Start.
It is often necessary to find in a bunch of wires where which one goes, to find out the integrity of the circuit, to check if there is a short circuit or an open, it is also often necessary to find out p-n integrity transition of diodes, transistors and other semiconductors, such a tool as a continuity will help us with this. It will undoubtedly be useful to both electricians and electronics. The fact is that using the dialing mode in a multimeter is not always convenient, and some of them do not have this function at all, so such a simple dialing will solve this problem.
The continuity is very practical, its tone of sound depends on the resistance of the tested section of the circuit. The greater the resistance, the less often the clicks, respectively, with a small resistance, there will be a lot of clicks and they will be heard as a squeak, the tone of which can be adjusted by the denominations: That is, on an already finished board with soldered components, you can easily find a short circuit, and p-n junctions we will hear not as a short circuit, the tonality will be different. And if you get used to it a little, then by the sound you can easily tell where the transistor has an emitter and where the collector is (the second one has more clicks).
Frame.
The case is also very important, it will depend on how pleasant it will be to use the device, after all, aesthetics are important. In addition, it will protect the handkerchief and battery from the harsh conditions of everyday life of a person working with electricity.
I took a case from an ATB marker, it ideally includes one AA element and there is still room for the board, and it looks good for these purposes.
As probes, heaps of copper wire in enamel and a cylindrical piece of copper, namely an old soldering iron tip, this non-ferrous metal has low resistance and tolerates O2 more or less well, especially with solder :) On the board itself, the tip is fixed with molten tin on a certain area of copper.
In the picture you can see how the dialing is arranged from the inside, first there is a probe that moves away from the board, then the dialing board itself, then the battery / accumulator, which is tightly fixed with a "plug".
There is also a speaker here - this is an indication element, for loud sound reproduction there are many holes through which it sways the air. (he's not drawn!)
Components and replacements.
The parameter values of all the parts used in this circuit are not critical and may vary, for example, there is no 51k resistor, but there is 47k - then feel free to put it on. All transistors are any, the main thing is that the structure matches (3 - NPN, 1 - PNP).
Marking: BC847– 1 G , BC857 –3 F (and N on the side).
Notifiers.
The speaker, of course, is taken miniature - such as in headphones. Its resistance is usually 16 ohms, and the volume is quite sufficient. I had a loudspeaker (speaker) from the old Nokia 6303ay, very good telephone should be noted. I glued it to the back of the board with hot glue, it acted as a resonator.
If you work in a place where it is very noisy, then you should put an LED parallel to the sound emitter, which will serve as a light indication.
Food.
The dialing power is a 1.5 Volt finger battery, if you increase this value, then it will be possible to check the LEDs, in addition, the sound volume will increase significantly. But in that case high voltage may damage some sensitive radio components.
Adding sensitivity.
Want super-mega sensitivity? Then turn off the electrolytic capacitor C1. Now, if we just touch the probes of the device, then it will already begin to react violently to this. I don’t know why, but if you want such a crazy mode, then put a micro-button on one of the capacitor terminals.
And it’s better for you to have the same, but slightly modified circuit, so we get two modes: very low sensitivity and super-sensitivity up to 120 MΩ. You can easily switch between them using the S1 and S2 buttons.
A photo.
(almost finished board, but without speaker and probes)
(finished board with probe and spring, side view)
Many have encountered such a circumstance when there is no voltage at the outlet. The reason for this in most cases can be a broken wire. In this case, you need to ring the cable that feeds this outlet. Continuity is a check of electrical conductors for integrity, for an open and for the absence of short circuits between them. Such an action will help determine where the breakdown occurred in the electrical network. Next, we will tell you what devices can be used to dial wires and cables.
Dialing methods
There are several ways to ring wires at home:
With light bulb and battery. This is the simplest and fast method. In order to construct such a device, it is necessary to have a light bulb and a battery (several batteries can be connected together), as well as connecting conductors and a probe. In addition, do not forget that the voltage of the light bulb and the battery should be the same, or the battery has more, but not vice versa. The connecting wire must be long enough to ring the wire from a distance.
In order for the dialer to work correctly, it is necessary to mark the cable in any order. The method of operation of such a device is as follows: a wire is connected to one core, which comes from a battery, and a light bulb is attached to the probe. With this probe, touch the conductors at the opposite end of the cable in turn. If the light is on, then this wire is connected to the battery.
You can learn how to ring the wires with a light bulb and a battery from this video tutorial:
Using a multimeter. This device measures various parameters of the electrical network (for example, voltage, current, resistance). In the house, such a device will be indispensable if you need to check the socket or switch, the presence of a break, or find out where the wire goes.
You can ring the cable with a multimeter using the following method:
- The call function is set. Depending on which model of the device is used, this mode is designated differently. As a rule, it is indicated by a diode.
- Then you need to find the phase in the junction box. This is done as follows: turn on the power and check each cable with an indicator screwdriver. We mark the required one with adhesive tape or electrical tape and after that we determine zero.
- After that, you should find the voltage. To do this, set the multimeter to the "voltage measurement" mode. Using a probe, check each wire. If the next time you touch the probe, it lights up in the region of 220 V, then the right one has been found.
To check the wiring in the wall for integrity, you must disconnect the cable from the power source. Set the multimeter to resistance measurement mode. When the probes are closed, zeros should appear on the screen.
The video below clearly demonstrates the technology of cable continuity with a multimeter:
These two methods are convenient if the dialing is carried out at a short distance and one person can do it. If the cable is long and its ends are in different rooms in the apartment or outside it, then a different method is used.
Using handsets. Dialing with telephone headsets is carried out as follows: the capsules in the tube are connected to each other and a battery is connected to them, the voltage of which does not exceed two volts. Thanks to this technique, employees can talk to each other on the phone and coordinate their actions.
Scheme of cable continuity using handsets:
You can ring as follows: the cable on one side is connected to the tube conductor, and the other conductor to any core. On the other hand, the cable connects to the tube conductor, and the other to each core in turn. If the workers hear each other in the handset, then they are connected to the same conductor.
You can see the whole technology of work in this video example:
With the help of a transformer. There is another way by which you can ring cable lines - this is a continuity using a transformer, in which several taps extend from the secondary winding. The technique is as follows: the beginning of the winding is connected to the grounded conductor sheath, and the transformer taps are connected to the cores and feed each of them. If you measure the voltage that exists between the sheath at the other end and the cores, you can determine whether the end belongs to a particular conductor. The dialing will allow you to identify and mark the necessary cores. You can find out about that from our article.
Cable phasing
Phasing is the ability to determine in what order the phases alternate when connected in parallel. This is necessary in order to avoid. Indeed, in order to increase the reliability of the power supply, sometimes one conductor is not enough (or if the consumer's power is too high). In order for the electrical installation to work normally, another wire is placed in parallel. In this case, the phase sequence must be taken into account. The phasing diagram is shown below:
Phasing can be done in several ways: using a voltmeter or an incandescent lamp. A voltmeter is used for 380/220 V installations. The method is as follows: cable 2 in the first installation is connected thanks to a knife switch, and in the second installation, thanks to a voltmeter, it determines the voltage between the core and the bus to which it is planned to connect.
If the voltage is linear, then the core and bus have different phases, so it is forbidden to connect them. If the voltmeter shows zero, then this indicates that the wire and bus have the same potential, respectively, they have one phase and can be connected. Other conductors are checked by the same method.
If there is no voltmeter, then phasing can be done using two incandescent lamps that are connected in series and have rated voltage at 220 volts. If the lamps do not glow, then the wire and bus belong to the same phase.
You should also take into account the fact that after such actions, a certain voltage is stored on the cores of cable products, which is associated with a residual capacitive charge. Therefore, the cable should be discharged after the next passage of voltage. This is done by connecting the conductors to ground.
So we examined the main methods of ringing wires and cables, as well as devices that can be used for such work. We hope that the information provided was useful and interesting for you!
Today I will talk about one very simple and very necessary tool for beginner radio amateurs (and many motorists). This tool is an LED dialer. Used to test a short circuit in a circuit (in circuits with power off), check fuses (by motorists).
Scheme appearance dialing is shown in the figure below:
Such a tool consists of two probes (suitable for any multimeter), an LED, a case, a battery pack, a resistor (50-250 Ohm).
principled circuit diagram dialing is shown below: Nominal
The installation of such a dial is simply disgraceful, since it does not require any circuit boards - it is easy to get by with a simple hinged installation. The principle of operation is also very simple - we connect two probes to the fuse to be checked. If the LED lights up, then the fuse is intact. As batteries, I used two AAA (little finger batteries). A resistor is needed to limit the current (the more current flows through the LED, the brighter it burns, but the faster the batteries run out). Empirically settled on a 100 ohm resistor (selected depending on the type of LED). It is better to use an ordinary LED (an ultra-bright one burns well, but consumes more current and usually works at a voltage of at least 2-2.2 V, while I managed to pick up a regular LED (from those lying in a separate tin can), which quietly burns when 1.6 V and a resistor connected, which means that a probe with such an LED will burn longer with one set of batteries or accumulators.
The appearance of the tool with the housing cover removed is shown in the photo below:
The resistor is soldered to the leg of the LED and placed in heat shrink tubing. (in the photo it is under a layer of hot glue). The battery pack and case were bought in a regular radio market (at the time of writing the article, the battery pack cost 35 rubles, the case - 200 rubles). The probes are taken from an old Soviet multimeter. The battery pack is installed with superglue inside the case. A knot on the probe wires is needed so that the wires do not fly out of the case and solder joints are not damaged.
In the end, I want to add that the LED lights up not only when checking fuses and wire connections, but also when checking resistances of a small value. The resistance value at which the continuity stops working depends on the type of the selected LED and is determined empirically.
This design is a probe with sound indication, designed to monitor the integrity of electrical circuits [Lapkin V.A. We repair ourselves.], distinctive feature device is the simplicity of design, ease of use and undemanding to the power source. Schematically, a sound generator is single-ended multivibrator assembled according to the well-known scheme.
The multivibrator is assembled on MP41A transistors, but any other low-power low-frequency ones will do. pnp transistors(for example, MP25, MP26, MP39, MP40, MP42). Resistors R1 and R2 type MLT-0.25. Capacitor C1 of any type (for example, K73-17 or K10-17B), its capacitance is not critical and should be approximately 0.033 - 0.047 uF. A piezoceramic emitter taken from an old device was used as a sound emitter. The device is assembled on a pseudo printed circuit board.
The body of the probe is a travel case for a toothbrush. The device is powered by a single 1.5 V AA cell located in the front narrow part of the case. The width of the case almost exactly coincides with the diameter of the galvanic cell of a given standard size. That allows you to abandon a separate pad for the battery and install it directly into the case, fixing it with a homemade spring contact.
Pay sound generator together with the sound emitter is installed in the rear widest part of the body. There are ventilation holes near which the sound emitter is located. Through one of the holes, one of the probes of the device is output, made in the form of a wire, about 40 cm long with crocodile clips at the end. It should be noted that, according to operating experience, it is desirable to extend the wire up to 1 m. The second probe is a tin plate, which is simultaneously connected to the positive pole of the battery.
During operation, the user holds the device, similar to a fountain pen, by the part of the case where the battery is located. Since the galvanic cell is the heaviest part of the device, the user's hand holds the probe by the area close to the center of gravity, which increases the convenience of using the device. At the same time, due to the elongated shape of the body, the sound emitter is located close to the head, so that even relatively quiet sound, given by the device when the battery is discharged, is clearly audible to the user. It is convenient to use the device for wire continuity with one hand, unlike a conventional multimeter or avometer. The device was assembled repeatedly and, with serviceable parts, it started working immediately, the whole setting comes down to selecting the desired sound tone using resistor R1.
Most simple work related to electricity is difficult to perform without measuring tools.
It is not necessary to measure the parameters electrical circuit tester, in many cases it is more convenient to get by with a universal probe that infects the presence of these parameters by means of light signals. This is quite enough for convenient and safe work with electrical circuits.
The considered probe-indicator circuit does not contain batteries. Instead of the energy normally used in batteries, probes use the energy of a charged capacitor.
Functionality.
The probe allows you to control the presence of AC and DC voltage in the range from 24 to 220 V, carry out continuity of an electrical circuit with a resistance of up to 60 kOhm and determine the polarity in the circuits direct current.
When connecting probes XP1 and XP2 to a DC source in accordance with the polarity of the input, lights up green LED HL1, indicating not only the presence of a constant voltage in the controlled circuit, but also the presence of a plus at the touch point of the XP1 probe.
Reversing the polarity on the probes causes the red HL2 LED to light up, which, in addition to the presence of voltage, indicates contact with the plus of the HP2 probe.
Under control AC voltage Both LEDs light up at the same time.
The continuity of the circuit during continuity is indicated by the red LED HL2 lighting up.
This is the information you can get with just two LEDs built into this simple indicator probe.
Probe design.
Radio components. To implement the device, you must purchase or find in your stock the following parts:
Resistors R1-220 kOhm and R2-20 kOhm, power 2W, R3-6.8 kOhm;
LEDs HL1 - AL 307G, HL2 - AL 307B;
Diodes KD2 - VD5 - KD103 (possible replacement for KD 102);
Zener diode VD1 - KS222Zh (possible replacement for KS220Zh, KS522A);
Capacitor C1 - K50-6 1000x25.
Frame. Particular attention should be paid to the choice of case - the convenience of working with the probe depends on its configuration and dimensions. Let's consider two cases. In the first option, the relay cover is used, in the second, the case of an unknown gadget.
Holes are made in the cases for the output of the wire with the XP2 probe, LEDs are installed (only for the first option) and the XP1 probes are attached.
Pay. The package dimensions determine the board geometry. Mounting can be hinged, but it is not difficult to do it on a printed circuit board. All radio components (except LEDs in the first version) are mounted on a board that is mounted inside the case.
After installing the board in the case and soldering the conductors to the XP1 and XP2 probes, the probes-indicators are ready for operation. The device does not need to be adjusted.
The charge time of the probe capacitor at a voltage in the network in the range of 220-24V is 3-25 seconds. The capacitor discharge time in case of a short circuit of the probe probes is at least 2 minutes.
