Voltage indicator in the car. car indicator

In the article about “”, I raised questions about superheterodyne reception and the restructuring of the “UKV-2-08 S” block to the FM range, but they were lost in the long “sheet” of text. Therefore, I put everything in a separate entry.

Updated 06/15/19. Thanks to reader Dmitry for the inspiration!
The methodology is absolutely valid for VEF 214, VEF 216, VEF 222.

Before we begin. Unrebuilt "VEF" with its VHF ( 66 — 74 MHz) can quite tolerably catch powerful stations from the lower part of the FM range ( 87,4 — 95,4 MHz). Most often this is a hindrance, but sometimes it can help. For example, you can broadcast with an FM transmitter on the frequency 92 MHz, and set “VEF” to 70,6 MHz. . For those who don’t want to delve into it, just remember the words “mirror channel.”

VHF block diagram. We are interested in the line “VEF 221” - it had an FM band.
First of all, we change the capacitors. The block can not be removed from the chassis, but there is nothing to do here without tweezers.

C VHF FM
C3 33 pF -> 8.2 pF
C4 82 pF -> 33 pF
C6 47 pF -> 33 pF
C13 22 pF -> 5.1 pF
C14 75 pF -> 62 pF
C15 12 pF -> 5.1 pF
C19 15 pF -> delete

If the required denomination is not available either in your own warehouses or in stores, you can deviate a little from it. 5.1 pF is replaced by 5.6 pF, and 62 pF is replaced by 68 pF.

I highly recommend capacitors like NP0(“en-peh-zero”). Their design ensures that neither temperature nor time will affect the capacitance of the capacitor. For example, 33 pF. Of course, you can put a regular “flag” or a Chinese “yellow drop” in a suitable container, but their stability is much worse. On a hot sunny day the receiver may become a little upset. Do we need it?

The instructions for "VEF 221/222" indicate that C3 should be 82 pF. This is a typo, you need 8.2 pF. Previously, I myself set it to 82 pF, but by replacing it in “VEF 216” and “VEF 214” with 8.2 pF, I got higher sensitivity.

For aesthetes C13 can be tuning - 2/10 pF. Moreover, there are holes for it on the board.

After replacing the capacitors, you can turn on the receiver, but you still need to adjust the circuits. Thank you Siarzhuk from the “RadioKot” forum for the base of the described methodology.

1. Pull out the telescopic antenna.

2. Disable AFC and BSN (VEF 214), disable BSN (VEF 216, 222).

3. Using a receiver with a digital scale, determine where the boundaries of the FM range in VEF lie. There are three ways:

a) hear stations at the upper and lower edges of the “VEF” scale, and then find out their frequencies - for example, with the radio receiver built into the phone. A simple and democratic way;

b) using any FM transmitter (I have this one) make your own station at the edges of the range and find it with “VEF”, or vice versa - tune “VEF” to the edge of the scale and adjust the frequency of the transmitter. Costly, but more convenient way;

c) use the SDR receiver to see the harmonic from the VEF local oscillator. The most difficult and expensive, but the most visual and accurate way.

This harmonic will be on 10,7 MHz is higher than the frequency of the current station tuned. In my case, the local oscillator is tuned from 97,85 MHz up to 122,47 MHz, which gives the range 87,15 — 111,77 MHz. This is wider than "official" FM ( 88 — 108 MHz), but if you carefully select the values C13…C15, then you can definitely hit it.

4. Rotating the core of the heterodyne coil L3 shift the local oscillator frequency so that the stations are about 88 MHz were taken closer to the right edge of the scale. The core is brass, so to increase the generation frequency it must be tightened.

At frequency 86,6 MHz station can be received 108,0 MHz - this is called “mirror channel interference” (as well as the above mentioned 70,6 MHz and 92 MHz). Therefore, the local oscillator must be adjusted so that all “DSLRs” remain on the right side of the scale, behind the number “10”, and the scale itself begins, let’s say, with 87,5 MHz. This is especially true for those who rebuild the receiver based on another receiver, comparing the received frequencies.

Owners of FM transmitters grin sarcastically, it’s easier for them: they set 87,5 MHz on a hurdy-gurdy, whatever L3 until you hear your signal on VEF.

Owners of SDR receivers add to the desired beginning of the scale 10,7 MHz and catch this harmonic in the area 98 MHz. The first category of citizens SUDDENLY bursts in here, rebuilding “VEF” using a receiver with a digital scale - they will find a powerful signal of amazing silence.

There are rumors (I haven’t personally checked, I’ll leave it to you) that using a trimmer capacitor C13 you can set the upper limit of local oscillator tuning.

5. A microcircuit lives in the DFM block K174ХА6. You need to connect a multimeter to its 14th leg with a measurement limit of 2 volts. You can solder wires and connect to it.

I specifically disassembled my legendary “216” for the sake of these photos, so don’t be surprised by the large number of unnecessary parts in it.

6. Rotating core L2, we achieve the greatest tension in the position “about 87 MHz".

7. Rotating the rotor of the tuning capacitor C8 in the UHF circuit, we achieve the highest voltage in the position “about 108 MHz".

8. We repeat points 6-7 several times.

9. Rotating core L1, we achieve the greatest voltage in the middle of the range, the position “about 100 MHz". I have it almost unscrewed.

10. Coil L4 is responsible for the signal level from the VHF unit to the DFM unit, and when nothing works, and the reception is still unsatisfactory, it can be used to increase the level. However, if the signal is too powerful, previously unnoticed noise and “mirror images” may creep in.

11. C13…C15 It is advisable to pour paraffin over it; it can also be used to fix the coil cores in place. Since these capacitors are located in the frequency-setting circuits, temperature and vibration can affect the tuning of the receiver. And if we rotated the temperature on the capacitor leg NP0, then we will protect ourselves from vibrations mechanically.

That's all - the UKV-2-08S block has been successfully re-strung. And to the 14th leg K174ХА6 You can solder an LED - it will work as an indicator of fine tuning to the station.

Multifunctional and very simple automotive voltage indicator for checking automotive electrical equipment. More convenient than expensive devices when troubleshooting. Will help motorists on the road and in the workshop to troubleshoot vehicle electrical equipment. The indicator circuit is simple and accessible for self-production.

Song by V.S. Vysotsky - A case on the road 4.2 MB

(To troubleshoot vehicle wiring)

When searching for faults in cars using an Avometer, you have to face certain difficulties. It is not uncommon for a lamp or relay to not work due to increased contact resistance, but a voltmeter with a high internal resistance shows normal voltage. Sometimes in such cases a test lamp is used to determine faults, but the range of resistances and voltages that can be determined by the lamp is quite limited. In both cases, when measuring the voltage on the wire being tested, it is not always clear that the voltage comes directly from the battery, through a light bulb, relay or bad contact. If you check an electrical circuit with an ohmmeter, you need to spend time finding the other end of the circuit being tested. If the electric motor or lamp is switched on via a relay, then measures must be taken to avoid accidentally damaging the ohmmeter with battery voltage.
Of the large number of indicators described in the literature, most are poor analogues of a voltmeter or ohmmeter and therefore are not popular among motorists.
I bring to the attention of readers of the site a car voltage indicator site, designed for troubleshooting in the electrical equipment of a car, which, according to the principle of operation, is an improved version of the control lamp and in many cases is devoid of the mentioned disadvantages. The indicator has a wide range of voltages and resistances that it detects to determine the location of the fault, as well as acceptable accuracy for determining the battery voltage. Using this indicator, from one touch of the probe to the contact being tested, you can not only detect the presence of voltage, but also approximately determine the resistance of the electrical circuit being tested simultaneously in two ranges without switching. This makes it faster and easier to find faults.

Voltage indicator circuit

The proposed automobile indicator has a simple circuit, does not contain scarce parts, and it is possible to customize the indicator within a wide range according to the needs of each specific user. One contact is made in the form of a probe, and the second has an extended wire with a plug and a removable alligator clip. The body has holes for the NLO lamp, two-color LED NL1, NL2 and switch SA1. Installing a switch is optional. When assembling the indicator, you need to pay attention to the polarity of connecting semiconductor devices.
The voltage indicator works and is configured as follows: when a voltage greater than 10 V is supplied from an regulated source (+) from pin 2, the zener diode VD2 opens. The current begins to pass through the NLO lamp, the zener diode VD2 and the open diode VD1. When the voltage drop across the NLO lamp exceeds the forward voltage drop across the Schottky diode VD3, part of the current will flow through resistor R4, so the current through the indicator will increase, which means the voltage drop in the circuit under test, determined by the indicator, will increase. If you further increase the voltage, then at 11.5 V the NLO indicator lamp will glow noticeably, and at a voltage of 14.5 V the HLO lamp will glow at full intensity.
The minimum acceptable voltage for a car battery is considered to be 11.5 V, and a voltage higher than 14.5 V practically never occurs in a car with the engine not running. At a voltage greater than 15V, the lamp will glow overheated, which can shorten its service life. A small change in voltage leads to a noticeable change in the glow of the indicator lamp, which allows you to determine the battery voltage with sufficient accuracy.
If the HLO lamp glows before or after the voltage reaches 11.5 V, then the indicator needs to be adjusted. It is advisable to select the zener diode VD2 for the desired voltage or replace the diode VD1 with another one with a higher or lower forward voltage drop. Instead of one, you can put two diodes in series. To expand the range of detectable voltage, you can replace the HLO lamp with another one with a higher nominal voltage, for example, 3.5 V. Most often, the voltage of a car battery does not differ from a voltage of 13 V by more than 0.5 V in one direction or the other . Therefore, you should also test the indicator at a voltage of 13 V to see how the HLO lamp reacts to changes in the resistance value in the circuit being tested, and record the results. When the resistance increases by only 2–3 ohms, the indicator lamp will shine noticeably weaker and at a resistance of 10 ohms the lamp should go out. You can adjust the sensitivity of the indicator to changes in resistance by changing the value of resistor R4, taking into account not to exceed the zener diode current limit of 0.8 A at the maximum current on the lamp. In this mode, the indicator works as a load fork. In this way, you can find even a slight increase in the transition resistance in the electrical equipment of a car even before a malfunction occurs or determine, for example, the presence of a lamp, electric motor winding or other low-impedance load in the electrical circuit.
Sometimes it is necessary to determine the presence of resistance in a circuit of hundreds of Ohms and up to several kOhms. The test lamp does not respond to such resistance in the electrical circuit, and the voltmeter simply does not notice a small increase in resistance compared to the internal resistance of the device. To determine small conductivity, the red LED of the HL2 pair is intended. It starts to glow at 2 V on the indicator, gradually increasing in brightness as the voltage increases. Without resistor R3 at a voltage of 13 V, many LEDs will light when the resistance in the circuit under test increases to more than 100 kOhm. In this case, the glow of the NL2 LED may appear when checking the voltage on a de-energized wire with damp wiring, dirty insulation, or other minor leaks that do not affect the operation of electrical equipment (for example, a small reverse current of diodes in the mounting block). I recommend limiting the sensitivity of the LED using resistor R3 to 20 kOhm. These indicator parameters are sufficient to identify most faults.
Sometimes the voltage on the battery drops below the permissible 11.5 V for a battery, or it is necessary to check the functionality of the voltage regulator at high generator speeds, when the voltage may be higher than the 14.5 V safe for the indicator lamp. For such cases, another safer mode of operation of the indicator is provided. It can also be used to clarify some parameters of the circuit being tested. To do this, we change the polarity of the voltage applied to the indicator using switch SA1, or you can swap the 1st and 2nd terminals of the indicator. Diode VD3 is locked, and the current does not pass through resistor R4, but through the HLO lamp and the zener diode VD2 open in the forward direction. Diode VD1 will be closed, and the main current will flow through additional resistors R1 and R2. If you gradually increase the voltage applied to the indicator, the HLO lamp will light at a voltage from 8 V to 18 V. This range can be shifted to one side or the other by changing the value of the total resistance R1 and R2. If at a voltage of 13 V you gradually increase the resistance in the circuit, the HLO lamp will gradually go out and stop shining at a resistance of 70 Ohms. The resistance at which the HLO lamp will continue to shine can be increased by replacing the lamp with another one with a lower rated current, for example type MH 2.5-0.068. In this case, it is advisable to reduce the value of resistor R4 in order to maintain the indicator’s ability to detect low resistances. It will also be necessary to approximately double the values ​​of resistors R1 and R2.
A change in voltage polarity and operation of the indicator in safe mode will be signaled by the green LED NL1. Its glow will be visible when the voltage increases from 4 V or more. At a voltage of 13 V, it will go out when the resistance in the circuit increases to 300 Ohms. The setting of the green LED can also change and depends on the ratio of resistances R1 and R2. Quenching resistors R5 and R6 for LEDs HL1 and NL2 are selected so that the current through the LED does not exceed 70-80% of the maximum allowable for the LED at the maximum allowable current on the HLO lamp.
The maximum voltage on the indicator is in all cases limited by the maximum permissible current through the HLO lamp. A lamp with a nominal voltage of 2.5 V usually operates for a long time and reliably at a voltage of 3 V. Therefore, in order to determine the maximum permissible voltage on the indicator, when testing the indicator, it is necessary to determine at what voltage on the indicator the voltage measured on the NLO lamp will reach 3 V. If necessary, you can shift the range of the detected voltage. Other parts of the indicator operate in a lighter mode, which ensures high reliability of the indicator. Even if it is possible to destroy the HLO lamp, the red HL2 LED will continue to work and indicate the presence of voltage. Replacing a lamp is not much more expensive or more complicated than replacing a fuse.
Now a little about some ways to use the indicator. If a relay, electric motor, lamp or other device does not work, then most often it is either an open circuit in the power supply circuit of this device, or a significant drop in voltage across it due to increased contact resistance. Therefore, you should not strain your eyes too much to notice tenths of a volt that are unimportant for work. To determine this malfunction, it is enough, and even with a margin, that we notice a difference of 1 V by checking the voltage drop directly on the device. You can clarify the location of the voltage drop using the red LED of the HL2 pair, which will shine when the voltage is more than 2 V. With the starter running, we check with an indicator the presence of voltage between the negative terminal of the battery and the car body. The appearance of the red NL2 LED indicates poor contact at the negative battery wire. In this way, with a sufficiently powerful load, it is possible to determine the contact resistances of up to hundredths of an ohm.
Sometimes there is a break in the device being tested itself, which is also easily determined by the indicator. To do this, we connect the indicator in series to the circuit being tested and use the indicator probe to check the presence of voltage before and after the device being tested.
To check the insulation resistance on the housing, we connect one terminal of the indicator to the plus of the battery, and the other to the wire being tested or to the terminal of the electric motor winding.
You can also make sure that the capacitor at the ignition distributor is in good condition. To do this, connect the indicator clamp to the terminal of the capacitor that is not connected to the housing. The breaker contact must be open. We touch the positive terminal indicator of the battery with the probe. A short flash of the red LED HL2 means that the capacitor is working. The absence of a flash will mean a break, and a constant glow will indicate a breakdown of the capacitor. The condition of the breaker contacts is checked in the same way by the simultaneous appearance and disappearance of the HLO indicator lamp and the red HL2 LED when the ignition distributor shaft is slowly cranked.
The good condition of the contacts of a conventional relay or switch is determined by the absence of illumination of the indicator LED when checking the voltage on the closed contacts. You can check its diodes for short circuits without disassembling the generator.
If necessary, using a car indicator, you can determine the presence of alternating voltage by the simultaneous lighting of two LEDs and, of course, the polarity of direct voltage.
The indicator has a small volume and can have a body of any shape. If the indicator, in addition to the lamp being replaced, is filled with filler, then it is almost impossible to damage it if it falls.
Addition:
To ensure precise adjustment and smooth tuning, instead of a zener diode, you can use an adjustable transistor analogue of a zener diode. The indicator diagram was published in the magazine "Radio Amateur" 1996 No. 8 p. 20 and some other publications. A diode must be connected in parallel to the analogue in the forward direction.

In fact, all previous domestic cars have dial voltage indicators. on the battery. The indicators are simple, operating in a limited voltage range, and help the car owner promptly detect generator overload, contact loss, or problems with the relay-regulator.

In current domestic cars and in fact in all modern “foreign cars” there is no voltmeter. There is only an indicator lamp, which must light up when the voltage on the battery decreases significantly.

But, firstly, not only a significant decrease in voltage is scary for the battery, but also overcharging.

Secondly, as practice shows, the standard indicator does not actually respond to turning off the battery while the engine is running. That is, if, for example, a terminal is disconnected, you will only discover it when you try to start the engine.

Description of the operation of the voltmeter-indicator of the vehicle's on-board network

Figure 1 shows the electrical circuit of a car voltmeter operating on an analogue principle, but providing information to a two-digit digital indicator.

The measurement interval is from 10 to 17 volts. The electrical circuit contains a meter on the LM3914 comparator chip and an electrical indication circuit on a diode decimal-binary converter, a binary-seven-segment decoder and two seven-segment indicators.

Microcircuit A2, using trimmer resistances R4 and R5, is set to measure the input voltage going to the divider R1-R3 in the range from 10 to 17 V. In this case, A2 actually indicates from 0 to 7, that is, a voltage of 10 V is taken as zero. The display at output A2 operates as a moving point.

That is, at any moment only one of its output keys is open. Instead of indicator LEDs, the inputs of the decoder D1, pulled to one, are connected to the outputs of A2, but through an electrical circuit on diodes VD2-VD12, which, together with R7-R8, is a decimal-binary converter that converts decimal numbers from 0 to 7 into a three-digit binary code. This code goes to the terminals of the D1 decoder, designed to work together with a seven-segment LED indicator.

Capacitance C3 is necessary to ensure that the voltage is measured smoothly, with a slight delay. This prevents the appearance of erratic, unreadable readings due to impulse noise in the vehicle’s on-board circuit and excessively rapid voltage changes.

Stabilizer 7805 can be replaced with KR142EN5A. Diode 1N4007 is an arbitrary rectifier diode of low or medium power, for example, KD105. Diodes 1N4148 can be replaced with KD522, KD521. Capacitance C1 must be for a voltage of more than 20 V.

It is easier to set up a voltmeter using an regulated laboratory power supply. Apply a voltage of 17 V and rotate potentiometer R4 to get the reading “17”. Next, apply 10 V and rotate potentiometer R5 to get a reading of “10”. Then check whether the indication corresponds to the actual voltage within the entire range (10-17 V). If necessary, adjust using R4 and R5 several more times.

The device connects to the vehicle’s on-board network and is designed to quickly determine its status using four LEDs. Which indicate the following voltages:

If two adjacent LEDs blink, then the voltage is at the boundaries of the indicated intervals. Let's take a look at the diagram of the device, which is assembled on just one chip:

Before us are four operational amplifiers D1.1 - D1.4, connected according to the comparator circuit. Each of them, using resistive dividers, is tuned to its own range and controls its own LED. The controlled voltage is supplied to the inverse inputs of the amplifiers, and to the direct inputs - a reference voltage obtained using a simple stabilizer (VD1, R7, C1) and resistive dividers R1 - R6. Thanks to diodes VD2 - VD4, lighting each next LED (from bottom to top) turns off the previous one. Thus, at any given time, only one LED is lit or none is lit (voltage below 11.7 V). Inductor T1 and capacitors C2, C3 form a filter that eliminates impulse noise in the power supply circuits of the device.

The device can use any fixed resistors, which it is advisable to select as accurately as possible. Since there is no 500 Ohm rating in the standard series, resistor R4 is assembled from two 1 kOhm resistors connected in parallel. Trimmer resistor R5 is multi-turn, for example SP3-19a. Capacitors C2, C3 - K73-9 for an operating voltage of 250 V, C1 - type K10-17. In place of VD1, any zener diode of type D818 can work, but the most thermally stable ones are those with the letters E, D and G. Any indicator LEDs with the lowest possible glow current can be used as LEDs (ideally a series of instrumentation devices). Diodes VD2 - VD4 - any pulse.

The choke is made on a K10x6x3 ferrite ring made of 2000NM1 ferrite and contains two windings of 30 turns each, made with PELSHO-0.12 wire. When turning on the choke, it is very important to turn on the windings in concert (the beginning of the windings is indicated by dots), otherwise it will be of no use as a filter. Setting up the device comes down to adjusting resistor R5, which sets the lower indication threshold (below 11.7 V, HL4 has just gone out) and, if necessary, selecting R1 according to the upper threshold (above 14.8 V, HL1 has just lit up). All intermediate ranges will be set automatically. The current consumption of the device should be within 20 - 25 mA.

In any technology, LEDs are used to display operating modes. The reasons are obvious - low cost, ultra-low power consumption, high reliability. Since the indicator circuits are very simple, there is no need to purchase factory-made products.

From the abundance of circuits for making a voltage indicator on LEDs with your own hands, you can choose the most optimal option. The indicator can be assembled in a couple of minutes from the most common radioelements.

All such circuits are divided into voltage indicators and current indicators according to their intended purpose.

Working with a 220V network

Let's consider the simplest option - phase checking.

This circuit is a current indicator light found on some screwdrivers. Such a device does not even require external power, since the potential difference between the phase wire and the air or hand is sufficient for the diode to glow.

To display the mains voltage, for example, to check the presence of current in the socket connector, the circuit is even simpler.

The simplest current indicator on 220V LEDs is assembled using capacitance to limit the current of the LED and a diode to protect against reverse half-wave.

DC Voltage Check

Often there is a need to ring the low-voltage circuit of household appliances, or check the integrity of a connection, for example, a wire from headphones.

As a current limiter, you can use a low-power incandescent lamp or a 50-100 Ohm resistor. Depending on the polarity of the connection, the corresponding diode lights up. This option is suitable for circuits up to 12V. For higher voltages, you will need to increase the limiting resistor.

Indicator for microcircuits (logic probe)

If there is a need to check the performance of a microcircuit, a simple probe with three stable states will help with this. If there is no signal (open circuit), the diodes do not light up. If there is a logical zero on the contact, a voltage of about 0.5 V appears, which opens transistor T1; if there is a logical one (about 2.4 V), transistor T2 opens.

This selectivity is achieved thanks to the different parameters of the transistors used. For KT315B the opening voltage is 0.4-0.5V, for KT203B it is 1V. If necessary, you can replace the transistors with others with similar parameters.