The essential tool for an auto electrician! LED control with beeper! ← Hodor. Why is a control lamp dangerous and how does it check current? Making a 12-volt test lamp Valery Chkalov

Home wiring in normal conditions operation functions for a long time, reliably and safely.

But as soon as an emergency arises for which the protective devices are not designed, problems immediately appear with the operation of household appliances.

The owner has to look for faults in the electrical circuit and eliminate them.

The article gives advice to the home handyman on how to safely search for damage in household electrical wiring using various popular methods, explaining the main points with pictures, diagrams and a video.

Particular attention is paid to how dangerous warning lamp and why it is prohibited by the rules. Check electrical diagram You need a working voltmeter or indicator.

How does the warning light work?

An ordinary incandescent light bulb does not know what fate is in store for it.

In any circuit it works exactly the same as a control or lighting one:

• lights up when the rated voltage is applied to its thread through the wires;
• explodes or burns out when it is significantly exceeded;
• does not create a glow from small currents, the strength of which is not enough to heat up the tungsten coil.

People came up with the name “Indicator Lamp” when they began to use it to evaluate the presence of current in a problem circuit.

Almost until the end of the twentieth century, the test lamp was widely used by electricians to detect faults in wiring, even after its use was prohibited by regulations and severely punished by inspectors. But many people still use this dangerous scheme.

From the memories of an electrician

Two decades ago I had to work as part of a team of relay operators servicing the equipment of a 330 kV substation and a large number of traveling facilities with a lower voltage - 110/10 kV. The protection, automation and control equipment on them is located in cabinets, drawers or on panels with poor lighting.

And the relay contacts, all the details of the electronic circuit are very small and require good vision. They were illuminated in a variety of additional ways, including flashlights. There simply weren’t any convenient headlamps back then. Therefore, we decided to make our own lighting carrier.

They did it quickly and decided to show it to the labor inspector. He looked around and noticed that:

• The lamp device is taken from a lampshade with a housing that is well resistant to mechanical damage and durable glass;
• the power cable with high-strength electrical insulation is securely inserted into the housing with a rubber tube that protects it from breakage when kinked;
• In general, the installation was carried out reliably.

And his conclusion stunned us: this is not a carrier, but a control lamp, well disguised as a lamp. Therefore, he forbids using it...

There is no point in arguing with management in the energy industry. However, with his help, we were able to order and receive battery-powered carriers for lighting. It was not entirely convenient to work with them, but our issue was partially resolved.

Operating principle of the voltage indicator and control lamp

Both of these devices check for the presence of current with a light bulb, but it is implemented different ways. Let's look at them.

Common features

I would like to immediately draw your attention to one important point that will allow you to avoid many mistakes made by novice electricians.

When working with an indicator or measuring instruments, it is necessary to imagine a picture of the flow of current through them along the entire path from the source to the filament in a closed circuit and remember that voltage represents the potential difference between certain points, and not the potential of one of them.

This principle should be followed when analyzing circuits.

How to check voltage with a test lamp

Let's look at the example of a diagram of the operation of an ordinary room socket. The phase and zero potential are supplied to it from the secondary winding of the power transformer at the substation.

Current flows in a closed circuit through the supply cable, socket contacts, control wires, and its filament. By the way, the circuit of an ordinary table lamp works exactly the same.

Operation of a two-pole voltage indicator

Its design can be represented by two wires with contacts and a housing in which a current-limiting resistor with a neon or LED lamp is located.

The current flows exactly the same as in the previous circuit.

Operation of a single-pole voltage indicator

His light bulb glows according to a different principle: the path of current flow is changed.

Due to the current-limiting resistor, a small current is created, which safely passes through the electrician’s body and returns to the source of the transformer substation along the ground circuit. It is sufficient for the indicator to light up.

Differences

The current through the test lamp is a fraction of an ampere. For example, for a power of 40 watts it will be calculated using the formula: 40/220=0.18 A.

A few milliamps are enough to light an indicator LED, and even less - microamps for a neon light bulb. All measuring instruments voltages consume very little current to measure.

The load of the control is much greater than that of an indicator or voltmeter. This is its main advantage to which old electricians are accustomed.

Example from life

Human factor

Electricians who use controls at enterprises worked not only on 220-volt networks, but also on 36-volt networks, which are used to illuminate hazardous areas.

The design of the socket and the shape of the bulbs are interchangeable: when working in control, the bulbs were simply twisted to the appropriate voltage. If, when changing workplaces in a 220-volt network, they forgot about this, then the flask exploded. And for some reason small fragments fly straight into your eyes.

Mechanical damage

The glass of the flask is fragile and breaks easily, especially in a portable design. If a stationary lamp has a lamp screwed in and secured, then the control is usually held in the hands. She might slip out.

And a person does not always comply; he is capable of slipping and dropping it from his hands or falling with it and cutting himself on the glass.

A particular danger is falling with a lamp to which voltage is applied. The filament will break, and the electrodes for its attachment may short-circuit through a random conductive object or human body. immediately arises short circuit with all aggravating circumstances.

Possibility of touching live parts

To create an electrical contact when connecting a control, they usually leave the bare end of the metal on the wire or solder a simple tip with an alligator clip.

This point is under mains voltage and poses a danger.

Homemade warning lamp protection

Considering the risks of working with the controller, experienced electricians tried in every possible way to protect its design:

• put a tin or other lampshade on the cartridge:
• wrapped the flask with tape or rags;
• adapted a hook for hanging;
• mounted a fuse in front of the cartridge that protects against short circuits;
• used to connect wires with a high degree of insulation protection;
• used for connection were probes with safety limiting rings from measuring instruments designed to operate under voltage.

However, even a complete set of all these measures does not allow you to safely perform work with a control lamp. It is more reliable to work with an indicator and a voltmeter.

How to find phase and zero

Let us recall the voltage distribution diagram in a three-phase network, made.

During military service, during exercises, I had to practically solve a similar problem in the field conditions of a training ground. It was necessary to find phase and zero in a six-core power cable connected to voltage in order to power the lighting circuit from them.

There was no indicator or measuring instruments. A messenger was sent for the light bulbs, and we made do with an ordinary electric razor and a piece of insulated wire.

The test was carried out in two stages:

1. determination of phase ends;
2. search for zero.

Measurement of phase voltages

The work proceeded according to the following scheme:

• they hammered a piece of metal into the ground next to the cable;
• they attached one contact of an electric razor plug to it;
• a piece of wire was screwed to the second pin and secured with threads;
• with the free end of this conductor we touched all the cores of the cable in turn;
• We marked the three wires on which the razor motor started working - this is how we identified the phase ends and chose the one where it would be easier to install the subsequent circuit.

Search for zero

The electric razor plug was removed from the homemade grounding and, using the freed pin, a contact for current was created alternately on the remaining three wires of the cable with a section of wire connected to the selected phase.

When the engine started, it indicated a working zero, and the other two ends were simply in reserve.

Experienced electricians will see many safety violations in our actions. But this example is given for a different purpose - to show the technical feasibility of solving such a task and its implementation with awareness of the risks and dangers. And in a critical situation, a warning lamp or indicator can be replaced with any power tool, for example.

To better understand the principles of troubleshooting in electrical wiring, I recommend watching the owner’s video “Tips from an Electrician” about the practice of searching for short circuits with a test lamp. I think that they will be useful when using an ordinary voltmeter.

ASUSTENT
Funny.
Although today, popular car models are full of “helpers” for installing alarms.
They are called “installation cards”, they look like tables, or even a PDF with a table and photographs, with explanations of what to connect and where.
With such installation maps, sometimes you don’t even need to pierce anything.
More precisely, you pierce it only to check, then you immediately expose the wire and make the connection.

The wired blade is something new for me.

blow05
No offense - I'm surprised that the living example on the table with explanations is not clear to you.
It couldn't be simpler. I find it difficult to even explain it more simply. IT'S MEGA SIMPLE THERE.
Or you just didn't watch the video

I'll try to explain again, but if you don't understand, that's it.

I understand that you do not understand how to interpret the control indication when checking a fuse without removing the last one from the socket.

Let me explain.
The fuse is a jumper
The lamp is almost a jumper (low resistance)

Turn on the lamp switch.
Let the dimensions.
PLUS runs from the switch to the fuse. Let there be a conditional ENTRANCE leg.
Passing through the fuse it exits through the conditional leg OUTPUT
And connects to one of the terminals of the lamp spiral.
The other terminal of the lamp coil is connected to MINUS continuously.

If the fuse is good, then there will be a PLUS on both legs of the fuse (both at the input and output). (red control LED)
Which is logical, this is a jumper...

If the fuse is faulty, then its INPUT pin will have a plus (from the switch)
And the OUTPUT pin will be MINUS.
Those. when there is a PLUS on both terminals of the fuse, then it is 99% serviceable.

When one terminal is PLUS and the other is MINUS (or there is no current), then the fuse is faulty.

Where does the MINUS come from, on the second leg of the fuse when it burns out?
Let me explain.
The lamp is in fact almost a jumper, and electricity passes through it without global losses.
The second terminal of the spiral of our lamp is continuously connected to MINUS.
This MINUS, passing through the spiral, goes to the first terminal of the lamp, and comes to the OUTPUT leg of the fuse.

Thus, when the switch is turned on)))
On the leg INPUT fuse PLUS
On the leg there is a MINUS fuse OUTPUT

If the fuse is faulty.
Those. The difference in polarity on the fuse itself indicates its malfunction.

When PLUS hangs on the INPUT fuse leg
And there is NOTHING hanging on the fuse leg, which means that the load is disconnected at the moment (there is nothing in the cigarette lighter socket), or the wire going to the load is damaged, or the load itself is damaged.

Why can’t you ring the fuse without removing it from its socket, with the voltage turned off?

Let me explain.
When the voltage is turned off, it is easy to get false measurement results.

Let's play the same game?)

On the legs INPUT and OUTPUT of the fuse we have a minus.
Where is he from? Is this the same minus, on different legs?

In the case of a working fuse it will be something like this.

The minus (body) is constantly connected to one terminal of the lamp, passing through the spiral of the lamp, to the legs of the pre-OUTPUT INPUT.
Hence the minus on both legs.

In the case of a faulty fuse, this may happen.

On the legs INPUT AND OUTPUT of the fuse there are also (!) minuses hanging.
Where do they come from?
Let me explain.
On the fuse leg, the OUTPUT minus is taken according to the same scheme.
Constant minus, lamp spiral, and fuse OUTPUT to the leg.
It would seem that there should be nothing on the INPUT fuse leg, and sometimes it is so... But sometimes...
Another load is connected to the INPUT leg of the fuse, which, like our lamp, when turned off, passes the negative through itself, leading it to the INPUT fuse leg.

That is, when the power is turned off, we can see minuses on its terminals even if the fuse is working, and if it’s faulty, we can also see minuses.

Therefore, measurements cannot be taken when the power is turned off.

Such a “threesome” is present, for example, in the fuse circuit of headlight lamps.
They have one switch (relay), and then the plus splits into 2 separate fuses and 2 separate circuits with port and starboard lamps.

If we turn on the power, we exclude the possibility of a false negative that has passed through who knows what circuits.

The exception is the options where the load is constantly PLUS, and the switch turns on the minus.
But among lamps this is not a common case.

(I only remember Solaris and Hyundais, and some variants of Corolla where the low beam is controlled with a minus, having a constant plus. If the fuse on the positive burns out, then competitions begin, one of the headlights begins to shine half for the low beam, half for the high beam, etc.)) ))

And although today there are already special indicator screwdrivers for checking the phase, as well as universal measuring instruments, control lights are still valued and every electrician and car enthusiast has them. This is a simple and convenient device with which you can find out whether there is voltage in the outlet, and also determine which of the fuses in the car has failed, and which pin on the connector receives 12 volts. Next, we will tell you how to make a control for 12 and 220 Volts with your own hands, providing clear photo examples, diagrams and video instructions, according to which everyone can assemble this tool.

For home network

If you decide to make a test lamp for the presence of voltage in the house for a household electrical network, then all you need is:

1. 220 V light bulb.
2. Electric cartridge.
3. Two single-core copper wires, 50 cm long each.
4. Probes for ease of use of the control.
5. Protective cover for light bulb.

So, all you need to do is connect the wires to the socket and screw the lamp into it. As you already understood, a homemade 220 Volt control light has a fairly simple design, which allows even an inexperienced electrician to assemble it with his own hands.

To make it convenient to use the control, it is recommended to additionally connect the ends of each wire with probes, which will be much easier to use if necessary. Such probes can be made in various ways. For example, from the body of a ballpoint pen and a piece of thick single-core copper wire or a nail. It is imperative that the probes are well insulated, since even a small exposed area in the wrong place can lead to electric shock.

It is also recommended to additionally protect the incandescent lamp with a casing, be it a wire protection or a transparent plastic cap of a suitable size. It is necessary to protect the lamp because they are often subject to measurements and careless handling. Modern led light bulbs, because they are protected by a durable plastic dome, and they do not require a casing.

Photo examples of several homemade options from a light bulb and two wires can be viewed below:

For auto

If you want to make a 12 Volt control for your car yourself, we recommend using the following circuit:

In this example, VD1 and VD2 are LEDs that will signal the direction of current in the circuit. For greater clarity, you can take them in different colors and mark them on the body. HL1 is a regular 1.2 W, 12 volt light bulb that simply shows the presence of voltage between the terminals of the test lamp, just like in a 220 volt circuit. Checking with its help is carried out by pressing the button, which is also indicated in the diagram. The author of the diode test lamp used a regular wood screw as a probe; it can be replaced with any convenient nail or piece of wire. It is recommended to use a stranded wire, because it is flexible and will not be damaged so quickly during operation. Unlike the 220V control, car homemade must be equipped with a wire about 2 meters long so that measurements can be taken even inside or under the car. You should install a small alligator clip on the free end of the wire; with it you can connect to ground in almost any part of the car, which is very convenient. Well, the last thing to note is that to make the device neat, use a cigarette lighter plug, which will become an excellent housing for the control light.