LED voltmeter, 10,25-15 volts. Scheme, description

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LED voltmeter, 10,25-15 volts. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Measuring technology

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As you already understood by voltage, this is a voltmeter for a car or a car charger, but nothing prevents it from being used for other purposes, for example, as a receiver tuning scale or a power supply voltage indicator, moreover, the measurement limits are easy to change in the process of establishing .

The instrument displays voltage on a 20-point LED linear scale. With a range of 10,25 ... 15 V, the indication is in steps of 0,25 V, which is very convenient for assessing the voltage in the car's on-board network or when charging a car battery. The scheme is shown in the figure.

LED voltmeter, 10,25-15 volts

It is based on two LM3914 microcircuits for a 10-step indication with a linear dependence. To get a 20-step scale, they are connected in series with the measured voltage.

The power circuit is also a measuring input. Everything is assembled on one printed circuit board, the drawing and wiring diagram of which is given here. All LEDs are plate-shaped. Are located pressed to each other. Color - you can all the same, or you can highlight the zones with colors, for example, highlight the normal zone (from 12 to 13 V) in green, and the upper and lower ones in red and yellow, respectively.

Establishment comes down to adjusting the limits of measurement. You need a laboratory power supply with an accurate voltmeter, or you can measure the voltage at the output of the power supply with a multimeter.

Set the voltage to 12,5V first.

By adjusting R5, set the voltage to 1,2 V between pins 4 and 6 of A2. Then, with resistor R7, set the voltage to 6,25 V at terminals 5 A1 and A2 connected together. Next, by adjusting R3, set the ignition of the HL11 LED. This completes the setup.

Author: Abrashitov A.A.

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Comments on the article:

Sergei
R1 should have one end not on the ground, but on the 8th pin. Otherwise, the top, according to the scheme, indicator will not show at all. In order for HL11 to turn off, passing the "baton" to HL10, you need to connect the 11th output of the lower microcircuit through a 22kΩ resistor with (+).

Vladimir Kuznetsov
Assembled with an amendment in the scheme, as Sergei wrote, it all worked!

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