Identify diagram

Continuous monitoring of the primarys voltage is required in many ap-plications one of theses guide volt-age stabilisers and motor pumps. An ana-logue voltmeter, although cheap, has many disadvantages because it has shifting sections and that is delicate to vibrations. The stablestate voltmeter circuit described here indicates the primarys voltage with a decision that's related to that of a general-pur-pose analogue voltmeter. The standing of the principles voltage is available within the type of an LED bar graph. Presets VR1 through VR16 are used to set the DC voltages akin to the sixteen voltage degrees over the 50-250V vary as marked on LED1 through LED16, respectively, within the determine. The LED bar graph is multiplexed from the bottom to the excessiveest with the assist of ICs CD4067B (16-channel multiplexer) and CD4029B (counter). The counter clocked with the aid of NE555 timer-based astable multivibrator generates 4-bit binary ad-dress for multiplexer-demultiplexer pair of CD4067B and CD4514B. 

Digital Mains Voltage Indicator Circuit Diagram

The voltage from the wipers of pre-sets are multiplexed by means of CD4067B and the output from pin 1 of CD4067B is fed to the non-inverting input of comparator A2 (half of op-amp LM358) after being buff-ered through A1 (the other half of IC2). The unregulated voltage sensed from rectifier output is fed to the inverting input of com-parator A2. The output of comparator A2 is low except the sensed voltage is larger than the reference enter applied on the non-inverting pins of comparator A2 by means of buffer A1. When the sensed voltage goes below the reference voltage, the output of com-parator A2 goes high. The excessive output from comparator A2 inhibits the decoder (CD4514) that's used to decode the out-put of IC4029 and pressure the LEDs. This make certains that the LEDs of the bar graph are ‘on’ as so much as the sensed voltage-level pro-portional to the mains voltage.

The preliminary adjustment of each of the presets will also be carried out by way of feeding a recognized AC voltage thru an auto-transform after which adjusting the corresponding pre-set to make sure that only those LEDs which are up to the applied voltage glow. 

EFY now note.  It is a just right option to use ad-ditional transformer, rectifier, filter, and regulator associations for obtaining a regulated provide for the functioning of the circuit so that performance of the cir-cuit just isn't affected even when the primarys voltage falls as little as 50V or goes as high as 280V. During Lab checking out regu-lated 12-volt supply for circuit operation used to be used.)

Author : Pratap Chandra Sahu - Copyright : EFY

The modem off indicator is intended particularly for serious Internet surfers. It might be viewed that the circuit of the indicator can't be a lot more effective, or there may smartly be nothing left. In spite of its simplicity, it should show to be a cost-saving device, since it presentations at a glance whether the telephone line is free once more after the modem has been used. This obviates excessive phone costs in case for some motive the modem proceeds to operate. The circuit depends upon the very fact that there may be a attainable of about 40 V on the telephone line when it isn't busy. This voltage drops sharply when a phone call is being made. If, subsequently, the circuit is linked to telephone terminals a and b, the lighting of the golf green LED shows that the line is no longer busy in error.

 Modem Off Indicator Circuit Diagram

The bridge rectifier be certain thats that the polarity of the line voltage is of no end result. This has the extra benefit that polarity protection for the LED just isn't necessary. To guarantee that the phone line is just now not loaded unnecessarily, the LED is a excessive efficiency type. This sort gentles at a current as low as 2 mA, and that is, due to this fact the current arranged thru it by resistor R1.

In spite of the liberal age we live in, it's excessively probable that in many international areas it isn't allowed to attach the indicator throughout the phone strains. Seek recommendation of your native telephone company that owns or operates the phone network.

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