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How to make a tachometer with your own hands?

Before making a tachometer with your own hands, you need to understand the features of this device. The device serves to measure the number of revolutions of the power unit while driving. This information is displayed on a display panel located on the dashboard or a special screen. Consider the principle of the tachometer and how to make it yourself.

We use the microcontroller

To make a tachometer with your own hands based on a microcontroller, the following details are required:

  • Directly a microboard, Arduino's scheme will do.
  • A set of resistors.
  • For the LED option, an LED element is required.
  • Diodes (infrared and photoanalog).
  • Monitor. For example, LCD-display.
  • Shear register type 74HC595.

In the method considered below, a slit rather than an optical regulator is used. This will avoid problems with the thickness of the rotor, the number of blades will not affect the readings, and it will also be possible to read the information about the drum's revolutions.

Stages of work

Below is a step-by-step instruction on how to make a tachometer with your own hands based on a microcontroller:

  1. To begin with, fine-grained emery paper processes the light and photodiode until they take a flat shape.
  2. A similar element is made in the form of a strip, then both parts are connected by means of glue and painted in black color.
  3. At the next stage, diodes are mounted, wires are soldered to them.
  4. The critical values of the resistors can vary, depending on the photodiode used. The sensitivity of the controller will allow you to adjust the potentiometer.
  5. Having studied the scheme of the car LED tachometer, you can understand that it provides a shift register for eight digits. In addition, the circuit includes a liquid crystal display. To fix the bulb in the body a small hole is made.
  6. At the final stage, you need to solder a resistor (270 ohms) to the diode, then mount it into the socket. The controller is inserted into a cubic tube, which provides additional strength to the device.

We make a simple tachometer with our own hands

To produce this device, a microcalculator is used as the basis. This option is suitable for those who have problems with the element base. It is worth noting that such a device does not provide 100-percent accuracy, and the tachometer will not broadcast the number of rotations per minute on the display. Nevertheless, the calculator is a good alternative to other devices for calculating signals.

To manufacture the signal controller, inductive or similar controllers are used. When the disk rotates, the display shows one signal after each revolution. At this time, the contacts must be open. They close when the node passes the disk prong. The considered tachometer (with our own hands, as we see, making it simple enough) of this type is suitable for those cases when measurements are rarely performed. Those who want to install a regular speed controller, it is better to choose the more reliable devices.

Exploitation

The simplest tachometer, made on the basis of a calculator with its own hands, works after soldering the contacts to the computer's add-on button.

The rotation speed is measured as follows:

  1. The calculator turns on.
  2. Synchronously, the "+" and "1" keys are activated.
  3. The gadget starts and it is measured. To ensure the accuracy of the readings, a stopwatch should be activated at the same time as the calculator.
  4. Wait 30 seconds, then look at the screen. The corresponding value should appear on it.
  5. This indicator is the number of revolutions in 30 seconds. Multiplying the figure by two, we get the number of rotations per minute.

Analog version

Electronic tachometer, made for the diesel or gasoline engine, is aimed at converting the electronic pulse and transporting it to the display device. Unlike this device, digital models convert an analog pulse into a certain sequence of zeros and ones, which is read and decrypted by the controller.

The complete set of analog tachometers includes the following elements:

  • The microprogram, the purpose of which is the conversion of analog pulses.
  • Wiring connecting all the elements of the device.
  • Scale, serving for demonstration of indicators.
  • The arrow that exerts on the actual value.
  • A special coil with an axis, which ensures the correct operation of the arrow.
  • Reading device type inductive controller.

How to make a digital tachometer yourself

Devices of this type have an identical purpose, but differ in structural elements. To build the device yourself, the following details are required:

  • The converter is eight-bit.
  • A processor that allows you to convert the pulses into a chain of zeros and ones.
  • Display for demonstration of indications.
  • Device interrupting type (rotary controller) with an amplifier. Special shunts can be used for this purpose, depending on the specific situation.
  • Board to zero information.
  • In addition, it is possible to connect a temperature controller of antifreeze, air in the passenger compartment, engine fluid pressure, and the like to the processor.
  • To configure the normal operation of the device, you will need to install a special program.

Mechanical modification

Mechanical automobile tachometer, made by hand, does not require power and control circuits. The magnet is fixed permanently on the shaft. When it is rotated, a vortex field is created, which entrains a special container of magnetic material behind it. Rotating the thicket creates resistance to the coil spring. The higher the rotation speed, the more deflected the shaft equipped with an arrow.

The main advantage of a mechanical device is the simplicity of the design and the lack of the need for an electrical supply. Among the minuses, we can note the high error and the shifted lower limit of measurements. It is worth noting that at low speeds the shooter does not deviate.

Diagnostics

A self-made tachometer can also fail. In order to identify the cause of the problem, it is necessary to carry out a diagnosis. In vehicles equipped with the OBD II interface, the test is performed using a scanner. In addition, the electronic device can be monitored using any pulse generator. The best option would be a known device, an oscilloscope or a frequency meter.

A mechanical analog is diagnosed by means of a drill or a screwdriver. With a speed regulator, it is easier to check. The tail part of the cable is fixed in the chuck, and the body of the device is rigidly fixed.

Repairs

It is not very difficult to repair the device in question. The most difficult to repair an instance is the electrical circuit module. After the fault is localized, the defective element must be replaced. As a rule, the wiring, the indicator contacts, the sensor, the magnet on the crankshaft are most often out of order.

With a mechanical option, everything is much simpler. It is enough to replace the part that failed for a new part. With such tachometers, cars have a high mileage and belong to heavily used vehicles. Therefore, it will not be difficult to find an element in the car market or in disassembly. After repair, the device connection does not require calibration.

Customize

The tachometer on the car, made by own hands, can demand tuning. Since the indicator in the machines usually produces one pair of pulses per revolution of the motor shaft, then when the device is calibrated, the frequency of the generator should be set twice as high.

To adjust the tachometer does not cause difficulties, it is necessary to study the principle of operation of the bridge circuit. For example, if the ratio of the resistor values is equal, the voltages at the points are equal, which means that the current does not flow and the needle is at zero. If you reduce the value of the first resistor, the voltage at one point will rise, but in the second it remains unchanged. The current will go through the milliammeter and the needle will start moving. This means that with constant voltage at the second point and changing this index at the first point, the arrow of the tachometer will move relative to the scale.

Finally

It is quite possible to make a car tachometer with your own hands, if there is an elementary knowledge of electrical engineering and desire. All you need is a ready-made circuit, a soldering iron and basic parts. It will take no more than two days to work with the dismantling and installation. You can choose the product according to your needs: from a simple calculator-based device or a more advanced tachometer based on the ARDUINO scheme. Before you get started, learn how to operate a standard device on your car.

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