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Sensors / Detectors:
Light Detectors and
Optical Sensors Page 4
Sensors / Detectors -- Main Page
Light Detectors / Optical Sensors: #-C
D-K L M-R S-Z
Last Updated:
Sunday July 27, 2008 07:40:17 PM
| Circuits Designed by Dave Johnson, P.E. : |
- Modulated Light Monitor
This battery powered circuit will work from DC to 500KHz. It is designed to connect to an oscilloscope to monitor the light level changes and modulated signals. (added 7/06)
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- OPTICAL INTERRUPTER DRAWS MICROAMPS
This circuit is great for battery-powered systems that use slotted type optical interrupters. It draws only 10uA from a 3v battery that should allow up to 5 years of operation from a lithium
battery.
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- OPTICAL RFID TEST CIRCUIT
I designed this test the concept of using light techniques to send identification data instead of RF. A more detailed discussion on this scheme can be found in the Imagineered new products
section.
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| Links to electronic circuits, electronic schematics, designs for engineers,
hobbyists, students & inventors: |
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Optical Design Of
Ambient Light Sensor (AN-32): Application Note 32 from Microsem (app note added 6/06) |
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Optical sensor needs no tweaking: 06/13/02 EDN Design Ideas / (added 1/05) The transfer gain of optical sensors spans a 16-to-1 ratio because of variations in the
LED, phototransistor, ambient temperature, and optical path. The wide transfer-gain variation complicates output-resistor selection in dc-coupled circuits. You must size the output resistor to
prevent high transfer gains from causing output-stage saturation, but low transfer gains yield low output-voltage sw...... |
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Photodetector Sorts Objects: 03/04/99 EDN-Design Ideas / (added 8/03) Most object-sensing systemshave problems detecting
the presence of an object. The system in Figure 1 uses an oscillator to ease detection problems and allow sorting. The oscillator reduces power dissipation in the photodiode by operating the
diode at 50% duty cycle. The oscillator also enables a 50% increase in the noise-filter time constant, and it functions as a timebase to allow object sorting. The oscillator chops the
photodiode's bias. The signal the photodetector receives is a square wave; thus, a filter can remove optical noise. You normally need filtering when light shines through fans onto the optical
detector. When required, you can place a bandpass filter in series with Q3's output. The oscillator frequency has two limits: the response time of the phototransistor and.... |
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Photovoltaic Switch disables unused LEDs: 03/18/04 EDN Design Ideas / (added 1/05) In many applications, it's desirable to disable LEDs used for system
verification. Many options are available for the disabling function, including manual SPST (single-pole single-throw) switches, enhancement- and depletion-mode MOSFETs, bipolar-junction
transistors, and JFETs. The circuit in Figure 1 automatically disables the LEDs when a mechanical housing encloses the circuit card, thereby ...... |
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Pulsed Sensor Extends Battery Life: 01/01/98 EDN-Design Ideas / (Electronic Circuit diagram added 03/03) |
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Light Detectors / Optical Sensors: #-C
D-K L M-R S-Z |
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