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Light Detector – Circuit Schematic
Light Detector
The circuit"s threshold is set by resistor R2. When the intensity of the light falling on the LDR is lowered, resistance of ...
Optical Interruption Sensor – Circuit Schematic
Optical Interruption Sensor
Using only an 8-pin IC and a few discrete components, you can build the infrared optical interrupter. The NE567...
Proximity Detector – Circuit Schematic
Proximity Detector
In this proximity detector an NE567 tone decoder provides a signal of about 100 kHz that is fed to one sensor. The senso...
Relay Output Proximity Sensor – Circuit Schematic
Relay Output Proximity Sensor
Ql is used as an oscillator around 300 kHz. R9 is set so that the oscillator just begins to run. An object ne...
Ir Reflection Proximity Switch – Circuit Schematic
Ir Reflection Proximity Switch
IR radiation from LED2 (modulated by a 1-kHz wave) is keyed by Ul, and Ql is radiated. Reflected IR energy i...
Uhf Motion Detector – Circuit Schematic
Uhf Motion Detector
The UHF motion detector operates on the Doppler radar principle. Ql is an oscillator that creates a radiated signal. An...
Acoustic Doppler Motion Detector – Circuit Schematic
Acoustic Doppler Motion Detector
A high-frequency audio signal (15 to 25 kHz) generated by Ul is fed to buffer Ql and SPKR1. A portion is f...
Sensitive Low-Current-Drain Motion Detector – Circuit Schematic
Sensitive Low-Current-Drain Motion Detector
This highly sensitive movement detector is designed from bipolar transistors and draws a curren...
Diode Sensor For Lasers – Circuit Schematic
Diode Sensor For Lasers
Laser-receiver circuits must bias their avalanche photo diodes (APD) to achieve optimal gain. Unfortunately, an APD...
Latching Continuity Checker – Circuit Schematic
Latching Continuity Checker
This circuit detects brief shorts or opens. When S2 is in the up position, the circuit indicates if there is or...
Sensitive Continuity Checker – Circuit Schematic
Sensitive Continuity Checker
This continuity checker (built around an LM339 quad comparator with open-collector outputs) eliminates false r...
High-Gain Current Sensor – Circuit Schematic
High-Gain Current Sensor
A high-gain amplifier using a UA741 is used to sense relative voltage drop in a conductor, and therefore current i...
Hall-Sensor Current Monitor – Circuit Schematic
Hall-Sensor Current Monitor
The circuit uses a Hall-effect sensor, which consists of an IC that resides in a small gap in a flux-collector ...
Static Detector – Circuit Schematic
Static Detector
This circuit detects the presence of electrostatic fields by using an FET to alter the flash rate of two LEDs. The FET is i...
Low-Cost Barometer – Circuit Schematic
Low-Cost Barometer
Using Linear Technology LT1027 reference and LT1078 op amps, transducer T1 is fed with 1.5 mA. The pressure transducer f...
Infrared "People" Detector – Circuit Schematic
Infrared "People" Detector
This circuit uses an Amperex pyroelectric IR sensor, an LM324 op amp (configured as a high-gain amplifier in the...
Ir-Controlled Soldering Station – Circuit Schematic
Ir-Controlled Soldering Station
An IR-sensitive phototransistor is used to sense soldering-iron temperature. The phototransistor must see t...
Sound Sensor – Circuit Schematic
Sound Sensor
By using a microphone, high-gain amplifier (Fig. 37-10(b)), and detector-relay driver (Fig. 37-10(a)) a sound-detecting alarm ...
Ground-Fault Hall Sensor – Circuit Schematic
Ground-Fault Hall Sensor
No electrical contact exists between the circuit and the conductor. The 7474 flip-flop is triggered by the output ...
Water-Level Measurement Circuit – Circuit Schematic
Water-Level Measurement Circuit
Using a capacitor sensor to detect a water level is a simple method of sensing. This circuit uses C5, which...