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.
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.
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.
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.
Vehicle on-board voltage indicator, given in this article, is intended for visual monitoring of the voltage of the on-board network of a passenger car. Everyone knows that the normal voltage value available in the vehicle’s on-board network has a positive effect on the service life of the battery, especially in winter. Therefore, in severe frosts, it is advisable to use it to start a car engine.
It should be such that with the engine running well, the generator would be enough for all energy consumers. And at the same time, there should not be too much of it, as this can lead to overcharging the battery.
Optimal voltage of the vehicle's on-board network with a 12V battery, the range is considered to be from 11.7V to 14V. Going beyond these limits is extremely undesirable, since when it drops below 11.7V, the battery suddenly discharges, and when it exceeds 14V, it begins to recharge. You can monitor the vehicle’s on-board network using a simple indicator consisting of two comparators and three LEDs, the diagram of which is given below.
Indicator circuit very simple, the essence of its work is that the current voltage taken from the divider, built on resistors R2, R3, R4, is compared with the reference, built on the zener diode VD1 (5.6V). The optimal voltage is shown by a green LED, a state above 14V is indicated by a red LED, and accordingly a yellow LED indicates a state below 11.7V. The op-amp used in this circuit
Just like speed, fuel level, and oil pressure, it is desirable for every car to have an on-board voltage indicator. Widely used digital voltmeters are quite large, and even in our case, the exact voltage value is not required. We only need to know that the battery is discharged, charged or overcharged.
There is nothing to worry about if, when the starter is started, the voltage at the battery terminals drops, but if while driving it is too low, or at low engine speeds it is not too high, then this indicates that we are dealing with problems with on-board electrical equipment.
To check the level of charging voltage, it is enough to assemble one of the indicator circuits, which will show whether the level of the on-board network is in the required range.
The device, the diagram of which is shown in the figure, allows you to determine four voltage states in the vehicle’s on-board network: from 4 to 9 V - a two-color LED glows yellow (red + green); - the LED lights up red; from 13 to 15 V - the LED glows green; above 15 V - the LED flashes red and green.
The main element of the circuit is a 511 series microcircuit (HLL-H102, FZH261). It was selected from the condition of direct power supply to the board from the vehicle network. According to GOST 3940-84, this voltage ranges from 10.8 to 15 V. According to the passport data for the microcircuit, a supply voltage of 10.8 to 20 V is allowed. The microcircuit of this series has greater noise immunity due to the use of a Zener diode with a threshold in the electrical circuit itself voltage of 6 V, as well as a special configuration output circuit eliminates the surge of current at the output of the circuit when the output voltage changes from the log "0" level to the log "1" level. The device circuit consists of a voltage divider and resistors R1, R2, R3. Resistors R4, R5 are current limiters for LEDs, capacitor C1 is a timing element of the generator at a voltage greater than 15 V. The diode is used to prevent polarity reversal, and the zener diode is used to protect the circuit from overvoltages.
Element base: resistors R1, R2, R3 type C2-29V 0.125 V; resistors R4, R5 type OMLT 0.25 W; diode VD1 type KD209, zener diode VD2 type KS522V with a stabilization voltage of 20 V, capacitor C1 type K50-35 or foreign-made with a capacity of 100 μF at 16 V. The red-green switching frequency depends on the capacitance of this capacitor. LED HL1 type LHG3392. The device can be installed either in the instrument cluster, or just the LED lens can be placed next to it for visual observation.
The operating voltage of the on-board network of a car with a 12-volt battery is considered to range from 11.7V to 14V. Going beyond this range is fraught with problems, because if the voltage drops below 11.7V, the battery will suddenly discharge, and if it exceeds 14V, it will begin to recharge. To control the car’s on-board network, I propose to assemble a simple indicator consisting of two comparators made on one LM393 chip and three LEDs.
The current voltage is taken from a voltage divider built on resistances R2, R3, R4 and compared with the reference voltage on the zener diode VD1). Normal voltage - the green LED is on, more than 14V - red, and the yellow LED lights up if the voltage drops below 11.7V
The heart of the circuit is a TCA965 chip, several resistors and three LEDs. All radio components fit easily on a small printed circuit board, which can be easily installed in the cigarette lighter socket.
The measured voltage from the battery goes to the W CENTER input. Then divided by four using the R1/R2 divider. With the resistance values shown in the diagram we have:
When voltage increases:
0…11.66 V - LED D1 is on
11.66…14.46 V - D2
11.46…20 V - D3 When decreasing:
20…14.34 V - D3
14.34…11.54 V - D2
11.54….0 V - D1
To eliminate flickering due to interference, a capacitor filter is used on C1.
Multi-level voltage indicator at the op-amp |
This circuit is also used to monitor the state of the on-board network and allows you to extend the life of the battery, preventing it from being discharged by more than half. This indicator monitors the battery voltage level with very high accuracy and informs the driver about its condition.
The device circuit is made using just one domestic microassembly K1401UD2A and consists of four comparators on operational amplifiers, which, using LEDs HL1...HL4, inform the driver about the current voltage level in one of the intervals. Based on the simultaneous lighting of two indicators at once (or their “blinking”), you can accurately calculate the moment when the battery voltage is on the border between the intervals.
If none of the LEDs are lit, then this only means that the battery voltage is below 11.7V. The HL1 glow tells the driver about operational problems voltage regulator - generator- so when the engine is running, the generator must constantly charge the battery, but the voltage from the stabilizer should not be higher than 14.8 V. If the HL4 LED is on, this indicates that the battery is discharged by more than 50% and needs to be recharged.
The design uses capacitances C1 type K10-17, C2, C3 type K73-9 for 250 V, small-sized tuning resistance R5 type SP3-19a, and the remaining resistances C2-23 (or similar small-sized ones).
The T1 inductor is built on a K10x6x3 ring core made of 2000NM1 ferrite. The windings have 30 turns of wire type PELSHO-0.12. When the phases of the windings are switched on correctly, the choke protects the device from ripple and interference in the vehicle’s on-board network when the engine is turned on.
The device allows you to control the voltage of the on-board network in four intervals. When the battery voltage is below 11 volts, the red LED - VD1 lights up, with a normally charged battery, the green LED VD2 lights up from 11.1 to 13.2 volts, in the range from 13.4 to 14.4 volts the yellow LED - VD3 lights up, and when there is overvoltage more than 14.6 volts, the red LED VD4 will light up.
Adjusting the circuit consists of adjusting a 10K variable resistor to the range of a normally charged battery (12-13.8 V). The phototransistor controls the brightness of the LEDs depending on the level of external light. You can exclude it completely, then the brightness will be maximum.
As long as the voltage on the battery is in the range from 12 to 14 V, the green LED connected through resistors R5 and R9 and the zener diode VD3 lights up. VT2 is locked, and VTZ is closed.
If the voltage drops below a level of 11.5 Volts (regulated by potentiometer R4 and zener diode VD2), transistor VT2 is locked, and transistor VT3 opens, and the blue LED begins to glow. It indicates low voltage. Increased voltage (above the level of 14.4 V, set by potentiometer R2) is indicated by a red LED.
Printed circuit board in sprint layout format and assembled photographs, see the archive at the link above.
The device is assembled on the basis of an operational amplifier LM3914, it consists of ten comparators. The input signal is supplied to the inverse input of each, to the other input of which a resistance divider is connected. Using this, the input signal is compared with a given one and the required number of LEDs lights up. The indicator shows the battery voltage using ten light-emitting components. In this version of the circuit, there are no resistances connected in series with the LEDs to limit the flowing current, since the outputs of the comparators included in the LM3914 op-amp are generators of the flowing current.
The circuit receives power from the vehicle's on-board network, so there is no need to connect an external power source. The maximum operating voltage of such a measuring device is 15 V. The circuit assembled on a printed circuit board can be placed next to the dashboard in order to always see the state of charge of the battery.
I rarely use my car. In essence, it’s not clear why I need it. Well, as a result, the battery always runs out. And every time I have to connect a spare battery, and put the dead one on charge. It is always a painful problem - not to let the battery on your car discharge below normal.
Therefore, I put together this “Car Battery Voltage Indicator” circuit, which I found on the Internet a long time ago and kept with me.
But I changed it a little, and instead of 10 separate LEDs that were in the original circuit, I used a 10-segment LED indicator, because it takes up less space.
Required radio components:
1.tuning resistor 5k – 2 pcs.
2.chip LM3914
3.10 segment LED light bar (I used Kingbight DC-763HWA)
4.resistor R1 4.7k
5. resistor R2 1.2 k
6.For setup you will need a voltmeter and an adjustable power supply from 10 to 15 Volts.
Here is the circuit board of the device.
As you can see in the photo, I cut off one lead from the right tuning resistor.
After installing the parts on the board, the device needs to be configured. Apply a voltage of 10.5 Volts and adjust the right trimmer so that the first bar on the 10-segment indicator lights up.
Apply 15 volts and adjust until the last bar on the 10-segment indicator lights up. And remember, only one strip should always light up. Secure the device in a convenient place.
Now you have a 10-segment indicator showing battery voltage in 0.5 Volt increments.
Not all cars have on-board voltage control installed. Previously, domestic cars had a regular light in the dashboard, which signaled that the battery was charging. This, of course, is not enough information. It would not be amiss to install an additional digital voltmeter or at least an indicator of several multi-colored LEDs showing the main thresholds of permissible voltages. Below are three simple diagrams of LED car voltage indicators.
The operating voltage of the on-board network of a car with a 12-volt battery is considered to range from 11.7V to 14V.
If you go beyond this range, there can be bad consequences, since if the voltage drops below 11.7 V, the battery will suddenly discharge, and if it exceeds 14 V, it will begin to recharge.
To control the car’s on-board network, I propose to assemble a simple indicator consisting of two comparators made on one LM393 chip and three LEDs.
The current voltage is taken from a voltage divider built on resistances R2, R3, R4 and compared with the reference voltage on the zener diode VD1). Normal voltage - green LED lights up, more than 14V - red and yellow LED lights up if the voltage drops below 11.7V
The device allows you to control the voltage of the on-board network in four intervals.
Adjusting the circuit consists of adjusting a 10K variable resistor to the range of a normally charged battery (12-13.8 V). The phototransistor controls the brightness of the LEDs depending on the level of external light. You can exclude it completely, then the brightness will be maximum.
This circuit is also used to monitor the state of the on-board network and allows you to extend the life of the battery, preventing it from being discharged by more than half. This indicator monitors the battery voltage level with very high accuracy and informs the driver about its condition.
The device circuit is made using just one domestic microassembly K1401UD2A and consists of four comparators on operational amplifiers, which, using LEDs HL1...HL4, inform the driver about the current voltage level in one of the intervals. Based on the simultaneous lighting of two indicators at once (or their “blinking”), you can accurately calculate the moment the battery voltage is at the border between the intervals.
If none of the LEDs are lit, then this only means that the battery voltage is below 11.7V. The HL1 glow tells the driver about problems in the operation of the voltage regulator - generator - so when the engine is running, the generator must constantly charge the battery, but the voltage from the stabilizer should not be higher than 14.8 V. If the HL4 LED is on, this indicates that the battery is discharged more than 50% and it needs to be recharged.
The design uses capacitances C1 type K10-17, C2, C3 type K73-9 for 250 V, small-sized tuning resistance R5 type SP3-19a, and the remaining resistances C2-23 (or similar small-sized ones).
The T1 inductor is built on a ring core of standard size K 10 x 6 x 3 from ferrite grade 2000 NM 1. The windings have 30 turns of wire of the PELSHO-0.12 type. When the phases of the windings are switched on correctly, the choke protects the device from ripple and interference in the vehicle’s on-board network when the engine is turned on.
When installing the proposed indicators in a car, you must ensure that its corresponding elements are carefully isolated from the car body. The negative terminal must be isolated from the body, and the positive terminal from the ignition switch. In this case, the voltage indicator will register the battery voltage only while the vehicle is moving.
Always keep your car's on-board voltage under control!
After the board of an amplifier, color music, generator, power supply or other radio device is soldered and configured, the question arises: where does this board with all the radio components, connectors, regulators, etc. go? post? A suitable housing is needed. It can be difficult or even impossible to find a ready-made one of the right size. Then there is only one thing left to do - make the body yourself.
