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usb e kits presents
led volt meter

fuctionality



A very useful votmeter with indicator leds witout the need of power supply! It has 5 indicators for 5 voltage levels (5,9,12,24,30 volt dc)
The kit is based on a quad opamp LM324.


All the needed power is directly from the voltage you measure.


The first led turns on when the measured voltage reaches 5V.
The other four leds are connected to the for outputs of the opamps.

With the help of a voltage divider we can reduce the measured voltage from 0-30 volt to 0-3 volt.
This new voltage is driven to the non inverting  inputs of the opamp.
The voltage reference for the inverting inputs is taken from a voltage divider again.

Each opamp operates as a comparator that compares the tow inputs.
If the voltage level comes above the reference voltage ,
the output of the opamp goes high and drives the led that is connected to it.

When the measured voltage reaches 30 volts all the leds are turned on!

Picture
Led voltmeter schematic

part list

Reference    Type            Value
C1        Ceramic Capacitor    330nF
C2        Ceramic Capacitor    100nF
C3        Electrolytic Capacitor    22u
D1        3mm difussed led    Red
D2        3mm difussed led    Red
D3        3mm difussed led    Red
D4        3mm difussed led    Red
D5        Diode            1N4148
D6        Diode            1N4148
D7        3mm difussed led    Red
D8        Diode            1N4148
R1        Resistor 1/4 watt    100k
R2        Resistor 1/4 watt    10k
R3-R6        Resistor 1/4 watt    1k
R7        Resistor 1/4 watt    82k
R8        Resistor 1/4 watt    22k
R9        Resistor 1/4 watt    47k
R10        Resistor 1/4 watt    10k
R11        Resistor 1/4 watt    33k
R12        Resistor 1/4 watt    1.2k
R13        Resistor 1/4 watt    1k
U1        QUAD Op. Amplifier    LM324
U2        Voltage Regulator    7805
J1        Terminal Block        2 pin

construction help guide

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resistor color code definition
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LM7805
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LED
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1N4148
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LM324
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click for soldering and prototyping assistant


downloads

led_voltometer_datasheet.pdf
File Size: 342 kb
File Type: pdf
Download File


watch the presentation of the kit


Led Voltometer 3,6,12,24,30 vdc levels indicators

A very useful voltometer based on the lm324 quad amplifier. Every opamp is used as a comparator at the interested voltages. So if you have a power supply and every time you have to measure the output with a multimeter do this project and you are ready to display the interest levels of the voltage.
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Led voltmeter preview
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