A speedometer is a speed measuring device that saves you from paying fines for speeding, from wasting time and nerves. Of course, in the event of a breakdown, the easiest way is to purchase a factory device, but you can try to make it yourself.
Instructions
Step 1
Speedometers are divided into two types - mechanical and electronic. The mechanical device for measuring speed is based on the rotation of the magnetic disk caused by the movement of the transmission. As a result of the action of magnetic fields, the aluminum card is carried behind the disc, but it is held by a return spring. The position of the arrows on the dashboard depends on the stiffness of the spring. It is almost impossible to make a mechanical speedometer on your own, as it will be very difficult to get the correct readings. Even factory speedometers have a measurement error of 10%.
Step 2
The electronic speedometer is basically a meter for the number of pulses coming from the speed sensor. Its error is noticeably lower, and you can try to make it at home. You will need a graphic display from an old Nokia mobile phone, LEDs for backlighting, a microcontroller, a large capacitor, low-power resistors, a voltage regulator, a crystal resonator, a trimmer. Parts can be purchased from a radio store.
Step 3
Assemble the device diagram. You can find it here: https://speed-light.on.ufanet.ru/speedometr-mega16.shtml or a simpler version here: https://forum.jawaold.su/viewtopic.php?t=15873. There you will also find tips for making your own microcircuits
Step 4
Install the speed sensor and calculate the number of impulses per kilometer. If you are making a motorcycle, for example, the sensor can be mounted on the wheel. Measure the wheel circumference and calculate: one wheel revolution - one pulse from the sensor. If the wheel length is 2 meters, then the sensor emits 500 pulses per kilometer. Program the microcontroller to the required values and install the electronic speedometer on the dashboard. It can be placed in a housing from under a conventional mechanical speedometer.
