I present to your attention a small sample that can be assembled in half an hour. It allows you to ring various circuits and check the presence of alternating and direct voltage from 5 to 380 Volts.
I did not check above 380 V. Be careful and careful, safety comes first!
Probe diagram for auto electrician and electrician
The sampler is very convenient when repairing a car, so no matter how many times I made them, the drivers I knew immediately “privatized” them. The details can be absolutely anything. The choice of the KT312 transistor is determined solely by the convenience of wiring. Any low-power NPN silicon transistor can be used.
The probe has a small drawback, and perhaps another advantage - high sensitivity. Let's say the transformer is connected to a 380V network through fuse links, and if one fuse link burns out, then the probe at this end through the winding will still show the presence of voltage on the secondary.
In my opinion, if you connect a dinistor, for example KN102, in series with resistor R1, the situation should change. Since these samples do not stay with me for a long time for the reason described above, I was not able to test this modification in practice.
A secret document from the last century. Opened and carefully scanned.
Do you remember how it all began…
Operating procedure
And it couldn’t be simpler. We have two probes. Structurally, probe X2 comes out of the body in the form of a rigid spoke, and X1 - in the form of a wire with some margin and ends with an alligator clip. There are two LEDs installed on the body: green and red.When the probes are shorted (continuity), the green light turns on. If there is any resistance, then this will be noticeable by the intensity of the green light. Red is off at this time.
If some voltage is applied to the probes, both LEDs light up. In this case, when checking the DC voltage, the indication will only be if the connection is correct: pole to probe X2. The phase wire is determined as follows: we take probe X1 in our hand, and with probe X2 we touch the circuit under study. If the LED is on, it means there is a phase.
The probe runs on two batteries, you can use small “tablets” and remains operational for a couple of years.
The photo is not mine!
I don’t have a ready-made sample at the moment, but I’ll try to make one this weekend and attach photos. So far I have found some photos on the Internet, I think the essence is clear.
Sources
Unfortunately, this was a long time ago, so I can’t pinpoint the exact source. In general, based on materials from Radio magazine and the Internet.Health and good luck to everyone!
Addition from [email protected]- printed circuit board in LAY
▼ 🕗 01/24/15 ⚖️ 8.57 Kb ⇣ 53
In everyday work, electricians often need to take voltage measurements and test circuits and wires for integrity. Sometimes you just need to find out whether a given electrical installation is energized, whether the socket is de-energized, for example, before changing it, and similar cases. A universal option that is suitable for making all these measurements is to use a digital multimeter, or at least an ordinary pointer Soviet ABO meter, often called “ Tseshka”.
This name came into our speech from the naming of the device Ts-20 and more recent versions of Soviet production. Yes, a modern digital multimeter is a very good thing, and is suitable for most measurements carried out by electricians, with the exception of specialized ones, but often we do not need all the functionality of a multimeter. Electricians often carry with them, which is a simple continuity tester, powered by batteries, and indicating the continuity of the circuit on an LED or light bulb.
The photo above shows a two-pole voltage indicator. And to control the presence of a phase, use an indicator with a screwdriver. Two-pole indicators are also used, with an indication, as in the case of a screwdriver indicator, on a neon lamp. But we now live in the 21st century, and electricians used these methods in the 70s and 80s of the last century. Now all this is long outdated. Those who don’t want to bother with manufacturing can buy a device in the store that allows you to ring circuits, and it can also show, by lighting a certain LED, the approximate voltage value in the circuit being tested. Sometimes there is a built-in function for detecting diode polarity.
But such a device is not cheap, I recently saw it in a radio store for a price of around 300, and with extended functionality - 400 rubles. Yes, the device is good, there are no words, multifunctional, but among electricians there are often creative people who have knowledge of electronics that goes at least minimally beyond the scope of a basic college or technical school course. This article was written for such people, because these people who have assembled at least one or a couple of devices with their own hands, they can usually estimate the difference in the cost of radio components and the finished device. I can tell you from my own experience, if of course it is possible to choose a case for the device, the difference in cost can be 3, 5, or more times lower. Yes, you will have to spend the evening assembling it, learning something new for yourself, something you didn’t know before, but this knowledge is worth the time spent. For knowledgeable people, radio amateurs, it has long been known that electronics in a particular case is nothing more than assembling a kind of LEGO set, albeit with its own rules, which will take some time to master. But you will have the opportunity to independently assemble, and if necessary, repair, any electronic device, initial, and with gaining experience, medium complexity. Such a transition, from an electrician to a radio amateur, is facilitated by the fact that the electrician already has in his head the base necessary for study, or at least part of it.
Schematic diagrams
Let's move from words to action, I will give several probe circuits that can be useful in the work of electricians, and will be useful to ordinary people when carrying out wiring, and other similar cases. Let's go from simple to complex. Below is a diagram of the simplest probe - an arcade on one transistor:
This probe allows you to test wires for continuity, circuits for the presence or absence of a short circuit, and, if necessary, also tracks on a printed circuit board. The resistance range of the dialed circuit is wide, ranging from zero to 500 ohms or more. This is the difference between this probe and the arcade, which contains only a light bulb with a battery, or an LED connected with a battery, which does not work with resistances from 50 Ohms. The circuit is very simple and can be assembled even by surface mounting, without bothering with etching and assembly on a printed circuit board. Although, if foil PCB is available and experience allows, it is better to assemble a probe on the board. Practice shows that devices assembled by surface mounting may stop working after the first fall, while this will not affect a device assembled on a printed circuit board, unless, of course, the soldering was done well. Below is the PCB for this probe:
It can be made either by etching or, due to the simplicity of the design, by separating the tracks on the board from each other with a groove cut with a cutter made from a hacksaw blade. A board made in this way will be no worse in quality than an etched one. Of course, before applying power to the probe, you need to make sure that there is no short circuit between sections of the board, for example, by testing.
Second sample option, which combines testing functions that allow testing circuits up to 150 kiloOhms, and is even suitable for testing resistors, starter coils, transformer windings, chokes and the like. And a voltage indicator, both direct and alternating current. With constant current, the voltage is shown from 5 volts to 48, possibly more, I have not checked. AC shows 220 and 380 volts easily.
Below is the PCB for this probe:
Indication is carried out by lighting up two LEDs, green when dialing, and green and red when voltage is present. The probe also allows you to determine the polarity of voltage at direct current; the LEDs light up only when the probe probes are connected in accordance with the polarity. One of the advantages of the device is the complete absence of any switches, for example, the limit of the measured voltage, or dialing modes - voltage indication. That is, the device operates in both modes at once. In the following figure you can see a photo of the assembled probe:
I collected 2 such probes, both still work fine. A friend of mine uses one of them.
Third sample option, which can only ring circuits, wires, tracks on a printed circuit board, but cannot be used as a voltage indicator, is an Audio probe, with additional LED indication. Below is its schematic diagram:
I think everyone has used audio dialing on a multimeter, and they know how convenient it is. When making a call, you do not need to look at the scale or display of the device, or at the LEDs, as was done in previous probes. If our circuit rings, then a beeping sound is heard with a frequency of approximately 1000 Hertz and the LED lights up. Moreover, this device, like the previous ones, allows you to ring circuits, coils, transformers and resistors with a resistance of up to 600 Ohms, which is sufficient in most cases.
The picture above shows the audio probe circuit board. The audio dialing of a multimeter, as is known, only works with resistances up to a maximum of ten ohms or a little more; this device allows dialing in a much larger range of resistances. Below you can see a photo of the sound probe:
For connection to the circuit being measured, this probe has 2 sockets compatible with multimeter probes. I assembled all three probes described above myself, and I guarantee that the circuits are 100% working, do not need adjustment and start working immediately after assembly. It is not possible to show a photo of the first version of the sampler, as this sampler was recently given to a friend. Printed circuit boards of all these probes for the sprint-layout program can be downloaded in the archive at the end of the article. Also, in Radio magazine and on resources on the Internet, you can find many other probe circuits, sometimes supplied directly with printed circuit boards. Here are just a few of them:
The device does not require a power source and operates when dialing from the charge of an electrolytic capacitor. To do this, the probes of the device need to be plugged into a socket for a short time. When ringing, LED 5 lights up, voltage indication LED4 is 36 V, LED3 is 110 V, LED2 is 220 V, LED1 is 380 V, and LED6 is a polarity indication. It looks like this device is similar in functionality to the installer’s sample shown at the beginning of the article in the photo.
The figure above shows a diagram of a probe - a phase indicator, which allows you to find the phase, ring circuits up to 500 kiloOhms, and determine up to 400 Volts, as well as voltage polarity. On my own behalf, I will say that it is possible to use such a probe less convenient than the one described above and which has 2 LEDs for indication. Because there is no clear certainty about what this probe is showing at the moment, the presence of voltage or that the circuit is ringing. Of its advantages, I can only mention that it can determine, as already written above, a phase wire.
And at the end of the review, I will give a photo and diagram of a simple probe, in a marker body, which I assembled a long time ago, and which any schoolchild or housewife can assemble if the need arises :) This probe will be useful on the farm, if you don’t have a multimeter, for testing wires, determining the functionality of fuses and the like.
The figure above shows a diagram of this probe that I drew, so that anyone, even someone who does not know a school physics course, could assemble it. The LED for this circuit needs to be taken from the Soviet Union, AL307, which glows at a voltage of 1.5 Volts. I think, after reading this review, every electrician will be able to choose a sampler according to his taste and degree of complexity. Author of the article AKV.
Discuss the article REVIEW OF ELECTRICAL TESTS
Electrical voltage is invisible and often dangerous. This certainly applies to the electrical grid. Therefore, electricians and homeowners who have to repair appliances and wiring must use special probes to detect high voltage, where wiring is installed, and check the integrity of sections of wiring. They will help you find phase and zero.
Electricians often use an indicator screwdriver. This is a small screwdriver, rather "weak" in appearance, unable to tighten screws with a large torque. But she has a different purpose. This is a network phase indicator. The phase wires of the network are under increased voltage relative to the ground and the neutral wire, which is deadly to humans.
The indicator screwdriver is a simple and reliable voltage tester. It does not measure voltage, but it clearly indicates the presence of voltage, which CAN be dangerous. The most common indicator is based on a neon light bulb. This is a classic that is very difficult to compete with, and here's why:
- Simplicity of the device
- High reliability,
- High sensitivity,
- Cheapness.
It is worth paying detailed attention to it in a separate section and describing how this probe works.
Gas-discharge network voltage indicator
The operating principle of the indicator screwdriver is based on a particularly low glow discharge current in a neon light bulb, which can be visually detected. At the same time, the discharge voltage is very well located in the range of 70–80 volts and above.
A current-limiting resistor with a rating of 500–1000 kilo-ohms is connected in series with the light bulb. It protects the light bulb and the human body from excessive current.
The peculiarity of the neon indicator is that a person is part of an electrical circuit to which high voltage is applied. But since the human body has a resistance of about 1–4 kilo-ohms, the overwhelming majority of the voltage drops across the light bulb and the resistor connected to it.
Units of volts drop on the person himself, which is completely safe. Under no circumstances should you use a screwdriver without resistance!
You can't do almost anything with an indicator screwdriver except determine phase and zero. But this is a very important and mandatory task that is directly related to electrical safety. As a screwdriver, the indicator is quite weak and such a screwdriver cannot be used to tighten the screws with great force.
Hold the screwdriver in your hand and carefully touch live parts. In this case, be sure to touch the metal button or rim on the insulating handle of the screwdriver so that the circuit is closed through the body to the ground. If the light inside the screwdriver glows crimson, then this conductor is one of the phases of the network. Otherwise, it is a neutral connected to the ground, or grounding, or an isolated section of the circuit (conductor).
The glow can be observed even on those conductors that “do not give current”. This is network interference via capacitive coupling. You also need to be careful with them. If the capacitance is large enough, then such a conductor can be dangerous.
Other types of indicators
In addition to the classic neon probe circuit, there are several more indicators. Some of them are not designed to check the mains voltage, but they allow you to test the wiring for integrity and look for breaks and bad contacts. There are also devices with many functions.
On LED
A screwdriver voltage indicator can use other principles, for example, there are LED probes. The operating principle of an LED is to generate light quanta using transitions of excited electrons to lower levels. They practically do not heat up and work like ordinary diodes. However, the current at which the LED begins to noticeably glow already reaches several milliamps, so the simplest of these probes always have a grounding alligator.
Often a battery is built into an LED screwdriver and this allows it to be used as a tester for de-energized circuits. A battery-powered indicator screwdriver can contain a simple field-effect transistor electronic amplifier. The circuit of its shutter includes a probe - a screwdriver blade or an awl.
The LED is connected in series with the battery through a field-effect transistor channel. A very weak current flowing through the gate of the transistor and then the capacitance of the insulated handle into the human body opens the channel of the field-effect transistor. The current is amplified hundreds of times and this is quite enough to light up the LED.
This indicator is suitable for testing wires and switches. With its help, you can even detect the wiring phase in the wall if there is voltage. The field-effect transistor responds to the negligible current flowing through its gate capacitance, that is, the probe with it is able to detect weak electric stray fields from electrical wiring.
If you need to ring a wire or the serviceability of a closed switch, then one end of it needs to be connected to the probe, and the other to the “patch” at the end of the screwdriver. A lit LED will indicate the integrity of the circuit, which means there are no breaks and the contacts are in good condition.
ATTENTION! It is not recommended to test coils and electric motors in this way. Self-induced voltage can damage a FET probe and even a simple LED probe. For such purposes, it is better to use a multimeter in dialing mode.
The electronic indicator contains a miniature battery, an electronic chip and an LCD display. It may also contain two-color LEDs and a buzzer (“beeper”). You can even measure temperature with it.
The sonic screwdriver emits a signal, which is very convenient, since the eye is not distracted, and especially in bright light, when the glow of a neon indicator or LED may not be noticeable. The instructions for the device explain how to find the phase or perform other checks.
An electronic indicator is considered more advanced than an indicator screwdriver with an LED, but this is more of a marketing thing. In practice, electricians rarely use such probes due to their high cost and short service life. There are really high-quality models, but they cost tens of dollars, and besides, they are almost absent on the Russian market, which is occupied by inexpensive Chinese products.
This is not just an electrician's probe, it is a measuring device that allows you to get much more information than just “is” or “is not”. A multimeter can measure AC or DC voltage, as well as current and resistance. The multimeter has a special chip with an economical analog-to-digital converter and is powered by a battery (usually size 6F22 - “Krona”).
Here are some simple examples of what you can do with it, such as how to test an outlet with a multimeter.
How to check grounding in an outlet:
- Let's turn off the circuit breaker feeding the outlet!
- Set the multimeter switch to the dial position.
- Connect one probe to the ground terminal of the outlet.
- Let's connect the second probe to the ground bus.
- If there is sound, then the PE wire from the socket is working.
How to check the voltage in an outlet:
- Set the multimeter switch to the position of measuring alternating voltage at a limit of 700 V.
- Let's make sure that one probe of the device is connected to the Common terminal. (Common), and the second to terminal V. This is very important!
- Let's connect one probe to one socket of the socket, and the second to the second. The device should show an effective voltage value of 200 - 230 volts.
How to check a light bulb with a multimeter:
- Set the multimeter switch to the kilo-ohm position (ohmmeter).
- Let's connect the probes: one to the common terminal, and the other to terminal V.
- Let's connect the light bulb base to the probes in any order. If this is a working incandescent lamp, then the device will show a resistance of the order of tens or hundreds of ohms. If it does not show anything (or one in the most significant digit), then the light bulb is faulty.
ADVICE Testing LED lamps in this way can give very uncertain results, since they use an electronic circuit that begins to react at much higher voltages than what a conventional multimeter gives.
It is better to choose the appropriate tool for each task. When starting to repair wiring or install new devices, it is necessary to de-energize the area of the upcoming work and provide a warning to those who may turn it on! It is not allowed to work alone, it is dangerous! The best way to make sure there is no voltage is to use an indicator screwdriver. A multimeter will be inconvenient here.
After installation or repair in a de-energized area, it is necessary to check the absence of short circuits and measure the insulation resistance. A multimeter will be useful here.
Those who have tried to use testers where the indication is used by sound in, say, noisy workshops will say that this is extremely inconvenient. In such a situation, you have to simultaneously hold the probes of your device and click the tester operation switch, looking for indicators. Where special accuracy in measurements is not needed, as a rule, they look for short circuits, breaks, check whether the magnetic starter coil is intact or broken, and whether the necessary parts are energized.
Such a probe will allow you to check engines, check rectifier diodes, and much more. The probe does not have an operating mode switch or a power switch. It has two LEDs, one red, the other yellow, as well as a neon lamp. When the probes are closed, the current consumption is 100 mA; when they are open, there is no current consumption at all. It is powered by a Krona battery, the voltage of which is 9 volts. Even if the supply voltage drops to 4 V, the device will remain operational.
If you ring the circuit resistance between 0 and 150 ohms, you will see the green LED
. If the circuit resistance is in the range from 150 ohms to 50 kohms, only yellow LED
. When a voltage of 220 - 380 V is applied, the neon lamp will light up and the LEDs will begin to flicker slightly.
A probe is made of three transistors. In the initial state, all transistors will be closed, because the probe probes are open. As soon as you close the voltage probes, positive polarity through diode VD1 and resistor R5 begins to flow through the gates of field-effect transistor V1, which will open and connect to the negative wire of the source, passing through the base-emitter of transistor V3. At the same time, LED VD2 will light up. Transistor V3 will open and LED V4 will light up.
The V2 LED will turn off if you connect resistance probes within the range of 150 ohms - 50 kohms. As soon as we apply mains voltage to the probes, the neon light HL1 will flash. The mains voltage rectifier is assembled using diode VD1. As soon as the voltage on the zener diode VD3 reaches 12 volts, transistor V2 will open, which will block transistor V1. The LEDs will flicker slightly.
We replace transistors V2, V3 with 13003A from a conventional energy-saving lamp. We take a zener diode D814D, KS515A or any other with a voltage of 12-18 V. Small-sized resistors 0.125 W. We take the neon lamp from the screwdriver indicator. AL307 LEDs or similar ones, yellow and red. Rectifier diode with a current of at least 0.3 A and a reverse voltage of 600 volts.
If installation is done correctly, the probe will start working immediately after power is applied. The range of 0-150 Ohms can be shifted during setup by selecting resistor R2.
The probe must be placed in a housing made of special insulating material. Let's say you can use the case from a telephone charger. From the front we take out the probe-pin, where we put on a piece of PVC tube, but on the opposite side of the body there is a wire made of good insulation with a crocodile or pin.
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. In this article we will tell you what these devices are needed for, what principle they work on, and how to make an LED voltage indicator with your own hands.
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 N-P-N 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. Now you know how to make a voltage indicator based on a telephone earphone.
The manufacture and use of a simple voltage probe is clearly shown in the video:
Conclusion
In this material, we described how you can assemble an LED voltage indicator with your own hands, and also looked at the issue of making a simple diagnostic device based on an audio earphone.
As you can see, it is quite easy to assemble an LED indicator, as well as a sound detector, on your own - for this you just need to have a soldering iron and the necessary parts on hand, as well as have minimal electrical knowledge. If you don’t really like assembling electrical devices yourself, then when choosing a device for simple diagnostics, you should choose a regular indicator screwdriver, which is sold in stores.
