Immediately after purchasing a car (Mitsubishi Lancer, 2003), I was puzzled by installing a fuel consumption indicator. The Japanese saved a lot on this car and did not install some useful features- I had to correct the situation.
The first thought was either to buy a ready-made one - there are many industrial devices, including those tailored for Lancer 9, or self-assembly some kind of amateur design - and there are many of them. After studying the topic a little, I found out that all the proposed devices have redundancy of functions - but I just need a flow meter. That's why it was decided to do it myself. The only place on the panel where the device would fit is in place of the regular clock, so whether you like it or not, it should also show the time. Well, since when using a 2-line LCD, in this case there is an unfilled corner, which means that something more or less useful needs to be inserted there, for example, a temperature display. By the way, at first we planned to display some other parameters - battery charging, consumption per 100 km, instantaneous consumption in numbers, etc. I don’t even remember - and almost all the ideas were implemented in the first version of the indicator.
The engine is turned off, so there is no progress bar.
I think the advantage of the first version is that when installing it on the car, I didn’t have to drill, sharpen, etc. at all. Just unclip the standard clock and click the device in its place. Control buttons (3 pcs.) were located to the right of the display.
But after driving for a while I realized that out of all the functions I only need 3 (I have never used the rest during all this time). And just then I came across a new display, a prettier one - I decided to install it and at the same time rewrite everything again - throw out unnecessary functions. Simply rearranging the display would not have worked, firstly because different sizes and secondly, the new display is negative, the dimming system needs to be changed.
Because of large sizes the display buttons on the side did not fit, I had to drill 2 holes in the podium, but this did not affect the appearance and it became more convenient to use. Here is a photo of the new indicator
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And the rear view
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The device shows (I repeat)
- 1. Instant consumption in the form of a progress bar
- 2. Time
- 3. Temperature outside or in the cabin - optional (switchable by button)
Scheme
Nothing special - microcontroller PIC16F876 reads data from temperature sensors (DS18B20), from the clock chip (DS1307) and from the ECU, processes all this and displays it on the display (LCD 2x16). The signal from the ECU (Fuel) is one of those that goes to the injector; you can use any one. To generate (or rather even match) the signal, a node on an n-p-n transistor is used. The device is powered via a 7805 stabilizer. There is no separate power supply for the clock chip when the engine is off because backup batteries according to the datasheet should last for 10 years.
The device is controlled by 2 buttons, one of which - “Mode” - switches the display of internal and external temperatures, the second - “Set” - depending on which temperature is selected, it sets either the hours or minutes.
The display is any suitable two-line display, the main thing is that it has an extended temperature range.
Temperature sensors are installed - one in the cabin, the other located under the front bumper.
Dimmer - when the relay contacts open, they simply connect an additional resistor to the power supply circuit of the backlight LEDs, thereby dimming them. The relay is switched on by the dimensions. Dimmer, as already indicated, for a negative display, the difference between negative and positive is that in the first case, during the day the display should be illuminated brighter than in the dark. The second is the opposite - during the day the backlight is not needed at all, it turns on only with the dimensions.
By the way, you can use another, weaker MK. You just need to recompile the program for the new one. It’s just that this one remains from the previous version...
The diagram and wiring are also posted in the archive in the Splan and SprintLayout formats, respectively:
Control program
The firmware is written in one of the easiest compilers to learn and understand - PicBasic Pro.
Consists of the main program - mmc.pbp and 3 plug-ins
- LCD.inc - description of connecting an LCD display to the MK pins
- LCDchar.inc - add. LCD display symbols
- LCDbar.inc is a progressbar function, the same module contains a variable that determines the “sensitivity” of the progressbar BAR_range VAR WORD: BAR_range = 6000
The source codes are commented in sufficient detail, so that I think it won’t be difficult to figure it out and, if necessary, correct something “for yourself.” For example, change or even disable the splash screen animation when turned on - now it says “ Mitsubishi LANCER IX."
The firmware itself (hex) and sources.
Add. compiler information
The program is written in PicBasic Pro, v2.5b (it is necessary to patch it to 2.5b, version 2.5, as far as I understand, does not process OneWare commands correctly, I suffered with temperature sensors I haven't set it up yet. patch)
PicBasic website
You should also download Microcode Studio so as not to bother with the command line
Sergey - SSh
FUEL FLOW METER FOR CAR
The repetition and adjustment of this flow meter is associated with certain difficulties, since many of its parts require high precision processing. Its electronic unit needs good noise immunity due to high level interference in on-board network car. Another disadvantage of this device is the increase in measurement error with decreasing fuel flow rate (in idle move and low engine load).
The device described below is free from the listed disadvantages and has more simple design sensor and electronic unit circuit. It does not have a device for monitoring the rate of fuel consumption; its function is performed by a total consumption meter. The frequency of operation is proportional to the rate of fuel consumption and is perceived by the driver by ear. This does not distract from driving, which is especially important in city traffic.
The flow meter consists of two components: a sensor with an electrovalve built into the fuel line between the fuel pump and carburetor, and an electronic unit located in the vehicle interior. The design of the sensor is shown in Fig. 1. Between the body 8 and the tray 2, an elastic diaphragm 4 is clamped, dividing the internal volume into upper and lower cavities. The rod 5 moves freely in the guide sleeve 7 made of fluoroplastic. The diaphragm is clamped at the bottom of the rod with two washers 3 and a nut. A permanent magnet 9 is installed at the upper end of the rod. In the upper part of the body, parallel to the channel in which the rod is located, two additional channels. They are equipped with two reed switches 10. In the lower position of the magnet, and therefore of the diaphragm, one reed switch is triggered, and in the upper position, another.
Puc.1 
. 1-Fitting, 2-Pan, 3-Washers, 4-Diaphragm, 5-Stem,
6 - Spring, 7 - Bushing, 8 - Housing, 9 - Magnet, 10 - Reed switches
The diaphragm moves to the upper position under the influence of fuel pressure coming from the fuel pump, and spring 6 returns it to the lower position. To connect the sensor to the fuel line, three fittings 1 are provided (one on the pan and two on the body).
Hydraulic circuit flowmeter is shown in Fig. 2. Through channel 3 and the solenoid valve, fuel from the fuel pump enters channels 1, 2 and fills the upper and lower cavities of the sensor, and through channel 4 enters the carburetor. The valve is switched under the influence of signals from an electronic unit (not shown in this diagram), controlled by a reed switch of the sensor.
Puc.2 
In the initial state, the solenoid valve winding is de-energized, channel 3 communicates with channel 1, and channel 2 is closed. The diaphragm is in the lower position, as shown in the diagram. The gasoline pump creates excess fluid pressure in the lower cavity 6. As the engine produces fuel from the upper cavity and the sensor, the diaphragm will slowly rise, compressing the spring.
When the top position is reached, reed switch 1 will operate and the electrovalve will close channel 3 and open channel 2 (channel 1 is constantly open). Under the action of a compressed spring, the diaphragm will quickly move down to its original position and pass fuel through channels 1, 2 from cavity b to a. Then the flow meter operation cycle is repeated.
The electronic unit (Puc.3) is connected to the sensor and solenoid valve with a flexible cable through the XT1 connector. Gorkoms SF1 and SF2 (1 and 2, respectively, according to Fig. 2) are installed in the sensor (in the diagram they are shown in a position where the magnet does not act on any of them); Y1 - valve solenoid winding. In the initial position, transistor VT1 is closed, contacts K1.2 of relay K1 are open and winding Y1 is de-energized. The sensor magnet is located next to the SF2 reed switch, so the reed switch does not conduct current.
Puc.3 
As fuel is consumed from sensor cavity a, the magnet slowly moves from reed switch SF2 to reed switch SF1. At some point the SF2 reed switch will switch, but this will not cause any change in the block. At the end of the stroke, the magnet will switch the reed switch SF1 and the base current of the transistor VT1 will flow through it and resistor R2. The transistor will open, relay K1 will operate and contacts K1.2 will turn on the valve solenoid, and contacts K1.1 will close the power supply circuit of the pulse counter E1.
As a result, the diaphragm together with the magnet will begin to quickly move down. At some point the reed switch SF1 after reverse switching will break the base current circuit of the transistor, but it will remain open, since the base current now flows through the closed contacts K1.1, diode VD2 and reed switch SF2. Therefore, the rod with the diaphragm and magnet will continue to move. At the end reverse the magnet will switch the reed switch SF2, the transistor will close, the valve electromagnet Y1 and the counter E1 will turn off. The system will return to its original state and a new cycle of its operation will begin.
Thus, counter E1 records the number of sensor activation cycles. Each cycle corresponds to a certain volume of fuel consumed, which is equal to the volume of space limited by the diaphragm in the upper and lower positions. The total fuel consumption is determined by multiplying the meter readings by the amount of fuel consumed in one cycle. This volume is set when calibrating the sensor. For the convenience of measuring fuel consumption, the volume per cycle is chosen to be 0.01 liters. If desired, this volume can be slightly reduced or increased. To do this, it is necessary to change the distance between the reed switches in height. With the specified sensor dimensions, the optimal aperture stroke is approximately 10 mm. The duration of the sensor cycle depends on the engine operating mode and ranges from 6 to 30 s.
When calibrating the sensor, it is necessary to disconnect the pipeline from the car's gas tank and insert it into a measuring vessel with fuel, and then start the engine and produce a certain amount of fuel. Dividing this amount by the number of cycles on the counter, the value of the unit volume of fuel per cycle is obtained.
The flow meter has the ability to turn it off using toggle switch SA1. In this case, the sensor diaphragm is constantly in the lower position and fuel through channels 2 and 3 through cavity a will directly flow into the carburetor. To realize the possibility of turning off the device in the solenoid valve, it is necessary to remove the rubber cuff covering channel 3, but this will worsen the error of the flow meter.
The electronic unit is mounted on printed circuit board made of fiberglass 1.5 mm thick. The board drawing is shown in Fig. 4. The parts installed on the board are outlined in the diagram with a dot-dotted line. The board is mounted in metal box and is mounted in the car interior under the instrument panel.
Figure 4 
The device uses a RES9 relay, passport PC4.529.029.11; solenoid valve - P-RE 3/2.5-1112. Counter SI-206 or SB-1M. Permanent magnet You can use any one with an end arrangement of poles and a length of 18...20 mm, it is only necessary that it moves freely in its channel without touching the walls. For example, a magnet from a remote switch RPS32 will do; you just need to grind it down to required sizes.
The sensor body and tray are machined from any non-magnetic petrol-resistant material. The wall thickness between the channels of the reed switches and the magnet should not be more than 1 mm, the diameter of the hole for the magnet is 5.1+0.1 mm, the depth is 45 mm. The rod is made of brass or steel 45, diameter - 5 mm, length of the threaded part - 8 mm, total length- 48 mm. The thread on the sensor fittings is M8, the hole diameter is 5 mm, and on the solenoid valve fittings there is a conical thread K 1/8" GOST 6111-52. The spring is wound from steel wire with a diameter of 0.8 mm GOST 9389-75. The diameter of the spring is 15 mm, pitch - 5 mm, length - 70 mm, force full compression- 300...500 g.
If the rod is made of steel, then the magnet is held on it due to magnetic forces. If the rod is made of non-magnetic metal, then the magnet must be glued or strengthened in any other way. To ensure that the operation of the sensor is not interfered with by the pressure of air compressed above the magnet, a bypass channel with a cross-section of about 2 mm2 should be provided in the bushing.
The diaphragm is made of polyethylene film 0.2 mm thick. It must be molded before installation into the sensor. To do this, you can use the sensor pan assembled with a fitting. It is necessary to make a technological clamping ring from sheet duralumin 5 mm thick. The shape of this ring exactly matches the assembly flange of the pallet.
To form the diaphragm, the rod assembly with its blank is inserted with inside into the hole of the pallet fitting and clamp the workpiece with a technological ring. Then the assembly is evenly heated from the diaphragm side, holding it above the burner flame at a distance of 60...70 cm and, slightly lifting the rod, the diaphragm is formed. In order for the diaphragm not to lose elasticity during operation, it is necessary that it is constantly in the fuel. Therefore, when long-term parking car, it is necessary to clamp the hose from the sensor to the carburetor to prevent evaporation of gasoline from the system.
The sensor and solenoid valve are installed on a bracket in engine compartment near the carburetor and fuel pump and a cable is connected to electronic unit.
The performance of the flow meter can be checked without installing it on the car using a pump with a pressure gauge connected instead of a fuel pump. The pressure at which the sensor is triggered should be 0.1 ... 0.15 kg/cm2. Tests of the flow meter on Moskvich and Zhiguli cars have shown that the accuracy of measuring fuel consumption does not depend on the engine operating mode and is determined by the error in setting a unit volume during calibration, which can easily be adjusted to 1.5...2%.
V. GUMENYUK Kharkov
Our car costs us a pretty penny. No matter how grateful we are to him for his work, from time to time we still want to reduce expenses on it and more carefully control the consumption of fuel, oils and technical fluids. In order to monitor these processes, it is necessary to know exactly what fuel consumption is for a given period of time. It is natural that this task cannot be done manually and by eye - for quick and accurate measurements you need a modern device that will do everything necessary work and will not take up much of your time. The Innotech company invites all car enthusiasts to purchase a fuel flow meter in order to always be aware of the costs of gasoline or diesel.
Fuel flow meter
A fuel flow meter is a device designed specifically for measuring fuel in automotive and other systems. This device has a wide range of applications - it is widely used not only for vehicles, but also for watercraft, diesel generators and other units and equipment where the source of energy is fuel. Most of these devices are distinguished by impeccable accuracy, as they are mounted directly into the fuel line. This means that the readings that flow meters will give diesel fuel, will be deprived of even minimal error.
This type of flowmeter is a convenient and practical device for all types of equipment using liquid fuel. So, it’s worth starting with the fact that a fuel flow meter for a car is easy to install - you won’t need much time for this, and the flow meter can start working immediately after installation.
Advantages of a fuel flow meter
The idea of buying a fuel flow meter will seem even more profitable to you if you learn about the advantages of this device. Despite its compactness and affordable price, the number of its valuable characteristics is truly impressive!
- High accuracy - as we said, this device is distinguished by the absence of errors in readings, which makes it one hundred percent effective in the field of assigned tasks;
- Reliable and strong housing, which is important for a device operating inside another system. It is not afraid of accidental damage and can withstand high-intensity loads;
- The device is highly resistant to wear and can work long years- of course, provided that you used it correctly and followed all operating rules.
The fuel flow meter can work with different types liquids. In addition to diesel fuel, it is also mineral oil, heating oil, as well as other varieties liquid fuel with a certain density and viscosity. In order not to make a mistake when choosing a device based on this parameter, carefully read its description technical parameters on the package.
The Innotech company is waiting for you to help you choose a fuel flow meter for your vehicle or equipment. You can find different prices for fuel flow meters with us - suitable for any budget and needs. With us you will not have problems with measuring fuel!
Car meter fuel consumption.
A car is not a luxury, but a means of transportation, with these words I would like to open this topic. Any vehicle cannot move without fuel, which, as you know, costs money. How many of us know exactly how many liters a car burns per unit of time or distance? But knowing the current fuel consumption, you can easily choose a driving style that saves wasted fuel. Convenient to identify optimal modes from the point of view of a rational compromise between economy and sufficient throttle response, specifically for your engine. Many cars are already equipped with standard indicators, yes, exactly indicators (not meters) of consumption with the names ECONOMY or the like. This device displays the quality of fuel absorption by the engine rather than consumption. It measures the vacuum under throttle valve, - and this is not an accurate fuel consumption parameter...
Many injection control controllers have an external digital bus, from which you can read flow information, but descriptions of the exchange protocols on this bus are not freely available, and it is easier not to work with this bus.
The design I developed is a fairly accurate device for displaying the real, current fuel consumption of your car.
The only restriction on the use of this device is that the engine must be fuel injected (mono or multi point), and if diesel, then the injection must be electronic. Modern cars for the most part are just that.
This is due to the fact that the initial signal is taken directly from the injector solenoid terminal. Flow measurement is based on measuring the opening time of the injectors per unit of measurement time, taking into account the fact that the fuel pressure in the line is constant.
Consumption is displayed in liters per hour with an accuracy of 0.1 liters per hour. To connect, only 4 wires are required: ground, +12V constantly, +12V when the ignition is turned on, and a signal from the injector (if there are more than one, then from any one). There are two main operating modes - measurement and calibration. Why is calibration needed? For different car models different volume engines, different pressure in the fuel line, etc. For the calibration process, only one thing is necessary - to know the exact amount of fuel burned over a period of time. The beginning and end of this time is marked by the user. At the same time, in calibration mode, you can start and stop the engine and drive at any speed and mode. It is only important to note to the controller the beginning and end of the countdown of time during which it burned exactly known quantity fuel. After this procedure, the device will be calibrated specifically for your car. The calibration procedure working with 32-bit numbers is quite complex and detailed description her job won't be there.
The meter can be implemented on any processor with an 8051 instruction structure, for example 1816ve51,80s31,89s52..., with internal or external program memory of at least 4K.
The meter consists of an indication unit on a 1-2 row indicator with an HD44780 controller, a keyboard unit and the processor module itself. As an indicator, it is better to use a two-row 2x16 characters or a one-and-a-half row, in which the second row has a symbol matrix of 4x5 points. You can also use a single-row indicator, but in this case the peak flow indicator, implemented precisely in the second row of familiarization spaces, will not work.
The keyboard consists of five short-circuit buttons, we will designate them by numbers 1..5 for ease of mentioning them in the further description. The indicator block and keyboard block can be removed from the processor using almost any cable at a distance of more than two meters. This is done for ease of installation of the device in a car, for example: indicator on instrument panel, keyboard next to pen hand brake, and the processor to any other place, but always in the cabin. To ensure this possibility, sufficient low speeds exchange of the processor with the indicator and keyboard, and software control of keyboard chatter is implemented.
Functionally, the buttons have the following. Values:
1 decrease variable value
2 increasing the value of a variable
3 previous variable
4 next variable
5 master button
The controller turns on when the ignition is turned on, by generating a processor reset signal, and turns off automatically if there is no signal from the injector for more than 15 seconds. After turning off, the processor and indicator are switched to micro-consumption mode, while the main power is not interrupted.
When turned on, there may be three startup options
Cold start for first turn on or corrupted information in ROM
Warm start, the values of all parameters are taken from the ROM and RAM of the processor
Warm start, but only clearing the processor RAM to start a calibrated meter after battery disconnections or other failures in the electrical wiring system.
And now, actually, the operating instructions.
To install in a car, you need to install the indicator, keyboard and processor module in convenient places. Connect the ground to the car body, +12V to a constantly present power supply, for example to the battery terminal, the ignition to the wire on which +12V is present only when the ignition is on, and the last wire to the injector, if there is more than one injector, then to any of them. You need to connect through a 10 kOhm resistor to the wire of the injector electromagnet on which the voltage pulsates when the latter opens. For safety reasons, this resistor should be installed directly at the injector. The voltage from the injector should be close to zero when opening the injector and close to 12V when closing, otherwise you must independently install an additional inverter to change the phase of the signal from the injector in the controller circuit.
When you turn it on for the first time, before turning on the ignition, you must press buttons 1,2 and 5 simultaneously and then turn on the ignition. After turning on the ignition, release the buttons and wait for the controller to start. Next, press button 5, and after the symbol * appears in the rightmost familiar place, press buttons 1 and 2 until the inscription SETUP appears, then release all buttons.
The name of the first system variable and its value will appear on the screen. The variable is selected using buttons 3 and 4, and the value is changed using buttons 1 and 2. For the first case, you should not change anything and press button 5 until the normal display appears. In this case, the initial values will be written into the ROM and in the future the controller will start normally when turned on. It should be noted that when performing the initialization procedure described above, the calibration coefficient will remain erroneous; it will be registered only after a successful calibration cycle on the vehicle. This will only cause an erroneous flow indication! Therefore, it is more convenient to program ROM 24c02 in advance with the following values: 5,100,10,10,32,0,197,0,0,10. This data should be written from the zero address of the ROM.
The system menu has the following variables:
Mass time is the measurement time that should be selected to obtain the dynamics of changes in meter readings that are optimal for you
Mass offs introduction of a constant adjustment to the meter reading in the range from –100 to +100, which will correspond to an adjustment of the readings from – 10.0 l/h to + 10.0 l/h.
Mass /div These parameters allow you to multiply and then divide the flow measurement result by a number from 1 to 10 to adjust the readings proportionally. In other words, you can multiply or divide the readings by 0.1....10.
*-displ /div input signal division factor for the peak indicator, used to select the gain of the peak indicator.
*-displ mode mode peak indicator
0-one moving familiarity
1-regular peak indicator with a familiarity strip varying in length
*-works only with a two-row indicator.
Tank calibr this variable affects the calibration result when its reading decreases real consumption after calibration they increase and similarly in the opposite direction.
Read more about the last variable. The meter is designed to operate a processor with 11 MHz quartz, but other frequencies can be used. For ease of adaptation to another quartz frequency, this variable is used. To install the latter in correct position It is best to assemble and connect a calibration generator. The generator output is connected instead of the signal from the injector. Having turned on the meter with the generator, you should select the frequency and duty cycle of the generator pulses so that the readings are not zero and maximum (70 l per hour). Next, start the calibration for, say, 10 minutes and tell the controller that 2 liters have burned, after which the readings should become 6 liters per hour, if this does not happen, then you should select the tank calibr variable, repeating the calibration mode until the required flow reading is obtained.
After this procedure, the meter is ready for calibration on the car.
Calibration is started by pressing buttons 5 and 3 until the inscription calibr stsrt appears, to finish, press buttons 5 and 4, the inscription calibr stop appears, after pressing the buttons the controller will ask you to enter the actual amount of fuel burned (real tank), if you enter 0, the calibration will continue. This is done to prevent erroneous cancellation of the mode. If rough calculations occur during calibration calculations math errors, for example, division by zero, the controller will issue a calibr error message and return to the previous values. In calibration mode, you cannot enter the system menu; if you try, the message setup not run will appear. This is due to the measurement time value, which cannot be changed in calibration mode.
Despite the apparent complexity of installation, the meter is highly flexible in adapting to specific operating conditions. When setting the quartz to a frequency other than 11 MHz, double calibration is necessary, although with the required frequency value (11 MHz) of the quartz, a primary calibration may be required to improve measurement accuracy. In any case, it is better to perform both calibration steps.
A warm start with clearing the processor RAM only cancels all unfinished calibration procedures in case of failure.
Technical data
Measured flow rate 0.1-70.0 l. for an hour
Calibrated fuel volume 1-99 liters
Measurement time 0.2 – 1.5 sec
Controller circuit with external ROM
Controller circuit with internal ROM
Calibration generator circuit
Photo of the working meter indicator
Photo of the indicator from the controller side hd44780
Programs for flashing ROM in hex and bin formats
Schemes in format sPlan . Firmware files are provided in bin hex formats. Two versions of the controller are included:
0…for single-row indicator
1...for a two-row indicator, although this version can work with single-row indicators that have continuous familiarity addresses, of course without a peak indicator.
Indicators based on hd44780 have no less than three, known to me, varieties of addressing internal RAM and the advice is simple, Try both included versions, if this does not help, then use another indicator. If the indicator is incompatible, in any case, the left 8 acquaintances will be displayed correctly!
As already noted, any processor is compatible with the 8051 instruction system, with external or internal ROM with a capacity of 4 KB. When using internal ROM, ports P0 and P2 are not used.
And in conclusion I would like to note:
This device is part of my development of an on-board computer. The development as a whole will be commercial and upon completion there will be a separate article describing the design and conditions for the implementation of the device.
This version (beta) is free due to the fact that I am interested in the test results on different models auto.
I would be very grateful for such information.
Please do not contact us with questions about purchasing or ordering for now. Additional functionality It won't be in the free version either.
I wish you good luck and trouble-free driving!!!
In one of the articles in the first issue of Radio magazine in 1986, a version of the device was described that allows control over the amount of liquid and its speed (in in this case we are interested in car fuel), which leaks in the main pipes.
Due to the high requirements for processing accuracy, certain difficulties may arise when repeating the described flow meter, as well as in the process of setting it up. The electronic unit of this device must be well protected from interference, due to the fact that the level of interference in the vehicle on-board network is quite high. This device has another drawback. The point is that as the fuel flow rate decreases, the measurement error inevitably increases.
The device described below does not have these disadvantages; its sensor design is simpler, as is the circuit of the electronic unit. This device does not have a speed control device fuel consumption– the total flow counter is intended for this function. The driver audibly perceives the rate of fuel consumption, which is proportional to the frequency of operation. In urban environments heavy traffic this is especially important because it does not distract the driver from driving the car.
What does a flow meter consist of?
The device has two units:
1. Sensor with electric valve.
2. Electronic unit.
The sensor is built into the fuel line and is located between the carburetor and the fuel pump. The electronic unit is located in the cabin. The figure shows the design of the sensor. 1 Elastic diaphragm 4 is sandwiched between pan 2 and body 8. It divides the internal volume into two cavities - lower and upper.
The guide sleeve 7 is made of fluoroplastic. The rod 5 moves freely in it. The diaphragm is clamped in its lower part using a nut and two washers 3. A permanent magnet 9 is installed at the upper end of the rod. Parallel to the channel where the rod is located, at the top of the body, there are 2 additional channels. These channels include two reed switches 10. One reed switch is activated when the magnet and diaphragm are in the lower position, the other – in the upper position.
Figure 1. 1-Fitting, 2 – Pan, 3- Washers, 4 – Diaphragm, 5- Rod, 6 – Spring, 7 – Bushing, 8 – Housing, 9 – Magnet, 10 – Reed switches
The diaphragm moves to the upper position due to the action of fuel pressure supplied from the fuel pump. It returns to the lower position using spring 6. In order for the sensor to be included in the fuel line, there are two fittings on the body and one on the pan. Fittings 3. The figure shows 2 the hydraulic diagram of the flow meter. Fuel from the fuel pump, through the solenoid valve and channel 3, begins to flow into channels 1, 2, filling the lower and upper cavities in the sensor. And it enters the carburetor through channel 4. The valve is switched under the influence of the electronic unit and the signals coming from it (not shown in this diagram). The electronic block is controlled by a reed switch installed in the sensor.
Puc.2 Hydraulic diagram of the fuel flow meter.
The winding of the solenoid valve is de-energized in the initial state, channels 3 and 1 communicate with each other, while channel 2 is closed. The diagram shows that the diaphragm is in the lower position. In the lower cavity 6, excess fluid pressure occurs with the help of a gasoline pump. The diaphragm will begin to gradually rise, as the engine produces fuel, from the upper cavity of the sensor, compressing the spring.
Reed switch 1 will operate when it reaches the top position, then the solenoid valve will open channel 2 and close channel 3. In this case, channel 1 is constantly open. The diaphragm will immediately move downward under the action of the compressed spring. It will return to its original position, passing fuel from cavity b to a, through channels 1 and 2. Then the cycle is repeated in the operation of the flow meter.
An electronic unit is connected to the electrovalve and sensor using a flexible cable through the XT1 connector. City committees SF1 and SF2 are installed in the sensor. According to the diagram, none of them is affected by a magnet. Transistor VT1 is closed in its initial position, the winding of the valve electromagnet Y1 is de-energized, 2 relays K1 are open. There is a sensor magnet next to the SF2 reed switch, so the reed switch does not conduct current.
Puc.3 Electronic unit of the fuel flow meter.
The magnet gradually moves, as fuel is consumed, between the reed switches SF2 and SF1, from cavity a of the sensor. At a certain moment, the SF2 reed switch switches, but this will not cause any changes in the block. The magnet, at the end of the stroke, switches the reed switch SF1, and the base current of the transistor VT1 will flow through the resistor R2 through the reed switch SF1. The transistor opens, relay K1 is activated, and turns on the valve solenoid with contacts K1.2. In this case, the power supply circuit of the pulse counter E1 will be closed by contacts K1.1.
As a result, the magnet and diaphragm will quickly move downward. At a certain moment, after reverse switching, the reed switch SF1 opens the base current circuit of the transistor. At the same time, it remains open, since now the base current flows through the diode VD2, the closed contacts K1.1 and the reed switch SF2. This is the reason why the rod with magnet and diaphragm continue to move.
The magnet switches reed switch SF2 at the end of the return stroke. After this, the counter E1 and the electromagnet Y1 of the valve will turn off, the transistor will close and the system returns to its original state, after which it is ready for a new operating cycle. As you can see, the number of cycles is recorded by counter E1. In this case, one cycle corresponds to a particular volume of fuel equal to the volume of space limited by the diaphragm located in the lower and upper positions.
By multiplying the volume of fuel used during one cycle by the meter readings, the fuel consumption is determined, which is set during calibration of the sensor. To make it more convenient to calculate the fuel consumed per cycle, its volume is equal to 0.01 liters. This volume can be changed by increasing or decreasing, while changing the height distance between the reed switches.
The optimal diaphragm stroke, given the existing sensor dimensions, is about 10 mm. The duration of the sensor cycle ranges from 6 to 30 s, and depends on the engine operating mode. When calibrating it, you should disconnect the pipeline from the gas tank, inserting it into a measuring vessel filled with fuel, then you need to start the engine to produce a certain amount of fuel - divide it by the number of cycles (determined by the meter), and as a result we get the number of a unit volume of fuel , consumed in one cycle.
The ability to disable it is provided in the flow meter using toggle switch SA1. In this case, fuel will flow into the carburetor directly, through cavity a, through channels 2 and 3, since the sensor diaphragm will always be in the lower position at this time. To turn off the device’s solenoid valve, you will have to remove the rubber cuff blocking channel 3, however, the error of the flow meter will worsen. The electronic unit is mounted on a printed circuit board made of fiberglass - a 1.5 mm thick plate. Its drawing is shown in Figure 4. The parts installed on the board are circled with dash-dot lines in the diagram. The board is mounted in a metal box. Its mounting is made under the instrument panel in the car interior.
Puc.4 Drawing of the fuel flow meter electronic unit board
What was used in the device:
– Relay RES9
– Electrovalve – P-RE 3/2.5-1112
– Passport PC4.529.029.11
– Counter SI-206 or SB-1M.
- Permanent magnet.
In this case, you can take any magnet, where the length is 18...20 mm, and the poles have an end arrangement. It is important that the magnet can move freely within its channel without affecting the walls. The magnet from the RPS32 remote switch is quite suitable for this, but you will have to grind it down to the required size. The sensor pan and body are machined from any material with non-magnetic and petrol-resistant properties.
Between the magnet and reed switch channels, the wall thickness should be up to 1 mm, the hole depth under the magnet should be 45 mm, and the diameter should be 5.1+0.1 mm. The rod is made of steel 45 or brass, the length of the threaded part is 8 mm, the diameter is 5 mm, the total length is 48 mm. The thread on the sensor fittings is M8; hole with a diameter of 5 mm. The solenoid valve fittings have a conical thread K 1/8″ GOST 6111-52.
A spring with a diameter of 0.8 mm, made of steel wire, GOST 9389-75 is used. Full compression force – 300...500 g, spring diameter – 15 mm, length – 70 mm, pitch – 5 mm. In the case where the rod is made of steel, the magnet itself is held on it.
When the rod is made of non-magnetic metal, it is necessary to strengthen the magnet in another way. To ensure that the compressed air pressure does not interfere with the operation of the sensor, a bypass channel with a cross-section of about 2 sq. mm should be provided in the bushing. The diaphragm is made of 0.2 mm polyethylene. It will have to be molded before installation in the sensor. A sensor tray can be used for these purposes.
Made from sheet duralumin 5 mm. a pressure ring should be made that matches the shape of the pallet flange. To form the diaphragm, the rod, complete with its workpiece, is inserted into the hole in the pan fitting from the inside, and the entire workpiece is clamped with a technological ring.
Next, the assembly is heated evenly from the diaphragm side, holding it at a distance of 60...70 cm from the burner flame. The diaphragm is formed by slightly raising the rod. So that it does not lose elasticity in the future, it must be in the fuel constantly. Therefore, you will have to pinch the hose to the carburetor when parking the car for a long time. This will prevent gasoline from evaporating.
An electric valve and sensor are installed in the engine compartment. They are mounted near the fuel pump and carburetor on a bracket, connecting with a cable to the electronic unit. Using a pump with a pressure gauge, you can check the performance of the flow meter without installing it on the car.
In this case, a pressure gauge is connected instead of a fuel pump. The sensor is triggered at a pressure of 0.1 ... 0.15 kg/cm 2. The flow meter was tested on Zhiguli and Moskvich cars. During the inspection, it was found that the engine operating mode does not in any way affect the accuracy of fuel consumption readings. The exact flow rate is determined by calculating the error in setting a single volume when calibrated to 1.5...2%.
