Every car enthusiast knows what ice is. Unfortunately, during this period, the number of road accidents increases sharply, especially considering how our roads are cleaned. Therefore, especially if you still have not found the money for a winter set of tires, then this option of a cheap radio amateur development will not be superfluous for you at all. The first ice sensor design will tell you the ambient temperature so you can be more attentive.
In order not to wait for the moment when the water in the radiator boils, I propose to assemble a circuit, the basis of which is, it is also a temperature sensor.
To reduce the level of noise arising from the motor, the filter VD1, C1 is used. A flashing red LED can be used in the annunciator.
As soon as the air temperature outside the car drops to 4 degrees Celsius, the device will warn the driver about the possibility of ice formation on the road. For this, in addition to the temperature indicator, an LED and a speaker are integrated into the front panel.
Seat belt sensor |
If you drive with unfastened seat belts, you can get injured in an accident, or run into a fine, well, even give a bribe to a traffic cop. In expensive foreign cars there are special sensors that signal to the driver that the belt is not fastened.But in Russian basins and even in foreign cars made in Russia, they often do not exist. However, this is a necessary thing, and with simple manipulations, you can install at least in Zaporozhets for this, a seat belt lock must be supplied with a sensor from a spring ring. If the metal tongue of the lock is in the groove, then it closes this ring to the body-to-ground of the car. Therefore, if the belt is not fastened at the output of the microcircuit 1 D1, there will be a logical unit, which will lead to the start of the multivibrators, and the piezoelectric emitter B1 will begin to whistle intermittently.
The device for monitoring the water level in the radiator is designed to signal a decrease in the water level, which will lead to overheating of the motor.
The basis of the device is a multivibrator on transistors T2 and T3. Its load is a signal lamp L1. Transistor T4 contributes to a clearer fixation of the operating state of the transistor T2. When the probe in the radiator is submerged in water, a bias voltage is applied to the base of transistor T1 and it is open. In this case, transistors T2 and T3 are closed, lamp L1 does not burn. When the water level in the radiator drops, the probe is in the air, the transistor T1 is locked, and T2 is opened. The multivibrator starts working with a frequency of 2 Hz, and the signal lamp flashes at the same frequency. Transistors T1, T2 can be taken of the type KT361, T3 - KT602, T4 - KT315. Diode type KD510 or other point silicon
Most cars do not have a device, according to the readings of which the driver could judge the voltage on-board network... The voltage of the vehicle's on-board network varies widely, depending on the operating mode of the power supply system. The accuracy of measuring its value is usually not required.
All the schemes described in the article are used to receive a timely warning about the discharge of the battery in the car, which will help the driver to avoid many unnecessary problems.
As you know, up to 25-30% of traffic accidents are caused by drivers falling asleep while driving. To assess the psychophysiological state of a driver in the process of driving a vehicle, telemetric systems have been developed for monitoring the frequency of blinking of his eyelids, recording biopotential, galvanic skin response, and motor activity. All of the above methods have not found wide application in practice due to their complexity, high cost, the need to fix various sensors on the driver's skin.
In order to eliminate these shortcomings, a fundamentally new technical solution has been developed and tested in practice, characterized by simplicity, operational reliability, and low cost indicators. The principle of operation of the pre-sleep signaling device is based on automatic tracking of the force of compression of the steering wheel by the driver in the process of driving a vehicle.
Psychophysiological studies have established that the initial stages of a decrease in mental activity (the initial stages of the onset of a pre-sleep state) of a driver are accompanied by a decrease in the force of compression of the steering wheel. For continuous recording of the steering wheel compression force, the driver has developed a sensor device made in the form of a resistive sensor fixed on the steering wheel, galvanically connected through an electronic setpoint switch with an acoustic and sound signaling device
where 1- wheel
2-elastic sheath (rubber tube) of the sensor
3-graphite powder
4-conductive sensor electrode plugs
5-electronic unit 6-sound signaling device
Structurally, the resistive sensor is made in the form of a rubber tube filled with graphite powder and equipped with plugs-electrodes. When the sensor, fixed on the steering wheel, is compressed, its electrical resistance decreases due to a decrease in the contact resistance between the graphite particles of the filler.
This phenomenon is used to monitor the condition of the driver. The electrical schematic diagram of the driver's sleep state indicator is shown in Fig. 2. The circuit contains a comparator DA1, a low-frequency generator based on elements DD1.1 and DD1.2, an inverter on an element DD1.3, an amplifier on a transistor VT1 and an electrodynamic speaker BA1. The output electrical signal of the sensor R1 is fed to the inverting input of the DA1 comparator, where it is compared with the reference voltage taken from the resistor R4 and applied to the non-inverting input DA1.
If the voltage at the non-inverting input of the comparator becomes more than at the inverting one, then there is no voltage at the output of the comparator DA1, which is used to power the audio frequency generator (DD1.1 and DD1.2). When the driver's compression force on the steering wheel of the car reaches its minimum allowable value, the voltage at the non-inverting input becomes lower than at the inverting input, and the voltage is supplied to the audio generator.
The signal taken from the audio frequency generator is amplified by the VT1 transistor and fed to the BA1 loudspeaker. The threshold of the sound alarm is set by the resistor R4, the volume of the sound - by the resistor R5. For the manufacture of the device, you can use constant resistors such as MLT-0.125 W; variable R4 - SP-33-48; and the trimmer R6 is SP3-22. Oxide capacitor C3, type K50-40; C1, C2 - K10-23. Transistor VT1-KT315G or with any other letter index. Loudspeaker diffuser electrodynamic VA1-0.5-GD-17 or any other similar.
The device is mounted on a single-sided foil-clad fiberglass board with a thickness of 1 ... 1.5 mm and a size of 32x55 mm. One of possible options The arrangement of the circuit elements and, accordingly, the drawing of the printed circuit board are shown in Fig. 3. Thus, any unacceptable relaxation accompanied by a decrease in the contact force of the driver's fingers - steering wheel system will be accompanied by a corresponding alarm.
This ensures the implementation of the mode of continuous monitoring of the physiological parameter, which is a potentially initiating factor in pre-emergency situations. The proposed development compares favorably with known analogs in functional parameters and technical advantages, in particular, the possibilities of its practical use without introducing any technical, psychological, ergonomic and aesthetic inconveniences into the natural driver control algorithm of any Vehicle... In our opinion, the simplicity of the design solution of the development and the general availability of its reproduction create real prerequisites for its widespread implementation within the framework of the implementation of programs to reduce accidents in transport.
This article provides diagrams of the simplest electronic alarms, which can be made by anyone who is at least minimally familiar with electronics or just knows how to hold a soldering iron in his hand. Such alarms will come in handy in many cases. They can be placed on the windows if there is a small child in the house who can open them. There is a guarded parking lot on the doors of an apartment or garage. And when triggered, the watchman will call the police. You can put such an alarm in the apartment if you are friends with your neighbors. Even if you go on a hike, it is not a sin to spread a security loop around the camp at night in case wild animals or strangers appear.
The first scheme electronic alarm is simple to the extreme, it couldn't be easier. This is just one transistor, resistor and an executive relay. If an audible alarm is supposed, then instead of a relay, an audible siren or a howler is turned on.
Principle of operation: The security loop is a thin wire, or closed contact. When the wire is intact (or the contact is closed), the base of the transistor is grounded and the transistor is off. No current flows between collector and emitter.
If you break the guard wire, or open the contact, the base will be connected to the power source through the resistor R1, the transistor will open and the relay (or siren) will work. It can be turned off only by turning off the power supply or by restoring the security loop.
Such an alarm can be used to guard your belongings, for example. A reed switch is used as a security contact, the alarm is hidden in the side pocket of a bag or backpack, and a magnet is placed next to it. If you remove the magnet from the alarm itself (move the thing), the siren will squeal in all voices.
Second circuit with more advanced custom functions
As in the first case, a security loop, a normally closed (in armed mode) contact or a reed switch closed by a magnetic field serves as a sensor. If the loop is violated, the alarm is triggered and its operation continues until the power is turned off. Loop recovery does not turn off the alarm, it will still continue to work for some time. The alarm has a temporary blocking button, which is necessary for the owner to leave the protected area. The alarm also has a response delay, which is necessary for the owner to turn it off when he enters the protected area.
Let's analyze how the circuit works. Before arming the alarm, you must turn off (open) the S1 switch. It must be installed in a secret place near the entrance. You can use, for example, a hidden reed switch, which closes - opens by rearranging an object with a built-in magnet, etc. This switch blocks the operation of the system and it stops responding to a loop break. When leaving, the switch S1 opens and the capacitor C2 begins to charge through the resistor R2. Until the capacitor is charged to a certain value, the system is "blind". And you have time to leave the facility by restoring the security loop or by closing the contacts. By choosing the values of the resistor R2 and the capacitor C2, achieve an acceptable exit delay for yourself.
If the security loop is violated, then capacitor C1 will start charging through the resistor R1. This pair creates a slight delay in the alarm, and the owner has time to neutralize it by turning on the S1 switch. It is necessary to select the values of the resistor and capacitor for a comfortable response delay time.
If the loop is violated by an intruder who does not know how to turn off the alarm, then some time after the loop is broken, the alarm will be triggered (both inputs of the D1.1 element will be logic "1", respectively, at the output "0". Having passed through the inverter D1 .2 it will again become "1" and open the transistor VT1. The transistor will discharge the capacitor C3 and through the inverter will open the transistor VT2, which will make the executive relay work or turn on the siren.
Even if the attacker quickly restores the loop, the siren will continue to work, since the capacitor C3 will be charged for a sufficient time through the resistor R3. It is the denominations of this pair that determine the operating time of the alarm after the recovery of the loop. If the loop is not restored, the alarm will work continuously.
Microcircuit - K561LA7, transistors - any n-p-n (KT315, KT815, etc.) Power supply - any with a voltage of +5 - +15 Volts. The executive relay or siren can be connected to a more powerful power source than the circuit itself. In standby mode, the circuit consumes practically no current (at the self-discharge level of the batteries).
A simple home-made device will help to accompany the light indication of events with sound signals. The dashboard of the car is intended not only to indicate the speed of movement, in addition to the dial gauges, it also has indicator lights - bulbs.
Some of them are designed to indicate the normal state of the car - turning on headlights, turn signals. Others to indicate alarm conditions - low battery, low oil pressure, low level oil, brake malfunction, low level brake fluid, coolant leakage, movement with the door open, and the like.
It is the emergency indicators that are most important, but the lighting of the light on dashboard, especially on a bright sunny day, may not be noticed at the time. And this can have very unpleasant and even disastrous consequences.
Fig. 1. Schematic diagram connecting the signaling device.
In some cars, there is a sound backup of the light bulb to indicate a malfunction, in other cars this is not provided. However, it is possible to equip almost any car, both domestic and foreign production... The diagram is shown in the figure.
As a signaling device, a "buzzer" with a built-in generator is used, in series of which a blinking LED is switched on. A blinking LED is only needed to interrupt the current through the "buzzer" and it squeaked intermittently.
Most domestic cars and many foreign ones, to turn on the indicator lamps, contact sensors are used, which, for example, such as an oil pressure sensor, connect the lamp to the body (to "ground"), and those that connect the lamp to the plus of the on-board network (for example, a brake health sensor).
Both of them can work in this scheme. Sensors connecting bulbs to ground - S4-S6. When they close, the corresponding VD4-VD6 diode opens and through it power is supplied to the signaling device. And the inclusion of the indicator lamp is accompanied by the sound of the signaling device. Sensors S1-S3 connect the bulbs to the plus of the onboard network.
When they are closed, the VD1-VDЗ diodes (or one of these diodes) open. This leads to the supply of an opening voltage to the base of the transistor switch VT1, in the collector circuit of which a circuit is connected from series-connected "tweeters" BF1 and a blinking NI LED. The transistor opens and the alarm sounds. The transistor acts as an inverter here.
The entire circuit can be easily mounted in a volumetric manner on the back of the dashboard, or made in a separate case and positioned in a convenient place. I see no point in developing a board for it. The diagram conventionally shows three sensors of different types. In a particular car, there may be a different number. If all sensors are shorted to ground, the cascade to VT1 can be excluded.
At the first moment after turning on the ignition, the indicator sounds until the engine is started (the oil pressure lamp is on). This is perhaps the only drawback of the signaling device.
No adjustment is required. After a number of years ago, the rule appeared road traffic requiring you to drive with the dipped headlights on in daytime days, some drivers began to have problems due to the fact that the headlights are not particularly noticeable during the day, and it is quite possible to put the car in the parking lot forgetting to turn off the headlights.
Of course, when the ignition is turned off, the dipped headlights turn off automatically, but the side lights continue to work - they must be turned off. And if they are not turned off, the battery can be discharged during several hours of parking, and starting the engine will be difficult, especially in winter.
To remind the driver of the need to both turn on the headlights and turn them off, a very simple warning device is designed, the diagram of which is shown in Figure 2.
The circuit is a signaling device from a series-connected "buzzer" with a built-in generator and a blinking LED that interrupts the current through the "buzzer". The signaling device is connected to the electrical circuit of the car through a diode bridge on diodes VD1-VD4, which allows the signaling device to sound at any polarity of the supply current.
Fig. 2. A very simple oil pressure indicator.
One input of the rectifier is connected to the oil pressure sensor, and the other to the side lights.
This is how it works:
- The engine is running, the headlights are off. This means that the contacts of the oil pressure sensor are open, and the contacts supplying current to the side lights (and headlights) are also open. The current flows through the oil pressure light and through the side light bulbs. The signaling device sounds.
- The engine is off, the headlights are off. This means that the contacts of the oil pressure sensor are closed, but the contacts that supply current to the side lights (and headlights) are open. No current flows since both bridge inputs are connected to negative. The signaling device does not sound.
- The engine is on, the headlights are on. This means that the contacts of the oil pressure sensor are closed, and the contacts that supply current to the side lights (and headlights) are closed. No current flows since both inputs of the bridge are connected to positive. The signaling device does not sound.
- The engine is off, the headlights are on. This means that the contacts of the oil pressure sensor are closed, and the contacts supplying current to the side lights (and headlights) are also closed. Current flows through the oil pressure sensor and through the side light switch contacts. The signaling device sounds.
All parts indicated in the diagram can be replaced by any analogs. The "squeaker" must have a built-in generator and a rated power supply of 12V.
A simple home-made device will help to accompany the light indication of events with sound signals. The dashboard of the car is intended not only to indicate the speed of movement, in addition to the dial gauges, it also has indicator lights - bulbs.
Some of them are designed to indicate the normal state of the car - turning on headlights, turn signals. Others to indicate an alarm condition - low battery, low oil pressure, low oil level, brake failure, low brake fluid level, coolant leakage, driving with the door open, and the like.
It is the emergency indicators that are most important, but the lighting of the light on the dashboard, especially on a bright sunny day, may not be noticed at the time. And this can have very unpleasant and even disastrous consequences.
Fig. 1. Schematic diagram of the signaling device connection.
In some cars, there is a sound backup of the light bulb to indicate a malfunction, in other cars this is not provided. However, almost any car, both domestic and foreign, can be equipped with an additional audible malfunction indicator. The diagram is shown in the figure.
As a signaling device, a "buzzer" with a built-in generator is used, in series of which a blinking LED is switched on. A blinking LED is only needed to interrupt the current through the "buzzer" and it squeaked intermittently.
In most domestic cars and many foreign ones, contact sensors are used to turn on indicator lamps, which, for example, such as an oil pressure sensor, connect a light bulb to the body (to ground), and those that connect a light bulb to the plus of the onboard network (for example, a sensor serviceability of the brake).
Both of them can work in this scheme. Sensors connecting bulbs to ground - S4-S6. When they close, the corresponding VD4-VD6 diode opens and through it power is supplied to the signaling device. And the inclusion of the indicator lamp is accompanied by the sound of the signaling device. Sensors S1-S3 connect the bulbs to the plus of the onboard network.
When they are closed, the VD1-VDЗ diodes (or one of these diodes) open. This leads to the supply of an opening voltage to the base of the transistor switch VT1, in the collector circuit of which a circuit is connected from series-connected "tweeters" BF1 and a blinking NI LED. The transistor opens and the alarm sounds. The transistor acts as an inverter here.
The entire circuit can be easily mounted in a volumetric manner on the back of the dashboard, or made in a separate case and positioned in a convenient place. I see no point in developing a board for it. The diagram conventionally shows three sensors of different types. In a particular car, there may be a different number. If all sensors are shorted to ground, the cascade to VT1 can be excluded.
At the first moment after turning on the ignition, the indicator sounds until the engine is started (the oil pressure lamp is on). This is perhaps the only drawback of the signaling device.
No adjustment is required. After a number of years ago, a traffic rule appeared that required driving with the dipped beam on during the daytime, some drivers began to have problems due to the fact that the headlights were not particularly noticeable during the day, and it is quite possible to put the car on forgetting to turn off the headlights in the parking lot.
Of course, when the ignition is turned off, the dipped headlights turn off automatically, but the side lights continue to work - they must be turned off. And if they are not turned off, the battery can be discharged during several hours of parking, and starting the engine will be difficult, especially in winter.
To remind the driver of the need to both turn on the headlights and turn them off, a very simple warning device is designed, the diagram of which is shown in Figure 2.
The circuit is a signaling device from a series-connected "buzzer" with a built-in generator and a blinking LED that interrupts the current through the "buzzer". The signaling device is connected to the electrical circuit of the car through a diode bridge on diodes VD1-VD4, which allows the signaling device to sound at any polarity of the supply current.
Fig. 2. A very simple oil pressure indicator.
One input of the rectifier is connected to the oil pressure sensor, and the other to the side lights.
This is how it works:
- The engine is running, the headlights are off. This means that the contacts of the oil pressure sensor are open, and the contacts supplying current to the side lights (and headlights) are also open. The current flows through the oil pressure light and through the side light bulbs. The signaling device sounds.
- The engine is off, the headlights are off. This means that the contacts of the oil pressure sensor are closed, but the contacts that supply current to the side lights (and headlights) are open. No current flows since both bridge inputs are connected to negative. The signaling device does not sound.
- The engine is on, the headlights are on. This means that the contacts of the oil pressure sensor are closed, and the contacts that supply current to the side lights (and headlights) are closed. No current flows since both inputs of the bridge are connected to positive. The signaling device does not sound.
- The engine is off, the headlights are on. This means that the contacts of the oil pressure sensor are closed, and the contacts supplying current to the side lights (and headlights) are also closed. Current flows through the oil pressure sensor and through the side light switch contacts. The signaling device sounds.
All parts indicated in the diagram can be replaced by any analogs. The "squeaker" must have a built-in generator and a rated power supply of 12V.
Car battery voltage indicator
The device shown in Figure 1 signals the status using indicator LEDs. battery car.
Fig. 1
When the battery voltage is low (less than 11.8 V), the LED is weakly lit HL 1 red glow. During battery charging (voltage 12.8 ... 14.8 V), the comparator is activated DA 1.2 – LED turns on HL 2 green glow. A further increase in voltage (more than 14.8 V) leads to the fact that part of the output current of the comparator DA 1.2 flows through the opened zener diode VD 2, diode VD 3 and resistor R 6, therefore, the LED also starts to shine. HL 1. When the battery voltage is about 15 V, the LED HL 1 shines with normal brightness and is paired with an LED HL 2, they signal that the battery is overcharging. Turning on red ( HL 1) LED serves as an alarm signal. At a voltage of 11.8 ... 12.8 V, when there is no charging, the LEDs are off.
The adjustment of the device is reduced to setting the lower (11.8 V) threshold of the comparator by selecting a resistor R 2, the rest of the thresholds are set automatically.
Serebrovsky O.
Zaporozhye
Inertial sensor for "highway"
The inertial sensor is based on the P1 microammeter, Fig. 2.
Fig. 2
The microammeter is not altered in any way. In the scheme, it is used with an end scale with a zero in the center of the scale. The maximum deflection current of the arrow in any direction from zero is 150 μA, the resistance of the frame is 320 Ohm. The arrow swings freely with any even slight change in the position of its body.
The EMF induced in the microammeter coil is amplified by the operational amplifier A1, and its oscillations are converted into pulses by a pulse amplifier on VT 1. The sensitivity can be set with a resistor. Zener diode VD 1 protects the op-amp from voltage surges in the vehicle's electrical network.
The P1 microammeter can be replaced with a domestic type M470, but its arrow must be adjusted as close as possible to the middle of the scale (shifted from the extreme zero mark so that it moves freely in either direction).
Kapelkin V.S.
Car alarm circuit
f. Radioconstructor No. 2
2002, p. 38
Automatic switching off of low beam
Figure 3 shows a device that turns on the dipped beam after starting the engine.
Fig. 3
The car's circuitry has an oil pressure sensor, which is a spring-loaded contact that normally closes and opens when the spring is compressed under oil pressure. Thus, when the engine is not running, the sensor contacts are closed, and they open one to two seconds after the engine starts, that is, when the oil pressure rises.
The transistor stage is connected to the indicator lamp insufficient pressure oils. When the ignition is turned on, but the engine is not running yet, the oil pressure is low and the contacts are closed. The lamp is on, but the transistor is closed and the contacts of the K1 relay are open. After starting the engine, the sensor opens and current flows through the resistor and lamp to the base of the transistor. It opens and relay K1 turns on the headlights.
The condenser creates an additional delay and prevents the headlights from flashing in the event of a short drop in oil pressure. Diodes protect the transistor from negative voltage surges.
Instead of a composite transistor KT972, you can use some kind of imported analog, or assemble a Darlington circuit on two transistors (KT315 and KT815). The relay is standard automobile, in this case, imported SCB - 1 - M1240.
Timofeev P.S.
Buzzer
The indicator shown in Fig. 4 can be used in various devices, for example, in conjunction with a relay for a car's direction indicator.
Fig. 4
The TK-67-N telephone capsule serves as the sound source in the indicator. The peculiarity of the indicator is that it is assembled entirely in the capsule body.
The indicator is assembled according to the circuit of a generator with an inductive feedback on primer coils L 1 and L 2. Instead of MP25A, you can use any low-frequency p - n - p transistor. The device reliably operates from both 6 and 12 V. If the indicator generator does not work immediately after switching on, the terminals of one of the coils should be reversed. After setting up, the primer should be poured to the upper edge of the coil frames with epoxy, paraffin or bitumen.
Kozlov L.
the village of Chernukhino
Lugansk region.
Switch off the headlights on the microcircuit
Now traffic rules require driving with headlights on on a suburban highway, even during daylight hours. In some countries, driving is required in the city as well. And in this there is one nuisance associated with the fact that during the day the headlights are especially imperceptible, it does not attract the attention of the driver who gets out of the car. And this leads to the fact that it is very easy to forget to turn off the headlights and be left with a discharged battery.
Fig. 5
The device shown in Figure 5 warns the driver with a sound signal leaving the car that it is necessary to turn off the headlights. The circuit is powered by a circuit of lamps side lights(from the headlights). And to beep or not to beep is determined by the state of two sensors - the oil pressure sensor (it is contact, to the indicator light) and the door open sensor (it turns on the light in the car in the car and is also used for signaling).
In general, in order for the signaling device to beep, the headlights must be on (it is powered) and both of these sensors must be closed. Then the annunciator emits an intermittent high-pitched sound.
The low oil pressure sensor is used here to detect engine operation. If the engine is in good working order, then during operation the oil pressure in it is high enough and the pressure sensor contacts are open. If the engine is off, the oil pump does not work and the oil pressure is low, and the sensor contacts are closed. Thus, when the motor is running, on pin 2 D 1.1 the voltage of the logical unit comes in and blocks the tone multivibrator D 1.1 - D 1.2.
The second blocking input of this multivibrator receives the level from the infrasonic multivibrator D 1.3 - D 1.4, whose task is to interrupt the sound. When the door is closed, the door sensor contacts are open and on pin 12 D 1.4 a logical one arrives. This blocks the multivibrator D 1.3 - D 1.4, and with it the tone multivibrator is also blocked D 1.1 - D 1.2.
And the result is the following. When the headlights are on, the circuit is powered from the side light circuit through a resistor. R 5. If the motor is running, then to pin 2 D 1.1 a unit arrives and the circuit is blocked. The circuit will also be locked when the door is closed, as on pin 12 D 1.4 the unit will arrive through R 2.
As soon as we turn off the engine, the voltage at pin 2 D 1.1 drops to zero. But at pin 9 D 1.2 there is still one, so the signaling device does not sound. Further, if we open the door with the headlights on and the engine off, then the voltage at terminal 12 D 1.4 drops to zero and both multivibrators start working. Piezoelectric sounder F 1 starts beeping intermittently, reminding you to turn off the headlights before getting out of the car.
Zener Diodes VD 1- VD 3 are needed to protect the microcircuit from voltage instability in the car's electrical network, from emissions from the ignition system and other troubles.
A piezo emitter can be used, for example, ZP-1, ZP-22, or from an imported telephone or electronic clock.
To get the highest volume, you need to select the resistance R 3 so that the piezo emitter enters into resonance, while the volume rises sharply.
The K561LE5 microcircuit can be replaced with K176LE5 or an imported analog.
Apart from tuning into resonance, no tuning is required. If you wish, you can change the ripple frequency by selecting the circuit parameters R 4- C 2.
Zakharov A.N.
Car brake light controller
The circuit, which is useful to equip the car - "controller" of the brake light, fig.6.
Fig. 6
Unlike the well-known ones, the proposed "controller" does not require any intervention in the wiring of the car, it is simply connected in parallel with the brake light lamp.
The circuit is a photo relay, the sensitive element of which is a photoresistor R 1 - when illuminated by a stop lamp, the signal sharply decreases its resistance, as a result of which the transistors VT 1, VT 2 open and the LED placed on the front dashboard of the car HL 1 flashes, signaling that the brake light is not only energized, but also shining.
Setting up the controller consists only in choosing the best position of the photoresistor R 1 relative to the lamp and in the selection of the resistor R 2, providing the desired sensitivity.
Ivanov A.
Tashkent city
Uzbekistan
Turn off the headlights warning light
The signaling device is made from the board of the Chinese quartz alarm clock, Fig. 7.
Fig. 7
It is powered by a circuit - side light lamps - insufficient oil pressure sensor. And the door sensor is used to turn on the signaling device. If three conditions are met at once, - the headlights are on s, the engine is turned off and the door is opened, the audible alarm is activated.
The board with the alarm clock is designed to be powered from a 1.5V source, so here it is powered by the voltage on the LED HL 1 (it serves as a parametric stabilizer).
Voltage indicator for car battery
When charging a storage battery, it is not at all necessary to control the voltage with a voltmeter; you can get by with a simple LED indicator (Fig. 8), which allows you to judge the limit voltage values.
Fig. 8
The indicator has two identical LEDs, connected almost oppositely - in parallel. If the battery voltage is below the minimum allowable (11.4 V), the LED is on HL 1, and if it exceeds the upper limit of the permissible (14.5 V) - HL 2. In the interval between these values, the LEDs are off.
When the voltage on the probes X1, X2 is less than 11.4 V, the zener diode VD 2 is open and to the chain R 1 HL 1 its stabilization voltage is applied - approximately 3.5 V. LED is on HL 1.
As the voltage rises to a predetermined threshold level (11.4 V), a zener diode begins to open VD 1, the voltage between the anode and cathode of the LED HL 1 falls and soon becomes insufficient to keep the indicator glowing.
With a further increase in voltage and reaching a value of 14.5 V, the voltage drop across the resistor R 3 (from the current through the zener diode VD 2) will exceed the stabilization voltage of the zener diode VD 1 so that the LED lights up HL 2.
Volkov S.
Chelyabinsk
So that the radio tape recorder does not burn out
One of the main reasons for the failure of the car radio is a malfunction of the relay - the car's regulator, as a result of which, in some operating modes of the car, the voltage in the board - the network can rise significantly more than 15 V, up to 17 - 18 V. In this case, the radio tape recorders are usually designed for a supply voltage of 11 - 15 V (nominal 13.2 V).
Fig. 9
Figure 9 shows a diagram of a simple and reliable device that turns off the power of the radio if the voltage of the on-board network rises above 14.5 ... 15 V. The circuit consists of a thyristor VS 1, in the anode circuit of which relay P1 is switched on with open contacts. The current flows to the control electrode of the thyristor through a chain of zener diodes VD 1 - VD 3 with a total stabilization voltage of 14.1 V.
While the voltage in the on-board network does not exceed 14.5 ... 15 V, the zener diodes are closed and the current through them is insufficient to open the thyristor. In this case, the winding of relay P1 is de-energized and through its contacts the voltage is supplied to the radio tape recorder.
As soon as the voltage of the on-board network reaches a critical level, the zener diodes open and the current flowing through them opens the thyristor VS 1. Relay triggered cuts and disconnects the power supply circuit of the radio, protecting it from damage. The relay will remain in this state until the button is briefly pressed. S 1 shutdown thyristor.
Thyristor KU202 with any letter index, automobile relay with break contacts. Zener diodes can be taken by others, there can be any number of them, it is important that they have a total voltage of 14 - 14.5 V (for example, two KS170 zener diodes). Button - any opening button.
Alekseev V.V.
One-button car alarm switch
In many designs of car alarms, a "secret toggle switch" is used as a switch for the alarm circuit, and to exclude the alarm from the actions of the owner of the car, a reed switch is used, which introduces a delay into the circuit when a magnetic key fob is brought to it.
Fig. 10
Figure 10 shows a diagram of a simple alarm switch that is controlled by a single reed switch or push button - S 1. If the circuit is in the on position (relay P1 is de-energized and its normally closed contacts K1.1 supply power to the alarm), to turn it off, close S 1, while through R 1 voltage will be supplied to the control electrode of the thyristor VS 1, it will open and turn on relay P1, which will transfer its contacts to the opposite position shown in the diagram. When opening contacts S 1 capacitor C 1 is charged via R 1.
To turn on the alarm, you need to close again S 1, in this case, the voltage from the capacitor C1 will go to the thyristor in reverse polarity and close it. Relay P1 will de-energize and its contacts will return to the position shown.
In the on state, the circuit does not consume current, and does not discharge the battery. When the alarm is off, the relay coil P1 is energized and the circuit consumes a current equal to the rated current of the relay coil. But this does not matter, since during the operation of the car, the battery is recharged from the generator.
Vehicle electrical system voltage indicator
Fig. 11 Figure 11 shows a schematic diagram of a vehicle voltage indicator. It uses three zener diodes with different stabilization voltages: D814A - 7.5V, D814V - 9.5V and D814D - 12V. Three bright LEDs with voltage drops of 2.5V are used as indicators.
As a result, when the voltage U input below 10V, none of the LEDs are on.
At voltage from 10V to 12V it is onHL 1... At voltage from 12V to 14.5V, two LEDs will be onHL 1 and HL 2... And when the voltage is more than 14.5V, all three LEDs are on.
