With the progress of science and technology, motorcycle display instrument from the pointer to the digital development. Digital display instrument is used in the microprocessor measurement and control and sensor measurement technology, through the control of digital display light-emitting diodes and light combination to display the speed, mileage, with the article that the amount of oil, and auxiliary display speed.
Compared with the ordinary pointer meter, digital instrument has the advantages of accurate detection, low failure rate and compact structure. I developed the digital display instrument, through the middle of the instrument panel to display the five digits of the motorcycle speed, engine speed, total mileage and one-way mileage, the light brightness can be adjusted (daytime brightness is higher, lower brightness at night), through According to the function keys, you can select four kinds of functions: speedometer (the middle of the three displays, 5km / h), tachometer (5 display, 100r / min), odometer (5 display, 1km) Single-way odometer (5 display, is in decimal, 100m); instrument panel upper 23 light-emitting diodes can display the speed of the car; dashboard lower indicator lights show oil and oil alarm, voltage alarm, Left and right turn display and other functions.
First, the working principle of electronic digital instrumentation
1, speed detection
The Hall device and the motorcycle front wheel phase, when driving through the rotation to produce a change in the magnetic field, resulting in pulse signal to measure the speed. As is known: the wheel circumference s (m), the wheel turns 1 week to drive the number of revolutions of the Haller n (r / min), the number of pulses emitted by the Hall 1 turn Pulse number B2, you can get the speed of the motorcycle v (km / h).
By the formula: B2 = (1000/60 × 60) × (nvB1 / S)
Derived: v = (36s / 10nB1) B2
Let a = 36s / 10nB1, the unit is "s", the speed formula can be simplified as: v = aB2, that is, a second Hall device issued by the number of pulses for the motorcycle speed.
2, mileage test
Known conditions above, can be obtained when driving a motorcycle 500m Hall device issued by the number of pulses B3, B3 = 500nB1 / s
3, oil detection
The more oil, the greater the oil pressure, the smaller the oil sensor resistance, so the oil quantity can be measured by the oil sensor resistance to determine the amount of oil. According to the standard requirements of the oil sensor resistance by size is divided into 7 equal parts, the corresponding oil display section also has seven cells.
The digital instrument is controlled by the single-chip computer, the use of Hall device to complete the speed of detection, Hall device every turn of a circle issued two square wave pulse; oil pressure reflects how much oil, oil pressure can make the oil sensor resistance value Change; power module provides a single chip, memory, decoder driver power, light control circuit, fuel display and alarm circuit power. Motorcycle due to the impact of igniter and starter motor, often appear peak up to 350V, pulse width <0.1mm continuous interference pulse, in order to ensure the reliability of the power supply, the circuit used to absorb high-pressure narrow pulse interference, absorption of high frequency Interference and other technologies, so that the circuit can resist a variety of interference on the motorcycle to ensure the stability of the entire system. The main control unit is responsible for signal processing, algorithms, display control and effect processing and mileage maintenance and other functions, and ultimately to achieve motorcycle speed, cumulative mileage, oil, height automatic adjustment and other functions.
Second, the electronic digital instrumentation hardware design
As the master speed and mileage sampling, display and storage and other parts of the block diagram. Using the 97C2051 microcontroller to sample the speed sensor signal, the calculated speed and mileage to the decoding drive circuit, and the mileage value stored in the E2PROM 24L01B, the speed display updated once per second, mileage display per 0.1km update 1 time. The function key circuit is used to select the speed, speed, mileage, one-way mileage display function. In order to ensure that the microcontroller can be reliably reset after an instantaneous power failure, especially the CPU monitoring circuit.
Fuel flow display and alarm circuit block diagram, composed of 8-bit analog comparator, drive 7-bit LED oil indicator light and oil alarm indicator, the voltage alarm light driven by a 1-bit analog comparator.