Simple Mains Voltage Monitor Circuit Diagram

This is a project of Simple Mains Voltage Monitor Circuit Diagram. Many electronics hobbyists will have experienced the following: you try to finish a project late at night, and the mains supply fails. Whether that is caused by the electricity board or your carelessness isn’t really important. In any case, at such times you may find yourself without a torch or with flat batteries. There is no need to panic, as this circuit provides an emergency light. When the mains fails, the mains voltage monitor turns on five super bright LEDs, which are fed from a 9 V battery (NiCd or NiMH) or 7 AA cells. A buzzer has also been included, which should wake you from your sleep when the mains fails.

You obviously wouldn’t want to oversleep because your clock radio had reset, would you? When the mains voltage is present, the battery is charged via relay Re1, diode D8 and resistor R10. D8 prevents the battery voltage from powering the relay, and makes sure that the relay switches off when the mains voltage disappears. R10 is chosen such that the charging current of the battery is only a few milliamps. This current is small enough to prevent over-charging the battery. D6 acts as a mains indicator. When the relay turns off, IC1 receives power from the battery. The JK flip-flops are set via R12 and C4.

Mains Voltage Monitor Circuit Diagram

This causes T1 and T2 to conduct, which turns on D1-D5 and the buzzer. When the push button is pressed, a clock pulse appears on the CLK input of flip-flop IC1b. The output then toggles and the LEDs turn off. At the same time IC1a is reset, which silences the buzzer. If you press the button again, the LEDs will turn on since IC1b receives another clock pulse. The buzzer remains off because IC1a stays in its reset state. R11, R3 and C3 help to debounce the push button signal. In this way the circuit can also be used as a torch, especially if a separate mains adapter is used as the power supply.

As soon as the mains voltage is restored, the relay turns on, the LEDs turn off and the battery starts charging. The function of R13 is to discharge C4, preparing the circuit for the next mishap. If mains failures are a regular occurrence, we recommend that you connect pairs of LEDs in series. The series resistors should then have a value of 100 ?. This reduces the current consumption and therefore extends the battery life. This proves very useful when the battery hasn’t recharged fully after the last time. In any case, you should buy the brightest LEDs you can get hold of. If the LEDs you use have a maximum current of 20 mA, you should double the value of the series resistors! You could also consider using white LEDs.

Author: Goswin Visschers - Copyright: Elektor July-August 2004

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Simple Line Current Detector Circuit Diagram

This is a simple Line Current Detector Circuit Diagram. This circuit will detect line currents of about 250 mA or more without making any electrical connections to the line.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 the Telephone 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. 

 Simple Line Current Detector Circuit Diagram

The H ll A Al allows line currents of either polarity to be sensed without discrimination and will ignore noise up to approximately 2.5 mA. In applications where greater noise immunity or polarity- sensitive line-current detection is required, the HllAlO threshold coupler can be used. This phototransistor coupler is specified to provide a minimum 10% current transfer ratio at a defined input current, while leaking less than 50 p.A at half that input current over the full -55°C to + 100°C temperature range. The input current range, at which the coupler is on, is programmable by a single resistor from 5 to 10 mA.

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Build a Voltage Controlled Oscillator Circuit Diagram

Build a Simple Voltage Controlled Oscillator Circuit Diagram. This circuit is a voltage-controlled oscillator, which is an oscillator whose frequency is determined by a control voltage. With the component values shown, the oscillator has a frequency of 8 kHz. 

 Voltage Controlled Oscillator Circuit Diagram

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 The output may be used to trigger a bistable flip-flop.

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Simple Gasoline Engine Tachometer Circuit Diagram

Simple gasoline engine tachometer circuit diagram is the simple project for hobbyist and students,  Gasoline Engine Tachometers. For gasoline engine measurement applications. For gasoline/diesel engines and general rotating objects.This tachometer can be set up for any number of cylinders by linking the appropriate timing resistor as illustrated. 

 

 Simple Gasoline Engine Tachometer Circuit Diagram

 

 

A 500 ohm trim resistor can be used to set up final calibration. A protection circuit composed of a 10 ohm resistor and a zener diode is also shown as a safety precaution against the transients which are to be found in automobiles. If you like this project share your affordable comments leave below for us.

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