LED voltage indicator: diagram of how to make a homemade network voltage indicator with your own hands. Do-it-yourself phase indicator on an LED

Even for the simplest work in electrical circuits on the farm, a voltage indicator is useful - a device that shows the presence or absence of electric current and voltage in networks from 220 to 1000 V (depending on the device). The expediency of its use is dictated primarily by the fact that the electric current cannot be seen with the eyes - its presence can only be judged by whether the device plugged into the outlet is working or not.

Indicator circuit

The operation of the device is based on the initial turn-on voltage of the LED. Any LED is a semiconductor device that has a voltage limit point, only exceeding which it begins to work (shine). Unlike an incandescent lamp, which has almost linear current-voltage characteristics, the LED is very close to the characteristics of a zener diode, with a sharp slope of the current as the voltage increases. If you connect LEDs in a circuit in series with resistors, then each LED will start to turn on only after the voltage exceeds the sum of the LEDs in the circuit for each section of the circuit separately. The voltage threshold for opening or starting to light an LED can range from 1.8 V to 2.6 V. It all depends on the specific brand. As a result, each LED lights up only after the previous one lights up.

How to choose the right one

The choice of UN should be based on the area of use - for household or permanent industrial needs. In everyday life, single-pole indicators are used. In production, it is better to use a two-pole device, as it shows more accurate voltage figures and is high-voltage.

When choosing a device, you need to pay attention to the following points:

Percentage of reading error. Should not be more than 3%.
Response speed. Normally 70 – 300 samples/s.
Electrical safety class. Depends on the future purpose of the circuit: local, distribution or low voltage.
Fire safety level. Must be equipped with overload protection function and shut off automatically.

It is better to purchase a high-quality device in specialized lighting stores that are ready to provide a certificate and passport for the product, which indicates the serial numbers of each component and attaches a diagram. A high-quality device is marked on the case, the date of manufacture, and an indication of the rated current. Many UNIs are equipped with probes or current clamps, which allow measurements to be taken without violating the insulation of the conductors.

IMPORTANT! The device must have a warranty not only from the manufacturer, but also from the seller. It is preferable to purchase a product from a domestic or European manufacturer (Germany, Denmark, Sweden).

Wire colors and designations

In order to find the phase, neutral and ground wires of electrical wiring without instruments, they, in accordance with the rules of the Electrical Installation Code, are covered with insulation of different colors.

The photo shows the color marking of the electrical cable for single-phase electrical wiring with an alternating current voltage of 220 V.

This photo shows the color coding of an electrical cable for 380V AC three-phase wiring.

According to the presented diagrams, wires began to be marked in Russia in 2011. In the USSR, the color marking was different, which must be taken into account when searching for phase and zero when connecting installation electrical products to old electrical wiring.

What is the difference between N and PE wires in electrical wiring

According to modern requirements of the PUE, in addition to the phase and neutral wires, a yellow-green ground wire must also be supplied to the apartment.

The neutral N and grounding PE wires are connected to one grounded bus of the panel in the entrance of the house. But they perform different functions. The neutral wire is intended for electrical wiring, and the grounding wire is intended to protect people from electric shock and is connected to the housings of electrical appliances through the third contact of the electrical plug. If an insulation breakdown occurs and a phase gets into the body of an electrical device, then all the current will flow through the grounding wire, the fuse links will burn out or the circuit breaker will trip, and no person will be harmed.

If the electrical wiring is laid indoors with a cable without color marking, it is impossible to determine where the neutral conductor is and where the grounding conductor is, since the resistance between the wires is hundredths of an ohm. The only clue can be the fact that the neutral wire is inserted into the electric meter, and the grounding wire passes by the meter.

Attention! Touching exposed parts of a circuit connected to an electrical outlet may result in electric shock.

Necessary materials for making an indicator

To make a simple LED device that indicates phase or voltage (approximately), you need to find a working circuit. Then buy or obtain the following parts and tools:

LED of any type;
a diode opening with a current of 10-100 mA at a forward potential of 1 V, with a breakdown voltage (reverse) of at least 30-75 V;
resistor 100-200 kOhm;
bipolar transistors;
soldering iron;
wires;
metal plate (can be cut from a beer can);
plastic case, preferably transparent;
sting, you can take a regular nail.

Chinese soldering iron with USB charging.

Option for car

A simple circuit for indicating the vehicle's on-board voltage and battery charge. The zener diode limits the battery current to 5V to power the logic chip.

Variable resistors allow you to set the voltage level to trigger the LEDs. It is better to carry out the setup from a network stabilized power source.

Probe indicators for searching for phase and zero

A device designed to find zero and phase is called an indicator. Light indicators for determining the phase on neon light bulbs are widely used. Low price, high reliability, long service life. Recently, LED indicators have also appeared. They are more expensive and require additional batteries.

On a neon light bulb

It is a dielectric case, inside of which there is a resistor and a neon light bulb. Touching the electrical wiring wires one by one with the screwdriver end of the indicator, you find the phase by the glow of the neon light bulb. If the light bulb lights up when touched, it means it is a phase wire. If it doesn't light up, it means it's a neutral wire.

Indicator housings come in different shapes and colors, but the filling is the same for all. To prevent an accidental short circuit, I advise you to put a tube made of insulating material on the screwdriver shaft. The indicator should not be used to unscrew or tighten the screws with great force. The indicator body is made of soft plastic, the screwdriver shaft is pressed in shallowly and the body breaks under heavy load.

DIY LED voltage indicator: diagrams with description

LEDs have long been used in any technology due to their low consumption, compactness and high reliability as a visual display of system operation. An LED voltage indicator is a useful device needed by amateurs and professionals to work with electricity. The principle is used in the illumination of wall switches and switches in surge protectors, voltage indicators, and test screwdrivers. Such a device can be made with your own hands due to its relative primitiveness.

12 volt

The LED indicator circuit for determining the car's charge voltage contains 16 parts.

12 volt probe circuit.

The device has three voltage dividers: resistors, zener diodes and transistors. Their outputs are connected to a three-color LED.

Voltage (in volts) is determined by the color of its glow:

red – more than 14.4;
green – 12-14;
blue – less than 11.5.

The indicator consists of the following parts:

fixed resistors R1, R3, R5 and R6 – 1, 10, 10 and 47 kOhm, respectively;
potentiometers R2, R4 – 10 and 2.2 kOhm;
Zener diodes VD1, VD2 and VD3 for 10, 8.2 and 5.6 V;
bipolar transistors VT-VT3 type BC847C;
LED – LED RGB.

Potentiometers R2, R4 set the lowest and highest voltage limits.

Thematic video: How to make a hidden wiring detector with your own hands from scrap materials

The scheme works as follows:

at a low input potential, transistor VT3 opens and VT2 closes (blue light is on);
at rated voltage, the current flows through parts R5, VD3, R5 to the green crystal (VT2 is open and VT3 is closed);
when the potential is high, the divider R1, VD1, R2, VT1 turns on and lights up red.

At 220 volts

To protect yourself from electric shock, you need to place a resistance with a high value at the indicator input. The general scheme of the indicator is as follows:

one terminal of a 100-200 kOhm resistor is connected to the tip;
the diode anode and the LED cathode are soldered to the other end;
their remaining legs are connected to a metal plate.

Scheme of 220 volt current availability.

The diode in the circuit can be of the KD521, KD503, KD522 type (analogues of 1N914, 1N4148). Any craftsman can make a voltage indicator on LEDs with his own hands for 220 V.

AC voltage indicator 220 V

Let's consider the first, simplest version of a network indicator on an LED. It is used in screwdrivers to find the 220 V phase. To implement it we will need:

Light-emitting diode;
resistor;
diode.

You can choose absolutely any LED (HL). The characteristics of the diode (VD) should be approximately as follows: forward voltage, with a forward current of 10-100 mA - 1-1.1 V. Reverse voltage 30-75 V. Resistor (R) must have a resistance of at least 100 kOhm, but not more than 150 kOhm, otherwise the brightness of the indicator will decrease. Such a device can be made independently in a hinged form, even without the use of a printed circuit board.

The circuit of a primitive current indicator will look similar, only it is necessary to use capacitance.

AC and DC voltage indicator up to 600 V

The next option is a slightly more complex system, due to the presence in the circuit, in addition to the elements already known to us, of two transistors and a capacitance. But the versatility of this indicator will pleasantly surprise you. It can safely check the presence of voltage from 5 to 600 V, both direct and alternating.

The main element of the voltage indicator circuit is a field-effect transistor (VT2). The threshold voltage value that will allow the indicator to operate is fixed by the gate-source potential difference, and the maximum possible voltage determines the drop at the drain-source. It functions as a current stabilizer. Feedback is provided through a bipolar transistor (VT1) to maintain the set value.

The operating principle of the LED indicator is as follows. When a potential difference is applied to the input, a current will arise in the circuit, the value of which is determined by the resistance (R2) and the voltage of the base-emitter junction of the bipolar transistor (VT1). In order for a weak LED to light up, a stabilization current of 100 μA is sufficient. To do this, the resistance (R2) should be 500-600 Ohms, if the base-emitter voltage is approximately 0.5 V.

A capacitor (C) is required to be non-polar, with a capacity of 0.1 µF; it serves to protect the LED from current surges. We select a resistor (R1) with a value of 1 MOhm; it acts as a load for the bipolar transistor (VT1). The functions of the diode (VD) in the case of DC voltage indication are pole testing and protection. And to check the alternating voltage, it plays the role of a rectifier, cutting off the negative half-wave. Its reverse voltage must be at least 600 V.

As for the LED (HL), choose a super-bright one so that its glow is noticeable at minimal currents.

Voltage indicator on two-color LED

Another popular indication scheme is one that uses a two-color LED to display the state of charge of the battery or to signal when a lamp is turned on or off in another room. This can be very convenient, for example, if the light switch in the basement is located before the stairs leading down (by the way, do not forget to read an interesting article on how to illuminate the stairs with LED strip).

Before you go down there, you turn on the light and the indicator lights up red, when off you see a green glow on the key. In this case, you don’t have to go into a dark room and feel for the switch there. When you leave the basement, you know by the color of the LED whether the light in the basement is on or not. At the same time, you monitor the health of the light bulb, because if it burns out, the red LED will not glow.

Here is a diagram of a voltage indicator on a two-color LED.

In conclusion, we can say that these are only the basic possible schemes for using LEDs to indicate voltage. All of them are simple, and even an amateur can do them. They didn't use any expensive integrated circuits or anything like that. We recommend that all amateur and professional electricians acquire such a device so that they never endanger their health by starting repair work without checking the presence of voltage.

Pointer tests

Laboratory tests are carried out by organizations that have a special license for this. To carry out the test, a circuit is assembled, which includes a high or low voltage indicator.

The UNN is tested for the insulation condition and the indication voltage value. They also check its operation at increased voltage, while measuring the current. The voltage, gradually increased from zero, is brought to exceed the operating voltage by 10% and is maintained for 1 minute.

Electrical installation diagram for testing the insulation of the housing and wires of the ULV up to 1000 V

The UVN is tested starting from the working part, applying voltage to the tip and screw connection. If the indicator voltage is higher than 35 kV, the working part is not checked, only the condition of the insulating part and the handle is tested.

Scheme of the testing facility for UVN

The results obtained are documented in a protocol and entered into a journal. A product approved for use is equipped with a tag with a stamp indicating the date of the next verification.

Voltage gauges and indicators are used to ensure the safety of operating personnel during work; they can also be fraught with danger. Storage, correct use and daily visual inspection must be ensured by those directly using the indicator. It is prohibited to use the device if the inspection period has expired, or if it has been subjected to mechanical damage as a result of a fall or impact.

DIY LED voltage indicator

Checking the voltage in the circuit is a procedure necessary when performing various types of work related to electricity. Some amateur electricians, and sometimes professionals, use a homemade “control” for this - a socket with a light bulb to which wires are connected.

Although this method is prohibited by the “Rules for the Safe Operation of Consumer Electrical Installations,” it is quite effective when used correctly. But still, for these purposes it is better to use LED identifiers - probes. You can buy them in a store, or you can make them yourself.

What is a logic probe used for?

This device is successfully used when it is necessary to perform a preliminary check of the operability of the elements of a simple electrical circuit, as well as for the initial diagnosis of simple devices - that is, in cases where high measurement accuracy is not required. Using a logic probe you can:

Determine the presence of a voltage of 12 - 400 V in the electrical circuit.
Determine the poles in a DC circuit.

Check the condition of transistors, diodes and other electrical elements.
Determine the phase conductor in the AC electrical circuit.
Ring the electrical circuit to check its integrity.

The simplest and most reliable devices with which the above manipulations are performed are an indicator screwdriver and a sonic screwdriver.

Electrician's probe: principle of operation and manufacture

A simple identifier with two LEDs and a neon light bulb, which has received the name “arcashka” among electricians, despite its simple device, allows you to effectively determine the presence of a phase, resistance in an electrical circuit, and also detect a short circuit (short circuit) in the circuit. The universal electrician's tester is mainly used for:

Diagnostics for broken coils and relays.
Continuity checks of motors and chokes.
Checking rectifier diodes.
Definitions of terminals on transformers with multiple windings.

This is not a complete list of tasks that can be solved using a probe. But the above is enough to understand how useful this device is in the work of an electrician.

A regular battery with a voltage of 9 V is used as a power source for this device. When the tester probes are closed, the current consumption does not exceed 110 mA. If the probes are open, then the device does not consume electricity, so it does not need either a diagnostic mode switch or a power switch.

The probe is capable of performing its full functions until the voltage at the power supply drops below 4 V. After this, it can be used as a voltage indicator in circuits.

During the continuity of electrical circuits, the resistance of which is 0 - 150 Ohms, two light-emitting diodes light up - yellow and red. If the resistance value is 151 Ohm - 50 kOhm, then only the yellow diode lights up. When a network voltage of 220 V to 380 V is applied to the probes of the device, the neon lamp begins to glow, and at the same time a slight flickering of the LED elements is observed.

The diagram of this voltage indicator is available on the Internet, as well as in specialized literature. When making such a probe with your own hands, its elements are installed inside the housing, which is made of insulating material.

Often, for these purposes, the housing from the charger of any mobile phone or tablet computer is used. A probe pin should be removed from the front part of the case, and a high-quality insulated cable, the end of which is equipped with a probe or an alligator clip, should be removed from the end part.

Assembling a simple voltage tester with an LED indicator is shown in the following video:

How to make an electrician's tester with your own hands?

Some thrifty hobbyists can find many useful things in their “arsenal,” including an earphone (capsule) for the TK-67-NT telephone.

Another similar device, equipped with a metal membrane, inside which there is a pair of series-connected coils, is also suitable.

Based on such a part, a simple sound probe can be assembled.

First of all, you need to disassemble the telephone capsule and disconnect the coils from each other. This is necessary in order to free their conclusions. The elements are placed in the earphone under the sound membrane, near the coils. After assembling the electrical circuit, we will receive a completely working identifier with sound indication, which can be used, for example, to check the tracks of printed circuits for mutual bridging.

The base of such a probe is an electric generator with an inductive opposite relationship, the main parts of which are a telephone and a low-power transistor (preferably germanium). If you do not have such a transistor, then you can use another one with NPN conductivity, but in this case the polarity of the power supply should be changed. If you cannot turn on the generator, the terminals of one (any) coil must be swapped with each other.

You can increase the sound volume by choosing the frequency of the electric generator so that it is as close as possible to the resonant frequency of the earphone. To do this, the membrane and the core must be placed at an appropriate distance, changing the interval between them until the desired result is obtained.

Double pole design

A high voltage indicator with two measuring contacts works on the principle of detecting the passage of current through a section of the circuit. An internal circuit compares the potential difference between the measuring point and ground (or neutral contact). If the response threshold exceeds the set value, an indication is triggered.

The design may be different, depending on the purpose: indication only, search for breakdown, measurement of the exact voltage value, setting the range (220 V, 380 V). As an example, the illustration shows an electrical circuit of a device that determines the presence of a phase in the measured area and an approximate voltage threshold.

There are no complex integral elements, so this indicator is reliable and trouble-free under any operating conditions. If measurements are taken outdoors, in bright light - parallel to the light indicator (in this case, an LED element), a sound is added.

By adding a voltage measurement module to the measuring circuit, we get a single-mode multimeter designed for safe high voltage measurements.

Using such a device is not difficult: the passive contact on the connecting wire is applied to the ground (zero) bus of the electrical installation. Then the measuring contact must touch the potential measurement point.

Advantages:

high measurement accuracy, functionality can be expanded if necessary;
ability to work with high voltage without additional operator protection equipment;
operator protection is ensured: there is no direct contact with open areas of the body.

Flaws:

higher cost;
The meter is quite bulky.

Why does the indicator light up when you touch the neutral wire?

I have been asked this question many times. One of the reasons is the incorrect use of the LED indicator. How to properly hold the LED probe indicator when searching for a phase is written in the article above.

The second possible reason for this behavior of the indicator is a break in the neutral wire. For example, a circuit breaker installed after the meter on the neutral wire tripped. In old apartments this is not uncommon and is a gross violation of the electrical wiring. It is imperative to remove the machine from the neutral wire or short-circuit its terminals with a jumper.

When the neutral wire breaks, a phase is supplied to it through devices connected to the electrical network, for example, through a switch backlight indicator, a TV in standby mode, any charger, a computer turned off only by the start button and other electrical appliances. The indicator shows this. In this case, the neutral wire can be dangerous and touching it is unacceptable. It is necessary to find and repair a break in the neutral wire, which may also be located in junction boxes.

What is an indicator screwdriver?

This is a tool designed to detect voltage in the electrical network, including hidden ones. Externally, the model may look like a regular flat-head screwdriver with a transparent handle or have a different appearance. However, a probe in the form of a flat bit is required - this is what is used to check the contacts.

Insulation of the handle is also required - the metal part of the device should not come into contact with unprotected human skin, and any metal parts on the handle should not have direct contact with the probe.

They produce products of contact and non-contact types, with different options for sending signals - light, sound, in the form of information on a digital display - as well as with additional functions.

Simple

A working electrical circuit is installed in the case, with a standard set of elements: transistor, resistor, indicator - neon bulbs. The zero phase is the person who closes the contact plate. The tool is not functional - it detects the voltage on the wire, but often does not work when the network voltage is less than 60 Volts. Not suitable for searching for network breaks.

Universal

Portable devices with a wide range of capabilities. An instrument of this type performs contact and non-contact testing, determines open circuits and short circuits using “ringing” of networks, and light and sound warnings help with this. Universal probes are used when repairing or setting up electronic devices and vehicles; they are designed to work with direct and alternating current. The tester operates on a battery, the charge of which is monitored. If the battery loses charge, the universal screwdriver will not work.

The type of indicator screwdriver is selected depending on the intended work. For everyday use, a simple model is sufficient, but for working with electronic devices, choose a universal device.

Method of using an indicator screwdriver

Non-contact - for a network with voltage up to 600 V. The tip is passed along a wire or electrical appliance that requires testing. If there is voltage, the light will also light up. This is a convenient way to track breaks in the circuit.
Contact - an indicator screwdriver is used in networks up to 250 V. While holding your finger on the sensor, the tip of the probe is touched to the place that needs to be checked. If there is voltage, the indicator light will light up.

Types of devices

Indicators up to 1000 volts and above 1000 volts have different external and design features. For low-voltage measurements, up to 1 kV, there are two types of devices:

single-pole, responsive to the flow of capacitive current;
bipolar, gives an indication when active current flows through it.

The single-pole indicator is designed to work in alternating current circuits, to detect phase conductors, in lighting circuits, when phasing an electric meter, and checking cartridges in lamps. Simply put, to detect live wires.

Single-pole phase indicating devices have the same design and typically consist of a gas-discharge indicator lamp, with an ignition threshold of 90 to 120 volts, and a 1 MΩ resistor connected in series. The resistor limits the current to a safe value, about 0.5 mA.

The IN - 90 indicator is made in the form of a screwdriver.

The disadvantages of such indicators include low sensitivity (the indication threshold of some devices starts at 90 volts), as well as sensitivity to interference in neighboring wires.

For networks above 1000 volts, voltage indicators are made with handles made of insulating material and long, preventing a person from approaching current-carrying elements. The appearance of the UVN-10 is shown in the photo below:

When measuring voltages above 1000 volts, they resort to the use of additional protective equipment: rubber gloves, boots or an insulating mat. You can find out from our article!

A two-pole indicator consists of two housings made of insulating material and a flexible insulated copper conductor that connects them. Diagram of a two-pole voltage indicator type UNN-10:

In this circuit, the gas-discharge indicator is shunted by a resistor, which makes the circuit insensitive to induced voltages. Also based on it, an indicator with a voltage indicator UN-1 is produced:

This device uses a special linear gas-discharge lamp and a scale on the body with graduations of 127, 220, 380, 500 Volts.

There are also universal voltage indicators for checking the presence of voltage and indicating its value from 12 to 380 V. For operation in DC circuits, up to 500 volts, and alternating current, up to 380 volts. They can additionally be used to test the integrity of connections.

These devices use LEDs as light indicators, and a large capacitor as a power source.

The digital voltage indicator has an LCD screen with printed values in volts. At a maximum value of 220 volts, all values from minimum to maximum are displayed on the screen. Those. This tester shows an approximate value. The only advantage of this model is the lack of a power source.

Non-contact indicators are designed to detect live conductors, including those hidden in walls or panels. The circuitry of this device responds to an alternating electromagnetic field and is equipped with light and sound indication. We talked more about these devices when we talked about .

The ideal indicator for a trader

The question arises, if the EMA is already working at its limit and shows the most relevant price changes, then why do traders not use the EMA all the time? The fact is that for EMA it does not matter at all how long the trend being studied is. Any more or less significant price surge radically changes the direction of the forecast, which can be very misleading and lead to losses.

It turns out that traders do not need to have indicators with low lag - we need some balance between short reaction time and filtering out false emissions. The most famous of these developments is the adaptive moving average - AMA. There are also quite a lot of variations.

Operating principle of an indicator screwdriver

Regardless of the type of device, its main idea is to provide a signal about the presence of voltage in the network. In this case, contact models determine the voltage by touching a bare conductor (cable core, contact surfaces of devices, conductive liquid, etc.), while non-contact models “read” the electromagnetic field of the area.

However, in any case, the electrical circuit in a conventional indicator screwdriver must be closed to obtain information - namely, press the contact plate at the end of the product with your finger. A person is also a conductor of electricity, and this is the principle of operation of the device.

All products are divided into groups not only according to design features, but also according to sensitivity. High-quality electronic models are deservedly considered the most accurate, while those with a neon lamp are the most insensitive. The last type of tool accepts voltage from 60 V.

Digital multimeters

Digital instruments that measure voltage - multimeters - are very popular among professionals. This universal device for an electrician allows you to check several characteristics of an electrical circuit at once: voltage, current, resistance. In addition to sound and light signaling elements, the device is equipped with a digital display.

Additionally, special current clamps can be purchased that allow you to measure current without damaging the wiring insulation. Some models are equipped with a temperature sensor to check the temperature of electrical equipment - distribution cabinets, switches, electric motors. Such devices, as a rule, are used by those specialists who, due to their line of work, have to visit substations with complex electrical equipment.

Checking the functionality of the device

Before you start working with a screwdriver, you should make sure that the tool is in good working order.

A simple and quick way to check the device is to insert the conductor probe one by one into each hole of the socket. The electrical socket must be live. If the tool is working properly, then when it hits a phase, the indicator will light up, indicating the voltage at the contact. The absence of a light signal and a sound signal, if it is a universal type, indicates a malfunction of the tester; they cannot test electrical equipment.

Sources

https://SdelaySam-SvoimiRukami.ru/3867-prosteyshiy-indikator-urovnya-zaryada-batarei.html
https://YDoma.info/ehlektrotekhnika/electricity-kak-najti-fazu-i-nol.html
https://svetilov.ru/svetovye-pribory/svetodiody/indikator-napryazheniya
https://bestcom55.com/indikator-fazy-na-svetodiode-svoimi-rukami/
https://ues-company.ru/dom/shema-indikatora-fazy.html
https://ProFazu.ru/provodka/instruments/indikatornaya-otvertka.html
https://www.vseinstrumenti.ru/ruchnoy-instrument/elektromontazhnyj/probniki-napryazheniya/

[collapse]