JP2707669B2 - Wireless speedometer for bicycles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bicycle speedometer for displaying a running speed and a running distance of a bicycle.

2. Description of the Related Art Conventionally, as shown in FIG. 8, a magnet m is mounted on a spoke of a front wheel of a bicycle, and a reed switch 1 is mounted on a front fork correspondingly. The speedometer body M is attached to the handle or handle post,
It incorporates a battery, microcomputer, LCD display, etc., and is connected to the reed switch 1 by a cord.

Each time the magnet m passes near the reed switch 1 as the wheel rotates during traveling, the magnetic flux crosses the reed switch, closes its contact and the pulse generated at that time is applied to the microcomputer, and the number of applied pulses and the tire The running distance is calculated from the product of the circumference and the running speed and the like are calculated from the relationship between the number of pulses or the pulse interval within a predetermined time and the circumference of the tire, and are displayed on the LCD. The above is the conventional digital bicycle speedometer.

Problems to be Solved by the Invention However, in the conventional speedometer, since the main body and the reed switch are connected by a cord, (1) installation is troublesome.
(2) The cord is disconnected. (3) It is unsuitable for tour vehicles that are disassembled and carried. There were drawbacks such as.

Means for Solving the Problems In order to eliminate the above-mentioned drawbacks, the present invention emits a pulse in accordance with the rotation of the wheel, emits an infrared ray in response to the pulse, and receives the infrared ray from the transmitter to receive the infrared ray. This is a wireless speedometer for a bicycle comprising a receiving unit that returns to an original pulse by amplification detection and adds it to an opto-isolator.

Operation With such a configuration, each time the magnetic flux crosses the reed switch on the front fork, the contact is closed by the magnet rotating with the wheel, and the pulse generated at this time triggers the monostable multivibrator circuit, Generates a pulse of constant width. This pulse is modulated at a high frequency of about 40 KHz, and the infrared LED is turned on at this frequency. The infrared light from this LED is received (received) by the light receiving unit in the light receiving unit connected to the speedometer either integrally or with a short cord or connector, and the same number of pulses as the received signal is received by the opto-isolator (photocoupler). Give to primary side. Since the secondary side (output side) is connected to the pulse input circuit of the speedometer,
Each time the magnet passes near the reed switch, a pulse is applied to the speedometer, and the speed, running distance, and the like are displayed.

Embodiment In FIG. 1, block I is a transmitting side and block II is a receiving side. B ₁ represents the transmit power, for example, those of the AA batteries are connected two series. m is a magnet, one of which is mounted on the spoke of the front wheel. Therefore, during traveling, the magnet m also rotates due to the rotation of the front wheels. The reed switch 1 corresponding to the magnet m and mounted on the front fork closes its contact point because the magnetic flux crosses each time the magnet passes near the magnet. Reference numeral 1 denotes a monostable multivibrator circuit. When the reed switch 1 is closed, a pulse is applied to its enable terminal, and the output becomes H for 5 ms as shown in FIG.
Reference numeral 2 denotes an astable multivibrator circuit having an enable terminal, which starts oscillating in synchronization with the rise of the monostable multivibrator circuit 1. The frequency is 38KHz and the duty is 3
0%. This oscillation continues for 5 ms as shown in FIG. This oscillating current is amplified by the transistor Q _1, the collector current flows in the infrared LED (D ₁₎ via a current limiting resistor R _1. That is, a pulsed infrared ray of 38 KHz is transmitted for 5 ms for each rotation of the wheel. Block II of Block II on the receiving side
I is received by the light receiving unit element, for example an infrared pin diode D ₂ and the amplifier circuit, the band-pass filter, the detection circuit,
It incorporates a light-receiving IC 3 consisting of a comparator circuit and its peripheral elements. Its output is active low,
It is always H and becomes L only while receiving infrared rays.
However, as shown in FIG. 4, there may be a short time L due to noise such as ambient sunlight. In the figure, a is a signal,
b is noise, and the width of the noise is 1 ms or less. This noise must be cut so that the speedometer does not malfunction. Circuits for this are 4 and 5. Reference numeral 4 denotes an astable multivibrator circuit having an enable terminal. When the output L of the light receiving unit III is supplied to the enable terminal, oscillation occurs only during that time. The cycle is, for example, 1 ms (FIG. 5). 7 is a counter. A Johnson counter or a binary counter may be used. In the case of a Johnson counter, for example, when the reset terminal receives the output L of the light receiving unit III and the pulse input terminal receives the output pulse of the astable multivibrator circuit 4. , Counting, pulse period corresponding to the number of input pulses (1 ms)
A pulse having a pulse width equal to (FIG. 6) is output from the output terminal. Therefore, since the pulse width of the signal from the light receiving unit III is larger than the pulse width of the noise, if the number of pulses generated by the astable multivibrator circuit 4, for example, 5 pulses are counted, the noise and the signal can be completely read. Noise is cut. The output of the counter 5 is applied to the primary side of an opto-isolator (photocoupler) 6 and is electrically insulated, and the signal is transmitted to the secondary side. The secondary side is connected to the pulse input circuit of the speedometer 7. Built-in microcomputer and LE in speedometer 7
Built-in battery to drive D. Therefore, the output of the counter 5 and the circuit of the speedometer are electrically insulated.
Thus, a number of pulses equal to the number of rotations of the wheel
, The speedometer can correctly display the traveling distance, the traveling speed, and the like.

The power of the light receiving side block II is obtained by converting the voltage of a battery, for example, a 006P type battery (B ₂ ), into a constant voltage by the constant voltage element 8 and supplying the voltage to each of the above-described ICs.

Further, the signal and, as a distinguishing circuit noise, noise as is Figure 7 when less, a transistor Q _2, and connect the output terminal of the base and the light receiving IC ₃ by a resistor R _2, and its emitter A capacitor C is inserted between the bases, and the primary side of the opto-isolator 6 is connected to the current limiting resistor as a collector load. Noise can be completely eliminated by choosing a time constant appropriate for the capacitor C and a resistor R _2.

As described above, since the bicycle digital speedometer is wireless, installation of the speedometer is simplified, and it is particularly convenient for a tour car to be disassembled and carried. Further, since infrared rays are used for signal transmission, there is an advantage that noise generated by other transportation means, for example, spark noise of a single vehicle is not affected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a bicycle speedometer according to one embodiment of the present invention, FIG. 2 is a pulse waveform diagram of the monostable multivibrator circuit 1 of block I of FIG. 1, and FIG. 3 is a block diagram of FIG. FIG. 4 is a pulse waveform chart of the astable multivibrator circuit 2 of FIG. 1, FIG. 4 is an output waveform chart when a signal of the light receiving IC ₃ of the block III of FIG. 1 is received, and FIG.
FIG. 6 is a pulse waveform diagram generated by the astable multivibrator circuit 4 for discriminating a signal and noise due to II, FIG. 6 is an output waveform diagram of a counter 5 for counting the number of pulses generated by the astable multivibrator circuit 4, and FIG. FIG. 7 is a circuit diagram of another embodiment for discriminating signals and noise according to the block diagram II of FIG. 1, and FIG. 8 is a schematic connection diagram of a conventional bicycle speedometer.

Claims (1)

(57) [Claims] A magnet attached to a wheel of a bicycle, a multivibrator for generating a pulse of a fixed width by a trigger signal generated by opening and closing a reed switch mounted on a vehicle body corresponding to the magnet, and a pulse generated by the multivibrator. A transmitting section that modulates to a high frequency and applies it to an infrared LED to emit infrared light, and a receiving section that receives infrared light from the LED by an infrared light receiving element, returns the original pulse by amplification detection, and applies the same number of pulses to the opto-isolator. Wireless speedometer for bicycles consisting of