Car enthusiasts know how important it is correct installation initial ignition timing in carbureted engines for a good ride. The proposed device can not only set the initial ignition timing at idle speed, but also find a non-working spark plug, check the operation of the ignition coil, control the operation of the centrifugal and vacuum regulator of the ignition timing advance angle up to 3000 rpm. A high frequency is simply dangerous for an engine running without load. The stroboscope scheme is given in Figure 1.
Pulses from a high-voltage wire through a differentiating circuit C1, R2 and resistor R1 start a waiting one-shot on the elements DD1.1, 1.2. Single vibrator pulses, lasting about 1.5 milliseconds, pass through the key stage on transistors VT1, VT2 and turn on the laser pointer LED. The laser pointer is used with a line-extending nozzle. It can be a nozzle with a picture of a person, a dinosaur, a fish or a bird - the main thing is that the image resembles a line. In sunny weather, but in the shade, you can use the pointer without a nozzle, directing the beam only at the moving mark. Without the attachment, the brightness of the laser beam increases. The fixed mark on the engine housing is clearly visible in sunlight.
The printed circuit board of the stroboscope is shown in Figure 2 for the option using a chip with planar pins - a and chips with pins in the DIP-14 package - b. The numbers under the board indicate the installation locations of resistors with a number corresponding to the diagram in Figure 1. Thin lines indicate the conductors from the side of the microcircuit installation. On the same side, a transistor VT1 is installed in the holes (E-K-B). Transistor VT2 and capacitor C2 are installed on the side of printed conductors. Resistor R3, for the version with a chip with planar pins, can also be placed on this side of the printed circuit board. The printed circuit board is designed to fit into the battery compartment of the laser pointer. The input circuit (C1, R1, R2) is located at the end of a wooden clothespin (Fig. 3b).
First check the operation of the board on an engine with any LED, connecting it in the appropriate polarity instead of a laser.
The pointer can be disassembled in two ways - by squeezing out from the side of the battery compartment or pulling out from the side of the nozzle. The nozzle is unscrewed, and a suitable ring 1-2 mm thick is installed under it so that the ring rests against the body. Then the nozzle is screwed in, gradually pressing out the body with the laser. If necessary, the operation is repeated with a thicker ring. You can do without rings by placing a screwdriver under the nozzle, but then the edges of the aluminum body of the pointer are damaged. In the second way, an M5, M4 nut or any other round dense object is placed under the battery compartment cover. Gradually, twisting the lid, we squeeze out the body with the laser. Here you need to make sure not to damage the laser power button. When the button is released, it must be pulled out of the case. This method of disassembling the pointer must be used CAREFULLY, without much effort, as the laser may be damaged.
A push-button switch is soldered in the disassembled pointer (Fig. 4).
The board is shortened with side cutters so that one strip of printed conductor remains, which was used by the switch. Here you need to work carefully so as not to damage the 68-82 ohm surface mount resistor. If you still damaged it - it does not matter. Increase the value of resistor R5 to 270 ohms, and short out the conductors where the surface mount resistor was. Transistor VT2 and capacitor C2 are installed on the side of printed conductors. Capacitor C1 is better to take the type CT - tubular, as they are designed to work with high voltage. Under the 564LE5 chip and the KT815 transistor, place insulating spacers made of paper or cellophane. Check the assembled board by inserting it into the barrel of the pointer body. Inside the case, where the board will stand, insert cellophane if there is no regular one. After checking the board for free passage into the body of the pointer, you can solder the pointer and the board into a monolith with a copper wire passed through the holes for installing the push-button switch. You can connect the board and the pointer with the MGTF-0.07 wire. Be sure to solder the power plus wire to the printed conductor near the laser, going to the case, the soldering point is shown in Figure 4. Insert the board and press the pointer into the case.
Supply the power wires of the required length with crocodile clips with markings or a connector that is included in the connector of a standard portable lamp-backlight. If the connection to the connector of the backlight is not unambiguous, then any diode must be put in the gap of the positive wire with a plus to the connector to protect against polarity reversal. The wire going to the clamp to the high voltage wire must be shielded. For safe operation with the engine running, the clamp to the high-voltage wire is made of a wooden clothespin (Fig. 3). From a pack of wooden clothespins, not a single one was found with matching holes, so it's better to drill a new hole Ф6 mm closer to the edge of the jaws. The hole is easy to drill if the clothespin is clamped in a vise. One of the sponges of the clothespin is wrapped in tin, no more than 3 mm wide or several turns of tinned wire. On the outside of the clothespin, the ends of the tin are soldered together. Capacitor C1 is also soldered here. The shielded wire is attached to a clothespin with a copper clip. High-voltage wires on a vehicle may have cracks that are not visually detectable. If the current collector-clothespin is installed on a wire with a crack, then a breakdown will occur and the stroboscope will burn out. Therefore, it is necessary to wrap the current collector with several turns of electrical tape or fill it with sealant.
Check the strobe for operability (first with an LED!) And seal the case from the side of the board and wires, as well as the divider on the clothespin with silicone sealant. To prevent the laser nozzle from becoming clogged with dirt in the “glove compartment” of the car, pick up a cover from medical bubbles on it.
Working with a stroboscope is easy. Before work, wipe the white paint on the marks on the housing and crankshaft pulley. If the marks are not painted, then paint them with white paint - this will come in handy in the future. Turn on a well-warmed engine at idle (600-800). Connect the supply voltage clamps. Clamp the high-voltage wire of the first spark plug with a clothespin and point the laser at a fixed mark located on the body. Then find the moving mark on the flywheel pulley with a laser beam. If your vehicle's ignition timing is incorrect, the movable mark may be far away from the fixed mark. By rotating the housing of the ignition distributor, match the movable (on the crankshaft pulley) and fixed marks. Fix the distributor in this position. Then you can briefly increase the speed and observe the discrepancy between the marks. With an increase in speed, the ignition should be earlier, to check which there are two other fixed marks located 5 degrees ahead of the ignition. At 3000 rpm, the ignition timing for VAZ vehicles should be within 15-17 degrees. Do not increase the speed over 3000! This is dangerous for the engine and laser pointer! To check the operation of the spark plugs, alternately clamp the high-voltage wires with a clothespin. If the spark plug pierces the body or a misfire occurs, then the laser flashes will be of a lower frequency. ATTENTION! Do not direct the laser beam into your eyes! Remember that the stroboscope housing is powered by plus 13.8 volts (or other voltage supplied by the regulator), so you can not put it on the car body with the laser on, unless the stroboscope housing is insulated.
Literature.
Belyatsky P. LED automotive strobe. - Radio, 2000, 9, p. 43.
N. ZAETs, pos. Veydelevka, Belgorod region
Motorists know how important it is to correctly set the ignition timing of fuel in the cylinders of a carburetor engine. For this, strobe lights are used. P. Byalyatsky's article "LED automotive strobe" ("Radio", 2000, No. 9) describes a simple device with a flashlight in the form of an assembly of bright LEDs instead of a flash photolamp.
The author of this article proposes to assemble a device based on a laser pointer.
The stroboscopic device offered to the attention of readers allows not only to set the optimal ignition timing (O3) at idle engine speed, but also to find a faulty spark plug, check the operation of the ignition coil, control the operation of the centrifugal and vacuum regulators of the O3 angle at a crankshaft speed of up to 3000 rpm (high frequency is dangerous for the motor running without load). The device is not designed for use at service stations, but can be of invaluable service to a car enthusiast who is stuck on the road due to malfunctions in the ignition system.
The stroboscope scheme is shown in fig. one.
Pulses from a high-voltage candle wire, passing through the input node, consisting of a differentiating circuit C1, R2 and a limiting resistor R1, start a single vibrator assembled on elements DD1.1, DD1.2. The output pulses of a single vibrator with a duration of about 0.15 ms are fed to the base of the composite transistor VT1VT2, which operates as a current amplifier. The collector circuit of the transistor includes a laser pointer BL1, which serves as the load of the amplifier. Since the output pulses of the single vibrator have a high level, for the duration of their action, the composite transistor opens and the laser of the pointer forms light flashes.
The pointer is designed for a supply voltage of 4.5 V, and in the stroboscope it operates from the on-board network with a voltage of 13.8 V, so the duration of the output pulses of the single vibrator should not exceed 0.15 ms - the value was selected experimentally and cost several "burned out" lasers. With a pulse duration of more than 0.15 ms, the average power dissipated by the laser reaches the maximum allowable and the risk of burning the pointer increases sharply, and with a shorter mark on the crankshaft pulley it becomes visually "hard to see". It must also be remembered that a flash frequency of more than 100 Hz (corresponding to an engine speed of 3000 rpm is dangerous for a pointer operating at high voltage.
Structurally, the stroboscope consists of an ignition pulse sensor attached to the spark plug wire of the first cylinder of the engine, and the pointer itself, inside which all other parts are placed. The sensor is connected to the pointer with a shielded cable 50 cm long.
The basis of the ignition pulse sensor is a clothespin, on the side of which there are parts C1, R1, R2 of the input node. On one of the halves of the clothespin in the place where the working half-hole is located, a coil of tape no more than 3 mm wide is wound from tin or thin-sheet copper in the form of a bandage (Fig. 2).
The output of the capacitor C1 is soldered to it. The output of the resistor R1 is soldered to the central wire of the connecting cable, and the resistor R2 is soldered to the screen. The cable is attached to the handle of the clothespin with a wire bandage. From above, the details of the inlet assembly should be covered with silicone sealant and protected from impacts with a PCB strap (not shown in the figure).
To install the stroboscope parts, the pointer must first be disassembled. Having unscrewed the nozzle, a puller ring with an axial thickness of 1 ... 2 mm is installed under it so that it rests against the edge of the cylindrical casing. Then the nozzle is screwed on with force, gradually pressing out the "stuffing" from the casing. If necessary, the operation is repeated with a thicker ring.
Attempts to disassemble the pointer without a puller ring usually result in damage to the edge of the casing, made of soft aluminum alloy. Squeezing the “stuffing” out of the casing from the side of the battery compartment, as practice has shown, is also associated with a high risk of damage to the pointer.
A push-button switch is soldered from the board of the disassembled pointer (Fig. 3) and with side cutters, carefully, so as not to damage the resistor, shorten it to a dashed line (printed conductors are shown in gray).
If the resistor still turned out to be damaged, it does not matter, it is enough to close its conclusions with a jumper, and increase the resistance of the resistor R5 in the diagram (see Fig. 1) to 270 Ohms.
The details of the single vibrator and the output current amplifier are placed on a printed circuit board made of fiberglass laminated on both sides with a thickness of 0.5 mm. The board drawing is shown in fig. 4 (a - print side; b - detail side)
Both transistors and capacitor C2 are soldered from the print side directly to the printed pads.
The holes for the microcircuit should be such that it can be mounted as close to the board as possible - this will make it easier to insert the board into the casing of the pointer during assembly. Pin 7 of the microcircuit and one of the pins of the resistor R3 must be soldered on both sides of the board. Since the board is rather “cramped”, try to think over the sequence of mounting parts in advance so that you don’t have to solder the already installed ones later. Mount the chip last. The square-shaped contact pads on both sides of the board must be connected with pieces of copper wire and soldered. A thin insulating gasket should be placed under the transistor VT2.
Before connecting the assembled stroboscope board to the prepared pointer board, it is advisable to check its operation with an LED instead of a laser. An LED (for example, AL307B) is temporarily soldered with the anode to the positive power terminal, and with the cathode to the resistor R5.
In order to be able to adjust the stroboscope in the laboratory, it is advisable to assemble according to the scheme in Fig. 5 test multivibrator.
It generates short impulses high level with a repetition rate controlled by a variable resistor R2.
The pulses are fed to the input of the stroboscope and the resistor R3 is selected so that the duration of the output pulses does not exceed 0.15 ms.
After that, you need to make sure that the assembled board freely enters the casing of the pointer.
Three flexible leads are soldered to the assembled board - a common, input (to the sensor resistor R1) and positive power (+13.8 V), apply it to the pointer board with connecting foil pads outward, insert into both assembly holes of the boards along a piece of copper wire with a diameter of 0 .5 mm and solder. Do not forget to connect the positive output of the laser on the pointer board (see Fig. 3) to the positive power wire on the stroboscope board with a separate conductor. Check again if the structure will fit into the pointer housing.
If everything is in order, an insulator made of a thin rigid plastic film rolled into a tube is inserted inside the casing and a laser with a board is inserted into it. The end with the conclusions of the pointer is filled with sealant. Flexible power leads are equipped with alligator clips with polarity markings or a connector for connecting to a portable lamp socket.
In all cases, it is advisable to introduce a diode into the positive wire break, which protects the stroboscope from accidentally turning on the stroboscope in reverse polarity (this diode is not shown in the diagram in Fig. 1). Any diode with a reverse voltage of at least 50 V and an average rectified current of at least 100 mA will do. You can mount the diode near the crocodile clip.
In addition, given that the laser pointer housing is electrically connected to the positive power wire, it must be carefully insulated and not allowed to come into contact with vehicle parts during use. Nevertheless, it will be easier to work with a stroboscope if you turn on a miniature one in series with the protective diode. fuse for a current of 0.16 A (also not shown in the diagram).
For the operation of the stroboscope, the clothespin sensor is attached to the high-voltage spark plug wire of the first cylinder of the engine. Triggering pulses enter the device through a capacitance between the high-voltage wire and the bandage in the working opening of the sensor. The capacitance should be the minimum required for a stable start.
If the capacitance is chosen excessively large, the amplitude of the triggering pulse, under adverse circumstances, may exceed the allowable for the microcircuit and cause its damage. Therefore, at the beginning, the sensor should be installed on the wire through a dry gasket 1 mm thick made of polyethylene or PVC. If the strobe does not start - there is no blinking laser light at the lowest engine speeds - the gasket must be replaced with a thinner one.
It is more convenient to work with a stroboscope when its light spot has an elongated shape - this makes it easier to fix both marks in the field of view. Therefore, one of the attached nozzles is put on the pointer, pulling the stain into a line. When working in the daytime, but in the shade, you can do without a nozzle (the brightness of the spot will be greater), directing the beam only at the moving mark. The fixed mark on the case will be clearly visible under these conditions. To protect the laser and handpiece from dirt and dust during storage, choose a suitable plastic case for it.
Perhaps it will seem easier for someone to assemble a stroboscope single vibrator on a miniature K564LE5 chip.
The board drawing for this option is shown in fig. 6.
Here, on the side of the parts (Fig. 6, b), only the capacitor C2 and the transistor VT2 are soldered, the rest of the parts are on the print side. In addition, pin 2 of the microcircuit is connected to the input node.
Before working with the strobe light, wipe off the white paint on the marks on the body and crankshaft pulley of the car engine. If the marks are not colored, you should definitely do this - it will be very useful in the future. Move a well-warmed engine to idle speed of 600 ... 800 rpm. Connect the stroboscope power clamps so that its power wires do not come into contact with high-voltage ones. Install the sensor on the high-voltage wire of the first spark plug and point the laser beam at the fixed mark located on the housing. Then find the moving mark on the flywheel pulley with a laser beam - the brightness of the spot in this place increases due to reflection from the white paint. If the mark is not colored, the brightness of the reflected beam, on the contrary, will decrease, but this is more difficult to fix, especially in bright light.
You can make sure that the found place is really a mark by slightly changing the engine shaft speed, while the mark moves forward or backward along the pulley rotation.
If your vehicle's ignition timing is incorrect, the movable mark may be far away from the fixed mark. At idle, the mark on the flywheel pulley should be opposite the middle fixed mark, i.e., the ignition timing should be equal to 5 degrees. By rotating the body of the ignition switch-distributor, achieve the coincidence of the movable and fixed marks and fix it in this position.
Briefly increase the speed and observe the discrepancy between the marks. With an increase in the frequency of rotation of the crankshaft, the ignition should become earlier. At a speed of 3000 rpm, the ignition timing for VAZ vehicles should be within 15 ... 17 degrees. .
Do not increase the speed beyond 3000 rpm - this is dangerous for both the engine and the laser pointer.
Never direct the laser beam into your eyes!
The stroboscope uses a laser pointer with a power of up to 1 mW. IN Lately laser pointers five times brighter appeared on the market. They have the same dimensions, and their use in an automotive strobe is preferable.
LITERATURE
1. Belyatsky P. LED automotive strobe. - Radio, 2000, No. 9, p. 43, 44.
2. Ershov B. V., Yurchenko M. A. VAZ cars. - Kyiv. "Vishcha school." 1983._
[email protected]
the initial moment of fuel ignition
Car enthusiasts know the importance of proper ignition timing in carbureted engines for a good ride. The proposed device can not only set the initial ignition timing at idle speed, but also find a non-working spark plug, check the operation of the ignition coil, control the operation of the centrifugal and vacuum regulator of the ignition timing advance angle up to 3000 rpm. A high frequency is simply dangerous for an engine running without load. The stroboscope diagram is shown in Figure 1.
Pulses from a high-voltage wire through a differentiating circuit C1, R2 and a resistor R1 start a waiting single vibrator on the elements DD1.1, DD1.2. Single vibrator pulses, lasting about 1.5 milliseconds, pass through the key stage on transistors VT1, VT2 and turn on the laser pointer LED. The laser pointer is used with a line-extending nozzle. It can be a nozzle with a picture of a person, a dinosaur, a fish or a bird - the main thing is that the image resembles a line. In sunny weather, but in the shade, you can use the pointer without a nozzle, directing the beam only at the moving mark. Without the attachment, the brightness of the laser beam increases. The fixed mark on the engine housing is clearly visible in sunlight.
The printed circuit board of the stroboscope is shown in Figure 2 for the option using a chip with planar pins √ a and a chip with pins in a DIP-14 package √ b. The numbers under the board indicate the installation locations of resistors with a number corresponding to the diagram in Figure 1. Thin lines indicate the conductors from the side of the microcircuit installation. On the same side, a transistor VT1 is installed in the holes (E-K-B). Transistor VT2 and capacitor C2 are installed on the side of printed conductors. Resistor R3, for the version with a chip with planar pins, can also be placed on this side of the printed circuit board. The printed circuit board is designed to fit into the battery compartment of the laser pointer. The input circuit (C1, R1, R2) is located at the end of the wooden clothespin (Fig. 3b).
First check the operation of the board on an engine with any LED, connecting it in the appropriate polarity instead of a laser. The pointer can be disassembled in two ways - by squeezing out from the side of the battery compartment or pulling out from the side of the nozzle. The nozzle is unscrewed, and a suitable ring 1-2 mm thick is installed under it so that the ring rests against the body. Then the nozzle is screwed in, gradually pressing out the body with the laser. If necessary, the operation is repeated with a thicker ring. You can do without rings by placing a screwdriver under the nozzle, but then the edges of the aluminum body of the pointer are damaged. In the second way, an M5, M4 nut or any other round dense object is placed under the battery compartment cover. Gradually, twisting the lid, we squeeze out the body with the laser. Here you need to make sure not to damage the laser power button. When the button is released, it must be pulled out of the case. This method of disassembling the pointer must be used CAREFULLY, without much effort, as the laser may be damaged. A push-button switch is soldered in the disassembled pointer (Fig. 4).
The board is shortened with side cutters so that one strip of printed conductor remains, which was used by the switch. Here you need to work carefully so as not to damage the 68-82 ohm surface mount resistor. If you still damaged it - it does not matter. Increase the value of resistor R5 to 270 ohms, and short out the conductors where the surface mount resistor was. Transistor VT2 and capacitor C2 are installed on the side of printed conductors. Capacitor C1 is better to take type KT - tubular, as they are designed to work with high voltage. Under the 564LE5 chip and the KT815 transistor, place insulating spacers made of paper or cellophane. Check the assembled board by inserting it into the barrel of the pointer body. Inside the case, where the board will stand, insert cellophane if there is no regular one. After checking the board for free passage into the body of the pointer, you can solder the pointer and the board into a monolith with a copper wire passed through the holes for installing the push-button switch. You can connect the board and the pointer with the MGTF-0.07 wire. Be sure to solder the power plus wire to the printed conductor near the laser, going to the case, the soldering point is shown in Figure 4. Insert the board and press the pointer into the case.
Provide the power wires of the required length with ╚crocodile╩ clips with markings or a connector that is included in the connector of a standard portable lamp-backlight. If the connection to the connector of the backlight is not unambiguous, then any diode must be put in the gap of the positive wire with a plus to the connector to protect against polarity reversal. The wire going to the clamp to the high voltage wire must be shielded. For safe operation with the engine running, the clamp to the high-voltage wire is made of a wooden clothespin (Fig. 3). From a pack of wooden clothespins, not a single one was found with matching holes, so it's better to drill a new hole Ф6 mm closer to the edge of the jaws. The hole is easy to drill if the clothespin is clamped in a vise. One of the sponges of the clothespin is wrapped in tin, no more than 3 mm wide or several turns of tinned wire. On the outside of the clothespin, the ends of the tin are soldered together. Capacitor C1 is also soldered here. The shielded wire is attached to a clothespin with a copper clip. High-voltage wires on a vehicle may have cracks that are not visually detectable. If the current collector-clothespin is installed on a wire with a crack, then a breakdown will occur and the stroboscope will burn out. Therefore, it is necessary to wrap the current collector with several turns of electrical tape or fill it with sealant.
Check the strobe for operability (first with an LED!) And seal the case from the side of the board and wires, as well as the divider on the clothespin with silicone sealant. To prevent the laser nozzle from becoming clogged with dirt in the glove compartment of the car, pick up a cover from medical vials on it.
Working with a stroboscope is easy. Before work, wipe the white paint on the marks on the housing and crankshaft pulley. If the marks are not painted, then paint them with white paint - this will come in handy in the future. Turn on a well-warmed engine at idle (600-800). Connect the supply voltage clamps. Clamp the high-voltage wire of the first spark plug with a clothespin and point the laser at a fixed mark located on the body. Then find the moving mark on the flywheel pulley with a laser beam. If your vehicle's ignition timing is incorrect, the movable mark may be far away from the fixed mark. By rotating the housing of the ignition distributor, match the movable (on the crankshaft pulley) and fixed marks. Fix the distributor in this position. Then you can briefly increase the speed and observe the discrepancy between the marks. With an increase in speed, the ignition should be earlier, to check which there are two other fixed marks located 5 degrees ahead of the ignition. At 3000 rpm, the ignition timing for VAZ vehicles should be within 15-17 degrees. Do not increase the speed over 3000! This is dangerous for the engine and laser pointer! To check the operation of the spark plugs, alternately clamp the high-voltage wires with a clothespin. If the spark plug pierces the body or a misfire occurs, then the laser flashes will be of a lower frequency. ATTENTION! Do not direct the laser beam into your eyes! Remember that the stroboscope housing is powered by plus 13.8 volts (or other voltage supplied by the regulator), so you can not put it on the car body with the laser on, unless the stroboscope housing is insulated.
Literature: Bialiatsky P. LED automotive strobe. - Radio, 2000, 9, p. 43.
Motorists know how important it is to correctly set the ignition timing of fuel in the cylinders of a carburetor engine. For this, strobe lights are used. P. Byalyatsky's article "LED automotive strobe" ("Radio", 2000, No. 9) describes a simple device with a flashlight in the form of an assembly of bright LEDs instead of a flash photolamp.
The stroboscopic device offered to the attention of readers allows not only to set the optimal ignition timing (OZ) at idle engine speed, but also to find a faulty spark plug, check the operation of the ignition coil, control the operation of the centrifugal and vacuum angle regulators 03 at a crankshaft speed of up to 3000 min-1 (high frequency is dangerous for the motor running without load). The device is not designed for use at service stations, but can be of invaluable service to a car enthusiast who is stuck on the road due to malfunctions in the ignition system.
The stroboscope scheme is shown in fig. 1. Pulses from a high-voltage candle wire, passing through the input node, consisting of a differentiating circuit C1, R2 and a limiting resistor R1, start a single vibrator assembled on elements DD1.1, DD1.2. The output pulses of a single vibrator with a duration of about 0.15 ms are fed to the base of the composite transistor VT1VT2, which operates as a current amplifier. The collector circuit of the transistor includes a laser pointer BL1, which serves as the load of the amplifier. Since the output pulses of the single vibrator have a high level, for the duration of their action, the composite transistor opens and the laser of the pointer forms light flashes.
The pointer is designed for a supply voltage of 4.5 V, and in the stroboscope it operates from the on-board network with a voltage of 13.8 V, so the duration of the output pulses of the single vibrator should not exceed 0.15 ms - the value was selected experimentally and cost several "burned out" lasers. With a pulse duration of more than 0.15 ms, the average power dissipated by the laser reaches the maximum allowable and the risk of burning the pointer increases sharply, and with a shorter mark on the crankshaft pulley it becomes visually "hard to see". It must also be remembered that a flash frequency of more than 100 Hz (corresponding to an engine speed of 3000 min-1) is dangerous for a pointer operating at high voltage.
Structurally, the stroboscope consists of an ignition pulse sensor attached to the spark plug wire of the first cylinder of the engine, and the pointer itself, inside which all other parts are placed. The sensor is connected to the pointer with a shielded cable 50 cm long.
The basis of the ignition pulse sensor is a clothespin, on the side of which there are parts C1, R1, R2 of the input node. On one of the halves of the clothespin in the place where the working half-hole is located, a coil of tape no more than 3 mm wide is wound from tin or thin-sheet copper in the form of a bandage (Fig. 2). The output of the capacitor C1 is soldered to it. The output of the resistor R1 is soldered to the central wire of the connecting cable, and the resistor R2 is soldered to the screen. The cable is attached to the handle of the clothespin with a wire bandage. From above, the details of the inlet assembly should be covered with silicone sealant and protected from impacts with a textolite bar (not shown in the figure).
To install the stroboscope parts, the pointer must first be disassembled. Having unscrewed the nozzle, a puller ring with an axial thickness of 1 ... 2 mm is installed under it so that it rests against the edge of the cylindrical casing. Then the nozzle is screwed on with force, gradually pressing out the "stuffing" from the casing. If necessary, the operation is repeated with a thicker ring.
Attempts to disassemble the pointer without a puller ring usually result in damage to the edge of the casing, made of soft aluminum alloy. Squeezing the "stuffing" out of the casing from the side of the battery compartment, as practice has shown, is also associated with a high risk of damage to the pointer.
A push-button switch is soldered from the board of the disassembled pointer (Fig. 3) and with side cutters, carefully, so as not to damage the resistor, shorten it to a dashed line (printed conductors are shown in gray). If the resistor still turned out to be damaged, it does not matter, it is enough to close its conclusions with a jumper, and increase the resistance of the resistor R5 in the diagram (see Fig. 1) to 270 Ohms.
The details of the single vibrator and the output current amplifier are placed on a printed circuit board made of fiberglass laminated on both sides with a thickness of 0.5 mm. The board drawing is shown in fig. 4 (a - print side; b - detail side). Both transistors and capacitor C2 are soldered from the print side directly to the printed pads.
The holes for the microcircuit should be such that it can be mounted as close to the board as possible - this will make it easier to insert the board into the casing of the pointer during assembly. Pin 7 of the microcircuit and one of the pins of the resistor R3 must be soldered on both sides of the board. Since the board is rather "cramped", try to think over the sequence of mounting parts in advance so that you do not have to solder the already installed ones later. Mount the chip last. The square-shaped contact pads on both sides of the board must be connected with pieces of copper wire and soldered. A thin insulating gasket should be placed under the transistor VT2.
Before connecting the assembled stroboscope board to the prepared pointer board, it is advisable to check its operation with an LED instead of a laser. An LED (for example, AL307B) is temporarily soldered with the anode to the positive power terminal, and with the cathode to the resistor R5.
In order to be able to adjust the stroboscope in the laboratory, it is advisable to assemble according to the scheme in Fig. 5 test multivibrator. It generates short high-level pulses with a repetition rate controlled by a variable resistor R2.
The pulses are fed to the input of the stroboscope and the resistor R3 is selected so that the duration of the output pulses does not exceed 0.15 ms.
After that, you need to make sure that the assembled board freely enters the casing of the pointer.
Three flexible leads are soldered to the assembled board - a common, input (to the sensor resistor R1) and positive power (+13.8 V), apply it to the pointer board with connecting foil pads outward, insert into both assembly holes of the boards along a piece of copper wire with a diameter of 0 .5 mm and solder. Do not forget to connect the positive output of the laser on the pointer board (see Fig. 3) to the positive power wire on the stroboscope board with a separate conductor. Check again if the structure will fit into the pointer housing.
If everything is in order, an insulator made of a thin rigid plastic film rolled into a tube is inserted inside the casing and a laser with a board is inserted into it. The end with the conclusions of the pointer is filled with sealant. Flexible power leads are equipped with alligator clips with polarity markings or a connector for connecting to a portable lamp socket.
In all cases, it is advisable to introduce a diode into the positive wire break, which protects the stroboscope from accidentally turning on the stroboscope in reverse polarity (this diode is not shown in the diagram in Fig. 1). Any diode with a reverse voltage of at least 50 V and an average rectified current of at least 100 mA will do. You can mount the diode near the crocodile clip.
In addition, given that the laser pointer housing is electrically connected to the positive power wire, it must be carefully insulated and not allowed to come into contact with vehicle parts during use. Nevertheless, it will be easier to work with a stroboscope if you include a miniature 0.16 A fuse in series with the protective diode (also not shown in the diagram).
For the operation of the stroboscope, the clothespin sensor is attached to the high-voltage spark plug wire of the first cylinder of the engine. Triggering pulses enter the device through a capacitance between the high-voltage wire and the bandage in the working opening of the sensor. The capacitance should be the minimum required for a stable start.
If the capacitance is chosen excessively large, the amplitude of the triggering pulse, under adverse circumstances, may exceed the allowable for the microcircuit and cause its damage. Therefore, at the beginning, the sensor should be installed on the wire through a dry gasket 1 mm thick made of polyethylene or PVC. If the strobe does not start - there is no blinking laser light at the lowest engine speeds - the gasket must be replaced with a thinner one.
It is more convenient to work with a stroboscope when its light spot has an elongated shape - this makes it easier to fix both marks in the field of view. Therefore, one of the attached nozzles is put on the pointer, pulling the stain into a line. When working in the daytime, but in the shade, you can do without a nozzle (the brightness of the spot will be greater), directing the beam only at the moving mark. The fixed mark on the case will be clearly visible under these conditions. To protect the laser and handpiece from dirt and dust during storage, choose a suitable plastic case for it.
Perhaps it will seem easier for someone to assemble a stroboscope single vibrator on a miniature K564LE5 chip. The board drawing for this option is shown in fig. 6. Here, on the side of the parts (Fig. 6, b), only the capacitor C2 and the transistor VT2 are soldered, the rest of the parts are on the print side. In addition, pin 2 of the microcircuit is connected to the input node.
Before working with the strobe light, wipe off the white paint on the marks on the body and crankshaft pulley of the car engine. If the marks are not colored, you should definitely do this - it will be very useful in the future. Move the well-warmed engine to idle speed of 600...800 min-1. Connect the stroboscope power clamps so that its power wires do not come into contact with high-voltage ones. Install the sensor on the high-voltage wire of the first spark plug and point the laser beam at the fixed mark located on the housing. Then find the moving mark on the flywheel pulley with a laser beam - the brightness of the spot in this place increases due to reflection from the white paint. If the mark is not colored, the brightness of the reflected beam, on the contrary, will decrease, but this is more difficult to fix, especially in bright light.
You can make sure that the found place is really a mark by slightly changing the engine shaft speed, while the mark moves forward or backward along the pulley rotation.
If your vehicle's ignition timing is incorrect, the movable mark may be far away from the fixed mark. At idle, the mark on the flywheel pulley should be opposite the middle fixed mark, i.e., the ignition timing should be equal to 5 degrees. By rotating the body of the ignition switch-distributor, achieve the coincidence of the movable and fixed marks and fix it in this position.
Briefly increase the speed and observe the discrepancy between the marks. With an increase in the frequency of rotation of the crankshaft, the ignition should become earlier. At a speed of 3000 min-1, the ignition timing for VAZ vehicles should be within 15 ... 17 degrees. .
Do not increase the speed beyond 3000 min-1 - this is dangerous for both the engine and the laser pointer. Never direct the laser beam into your eyes!
The stroboscope uses a laser pointer with a power of up to 1 mW. Recently, laser pointers five times brighter have appeared on the market. They have the same dimensions, and their use in an automotive strobe is preferable.
Literature
- Belyatsky P. LED automotive strobe. - Radio, 2000. No. 9, p. 43, 44.
- Ershov B. V., Yurchenko M. A. VAZ cars. - Kyiv, "Vishcha school", 1983.
Addition
"Car stroboscope from a laser pointer" - under such a heading in "Radio", 2004, No. 1, p. 45, 46 an article by N. Zayets was published. I liked the idea of using a laser pointer as a strobe light. For those who would like to repeat this design, but do not know the device of the pointer, I propose to get acquainted with it in more detail.
The figure shows the "stuffing" of the keychain pointer. The light source is a semiconductor emitting crystal 3, soldered to a massive base that serves as a heat sink 2. The heat sink is attached to the board 1, on which the power button, current-limiting resistor and power battery spring contact are mounted. The heat sink with the board is tightly inserted into the slot of the sleeve-holder 4, at the other end of which the external and internal threads are cut.
Light from the crystal is strongly scattered and lens 6 collects it into a thin beam. The position of the lens relative to the crystal can be adjusted with a threaded sleeve 7. Spring 5 presses the lens against the sleeve.
To use the pointer as a strobe illuminator, it is better to defocus the beam of light by screwing the sleeve in until it stops (but do not press hard!). As a result, the diameter of the light spot at a distance of 1 m will increase to about 6 cm. At a shorter distance, the spot diameter will be smaller. In any case, with a spot wider than the dot, it is easier to "keep" the mark on the engine pulley, and there is less danger to vision if the beam accidentally hits the eyes.
Many articles emphasize that the pointer is powered by a 4.5 V source, but the presence of a current-limiting resistor in its design suggests that the voltage can be anything, just select the required current. This is how the laser is turned on in the strobe. To calculate the resistor, you need to measure the pointer laser current and the voltage drop across it. On the laser samples I have, 2.6 V dropped at 35 mA. When choosing a current limiting resistor, do not forget about the built-in 68 ohm resistor.
In the process of carrying out experiments on feeding the pointer with an overestimated current, one of them was damaged. But, as it turned out, the crystal remained intact, and its thin output burned out. The operation of the laser was restored with a drop of conductive glue. The tools used for this are a sewing needle and a lens 6.
One of the most important conditions for the correct operation of an automobile gasoline engine is the correct setting of the ignition timing. In VAZ car engines, the ignition timing is set using four marks, one on the crankshaft pulley, and three on the block body. Usually, to adjust the ignition, they use a rather bulky device - a stroboscope. For power, the stroboscope is connected to the car battery, and the third wire is connected to the spark plug wire of the first cylinder. When the engine is running, the strobe lamp flashes every time a high voltage pulse enters the candle of the first cylinder. The light of the lamp is directed to the marks as a result of the synchronous flashing of the lamp, we see four marks, three on the block and one on the pulley, which seems to us to be stationary on relative position these marks determine the correct installation of the ignition (the mark on the pulley should be opposite the middle mark on the block, if this is not the case, it must be corrected by turning the distributor housing).
A standard stroboscope is rather bulky, heavy and fragile, mainly due to the discharge lamp it contains and pulse transformer but, using a modern element base, you can make a stroboscope a little larger than a ballpoint pen.
Figure 1 shows a strobe circuit in which a 12V LED car light works instead of a gas discharge lamp (now it has become fashionable to install such LED lamps in sidelights instead of incandescent lamps).
The device is connected to the car systems with three wires with Crocodile clips. Two - to the battery, and the third to the wire of the 1st cylinder. The third "Crocodile" (connected to the candle wire) is slightly redesigned - its "teeth" are bent inward so as not to spoil the candle wire, and it is more like a metal clothespin.
As soon as a high voltage pulse enters the spark plug of the 1st cylinder, a surge of voltage enters pin 2 of the D1.1 element through the capacitance between the core of the spark plug wire and the body of the Crocodile-pins (Zener diode VD1 protects the input of the element from overvoltage). A single vibrator on elements D1.1-D1.2 generates a pulse, the duration of which is about 1 mS. This pulse through the buffer stage on the elements D1.3 and D1.4 is fed to the base of the transistor VT1, which is part of the pulse key VT1-VT2. The key opens and the LED light HL2 flashes.
Now about the details of the circuit C1, R1 and R2 are soldered directly in the Crocodile handle connected to the candle wire. Connecting cable - soft shielded, no more than 50 cm long. To connect to the battery - ordinary wires, as for "carrying", of any length (within reasonable limits). Diode VD2 serves to protect the circuit from accidental power reversal. LED HL1 - indicator of correct connection to the battery. The device was based on a cylindrical Chinese flashlight. All of its "insides" (light switch, batteries) are removed, leaving an empty case and a conical reflector. The base of the reflector is slightly widened so that an LED car light can be installed in it. Placed in the body printed circuit board(Fig. 2) on which most of the parts are mounted. Holes for connecting wires and LED HL1 are drilled in the case.
The trimmer resistor R4 is used to set the flash duration HL2 such that the mark on the rotating pulley of a running engine is visible stationary and not smeared, but visibility remains sufficient.
If the device does not respond to impulses in the candle wire to which the Crocodile clip is connected, or if it starts to react only when the Crocodile is strongly compressed, you need to increase the resistance R2.
Instead of an LED bulb, you can use a regular super-bright LED by turning it on through a resistor with a resistance of about 10 ohms. But using a strobe will not be so convenient, because due to the lower brightness of the light, it will need to be placed closer to the marks on the engine.
Magazine "Radio" Murovin S.I.
Literature:
1. N. Zaets. Car stroboscope from a laser pointer J. Radio No. 1, 2004.
