Sensors Detectors Circuits
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Null detector uses simple LED readout to indicate if test resistor R* is below, equal to, or greater than test resistance Rref. IfR* = Rref, the 741 output sits at midpoint value of 4 volts and LED A lights.. -
Sensing circuit detects either steady or fluctuating air flows. The heart of the circuit is a Radio Shack piezo buzzer (P/N 273-060) and an LM324 quad op amp. (Red wire from the piezo element connects to capacitor CI, and the black wire to ground) When a.... -
The MC1596/MC1496 makes an excellent SSB product detector. This product detector has a sensitivity of 3 microvolts and a dynamic range of 90 dB when operating at an intermediate frequency of S MHz. The detector is broadband for the entire high frequency.... -
The values of Rl, R2, and D1 are selected for the voltage applied. Using a 12-volt battery, Rl = 10 K, R2 = 5 K and D1 is a 5-volt zener diode, or a string of forward-biased silicon rectifiers equaling about 5 volts. Transistor Ql is a general-purpose UJT.... -
The circuit has negative feedback only for positive signals. The inverting input can only get some feedback when diode Dl is forward biased and only occurs when the input is positive. With a positive input signal, the output of the op amp rises until the.... -
The circuit will provide a dc output equal to the rms value of the input. Accuracy is typically 2% for a 20 Vpp input signal from 50 Hz to 100 kHz, although it"s usable to about 500 kHz. The lower frequency is limited by the size of the filter capacitor.. -
Detector uses three sections of an L144 and a CMOS NAND gate to make a very low power voltage monitor. The 1 MO resistors Rl, R2, R3, and R4 translate the bipolar ±10 V swing of the op amps to a 0 to 10 V swing acceptable to the ground-referenced CMOS logic.. -
The detector circuit is made up a two-amplifier multiple feedback bandpass filter followed by an ac-to-dc detector section and a Schmitt Trigger. The bandpass filter (with a Q of greater than 100) passes only 5Q0 Hz inputs whch are in turn rectified by Dl.... -
The timing cycle is continuously reset by the input pulse train. A change in frequency, or a missing pulse, allows completion of the timing cycle which causes a change in the output level. For this application, the time delay should be set to be slightly.... -
Fiber Optic applications require analog drivers and receivers operating in the megahertz region. This complete analog transmission system is suitable for optical communication applications up to 3 MHz. The transmitter LED is normally biased at 50 mA.... -
This circuit can detect smoke and a number of gases (CO, CO2, methane, coal gas and others) with a 10 ppm sensitivity. It uses a heated surface semiconductor sensor. Detection occurs when the gas concentration increase causes a decrease of the sensor element.... -
Battery-operated, ionization chamber smoke detector includes a circuit to generate a unique alarm when the battery reaches the end of its useful life. The circuit uses the MCMOS MC14572 for two alarm oscillators (smoke and low battery).. -
The sensor circuit is adaptable to different liquids and sensors. The constant-current source drives current through the sensing probe and a fixed resistor.. -
Use this circuit to keep the fluid level of a liquid between two fixed points. Two modes, for filling or emptying are possible by simple reversing the contact connections of Kl. The loads can be either electric motors or solenoid operated valves, operating.... -
The circuit draws so little current that the shelf-line of the battery is the limiting factor. The only current drawn is the leakage of the transistor. The circuit is shown in the form of a water level alarm but by using different forms of probe can act as a.... -
The alarm is built around two audio oscillators, each using two NAND gates. The detection oscillator is gated on by a pair of remote probes. One of the probes is connected to the battery supply, the other to the input of one of the gates. When water flows.... -
The circuit uses four NAND gates of a 4011 package. In each oscillator, while one gate is configured as a straightforward inverter, the other has one input that can act as a control input. Oscillator action is inhibited if this input is held low. The first.... -
The unit consists of a sensor, timer, and electric water pump. The sensor is embedded in the soil, and when dry, the electronics operate the water pump for a preset time. The circuit is composed of a level sensitive Schmitt trigger, variable time monostable,.... -
With SI open the circuit functions as a doorbell. With SI closed, rain falling on the sensor will turn on Ql, triggering Q2 and the thyristor and activating the bell, R4 provides the holding for the thyristor while Dl prevents any damage to the thyristor.... -
A commercial diode is the detector in this highly accurate radiation monitor. The lowdrift FET-input op amp amplifies detector current to a usable level, and the chopper-stabilized amplifier then provides additional gain while minimizing any error caused by.... -
A sensitive radiation monitor may be simply constructed with a large-area photodiode and a quad operational amplifier. Replacing the glass window of the diode with Mylar foil will shield it from light and infrared energy, enabling it to respond to such.... -
The Geiger tube needs a high voltage supply which consists of Ql and its associated components. The transformer is connected in reverse; the secondary is connected as a Hartley oscillator, and Rl provides base bias. Dl, D2, C4, and C5 comprise a voltage.... -
The LED predriver output pulses an external transistor which in turn, switches on the infrared light emitting diode at a very low duty cycle. The desired IR LED pulse period is determined by the value of the external timing resistor. The Smoke Sensitivity is.... -
This detector is useful in sine wave squaring circuits and A/D converters. The positive input may either be grounded or con-output nected a nulling voltage which cancels input offsets and enables accuracy to within microvolts of ground.. -
A window detector is a specialized comparator circuit designed to detect the presence of a voltage between two prescribed limits; that is, within a voltage window. This circuit is implemented by logically combining the outputs of two single-ended.... -
The primary advantage of this circuit, when compared to other comparators, is its ability to latch after the input has reached a predetermined threshold level. When the input exceeds the threshold level, the LM311N output increases. This transition enables.... -
A quad comparator forms the basis of a frequency detector that is faster and less expensive than more complex versions designed around frequency-to-voltage converter chips. Positive feedback through a 5MO resistor allows the circuit to resolve changes as.... -
When the upper or lower limit is exceeded, the LED lights up. Positive feedback to one of the nulling terminals creates 5 to 20 p,V of hysteresis on both amplifiers. This feedback changes to offset voltage of the LT1002 by less than 5 p,V. .. -
This window comparator generates an output pulse for each event that occurs within a specified window. That is, each output pulse signifies an input voltage pulse or level change that exceeds VREFLOW. but not VREFHIGH· The monostable multivibrators, IC2A.... -
When operated as an open loop without compensation, the HA-2400 becomes a comparator with four selectable input channels. The clamping network at the compensation pin limits the output voltage to allow DTLor TTL digital circuits to be driven with a fanout.... -
ICl and IC2 form an inverting half-wave precision-rectifier/peak-detector circuit. Negative input-signal, swings with peaks larger than the voltage on Cl, cause this capacitor to charge to the new peak voltage. The capacitor holds this voltage until a.... -
Analog peak detection is accomplished hy repeatedly measuring the input signal with an a/d converter and comparing the current reading with the previous reading. If the current reading is larger than the previous, the current reading is stored in the latch....
New Circuits
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This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of.... -
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is.... -
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to.... -
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This.... -
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the.... -
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,.... -
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the.... -
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power.... -
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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