Sensors Detectors Circuits
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This can be used to control entry on a Cat or Dog Door" NOTE: There may be some changes and improvements coming. However this circuit does work and you can build it as shown. The PCB Shown below is Available from me, or make it yourself. It Measures 2.75" by....
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A Simple design based on a CS209A IC that can give surprising results and draws very little current from a 9 volt battery. It worked good on the Bench, But not so good outside for general metal detecting. But Definately a good design for detecting studs in a....
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Old TV tubes are used as cold cathode x-ray emitters in a simple apparatus developed by Bob Templeman of Chicago, Illinois. With selected beam power tubes of the type used in the high voltage section of TV receivers, the intensity is adequate to make x-rays....
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This circuit was formed to create a wireless alarm from a normal magnetic contact. By fixing the magnet to the leaf of a door, or swing of a drawer, it is easy to reveal the opening. To transmit the signal to a control anti-theft we modify the circuit of a....
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One of the unusual features of the out-of-production Programmable Drum Set was its use of touch switches for control. Like most touch switches, these detect the difference in the capacitance of a plate when it is being touched by a finger versus the....
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Ions are defined as electrically charged atoms. Positively charged ions have a deficiency of electrons, and negatively charged ions have a surplus of electrons. An ion can also be classified as an atom or molecule with an electrostatic charge. Another....
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This basic oscillator will detect the Earth magnetic field. The ferrite rod and coil are taken from an old Medium Wave receiver and a small magnet is glued at one end. Tune to a medium wave commercial station until you hear a beat note. Any movement of the....
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This is a rather sensitive circuit which will detect minute variations of a magnetic field, particularly the Earth magnetic field. The principle is based on an audio beat tone generated by two identical oscillators. These must be built in the same manner....
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This circuit is the electronic emulation of the I Ching, a form of divination originating in China. In the classical form, the response is obtained by the manipulation of 50 sticks or, more practically, by tossing 3 coins. The process must be repeated 6....
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The circuit will come handy when you have to follow the mains wires buried in the wall or even water pipes provided they are not too far away (2-4cm max). It will also detect a conversation on a telephone cable without actually touching it (for testing....
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This circuit gives out an alarm when its sensor is wetted by water.
A 555 astable multivibrator is used here which gives a tone of about 1kHz upon detecting water.
The sensor when wetted by water completes the circuit and makes the 555 oscillate at about....
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This circuit not only indicates the amount of water present in the overhead tank but also gives an alarm when the tank is full.
The circuit uses the widely available CD4066, bilateral switch CMOS IC to indicate the water level through LEDs.
When the water....
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Here is an interesting circuit for a magnetic proximity switch which can be used in various applications.
The magnetic proximity switch circuit, in principle, consists of a reed switch at its heart. When a magnet is brought in the vicinity of the sensor....
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Dew (condensed moisture) ad- versely affects the normal per- formance of sensitive electronic devices. A low-cost circuit described here can be used to switch off any gadget automatically in case of excessive humidity. At the heart of the circuit is an....
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Colour sensor is an interesting project for hobbyists. The cir- cuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colours); and black and white. The circuit is based on the fundamentals of optics....
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This simple circuit using a single transistor turns ON the relay when light falls on the LDR.
The potentiometer is adjusted for the required sensitivity.
The power supply is 6V.
Be careful about the impedance of the relay. Its impedance should not be less....
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This is a circuit thich I originally included in my book, 22 Tested Transistor Projects, published by Babani Press in 1976 (ISBN 0 900162 63 S). It is one I had great fun with. It uses the PUT Complimentary Feedback Pair as a sensitive detector of changing....
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It operates by PWM (Pulse Width Modulation) - well, actually by PFM - Pulse Frequency Modulation. At power up, C1 charges up via D1 and R1. R2 will conduct, pulling the base of the emitter follower, Tr2, up and feeding gate voltage to the MOSFET. Tr4.....
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This is a very simple circuit to interface a current loop sensor to an input which is designed for a voltage, such as that from a standard potentiometer. This page is technical so that interested persons can build the circuit themselves, but 4QD can also....
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These controllers have an inhibit input and the effect of shorting this down to ground is to turn down the internal demand speed. So with the battery current limiter fitted, the internal demand speed can only ramp up to a value which engages the limit. Some....
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This circuit will automatically switch on several mains-powered "slave" loads when a "master" load is turned on. For example, it will switch on the amplifier and CD player in a stereo system when the receiver is turned on. It works by sensing the current....
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This moisture detector with pump controller is built around the special purpose LM1830 IC. The LM1830 is designed to detect moisture by passing an AC current through a set of probes. An internal comparator compares the resistance of the probes to an internal....
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When the tank is cleaned the fish are removed and placed in a small amount of the tank water. The problem is that fish don’t like rapid temperature fluctuations. I guess a simple in tank or stick on thermometer would have done the trick but what is the fun....
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When the phototransistor is stroken by IR light it conducts and the voltage between the 1Mohm resistor(arbitrary) and the phototrans drops from VCC to lower values. When the voltage drops lower than VCC/3 the 555 is triggered and goes high (from 0 TO VCC).....
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The following circuit can be used to detect those annoying piezo whistles that one can get from Radio Shack. For the Trinity Home Fire Fighting Contest, additional points accrue when the robot is started by a sound similar to a fire alarm. The actual....
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The cooling is not only a PC using a small fan with an electronic commutator [1]. A special feature of these fans is that their removal is less dependent on the load. Indicators monitoring the DC component of current may therefore be very reliable.....
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The circuit on the right uses three bipolar transistors to accomplish the same result with the touch contact referenced to the negative or ground end of the supply. Since the base of a bipolar transistor draws current and the current gain is usually less....
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This circuit will detect AC line currents of about 250 mA or more without making any electrical connections to the line. Current is detected by passing one of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800....
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Here is a simple circuit based on 555 IC that generates a pulsed magnetic field. You may use this field for pulsed magnetic field therapy. Human body is influenced by natural magnetic fields such as Earth’s magnetic field, fields due to geomagnetic storms,....
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This is a schematic for a straightforward direct-conversion heterodyne detector, having a tuning range of about 10 kHz to 120 kHz. It has been optimised for the use of an electret microphone. The current consumption is very low at only 8 mA, which allows it....
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This circuit may look simple, but that`s because I made considerable effort to simplify the circuit. It requires only a small amount of components and it has low current consumption (15 mA). From the left to the right, this circuit consists of a tranducer, a....
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The lie detector presented here has been designed to detect skin resistance and to give visual indication, verified electronic project...