electronic Schematic Circuit Diagram of Pulse sequence detector Circuit. The resistor divider connected between Ql and Q2 supplies IH to Ql after input A triggers it.  Pulse Sequence Detector Circuit Diagram: It also prevents input from triggering Q2 until Ql conducts.Consequently, the first input pulse after input A is applied will supply current to RL.

Excellent Electronics Heterodyne Detector The bat ultrasounds are best up by the microphone SPKR1 and go through two stages of addition at Q1 and Q2. Separately, a tunable (R12) distinct abundance is produced by the LM567 oscillator U1. The LM567 is a accent decoder but actuality its ascribe is ashore and its voltage controlled oscillator is acclimated as a attention oscillator. The oscillator abundance is accustomed by f = 1/(1.1*C4*(R10 + R12)) = 1/(1.1*0.0022*10 -6 *(4.7 + [0-50])*10 3 ) = [88-7.5] khz The two signals are alloyed at Q3 to aftermath both a arresting in the audio ambit and college frequencies that are again filtered out. The actual audio arresting undergoes a aftermost date of controlled (R13) addition with the LM386 at U2 afore actuality accessible for achievement at AUDIO OUT. The ability antecedent is a simple 9V battery, so this apparatus is absolutely portable.

This simple circuit helps you sniff out RF radiation from your transmitter, improper joints, a broken wire or poor equipment with RF shielding. The tester is designed for the radio band amateur 2 meter (144-146 MHz in Europe). The instrument has a reading of 4-step LED and an audible alarm for high voltage radiation. The RF signal is received by an antenna and made to resonate by C1-L1. After rectification by the diode D1, the signal is fed to a two transistor Darlington amplifier HighGain, T2-T3. Assuming a 10-inch telescoping antenna using the RF level scale established for the LEDs is as follows: When all the LEDs light, the (optional) UM66 sound / melody generator chip (IC1) also operates and provides an audible alarm. By changing the zener diode values ​​of D2, D4, D6 and D8, the step size and duration of the instrument may change as needed. To operate in other bands of ham or PMR, simply change the network-L1 C1 resonance. For example, a transceiver 5 watt handheld equipped with ...

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 wi...

Here is a simple, low-cost 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 ectifier 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 photodetector 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 u...

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 disturbi...