Homemade voltmeter with LEDs. DIY digital voltmeter. Schematic diagram of an ammeter

This article describes simple voltmeter, the indicator of which is twelve LEDs. This allows you to display the measured voltage in the range from 0 to 12 volts in steps of 1 volt, and the measurement error does not exceed 2 percent.

The most suitable area of ​​application for this LED voltmeter indicator is use in regulated power supplies. If you have all the necessary radio components at hand, then the circuit can be assembled in literally an hour or two.

Description of the LED voltmeter device

there will be a logical zero, so the LEDs do not light up.

When voltage is applied to the input of the voltmeter, a low logic level will appear at certain outputs of comparators DA1...DA3 (in accordance with the voltage level at the non-inverting terminals of the op-amp).

As follows from the circuit diagram, at different voltage levels at the inputs of integrated circuits DD1...DD3, a high logic level is set at their outputs, as a result of which the corresponding LED begins to light. To limit the voltage at the voltmeter input to 12 volts, a zener diode VD2 is included in the circuit.

LED Voltmeter Parts

The circuit uses LM324 op-amps as comparators. Their use contributed to reducing the total number of microcircuits and other radio elements for pairing the analog part of the circuit with integrated circuits. Capacitors - KM. All resistances are MLT-0.125, MLT-0.25.

LEDs HL1 - HL12 can be used AL307. The DA5 78L12 integrated voltage stabilizer can be replaced with a KREN8B or 7812. The VD2 zener diode can be replaced with a KS212 with the letter E or Zh. The voltmeter circuit is powered from an unstabilized source DC voltage from 13 to 16 volts with a load current of at least 12 mA.

Source Radioamator, 8/2001

When working with various electronic products, there is a need to measure the modes or distribution of alternating voltages on individual elements schemes. Conventional multimeters turned on in AC mode can only record large values ​​of this parameter with a high degree of error. If you need to take small readings, it is advisable to have a millivoltmeter AC, allowing measurements to be made with millivolt accuracy.

In order to make a digital voltmeter with your own hands, you need some experience working with electronic components, as well as the ability to handle an electric soldering iron well. Only in this case can you be sure of the success of assembly operations carried out independently at home.

Microprocessor based voltmeter

Parts selection

Before making a voltmeter, experts recommend carefully studying all the options offered in various sources. The main requirement for such selection is the extreme simplicity of the scheme and the ability to measure variable voltage accurate to 0.1 Volt.

An analysis of many circuit solutions has shown that for self-manufacturing a digital voltmeter, it is most advisable to use a programmable microprocessor of the PIC16F676 type. For those who are new to the technique of reprogramming these chips, it is advisable to purchase a chip with ready-made firmware for a homemade voltmeter.

When purchasing parts, special attention should be paid to choosing a suitable indicator element on LED segments (the option of a standard pointer ammeter in this case is completely excluded). In this case, preference should be given to a device with a common cathode, since the number of circuit components in this case is noticeably reduced.

Additional information. Conventional purchased radioelements (resistors, diodes and capacitors) can be used as discrete components.

After purchasing all the necessary parts, you should proceed to wiring the voltmeter circuit (making its printed circuit board).

Preparing the board

Before making a printed circuit board, you need to carefully study the circuit of the electronic meter, taking into account all the components present on it and placing them in a place convenient for unsoldering.

Important! If you have available funds, you can order the production of such a board in a specialized workshop. The quality of its execution in this case will undoubtedly be higher.

After the board is ready, you need to “stuff” it, that is, place all the electronic components (including the microprocessor) in their places, and then solder them with low-temperature solder. Refractory compounds are not suitable in this situation, since they will require high temperatures. Since all the elements in the assembled device are miniature, their overheating is extremely undesirable.

Power supply (PSU)

In order for the future voltmeter to function normally, it will need a separate or built-in power supply DC. This module is assembled according to the classical scheme and is designed for an output voltage of 5 Volts. As for the current component of this device, which determines its calculated power, half an ampere is quite enough to power the voltmeter.

Based on these data, we prepare ourselves (or send it to a specialized workshop for manufacturing) a printed circuit board for the power supply.

Pay attention! It would be more rational to prepare both boards at once (for the voltmeter itself and for the power supply), without spacing these procedures out over time.

At self-production This will allow you to perform several similar operations at once, namely:

• Cutting blanks of the required size from fiberglass sheets and cleaning them;
• Making a photomask for each of them with its subsequent application;
• Etching these boards in a ferric chloride solution;
• Stuffing them with radio components;
• Soldering of all placed components.

In the case when boards are sent for manufacturing on proprietary equipment, their simultaneous preparation will also allow you to benefit both in price and in time.

Assembly and configuration

When assembling a voltmeter, it is important to ensure that the microprocessor itself is installed correctly (it must already be programmed). To do this, you need to find the marking of its first leg on the body and, in accordance with it, fix the body of the product in the mounting holes.

Important! Only after you have complete confidence in the correct installation of the most important part, you can proceed to soldering it (“fitting on solder”).

Sometimes, to install a microcircuit, it is recommended to solder a special socket under it into the board, which significantly simplifies all working and configuration procedures. However, this option is beneficial only if the socket used has high-quality execution and ensures reliable contact with the legs of the microcircuit.

After soldering the microprocessor, you can fill and immediately place all other elements on the solder electronic circuit. During the soldering process, the following rules should be followed:

• Be sure to use an active flux that promotes good spreading of liquid solder over the entire landing area;
• Try not to hold the tip in one place for too long, which will prevent overheating of the mounted part;
• Upon completion of soldering, be sure to wash the printed circuit board with alcohol or any other solvent.

If no errors were made when assembling the board, the circuit should work immediately after connecting power to it from an external source of stabilized voltage of 5 Volts.

In conclusion, we note that your own power supply can be connected to the finished voltmeter after completing its configuration and testing, carried out according to standard methods.

Video

Quite a few motorists are faced with such a problem as unexpected battery discharge. It is especially unpleasant when this happens on the road far from home. One of the reasons may be the failure of the car's generator. Helps prevent impending battery drain car voltmeter. Below are a few simple circuits similar device.

Automotive voltmeter on LM3914 chip

This is a car voltmeter circuit designed to monitor voltage on-board network car in the range from 10.5V to 15V. 10 LEDs are used as indicators.

The basis of the circuit is integrated. This microcircuit is capable of estimating the input voltage and displaying the result on 10 LEDs in dot or column mode. The LM3914 chip is capable of operating in wide range power supply (3V...25V). The brightness of the LEDs can be adjusted using an external variable resistor. The outputs of the microcircuit are compatible with TTL and CMOS logic.

Ten LEDs VD1-VD10 display the current value of the battery voltage or the voltage of the vehicle’s on-board network in dot mode (pin 9 is not connected or connected to the minus) or column mode (pin 9 is connected to the power plus).

Resistor R4 connected between pins 6,7 and the power supply minus sets the brightness of the LEDs. Resistors R2 and variable resistor R1 form a voltage divider. Using variable resistor R1, the upper voltage level is adjusted, and using R3, the lower one.

As mentioned earlier, this car voltmeter provides an indication of 10.5 to 15 volts. Calibration of the circuit is performed as follows. Apply 15 volts from the power supply to the input of the voltmeter circuit. Then, by changing the resistance of resistor R1, it is necessary to ensure that the VD10 LED (in dot mode) or all VD...VD10 LEDs (in column mode) light up.

Then apply 10.5 volts to the input and use variable resistor R3 to ensure that only LED VD1 lights up. Now increasing the voltage in 0.5 volt increments, the LEDs will light up one by one, and at a voltage of 15 volts, all the LEDs will light up. Switch SA1 is designed to switch between dot/column indication modes. When the SA1 switch is closed, it is a column; when it is open, it is a dot.

Car voltmeter using transistors

The following circuit of a car voltmeter is built on two. When the voltage on the battery is less than 11 volts, the zener diodes VD1 and VD2 do not pass current, which is why only the red LED lights up, indicating low voltage on the vehicle's on-board network.

If the voltage is between 12 and 14 volts, the zener diode VD1 opens the transistor VT1. The green LED lights up indicating normal voltage. If the battery voltage exceeds 15 volts, the zener diode VD2 opens the transistor VT2, as a result of which the yellow LED lights up, indicating a significant excess of voltage in the vehicle network.

Voltmeter on operational amplifier LM393

This simple car voltmeter is built on operational amplifier. As an indicator, as in the previous circuit, three LEDs are used.

When the voltage is low (less than 11V), the red LED lights up. If the voltage is normal (12.4…14V), then the light turns green. If the voltage exceeds 14V, the yellow LED lights up. Zener diode VD1 forms the reference voltage. This scheme similar to the diagram.

Automotive voltmeter on K1003PP1 microcircuit

This voltmeter circuit for a car is built on the K1003PP1 microcircuit and allows you to monitor the voltage of the on-board network by the glow of 3 LEDs:

• When the voltage is less than 11 volts, the HL1 LED lights up
• At a voltage of 11.1…14.4 volts, the HL2 LED lights up
• When the voltage is more than 14.6 volts, the HL3 LED lights up

Setup. After applying voltage to the input from any power supply (11.1...14.4V), variable resistor R4 must be used to make the HL2 LED glow.

The task arose of determining the state of the battery during discharge, storage and charging; I had to remember my skills and take up a soldering iron. All the circuits with a bunch of comparators and other tricks were depressing due to their size - it would have been easier to connect a multimeter to a battery. Therefore, it was decided to come up with something simple and elegant, and as a result, a scheme was born that can be scaled to suit your needs, both in width and depth. For one voltage step, only three elements are used - a zener diode, a resistor and an LED (at this point slap yourself on the forehead and exclaim: “How did I not think of that before!”

In general, catch the diagram and photo of the finished device based on one 12 Volt lead acid battery like in UPSs and cars. Indication from completely discharged (voltage less than 9.5V) to fully charged (voltage more than 14.6V). If you need other ranges or want a wider scale, then take the nearest zener diode in terms of voltage and calculate the current-limiting resistor for the LED. (1.5V drop, 20mA current).
In general, everything is simple.

If you use SMD components, then you can fit into this ten-kopeck coin, well, I didn’t have the task of miniaturization, so I assembled it on a breadboard.

The first red LED shows that the circuit is connected and there is some voltage. the second - more than 9 Volts, the third, yellow, - more than 10V, the fourth - more than 11V, the fifth, green, - more than 12V and the sixth - more than 13V. The gradations between these points are clearly visible in the degree of luminescence of the corresponding LEDs. In this case, the battery is on charge and is about to be charged.

This is a description of a simple pseudo-analog voltmeter. The measured value is read in the form of LED points, stylized as a pointer sensor (although it can also be done in the form of an LED ruler), but the measurement occurs in digital form, using a microcontroller. The voltmeter was created as a complement to adjustable block power supply and was made from radioelements available at hand.

Schematic diagram

The voltmeter consists of two parts: a display and a measuring module. Here is a regular 5 V power supply, Atmega8 MK with external source reference voltage and registers with 32 LEDs.

The main voltage measurement range is 1-32 V with a resolution of 1 V, but it was decided to add an automatic range change of 0.1-3.2 V with a resolution of 0.1 V.

The operating principle is based on voltage measurement using two converters ADC0 and ADC1. Converter ADC1 is used to determine the measuring range. The value from this sensor allows you to control and add resistor R9 through the PC2 port pin - forming a 1:10 divider, or turning it off. For voltages of 0.1-3.2 V, the input voltage from CON2 is supplied through resistor R8 and goes directly to the input of the converter ADC0. If the voltage exceeds the set value of 3.3 volts, it switches from the low range (the green LED33 diode lights up) to the high range.

To use such a voltmeter for a 15 V power supply, instead of a 1:10 divider, you can install a 1:4 divider, which gives a range of up to 16 V with a resolution of 0.5 V. Since not everyone will like switching ranges, you can refuse this and make one range by connecting R9 directly to ground, cutting the connection to PC2 pin, ADC1 unused, you can also connect to ground.

Diodes D2-D5 (together with R8, R10) represent simplest protection converters from supplying a voltage higher than the Atmega supply voltage, that is, 5 V. Capacitors C7, C8 additionally filter the calculated voltage. The Atmega's internal voltage reference was abandoned due to its instability. The reference voltage is performed on TL431. The reference voltage was fixed at 3.3 V. Fine tuning is done using a potentiometer. Resistors R3 and R4 allow you to select the voltage adjustment range of the potentiometer.

The power supply for the analog part of the MK is also typical, using a 10 µH inductor and a 100 nF capacitor. Divided the mass digital and analog.

The measurement voltages are transmitted sequentially to the registers by signals labeled CLK, D and C., which are output to the CON4 connector.

Switching modes

The voltmeter can operate in “luminous point” mode according to the standard setting, or in LED ruler mode. Changing the mode is carried out by changing the state of contact PB0, pin 14. Connecting to ground is a point mode, disconnecting this contact from ground is switching to ruler mode.

Transistor T1, R6, R7 and LED1 form a simple current source, eliminating the need for separate resistors for each of the display's 32 LEDs. The current of such a current source is determined by the rating of R7. The voltmeter is made on single-sided printed circuit boards. Files and firmware - .