Inside Circuits

This tachometer can be set up for any number of cylinders by linking the appropriate timing resistor as illustrated. A 500 ohm trim resistor can be used to set up final calibration..

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With the component values shown, the oscillator has a frequency of 8 kHz. When an input signal is applied to the base of Ql the current flowing through Ql is varied, thus varying the time required to charge Cl. Due to the phase inversion in Ql the direction of output frequency change is 180 degrees out of phase with the input signal..

Views: 4028 | Votes: 63 | Comments: 0 | Rating: 3 | Rank: 5 | Added: Apr 1, 2013 |

Detection of line-current flow and indicating the flow to an electrically remote point is required in line status monitoring at a variety of points in theJelephone system and auxiliary systems. The line should be minimally unbalanced or loaded by the monitor circuit, and relatively high levels of 60-Hz induced voltages must be ignored. The HllAAl allows line currents of either polarity to be sensed without discrimination and will ignore noise up to approximately 2.5.....

Views: 7 | Votes: 1 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Apr 1, 2013 |

Each and every time a phone on the same line or calling numberis taken off-hook, the circuit will be activated to control an external electronic circuit. If several extension telephones are used on one phone line, the circuit can be useful as a busy indicator. LEDl contains a special flashing red LED that makes an excellent indicator for a busy circuit condition. The solid-state switch can be used for several other phone-activated applications, such as automati cally.....

Views: 7 | Votes: 13 | Comments: 0 | Rating: 3 | Rank: 5 | Added: Apr 1, 2013 |

Used in electronic roulette or dice games, this circuit produces a clock signal that initially is several te..

Views: 7 | Votes: 1 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Apr 1, 2013 |

The relay operates a certain time, td, after power is applied to it, and then it operates for a length of time, tc. The SCR fires when the voltage on Ci reaches VA. This operates the relay, which stays activated until the current charging C2 drops below the dropout current. To keep the relay in its activated position indefinitely (tc =00), eliminate C2 and choose R2 just large enough to keep the relay coil current within its related limits. ..

Views: 2184 | Votes: 50 | Comments: 0 | Rating: 9 | Rank: 6 | Added: Mar 31, 2013 |

This circuit has a flat response from 8Hz to 50 kHz at -3 db on tbe 10-mV range. ..

Views: 9 | Votes: 1 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Mar 31, 2013 |

This amplifier is useful for audio and video applications. Gain is set by Rf and the voltage gain of this amplifier ..

Views: 36 | Votes: 66 | Comments: 0 | Rating: 8 | Rank: 5 | Added: Mar 31, 2013 |

A 5.1-V zener diode clamps positive-going transients, and a Schottky rectifier clamps negative-going transients. Th..

Views: 2 | Votes: 47 | Comments: 0 | Rating: 9 | Rank: 5 | Added: Mar 31, 2013 |

An NE567 tone decoder, tuned to the transceiver"s CW offset frequency, ensures that the transceiver will be tran..

Views: 8 | Votes: 13 | Comments: 0 | Rating: 5 | Rank: 5 | Added: Mar 31, 2013 |

This inverter uses a 12.6-V to 120-V transformer to deliver a quasi-sine wave that has the same rms and peak voltage ..

Views: 19 | Votes: 88 | Comments: 0 | Rating: 7 | Rank: 5 | Added: Mar 31, 2013 |

Transistors Ql and Q2, together with resistors Rl through R7, make up the input balancing stage, which senses the resistance between points X and Y. The input stage is essentially a bridge, consisting of Rl, R2, R6, R7, and the resistance between points X and Y. Transistors Q3 and Q4 and their associated passive components form a buzzer, which sounds when the tester detects a short. The buzzer is controlled by the output from Q2. When the input resistance is high (more.....

Views: 6 | Votes: 76 | Comments: 0 | Rating: 3 | Rank: 5 | Added: Mar 31, 2013 |

This simple Bell circuit uses two 555 timers. The frequency is controlled by the capacitors that must be preserved almost identical in value to each other for best results. Fine tuning is done with R1 and R2. ..

Views: 1521 | Votes: 88 | Comments: 0 | Rating: 4 | Rank: 2 | Added: Mar 30, 2013 |

Timer Ul operates as a free-running oscillator at 60 Hz, providing trigger pulses to timer U2 which operates in the monostable mode. Resistor Rl is fixed and capacitor Cx is the capacitor being measured. While the output of U2 is 60 Hz, the duty cycle depends on the value of Cx. U3 is a combination low-pass filter and unity-gain follower whose dc voltage output is the time-averaged amplitude of the output pulses of U2, as shown in the timing diagram. ..

Views: 1055 | Votes: 106 | Comments: 0 | Rating: 7 | Rank: 7 | Added: Mar 30, 2013 |

Resistors Rl, R2, and the two 2.2 k resistors form a bridge circuit. R2 is a thermistor, and Rl sets the temperature at which L2 lights...

Views: 5104 | Votes: 87 | Comments: 0 | Rating: 3 | Rank: 3 | Added: Mar 30, 2013 |

An inexpensive electronic thermometer is capable of measuring temperatures over a range of from -30°F to +120°F. A diode-connected 2N3904 transistor used as the temperature sensor forms a voltage divider with Rl. As temperature increases, the voltage drop across the transistor changes by approximately -1.166 millivolts-per°F. As a result, the current at pin 3 of IC1, a 741 op amp with a gain of 5, decreases as the temperature measured by the sensor increases. A second.....

Views: 5645 | Votes: 30 | Comments: 0 | Rating: 0 | Rank: 2 | Added: Mar 30, 2013 |

The injector is a CMOS oscillator with period approximately equal to 1 x Cl x R2 seconds. The values are given for 1 kHz operation. Resistors R3 and R4 divide theoutput to 1 V; Whereas the oscillator employs the gates in their digital mode, the tracer used them in a linear fashion by applying negative feedback from output to input. They are used in much the same way as op amps. The circuit uses positive ground..

Views: 887 | Votes: 9 | Comments: 0 | Rating: 1 | Rank: 5 | Added: Mar 30, 2013 |

This monitor uses a common 7 41 amp configured as a comparator and a low cost nontransistor as an output driver. With no liquid detected, a voltage of about 2. 92 V is present in the op amp"s inverting input at pin 2. The 100-KO resistors establish a reference voltage of +2. 5 V at the noninverting input at pin 3 of the op amp. Under those conditions, the op amp"s output is -3.56 V, which keeps the 2N2222 transistor turned off and the voltage across its 1-KO.....

Views: 12 | Votes: 104 | Comments: 0 | Rating: 0 | Rank: 5 | Added: Mar 30, 2013 |

This is a simpie Colpitis crystal oscillator for 1 to 20 MHz, can be easily made from junk-box part..

Views: 23 | Votes: 85 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Mar 30, 2013 |

This circuit detects brief shorts or opens. When S2 is in the up position, the circuit indicates if there is or..

Views: 2 | Votes: 21 | Comments: 0 | Rating: 4 | Rank: 5 | Added: Mar 30, 2013 |