Light Sensing

This two-chip receiver with minimum external component count has been designed for low-cost fiber optic applications to 100-M baud (50 MHz). The receiver is divided into pre-and postamplifier !Cs for increased stability. The preamplifier IC features low noise with a differential transresistance design. The postamplifier IC incorporates an auto-zeroed first stage with noise shaping, high-gain symmetrical-limiting amplifier, and a matched rise/fall time TTL output.....

Views: 5 | Votes: 85 | Comments: 0 | Rating: 1 | Rank: 5 | Added: Feb 12, 2013 |

Provides remote control for ac-powered devices by using the beam of a flashlight as a magic wand. The important aspect of this gadget is that it remembers. Activate it once to apply power to a device and it stays on. Activate it a second time and power goes off and stays off..

Views: 2495 | Votes: 46 | Comments: 0 | Rating: 2 | Rank: 5 | Added: Feb 11, 2013 |

This transmitter uses a 741 op amp as a high-gain audio amplifier, which is driven by a microphone. The output of the 741 is coupled to Ql, which serves as the driver for a LED. Potentiometer R1 is the amplifier`s gain control. Miniature trimmer resistor R6 permits adjustment of the base bias of Ql for best transmitter performance. Gain control R1 can be eliminated if CI and R2 are connected directly to pin 2 of the 741...

Views: 18 | Votes: 90 | Comments: 0 | Rating: 0 | Rank: 5 | Added: Feb 2, 2013 |

When a beam of light strikes the photocell, the voltage across neon lamp NE-1 rises sharply. NE-1 turns on and fires the SCR. Kl is an impulse relay whose contacts stay in position even after coil current is removed..

Views: 4446 | Votes: 88 | Comments: 0 | Rating: 5 | Rank: 5 | Added: Jan 23, 2013 |

This receiver for amplitude-modulated light signals uses phototransistor Ql mounted in a parabolic reflector (to increase range). Any npn phototransistor should work. Emitter-follower Q2 drives amplifier Q3. The output from Q3 feeds volume control R7 and audio.amplifier Ul...

Views: 14 | Votes: 98 | Comments: 0 | Rating: 2 | Rank: 5 | Added: Jan 17, 2013 |

A resonance-tuned narrow-band amplifier reduces this optical object detector"s sensitivity to stray light. C1 and L1 in IC2A"s feedback loop cause tbe op amp to pass only those frequencies at or near the LED"s 5-kHz modulation rate. ..

Views: 14 | Votes: 106 | Comments: 0 | Rating: 4 | Rank: 5 | Added: Jan 7, 2013 |

Capacitor Cl is connected continuously through the supply of 3 volts to 10 megohm resistor Rl. The capacitor is charged (relatively slowly) to 3 volts. The wink SWI is closed, it connects the charged capacitor (Cl) in series with C2 and R2. The capacitor C2 begins to charge, by placing a positive voltage during the gate of the SCR and turn it on. The two parallel "self-flashing" bulbs I1 and 12 on Tum. ..

This circuit consists of a L14G2 detector, two stages of gain, and a FM demodulator..

Views: 4831 | Votes: 63 | Comments: 0 | Rating: 1 | Rank: 5 | Added: Dec 11, 2012 |

Use this circuit to sense four quadrant motion of a light source..

Views: 4376 | Votes: 6 | Comments: 0 | Rating: 8 | Rank: 5 | Added: Dec 10, 2012 |

Rl sets the comparison level. At comparison, the photodiode has less than 5 mV across it, decreasing dark current by an order of magnitude..

Views: 676 | Votes: 102 | Comments: 0 | Rating: 8 | Rank: 5 | Added: Dec 8, 2012 |

When the light incident on the LASCR is interrupted, the voltage at the anode to the 2N4990 unilateral switch goes positive on the next positive cycle of the power which in turn triggers the switch and the C230 SCR when the switching voltage of the unilateral switch is reached..

Views: 3502 | Votes: 108 | Comments: 0 | Rating: 8 | Rank: 5 | Added: Nov 25, 2012 |

Both circuits use the GE. SC146B, 200 V, 10 A Triac as load current contacts. These triacs are triggered by normal SBS (2N4992) trigger circuits, which are controlled by the photo-Darlington, acting through the DA806 bridge as an ac photo switch. To operate the relays at other line voltages the asterisked (*) components are scaled to supply identical current..

Views: 3814 | Votes: 102 | Comments: 0 | Rating: 8 | Rank: 5 | Added: Nov 12, 2012 |

Using a simple 741 amplifier connected as a current-to-voltage converter with the LED as the current source, the voltage at the output is proportional to incident light. The junction is Q biased only by the difference between the output summing node junction potential and ground, preventing the possibility of reverse breakdown. The photon-generated current equals the short-circuit current of the junction, which is linearly related to incident light...

Views: 3746 | Votes: 105 | Comments: 0 | Rating: 8 | Rank: 3 | Added: Nov 11, 2012 |

The simple modulator stage will accommodate most common LEDs. By adjusting the potentiometer, the bias of the transistor is varied until the LED is at its half output point. Then, audio will cause it to vary above and below this point..

Views: 2755 | Votes: 86 | Comments: 0 | Rating: 5 | Rank: 5 | Added: Nov 4, 2012 |

In the visible-light transmitter, a 7805 voltage regulator is connected in a variable-voltage configuration, and an audio signal is fed to the common input, to modulate the output voltage. ..

Views: 7 | Votes: 1 | Comments: 0 | Rating: 4 | Rank: 5 | Added: Nov 1, 2012 |

The optical signal is coupled to the pin diode. Current flowing in the diode also flows into the input of the NE5211 preamplifier. The preamplifier is a fixed-gain block that has a 28-K!J differential transimpedance and does a single-ended to differential conversion. With the signal in differential form, greater noise immunity is assured. The second stage, or postamplifier NE5214, includes a gain block, auto-zero detection, and limiting. The auto-zero circuit allows de.....

Views: 1 | Votes: 64 | Comments: 0 | Rating: 5 | Rank: 5 | Added: Oct 23, 2012 |

The output state changes at a photo diode current of 0 µA..

Views: 3450 | Votes: 101 | Comments: 0 | Rating: 2 | Rank: 5 | Added: Oct 12, 2012 |

A common method of transforming the output current of a photodiode into a voltage signal, paralleling the photodiode with a high-value load resistor, produces a nonlinear response. Also the combination of the load"s transresistance, Rr. and the photodiode"s junction capacitance, C" slows the circuit"s response time. Figure 67-11B shows virtually the same components as Fig. 67-llA rearranged to maximize the inherent speed and linearity of the photodiode. ..

Views: 8 | Votes: 57 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Oct 10, 2012 |

The project is designed for LED based street lights with auto intensity control using solar power from photovoltaic cells. As awareness for solar energy is increasing, more and more individuals and institutions are opting for solar energy. Photovoltaic panels are used for charging batteries by converting the sunlight into electricity. A charge controller circuit is used to control the charging. Intensity of street lights is required to be kept high during the peak.....

Views: 61 | Votes: 95 | Comments: 0 | Rating: 8 | Rank: 10 | Added: Oct 9, 2012 |

The MFODllOO PIN diode requires shielding..

Views: 3003 | Votes: 63 | Comments: 0 | Rating: 7 | Rank: 5 | Added: Oct 6, 2012 |