How to make a tachometer with your own hands?

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

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

Using a microcontroller

To make a do-it-yourself tachometer based on a microcontroller, you will need the following parts:

• Directly microboard, Arduino circuit will do.
• Resistor set.
• The LED option will require an LED element.
• Diodes (infrared and photoanalog).
• Monitor. For example, LCD display.
• Shift register type 74HC595.

In the method discussed below, not a slotted regulator is used, but an optical regulator. 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 information about the speed of the drum.

Stages of work

The following is a step-by-step instruction on how to make a do-it-yourself tachometer based on a microcontroller:

1. Start with fine sandpaperthe light and photodiode are processed until they take a flat shape.
2. A similar element is made in the form of a strip, then both parts are connected with glue and painted black.
3. At the next stage, diodes are mounted, wires are soldered to them.
4. Critical resistor values may vary depending on the photodiode used. The sensitivity of the controller will allow you to adjust the potentiometer.
5. After examining the circuit of an automobile LED tachometer, one can understand that it has an eight-bit shift register. In addition, the circuit includes a liquid crystal display. To fix the light bulb, a small hole is made in the housing.
6. At the final stage, you will need to solder a resistor (270 Ohm) to the diode, then mount it in the socket. The controller is inserted into the cube tube, which provides additional strength to the fixture.

Making a simple do-it-yourself tachometer

For the manufacture of this device, a microcalculator is taken 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 revolutions per minute on the display. Nevertheless, the calculator is a good alternative to other signal counting devices.

Inductive or similar controllers are used to manufacture the signal regulator. When the disc is rotatedThe display shows one beep after each revolution. The contacts should be open at this point. They close when the node passes the disc tooth. The tachometer in question (with our own hands, as we can see, it is quite simple to make it) of this type is perfect for those cases where measurements are rarely taken. For those who want to install a regular speed controller, it is better to opt for more reliable devices.

Operation

The simplest tachometer, made on the basis of a calculator, works after soldering the contacts to the addition button of the computer.

Measuring the speed of rotation is performed as follows:

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

Analogue version

An electronic tachometer, made by hand for a diesel or gasoline engine, is focused on converting an electronic impulse and transporting it to a display device. Unlike this device, digital models convert an analog pulse into a certain sequence of zeros and ones, which is readand decrypted by the controller.

Analogue tachometers come with the following items:

• Microboard designed to convert analog pulses.
• Wiring connecting all elements of the device.
• A scale used to demonstrate performance.
• An arrow that affects the effective value.
• Special spool with axle to ensure correct operation of the needle.
• Inductive controller type reader.

How to make a digital tachometer with your own hands

Devices of this type have an identical purpose, but differ in structural elements. To build your own device, you will need the following parts:

• Eight-bit converter.
• A processor that allows you to convert pulses into a chain of zeros and ones.
• Display for demonstrating readings.
• Interrupting type device (rotation controller) with amplifier. Special shunts may be used for this purpose, depending on the specific situation.
• Fee for resetting information.
• Additionally, you can connect a temperature controller for antifreeze, cabin air, engine fluid pressure, and the like to the processor.
• To set up the normal operation of the device, you will need to install a special program.

Mechanical modification

Mechanical car tachometer, made by hand, does not require power andcontrol schemes. A permanent type magnet is rigidly fixed on the shaft. When it rotates, a vortex field is created, which carries along a special container made of magnetic material. The rotation of the bowl is resisted by a spiral spring. The higher the rotation speed, the more actively the shaft equipped with the arrow deviates.

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

Diagnosis

A DIY tachometer can also fail. Diagnostics will be required to identify the cause of the problem. In vehicles equipped with an OBD II interface, the check is performed using a scanner. In addition, an electronic device can be controlled using any pulse generator. The best option would be a known-good device, an oscilloscope or a frequency counter.

The mechanical analogue is diagnosed with a drill or screwdriver. If there is a speed controller, it is easier to check. The tail of the cable is fixed in the cartridge, and the body of the device is rigidly fixed.

Repair

Repairing the device in question is not very difficult. The most difficult instance to repair is the electrical circuit module. After localizing the malfunction, it will be necessary to replace the defective element. Howas a rule, most often the wiring fails, the indicator contacts, the sensor, the magnet on the crankshaft.

With the mechanical version, everything is much simpler. It is enough to replace the part that has failed with a new spare part. With such tachometers, cars have high mileage and are classified as heavily used vehicles. Therefore, it will not be difficult to find an element in the automotive market or in disassembly. After repair, the connection of the device does not require calibration.

Settings

A hand-made tachometer on a car may require adjustment. Since in machines, usually, for one revolution of the motor shaft, the indicator gives out a couple of pulses, when calibrating the device, the generator frequency should be set twice as high.

To set up the tachometer without causing difficulties, it is necessary to study the principle of operation of the bridge circuit. For example, if the ratios of the resistor values are equal, the voltages at the points are equal, which means that the current does not flow and the arrow is at zero. If you reduce the value of the first resistor, the voltage at one point will increase, and at the second it will remain unchanged. The current will go through the milliammeter and the needle will start moving. This means that with a constant voltage at the second point and a change in this indicator at the first point, the tachometer needle will move relative to the scale.

In closing

It is quite possible to make a car tachometer with your own hands if you have elementary knowledge in electrical engineering anda wish. All you need is a ready-made circuit, a soldering iron and basic parts. The work will take no more than two days, including dismantling and installation. You can choose a product according to your needs: from a simple calculator-based instrument or a more advanced tachometer based on the ARDUINO circuit. Before starting work, study the principle of operation of the standard device on your car.